Defense potential of secondary metabolites in medicinal plants under UV-B stress

Metabolomic responses to the mechanical wounding of Catharanthus roseus' upper leaves

Purpose

Plant secondary metabolites are used to treat various human diseases. However, it is difficult to produce a large number of specific metabolites, which largely limits their medicinal applications. Many methods, such as drought and nutrient application, have been used to induce the biosynthetic production of secondary metabolites. Among these secondary metabolite-inducing methods, mechanical wounding maintains the composition of secondary metabolites with little potential risk. However, the effects of mechanical stress have not been fully investigated, and thus this method remains widely unused.

Methods

In this study, we used metabolomics to investigate the metabolites produced in the upper and lower leaves of Catharanthus roseus in response to mechanical wounding.

Results

In the upper leaves, 13 different secondary metabolites (three terpenoid indole alkaloids and 10 phenolic compounds) were screened using an orthogonal partial least squares discriminant analysis (OPLS-DA) score plot. The mechanical wounding of different plant parts affected the production of secondary metabolites. Specifically, when lower leaves were mechanically wounded, the upper leaves became a strong source of resources. Conversely, when upper leaves were injured, the upper leaves themselves became a resource sink. Changes in the source-sink relationship reflected a new balance between resource tradeoff and the upregulation or downregulation of certain metabolic pathways.

Conclusion

Our findings suggest that mechanical wounding to specific plant parts is a novel approach to increase the biosynthetic production of specific secondary metabolites. These results indicate the need for a reevaluation of production practices for secondary metabolites from select commercial plants.

Photosynthetic, Biochemical and Secondary Metabolite Changes in a Medicinal Plant Chlorophytum borivillianum (Safed musli) against Low and High Doses of UV-B Radiation

Plants are inevitably grown in presence of sunlight, therefore bound to be exposed to natural UV-B radiation. Several studies have already been conducted with UV-B and medicinal plants and only few studies showed dose dependent variation. The present study aims to find out the variations and adaptation in Chlorophytum borivillianum under two different doses of UV-B radiation; ambient + low (3.2 kJm^-2  d^-1 ) and high (7.2 kJm^-2  d^-1 ) UV-B dose, denoted as LD and HD, respectively. Reduction in photosynthetic rate was higher at HD, while plants receiving LD displayed nonsignificant variation. During vegetative and reproductive stage, significant reduction (P ≤ 0.001) in stomatal conductance was obtained when exposed to HD-eUV-B. F_v /F_m showed more reductions in HD-eUV-B (12.6%) followed by LD-eUV-B (7.9%). Low and high doses of UV-B enhanced the anthocyanin content but the increase was significant in HD, indicates epidermal protection strategy by the plants. Under LD-eUV-B, the content of saponin, a major phytochemical constituent was enhanced by 26%. Phytochemical analysis of roots revealed reduction mostly in fatty acid components whereas the steroidal components (stigmasterol and sarsasapogenin) showed enhancement in response to LD. The study suggests the importance of LD-eUV-B in the stimulation of medicinal compounds in C. borivillianum.

Identification of bioactive compounds and cytogenotoxicity of the essential oil from the leaves of Croton heliotropiifolius Kunth

Croton heliotropiifolius Kunth, popularly known as "quince" and "velame," contains a high concentration of volatile oils in the leaves, and widely used in folk medicine as an antiseptic, analgesic, sedative, anti-inflammatory, spasmolytic and local anesthetic. The objectives of this investigation were to (1) identify the phytochemical compounds and (2) assess the cytogenotoxicity of the essential oil extracted from the leaves of C. heliotropiifolius Kunth. The oil was extracted utilizing hydrodistillation and phytochemical profile determined using gas chromatography and mass spectrometry (GCMS). In the toxicogenetics analysis, Allium cepa roots were exposed to 1% dimethylsulfoxide or methylmethanesulfonate (MMS, 10 µg/ml) negative and positive controls, respectively, and to C. heliotropiifolius oil at 6 concentrations (0.32; 1.6; 8; 40; 200 or 1000 µg/ml). The phytochemical profile exhibited 40 chromatographic bands, and 33 compounds identified. α-pinene (16.7%) and 1,8-cineole (13.81%) were identified as the major compounds. Some of these identified secondary metabolites displayed biological and pharmacological activities previously reported including antiseptic, analgesic, sedative, anti-inflammatory as well insecticidal, antiviral, anti-fungal actions. In the A. cepa test, C. heliotropiifolius leaves oil induced cytotoxicity at concentrations of 0.32, 1.6 or 200 µg/ml and genotoxicity at 200 or 1000 µg/ml as evidenced by increased presence of micronuclei and significant chromosomal losses. Based upon our observations data demonstrated that the essential oil of C. heliotropiifolius leaves contain monoterpene hydrocarbons, and oxygenated monoterpenes, sesquiterpenes, and oxygenated sesquiterpenes which are associated with cytotoxic and genotoxic responses noted in on A. cepa cells.

Phytochemistry and Antihyperglycemic Potential of Cistus salviifolius L., Cistaceae

Cistus salviifolius has been previously reported as a traditional remedy for hyperglycemia. However, the plant has been scarcely investigated from scientific point of view. Thus, the aim was to examine the chemical composition and to evaluate its antioxidant and antihyperglycemic potential in vitro. Aqueous and ethanolic extracts were evaluated for total phenolic, tannin, and flavonoid content using spectrophotometric methods. Detailed chemical characterization was performed by high-performance liquid chromatography (HPLC-DAD). The volatile organic compounds (VOCs) profile was assessed by gas chromatography technique. The potential in diabetes treatment was evaluated through tests of free radicals neutralization, inhibition of lipid peroxidation process, and test of ferric ion reduction; activity in tests of inhibition of α-amylase, α-glucosidase and dipeptidyl peptidase-4 was also evaluated. High content of phenolics (majority being tannins) was detected; detailed HPLC analysis revealed high content of gallic acid, followed by rutin, chlorogenic and caffeic acids. The VOCs analysis determined sesquiterpene hydrocarbons and oxygenated sesquiterpenes as the main groups of compounds. The assays classified extracts as potent neutralizers of 2,2-diphenyl-1-picrylhydrazil and nitroso radicals formation and potent inhibitors of α-amylase and α-glucosidase. In conclusion, Cistus salviifolius represents a rich source of phenolics and essential oil with sesquiterpenes. The established results suggested its promising antioxidant and antihyperglycemic activities.

A chromosome-level genome assembly for Dracaena cochinchinensis reveals the molecular basis of its longevity and formation of dragon's blood

Dracaena, a remarkably long-lived and slowly maturing species of plant, is world famous for its ability to produce dragon's blood, a precious traditional medicine used by different cultures since ancient times. However, there is no detailed and high-quality genome available for this species at present; thus, the molecular mechanisms that underlie its important traits are largely unknown. These factors seriously limit the protection and regeneration of this rare and endangered plant resource. Here, we sequenced and assembled the genome of Dracaena cochinchinensis at the chromosome level. The D. cochinchinensis genome covers 1.21 Gb with a scaffold N50 of 50.06 Mb and encodes 31 619 predicted protein-coding genes. Analysis showed that D. cochinchinensis has undergone two whole-genome duplications and two bursts of long terminal repeat insertions. The expansion of two gene classes, cis-zeatin O-glucosyltransferase and small auxin upregulated RNA, were found to account for its longevity and slow growth. Two transcription factors (bHLH and MYB) were found to be core regulators of the flavonoid biosynthesis pathway, and reactive oxygen species were identified as the specific signaling molecules responsible for the injury-induced formation of dragon's blood. Our study provides high-quality genomic information relating to D. cochinchinensis and significant insight into the molecular mechanisms responsible for its longevity and formation of dragon's blood. These findings will facilitate resource protection and sustainable utilization of Dracaena.

Emerging trends in genomic and epigenomic regulation of plant specialised metabolism

Regulation of specialised metabolism genes is multilayered and complex, influenced by an array of genomic, epigenetic and epigenomic mechanisms. Here, we review the most recent knowledge in this field, drawing from discoveries in several plant species. Our aim is to improve understanding of how plant genome structure and function influence specialised metabolism. We also highlight key areas for future exploration. Gene regulatory mechanisms influencing specialised metabolism include gene duplication and neo-functionalization, conservation of operon-like clusters of specialised metabolism genes, local chromatin modifications, and the organisation of higher order chromatin structures within the nucleus. Genomic and epigenomic research to-date in the discipline have focused on a relatively small number of plant species, primarily at whole organ or tissue level. This is largely due to the technical demands of the experimental methods needed. However, a high degree of cell-type specificity of function exists in specialised metabolism, driven by similarly specific gene regulation. In this review we focus on the genomic characteristics of genes that are found in different types of clusters within the genome. We propose that acquisition of cell-resolution epigenomic datasets in emerging models, such as the glandular trichomes of Cannabis sativa, will yield important advances. Data such as chromatin accessibility and histone modification profiles can pinpoint which regulatory sequences are active in individual cell types and at specific times in development. These could provide fundamental biological insight as well as novel targets for genetic engineering and crop improvement.

EVALUATION OF PLANT-BASED UV FILTERS POTENTIAL IN MODERN CONCEPT VIEW OF SKIN PHOTOPROTECTION

A therapeutic plants potential is based on the pharmacological effects due to their phytochemical profile. Today, scientific interest in botanicals is increasing as a result of recent research that looks at the prospect of using these raw materials for the cosmetic industry as a means to protect the skin from the harmful effects of UV rays.

The aim of the study was to evaluate a potential of plant-based UV-filters in modern concept view of skin photoprotection.

Materials and methods. A systematic literature search was carried out using the electronic information arrays PubMed, Scopus, Google Scholar, eLibrary. The search depth was 10 years (the period from 2010 to 2021). The search was carried out by the following keywords: antioxidants, cosmetics, photoprotection, chemical composition, pharmacological action.

Results. In the paper, modern principles of skin photoprotection based on the use of chemical or physical UV-filters are considered and scientifically substantiated A trend for the use of plant-based materials and their components in the formulation of photoprotectors was notified. That is associated with a wide activity spectrum, the absence of a xenobiotic effect, and a high bioavailability of organic plant compounds.

Conclusion. The data analysis from scientific publications demonstrated a potential photoprotective activity of plant-based biologically active substances due to antioxidant, anti-inflammatory and anti-radical effects. The results of the study are a theoretical basis for a further comprehensive experimental study of plant objects in order to obtain a pool of evidence in the field of photoprotection in in vivo experiments.

Dose differentiation in elevated UV-B manifests variable response of carbon-nitrogen content with changes in secondary metabolites of Curcuma caesia Roxb

Despite acting as environmental stress, UV-B also plays a regulatory role in the plant's growth and secondary metabolism. UV-B-induced changes show variations between and among the species. The present study mainly focuses on variations in carbon and nitrogen contents and their relation with the phytochemical constituents of Curcuma caesia exposed to two different doses of UV-B (ambient ± elevated UV-B for 1 h (2.4 kJ m^-2 day^-1) and 2 h (4.8 kJ m^-2 day^-1)) under natural field conditions. Results showed that increasing the dose of eUV-B leads to high tuber biomass and reduced rhizome biomass (the medicinally important part). Increased expression of compounds at the initial rhizome formation stage might be due to the increased carbon content, whereas no such trend was found at the final growth or rhizome maturation stage. After final harvesting, carbon content was reduced, with an increase of nitrogen content which might be responsible for enhanced production of major components of essential oil (D-camphor and 1,8-cineole) in 2 h of UV-B exposure followed by 1 h. The phytochemical analysis at the final stage showed induction of compounds (15 and 10 in 1 h and 2 h, respectively) after UV-B exposure which was not detected in controls. The present study suggests that the change in carbon-nitrogen played an important role in the fraction of compounds at different stages, and a lower dose of UV-B (1 h) favoured the increased production of essential oil; however, 2 h dose is important for the enhanced production of major active compounds of essential oil.

Growth promotion and protective potentials of leaf infusions of Parkia biglobosa, Moringa oleifera and Vernonia amygdalina on Abelmoschus esculentus seeds

The germinability and protective potential of leaf infusion of Parkia biglobosa, Moringa oleifera and Vernonia amygdalina leaves on okra (Abelmoschus esculentus) seeds against infections simulated with suspended cells of Aspergillus niger, A. flavus, A. fumigatus, and Penicillium sp. were examined. Prior to planting, the okra seeds were first surface-sterilized in 5% sodium hypochlorite solution before steeping in known concentrations (0, 20, 40, 60, 80, and 100%) of the respective leaf infusions for a known duration. Seven of the steeped seeds were planted in plastic transparent containers, incubated for 7 days under light, and observed daily. Germination index, germination rate, germination time, and vigor index were calculated for each treatment, using standard procedures. The effective concentrations of the infusions of V. amygdalina, P. biglobosa and M. oleifera were 40, 40, and 60% respectively. Optimum steeping durations in leaf infusions were 1, 5, and 6 h, for P. biglobosa, M. oleifera and V. amygdalina, respectively. All the leaf infusions were observed to protect the okra seeds against infections with the test organisms. Furthermore, seeds steeped in the respective leaf infusions showed remarkably higher germinability potential than the control seeds steeped in water. The study confirmed that the leaf infusions may be attractive as economic alternatives for seed priming and protection.

Hairy roots: An untapped potential for production of plant products

While plants are an abundant source of valuable natural products, it is often challenging to produce those products for commercial application. Often organic synthesis is too expensive for a viable commercial product and the biosynthetic pathways are often so complex that transferring them to a microorganism is not trivial or feasible. For plants not suited to agricultural production of natural products, hairy root cultures offer an attractive option for a production platform which offers genetic and biochemical stability, fast growth, and a hormone free culture media. Advances in metabolic engineering and synthetic biology tools to engineer hairy roots along with bioreactor technology is to a point where commercial application of the technology will soon be realized. We discuss different applications of hairy roots. We also use a case study of the advancements in understanding of the terpenoid indole alkaloid pathway in Catharanthus roseus hairy roots to illustrate the advancements and challenges in pathway discovery and in pathway engineering.

Prediction of Phenolic Contents Based on Ultraviolet-B Radiation in Three-Dimensional Structure of Kale Leaves

Ultraviolet-B (UV-B, 280-315 nm) radiation has been known as an elicitor to enhance bioactive compound contents in plants. However, unpredictable yield is an obstacle to the application of UV-B radiation to controlled environments such as plant factories. A typical three-dimensional (3D) plant structure causes uneven UV-B exposure with leaf position and age-dependent sensitivity to UV-B radiation. The purpose of this study was to develop a model for predicting phenolic accumulation in kale (Brassica oleracea L. var. acephala) according to UV-B radiation interception and growth stage. The plants grown under a plant factory module were exposed to UV-B radiation from UV-B light-emitting diodes with a peak at 310 nm for 6 or 12 h at 23, 30, and 38 days after transplanting. The spatial distribution of UV-B radiation interception in the plants was quantified using ray-tracing simulation with a 3D-scanned plant model. Total phenolic content (TPC), total flavonoid content (TFC), total anthocyanin content (TAC), UV-B absorbing pigment content (UAPC), and the antioxidant capacity were significantly higher in UV-B-exposed leaves. Daily UV-B energy absorbed by leaves and developmental age was used to develop stepwise multiple linear regression models for the TPC, TFC, TAC, and UAPC at each growth stage. The newly developed models accurately predicted the TPC, TFC, TAC, and UAPC in individual leaves with R ² > 0.78 and normalized root mean squared errors of approximately 30% in test data, across the three growth stages. The UV-B energy yields for TPC, TFC, and TAC were the highest in the intermediate leaves, while those for UAPC were the highest in young leaves at the last stage. To the best of our knowledge, this study proposed the first statistical models for estimating UV-B-induced phenolic contents in plant structure. These results provided the fundamental data and models required for the optimization process. This approach can save the experimental time and cost required to optimize the control of UV-B radiation.

Integrated mRNA and miRNA Transcriptome Analysis Suggests a Regulatory Network for UV-B-Controlled Terpenoid Synthesis in Fragrant Woodfern (Dryopteris fragrans)

Fragrant woodfern (Dryopteris fragrans) is a medicinal plant rich in terpenoids. Ultraviolet-B (UV-B) light could increase concentration of terpenoids. The aim of this study was to analyze how UV-B regulates the terpenoid synthesis of the molecular regulatory mechanism in fragrant woodfern. In this study, compared with the control group, the content of the terpenes was significantly higher in fragrant woodfern leaves under UV-B treatment for 4 days (d). In order to identify how UV-B regulates the terpenoid metabolic mechanism in fragrant woodfern, we examined the mRNAs and small RNAs in fragrant woodfern leaves under UV-B treatment. mRNA and miRNA-seq identified 4533 DEGs and 17 DEMs in the control group compared with fragrant woodfern leaves under UV-B treatment for 4 d. mRNA-miRNA analysis identified miRNA target gene pairs consisting of 8 DEMs and 115 miRNAs. The target genes were subjected to GO and KEGG analyses. The results showed that the target genes were mainly enriched in diterpene biosynthesis, terpenoid backbone biosynthesis, plant hormone signal transduction, MEP pathway and MVA pathway, in which miR156 and miR160 regulate these pathways by targeting DfSPL and DfARF, respectively. The mRNA and miRNA datasets identified a subset of candidate genes. It provides the theoretical basis that UV-B regulates the terpenoid synthesis of the molecular regulatory mechanism in fragrant woodfern.

SWATH-based quantitative proteomic analysis of Morus alba L. leaves after exposure to ultraviolet-B radiation and incubation in the dark

Morus alba is a woody shrub of the family Moraceae and used as traditional Chinese medicine for a long history. Ultraviolet-B (UV-B) radiation, as a kind of abiotic stress factor, affected the growth and secondary metabolism in M. alba. Previous studies indicated that the contents of several secondary metabolites such as moracin N, chalcomaricin were significantly increased under high level UV-B radiation and dark incubation in M. alba leaves. To reveal the response mechanism under UV-B radiation and dark incubation in M. alba leaves, SWATH-based quantitative proteomic analysis was performed. Totally, 716 proteins were identified and quantified in the control, UVB, and UVD groups. Among them, 123 proteins and 96 proteins were identified as differentially abundant proteins in UVB group and UVD groups, respectively. Proteins related to photosynthesis, amino acid biosynthesis, and tocopherol biosynthesis were significantly altered in UVB group, while proteins related to the biosynthesis of phenolic compounds were significantly altered in UVD group. In addition, the abundances of proteins involved in the ubiquitin-proteasome system (UPS) were significantly increased in both UVB and UVD groups, indicating that UPS combined with secondary mechanism participated in the resistance to UV-B radiation and dark incubation. The obtained results provide novel insight into the effects of high level UV-B radiation on M. alba leaves and on the strategies used for maximizing the chemical constituents and the medicinal value of the M. alba leaves.

Evolution of Physicochemical Properties, Phenolic Acid Accumulation, and Dough-Making Quality of Whole Wheat Flour During Germination Under UV-B Radiation

The effects of ultraviolet-B (UV-B) radiation on the physiological properties, phenolic acid accumulation, and dough-making quality of wheat during germination were investigated. UV-B radiation inhibited the wheat sprout length and reduced the dry matter loss. As phenolic acids were principally present in the kernels' bran, UV-B radiation could promote their accumulation in the interior of germinated wheat (GW). The total phenolic compounds, ascorbic acid, and antioxidant activity were also enhanced significantly during germination with UV-B. UV-B improved the development time, stability time, rheological properties, and viscosity of GW, and inhibited the α-amylase activity, the destruction of the amorphous region of starch particles, and the proteins degradation process during germination, and thus the deterioration of dough-making quality caused by germination was inhibited. Therefore, UV-B radiation could be a potential approach to enhance the nutritional and dough-making quality of germinated whole wheat flour.

Plant growth and phytoactive alkaloid synthesis in kratom [Mitragyna speciosa (Korth.)] in response to varying radiance

Leaves harvested from kratom [Mitragyna speciosa (Korth.)] have a history of use as a traditional ethnobotanical medicine to combat fatigue and improve work productivity in Southeast Asia. In recent years, increased interest in the application and use of kratom has emerged globally, including North America, for its potential application as an alternative source of medicine for pain management and opioid withdrawal syndrome mitigation. Although the chemistry and pharmacology of major kratom alkaloids, mitragynine and 7-hydroxymitragynine, are well documented, foundational information on the impact of plant production environment on growth and kratom alkaloids synthesis is unavailable. To directly address this need, kratom plant growth, leaf chlorophyll content, and alkaloid concentration were evaluated under three lighting conditions: field full sun (FLD-Sun), greenhouse unshaded (GH-Unshaded), and greenhouse shaded (GH-Shaded). Nine kratom alkaloids were quantified using an ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method. Greenhouse cultivation generally promoted kratom height and width extension by 93-114% and 53-57%, respectively, compared to FLD-Sun. Similarly, total leaf area and leaf number were increased by 118-160% and 54-80% under such conditions. Average leaf size of plants grown under GH-Shaded was 41 and 69% greater than GH-Unshaded and FLD-Sun, respectively; however, no differences were observed between GH-Unshaded and FLD-Sun treatments. At the termination of the study, total leaf chlorophyll a+b content of FLD-Sun was 17-23% less than those grown in the greenhouse. Total leaf dry mass was maximized when cultivated in the greenhouse and was 89-91% greater than in the field. Leaf content of four alkaloids to include speciociliatine, mitraphylline, corynantheidine, and isocorynantheidine were not significantly impacted by lighting conditions, whereas 7-hydroxymitragynine was below the lower limit of quantification across all treatments. However, mitragynine, paynantheine, and corynoxine concentration per leaf dry mass were increased by 40%, 35%, and 111%, respectively, when cultivated under GH-Shaded compared to FLD-Sun. Additionally, total alkaloid yield per plant was maximized and nearly tripled for several alkaloids when plants were cultivated under such conditions. Furthermore, rapid, non-destructive chlorophyll evaluation correlated well (r2 = 0.68) with extracted chlorophyll concentrations. Given these findings, production efforts where low-light conditions can be implemented are likely to maximize plant biomass and total leaf alkaloid production.

Mild-Intensity UV-A Radiation Applied Over a Long Duration Can Improve the Growth and Phenolic Contents of Sweet Basil

UV-A radiation (320-400 nm) is an abiotic stressor that may be used to enhance the production of beneficial secondary metabolites in crops such as leafy vegetables. However, tradeoffs between enhanced phytochemical contents and overall growth/yield reductions have been reported. The responses varied depending on the UV-A intensity, spectral peak, exposure time, species, and varieties. We quantified the changes in growth, morphology, photosynthesis, and phenolic contents of sweet basil grown under a base red/blue/green LED light with four supplemental UV-A intensity treatments (0, 10, 20, and 30 W·m^-2) in an indoor environment over 14 days. The objective was to determine whether UV-A radiation could be utilized to improve both yield and quality of high-value sweet basil in a controlled production environment. Biomass harvested at 14 days after treatment (DAT) was highest under mild-intensity UV-A treatment of 10 W·m^-2 and lowest under high-intensity UV-A treatment of 30 W·m^-2. The total leaf area and the number of leaves were significantly lower under the 30 W·m^-2 treatment than under the 10 and 20 W·m^-2 treatments at 14 DAT. The maximum quantum efficiency of photosystem II (PSII) for photochemistry (F_v/F_m ) showed a gradual decrease under the 20 and 30 W·m^-2 treatments from 3 to 14 DAT, whereas F_v/F_m remained relatively constant under the 0 and 10 W·m^-2 treatments over the entire 14 days. The leaf net photosynthesis rate showed a significant decrease of 17.4% in the 30 W·m^-2 treatment compared to that in the 10 W·m^-2 treatment at 14 DAT. Phenolic contents (PAL enzyme activity, total phenolic concentration, and antioxidant capacity) were the highest under the 20 W·m^-2 treatment, followed by the 10, 30, and 0 W·m^-2 treatments. Overall, our results indicate that the biomass production and accumulation of beneficial phenolic compounds in sweet basil varied depending on the intensity and duration of UV-A application. Mild UV-A radiation (10-20 W·m^-2) can be a beneficial stressor to improve sweet basil yield and quality over relatively long-term cultivation.

Rational Synthesis of Solid-State Ultraviolet B Emitting Carbon Dots via Acetic Acid-Promoted Fractions of sp3 Bonding Strategy

Carbon dots (CDs) have received tremendous attention for their excellent photoluminescence (PL) properties. However, it remains a great challenge to obtain CDs with ultraviolet (UV, 200-400 nm) emission in solid state, which requires strict control of the CDs structure and overcoming the aggregation-caused quenching (ACQ). Herein, a new sp³ compartmentalization strategy is developed to meet these requirements, by employing acetic acid to promote fractions of sp³ bonding during the synthesis of CDs. It markedly decreases the size of sp² conjugating units in the CDs, and shifts PL emission to the ultraviolet B (UVB) region (λ_max  = 308 nm). Moreover, sp² domains are well spatially compartmentalized by sp³ domains and the ACQ effect is minimized, enabling the high quantum yield in solid state (20.2%, λ_ex  = 265 nm) with a narrow bandwidth of 24 nm and environmental robustness. The solid-state UVB emissive CDs are highly desired for application in photonic devices. Hence, a demo of UVB light-emitting diodes is fabricated for plant lighting, leading to a 29% increase of ascorbic acid content in the basil. Overall, a rational and efficient way to construct solid UVB-CDs phosphors for wide applications is provided.

Application of UV-B radiation for enhancing the accumulation of bioactive phenolic compounds in pigeon pea [Cajanus cajan (L.) Millsp.] hairy root cultures

UV-B radiation is an ideal elicitation strategy for promoting phytochemical accumulation in plant in vitro cultures, associated with various advantages of easy manipulation, cost-effectiveness, no residue, and instantaneous termination. For the first time, UV-B radiation was used to enhance the production of bioactive phenolic compounds (flavonoids and stilbenes) in pigeon pea hairy root cultures (PPHRCs). The total yield of eight flavonoids (414.95 ± 50.68 μg/g DW) in 42-day-old PPHRCs exposed to 4 h of UV-B radiation increased by 1.49-fold as against control, whereas the yield of cajaninstilbene acid (6566.01 ± 702.14 μg/g DW) in PPHRCs undergoing 10 h of UV-B radiation significantly increased by 2.31-fold over control. UV-B radiation was found to induce the oxidative stress in PPHRCs and cause the tissue damage to hairy roots, which improved the levels of endogenous salicylic acid thus triggering the expression of genes involved in phenylpropanoid biosynthesis pathway. And, a regulation competition in metabolic flow dominated by CHS and STS was responsible for the difference in accumulation trends of flavonoids and cajaninstilbene acid. Results of this study not only provide a feasible and simple UV-B supplementation strategy for the enhanced production of bioactive phenolic compounds (especially the high-value cajaninstilbene acid) in PPHRCs, but also contributed to the understanding of photobiological responses related to secondary metabolism.

Production of mycosporine-like amino acid (MAA)-loaded emulsions as chemical barriers to control sunscald in fruits and vegetables

BACKGROUND

Sunscald is a physiological disorder that occurs in many horticultural products when exposed to excessive solar radiation and high temperatures. Traditionally, sunscald is controlled using physical barriers that reflect radiation, however this practice is not always efficient. A possible alternative would be the use of chemical barriers, such as mycosporine-like amino acids (MAAs), which protect aquatic organisms against ultraviolet (UV) radiation. Thus, this study aimed to develop a lipid-based emulsion containing MAAs for using in the preharvest of horticultural products.

RESULTS

Emulsions were developed using 10% (w/v) of corn oil (CO) and soybean oil (SO), carnauba wax (CW), and beeswax (BW) as lipid bases (LBs). The emulsion containing CW and ammonium hydroxide was the most stable, resembling commercial wax. Therefore, this formulation was used as the basis for the incorporation of the commercial product Helioguard™ 365, a source of MAA, in concentrations of 0%, 1%, 2%, and 4% (v/v). The MAA incorporation resulted in little modifications in the stability of the emulsion, providing an increase in the absorbance with peaks in the UV-B ranging from 280 to 300 nm.

CONCLUSION

The lipid-base emulsion containing MAAs could be used as a chemical barrier to control sunscald in horticultural products. © 2021 Society of Chemical Industry.

Explicating the cross-talks between nanoparticles, signaling pathways and nutrient homeostasis during environmental stresses and xenobiotic toxicity for sustainable cultivation of cereals

Precision farming using nanoparticles is a cutting-edge technology for safe cultivation of crop plants in marginal areas afflicted with environmental/climatic stresses like salinity, drought, extremes of temperature, ultraviolet B stress or polluted with xenobiotics like toxic heavy metals and fluoride. Major cereal crops like rice, wheat, maize, barley, sorghum and millets which provide the staple food for the entire global population are mainly glycophytes and are extremely susceptible to abiotic stress-induced oxidative injuries. Nanofertilization/exogenous spraying of beneficial nanoparticles alleviates the oxidative damages in cereals by altering the homeostasis of phytohormones like abscisic acid, gibberellins, cytokinins, auxins, salicylic acid, jasmonic acid and melatonin and by triggering the synthesis of gasotransmitter nitric oxide. Signaling cross-talks of nanoparticles with plant growth regulators enable activation of the defence machinery, comprising of antioxidants, thiol-rich compounds and glyoxalases and restrict xenobiotic mobilization by suppressing the expression of associated transporters. Accelerated nutrient uptake and grain biofortification under the influence of nanoparticles result in optimum crop productivity under sub-optimal conditions. However, over-dosing of even beneficial nanoparticles promotes severe phytotoxicity. Hence, the concentration of nanoparticles and mode of administering need to be thoroughly standardized before large-scale field applications, to ensure sustainable cereal cultivation with minimum ecological imbalance.

UV-B Radiation as Abiotic Elicitor to Enhance Phytochemicals and Development of Red Cabbage Sprouts

Background: The main objective of this study was to evaluate the effect of periodical UV-B illumination during red cabbage germination on morphological development and the phenolics and carotenoid accumulation. Methods: During a sprouting period of 10 days at 20 °C in darkness, seedlings received 5, 10, or 15 kJ m−2 UV-B (T5, T10, and T15) applied in four steps (25% on days 3, 5, 7, and 10). UV untreated sprouts were used as control (CTRL). After 10 days of germination, the sprouts were harvested and stored 10 days at 4 °C as a minimally processed product. Phenolic and carotenoid compounds were analysed 1 h after each UV-B application and on days 0, 4, 7, and 10 during cold storage. Results: The longest hypocotyl length was observed in T10-treated sprouts. The total phenolic content (TPC), total flavonoid content (TFC), and total antioxidant capacity (TAC) increased during germination following a sigmoidal kinetic, especially in the UV-B-treated samples, which reported a dose-dependent behaviour. In this way, T10-treated sprouts increased the TPC by 40% after 10 days at 4 °C compared to CTRL, while TAC and TFC increased by 35 and 30%, respectively. Carotenoids were enhanced with higher UV-B doses (T15). Conclusions: We found that UV-B stimulated the biosynthesis of bioactive compounds, and a dose of 10 kJ m−2 UV-B, proportionally applied on days 3, 5, 7, and 10 days, is recommended.

Quantitative analysis of the profiles of twelve major compounds in Gentiana straminea Maxim. Roots by LC-MS/MS in an extensive germplasm survey in the Qinghai-Tibetan plateau

ETHNOBOTANICAL RELEVANCE

Gentiana straminea Maxim. is a well-known Tibetan traditional herb, which has been used to treat rheumatic arthritis, iceteric hepatitis, and other diseases for thousands years. However, there is still lack of comprehensive active constituents profiling of this species throughout the Qinghai-Tibet Plateau (QTP).

AIM OF STUDY

This study was designed to provide a comprehensive quality map of G.straminea germplasm based on twelve active constituents (loganic acid, gentiopicroside, swertiamarin, sweroside, 6-O-β-D-glucosylgentiopicroside, oleanic acid, morroniside, trilobatin, isoorientin, isovite, Shanzhisidemethylester and quercetin) on the QTP.

MATERIALS AND METHODS

G.straminea root samples collected throughout QTP in the flowering period were analyzed by the LC-MS/MS. Statistics analysis methods PCA, clustering and ecological regions analysis for G.straminea constituents differentiation was demonstrated.

RESULTS

The active constituents varied greatly across the QTP; the majority of constituents were secoiridoid derivatives, with gentiopicroside being the most abundant compound. Most constituents were significantly affected by the latitudes and altitudes other than longitudes. PCA and hierarchical clustering analysis showed that all samples could be separated into six distinct groups, and 15 populations showed the highest constituent abundances. Further, geographical region analysis showed that the highest quality populations mainly located near the source region of Yellow River, especially in the Qinghai and Sichuan areas. Additionally, correlation analysis showed that there were relationships among genetiopicroside, loganic acid, and other compounds, which might be related to the enzymatic pathways involved in the metabolism of these constituents.

CONCLUSION

LC-MS/MS method allowed separation of quality profiling of G.straminea on the QTP, 15 populations showed the highest constituent abundances. In six geographical groups, the highest quality populations mainly located near the source region of Yellow River, especially in the Qinghai and Sichuan areas, which may be due to the climate caused by the westerlies and Indian Ocean monsoons in the QTP.

Traditional in vitro strategies for sustainable production of bioactive compounds and manipulation of metabolomic profile in medicinal, aromatic and ornamental plants

Precursor feeding, elicitation and culture medium parameters are traditional in vitro strategies to enhance bioactive compounds of medicinal, aromatic, and ornamental plants (MAOPs). Machine learning can help researchers find the best combination of these strategies to increase the secondary metabolites content of MAOPs. Many requirements for human life, from food, pharmaceuticals and cosmetics to clothes, fuel and building materials depend on plant-derived natural products. Essential oils, methanolic and ethanolic extracts of in vitro undifferentiated callus and organogenic cultures of medicinal, aromatic, and ornamental plants (MAOPs) contain bioactive compounds that have several applications for various industries, including food and pharmaceutical. In vitro culture systems provide opportunities to manipulate the metabolomic profile of MAOPs. Precursors feeding, elicitation and culture media optimization are the traditional strategies to enhance in vitro accumulation of favorable bioactive compounds. The stimulation of plant defense mechanisms through biotic and abiotic elicitors is a simple way to increase the production of secondary metabolites in different in vitro culture systems. Different elicitors have been applied to stimulate defense machinery and change the metabolomic profile of MAOPs in in vitro cultures. Plant growth regulators (PGRs), stress hormones, chitosan, microbial extracts and physical stresses are the most applied elicitors in this regard. Many other chemical tolerance-enhancer additives, such as melatonin and proline, have been applied along with stress response-inducing elicitors. The use of stress-inducing materials such as PEG and NaCl activates stress tolerance elicitors with the potential of increasing secondary metabolites content of MAOPs. The present study reviewed the state-of-the-art traditional in vitro strategies to manipulate bioactive compounds of MAOPs. The objective is to provide insights to researchers involved in in vitro production of plant-derived natural compounds. The present review provided a wide range of traditional strategies to increase the accumulation of valuable bioactive compounds of MAOPs in different in vitro systems. Traditional strategies are faster, simpler, and cost-effective than other biotechnology-based breeding methods such as genetic transformation, genome editing, metabolic pathways engineering, and synthetic biology. The integrate application of precursors and elicitors along with culture media optimization and the interpretation of their interactions through machine learning algorithms could provide an excellent opportunity for large-scale in vitro production of pharmaceutical bioactive compounds.

Phenolics from Medicinal and Aromatic Plants: Characterisation and Potential as Biostimulants and Bioprotectants

Biostimulants and bioprotectants are derived from natural sources and can enhance crop growth and protect crops from pests and pathogens, respectively. They have attracted much attention in the past few decades and contribute to a more sustainable and eco-friendly agricultural system. Despite not having been explored extensively, plant extracts and their component secondary metabolites, including phenolic compounds have been shown to have biostimulant effects on plants, including enhancement of growth attributes and yield, as well as bioprotectant effects, including antimicrobial, insecticidal, herbicidal and nematicidal effects. Medicinal and aromatic plants are widely distributed all over the world and are abundant sources of phenolic compounds. This paper reviews the characterisation of phenolic compounds and extracts from medicinal and aromatic plants, including a brief overview of their extraction, phytochemical screening and methods of analysis. The second part of the review highlights the potential for use of phenolic compounds and extracts as biostimulants and bioprotectants in agriculture as well as some of the challenges related to their use.

Metabolic programming of Rhododendron chrysanthum leaves following exposure to UVB irradiation

Excessive UVB reaching the earth is a cause for concern. To decipher the mechanism concerning UVB resistance of plants, we studied the effects of UVB radiation on photosynthesis and metabolic profiling of Rhododendron chrysanthum Pall. by applying 2.3Wm-2 of UVB radiation for 2days. Results showed that maximum quantum yield of PSII (Fv/Fm) and effective quantum yield of PSII (φPSII) decreased by 7.95% and 8.36%, respectively, following UVB exposure. Twenty five known metabolites were identified as most important by two different methods, including univariate and multivariate statistical analyses. Treatment of R. chrysanthum with UVB increased the abundance of flavonoids, organic acids, and amino acids by 62%, 22%, and 5%, respectively. UVB irradiation also induced about 1.18-fold increase in 11 top-ranked metabolites identified: five organic acids (d-2,3-dihydroxypropanoic acid, maleic acid, glyceric acid, fumaric acid and suberic acid), four amino acids (l-norleucine, 3-oxoalanine, l-serine and glycine), and two fatty acids (pelargonic acid and myristoleic acid). In addition, UVB irradiation increased the intermediate products of arginine biosynthesis and the TCA cycle. Taken together, the accumulation of flavonoids, organic acids, amino acids and fatty acids, accompanied by enhancement of TCA cycle and arginine biosynthesis, may protect R. chrysanthum plants against UVB deleterious effects.

Assessment of Ultraviolet Impact on Main Pigment Content in Purple Basil (Ocimum basilicum L.) by the Spectrometric Method and Hyperspectral Images Analysis

This research is aimed at the assessing the impact of the ultraviolet radiation in the A, B, and C ranges (as additives to the main light) on general plan condition, the stress experienced by them, the pigment concentration in the leaves and leaf reflective characteristics. Under studying, there were the photo-protective reactions of the purple variety basil plants. The plants were grown in plastic pots in a phyto-chamber equipped with an automatic microclimate system. The phyto-chamber was divided into four compartments where, in addition to the main lighting, there were installed the additional LEDs emitting their radiation in the ranges UV-A, UV-B, and UV-C. Plant reactions were evaluated by the contents of the main pigments as detected by the spectrometric method. Then correlations were revealed between those values and the vegetative indices obtained based on the hyperspectral images. A strong correlation (R2 ˃ 0.83) was observed between the values of the vegetative indices ARI and mARI and the anthocyanins concentration in basil leaves. A weak correlation (R2 = 0.0479) was found between the ARI and mARI values and the carotenoids index CRI700, which is attributed to the shielding effect of the anthocyanins. Deviations in the results are influenced by leaf surface unevenness, its thickness and density. Additional research is needed including developing reflection indices taking into account the shielding effect of the purple pigments.

Comprehensive Evaluation of Amino Acids and Polyphenols in 69 Varieties of Green Cabbage (Brassica oleracea L. var. capitata L.) Based on Multivariate Statistical Analysis

The biological activities of the primary metabolites and secondary metabolites of 69 green cabbage varieties were tested. The LC-MS detection method was used to determine the content of 19 free amino acids (lysine, tryptophan, phenylalanine, methionine, threonine, isoleucine, leucine, valine, arginine, asparagine, glycine, proline, tyrosine, glutamine, alanine, aspartic acid, serine, and glutamate). The content of 10 polyphenols (chlorogenic acid, gallic acid, 4-coumaric acid, ferulic acid, gentisic acid, cymarin, erucic acid, benzoic acid, rutin, and kaempferol) was determined by the HPLC detection method. Considering the complexity of the data obtained, variance analysis, diversity analysis, correlation analysis, hierarchical cluster analysis (HCA), and principal component analysis (PCA) were used to process and correlate amino acid or polyphenol data, respectively. The results showed that there were significant differences between the different amino acids and polyphenols of the 69 cabbage varieties. The most abundant amino acids and polyphenols were Glu and rutin, respectively. Both amino acids and polyphenols had a high genetic diversity, and multiple groups of significant or extremely significant correlations. The 69 cabbage varieties were divided into two groups, according to 19 amino acid indexes, by PCA. Among them, seven varieties with high amino acid content all fell into the fourth quadrant. The HCA of amino acids also supports this view. Based on 10 polyphenols, the 69 cabbage varieties were divided into two groups by HCA. Based on 29 indexes of amino acids and polyphenols, 69 cabbage varieties were evaluated and ranked by PCA. Therefore, in this study, cabbage varieties were classified in accordance with the level of amino acids and polyphenols, which provided a theoretical basis for the genetic improvement of nutritional quality in cabbage.

An assessment of dose-dependent UV-B sensitivity in Eclipta alba: Biochemical traits, antioxidative properties, and wedelolactone yield

The UV-B-induced signals play a crucial role in improving the analeptic values of medicinally important plants. Eclipta alba L. (Hassak), commonly known as False Daisy, holds supreme stature with its pharmaceutical association in treating various ailments, particularly in Ayurvedic medicine. The present study aimed to evaluate the response of E. alba plants exposed to ambient (AT) and two different supplemental UV-B doses (eUV-B, ambient ±7.2 kJ m^-2 day^-1), i.e., intermittent (IT) and continuous (CT) UV-B treatment for 130 and 240 h respectively. Antioxidative activities and medicinally important compounds (wedelolactone) were measured in different plants' parts at three growth stages. Under both the eUV-B treatments, the photosynthetic pigments were adversely affected (along with reductions in protein content) with a concomitant increase in secondary metabolites. Substantial variations in enzymatic antioxidants and non-enzymatic compounds showed the adaptive resilience strategies of plants against eUV-B. The wedelolactone content increased in leaves but compromised in stem and roots under IT. The results concluded that IT UV-B exposure led to the improvement of plant growth and the yield of wedelolactone compared to CT, suggesting its ameliorative role in improving the test plant's medicinal value.

UV-B light and its application potential to reduce disease and pest incidence in crops

Ultraviolet-B radiation (280-315 nm), perceived by the plant photoreceptor UVR8, is a key environmental signal that influences plant growth and development and can reduce disease and pest incidence. The positive effect of UV-B on disease resistance and incidence in various plant species supports the implementation of supplemental UV-B radiation in sustainable crop production. However, despite many studies focusing on UV-B light, there is no consensus on the best mode of application. This review aims to analyze, evaluate, and organize the different application strategies of UV-B radiation in crop production with a focus on disease resistance. We summarize the physiological effects of UV-B light on plants and discuss how plants perceive and transduce UV-B light by the UVR8 photoreceptor as well as how this perception alters plant specialized metabolite production. Next, we bring together conclusions of various studies with respect to different UV-B application methods to improve plant resistance. In general, supplemental UV-B light has a positive effect on disease resistance in many plant-pathogen combinations, mainly through the induction of the production of specialized metabolites. However, many variables (UV-B light source, plant species, dose and intensity, timing during the day, duration, background light, etc.) make it difficult to compare and draw general conclusions. We compiled the information of recent studies on UV-B light applications, including e.g., details on the UV-B light source, experimental set-up, calculated UV-B light dose, intensity, and duration. This review provides practical insights and facilitates future research on UV-B radiation as a promising tool to reduce disease and pest incidence.

Nontargeted Metabolomics as a Screening Tool for Estimating Bioactive Metabolites in the Extracts of 50 Indigenous Korean Plants

Many indigenous Korean plants have been used in medicinal preparations and health-promoting foods. These plant species contain beneficial metabolites with various bioactivities, such as antioxidant and anti-inflammatory activities. Herein, we suggest a new screening strategy using metabolomics to explore the bioactive compounds in 50 Korean plants. Secondary metabolites were analyzed using UHPLC-LTQ-Orbitrap-MS/MS. The plant extracts were subjected to antioxidant and anti-inflammatory assays. We identified metabolites that contributed to bioactivities according to the results of bioassays and multivariate analyses. Using Pearson’s correlation, phenolics (e.g., casuarictin, 3-O-methylellagic acid) showed positive correlation with antioxidant activity, while biflavonoids (e.g., amentoflavone, rosbustaflavone) were correlated with nitric oxide (NO) inhibition activity. To compensate for the limitation of this new strategy, we further validated these by investigating three parts (branches, fruits, leaves) of Platycladus orientalis which showed high activities on both bioassays. Unlike the above observation, we identified significantly different metabolites from different parts, which was not the results of bioassays. In these validation steps, interestingly, biflavonoids (e.g., robustaflavone, sciadopitysin) contributed to both activities in P. orientalis. The findings of this work suggest that new strategy could be more beneficial in the identification of bioactive plant species as well as that of their corresponding bioactive compounds that impart the bioactivity.

Quantitative Assessment of Abiotic Stress on the Main Functional Phytochemicals and Antioxidant Capacity of Wheatgrass at Different Seedling Age

The wheat seedlings of 6 days old were daily subjected to ultraviolet irradiation (irradiating for 5, 10, 20, 40, and 60 min/day, respectively), Polyethylene glycol 6000 (5, 10, 15, 20, 25% in 1/2 Hoagland solution, respectively), and salinity solution (10, 25, 50, 100, 200 mM in 1/2 Hoagland solution, respectively), while the control group (CK) was supplied only with the Hoagland solution. The wheatgrass was harvested regularly seven times and the total soluble polysaccharides, ascorbic acid, chlorophyll, total polyphenol, total triterpene, total flavonoid, and proanthocyanins content were tested. The antioxidant capacity was evaluated through 2,2'-azino-bis (3-ethylbenzthia-zoline-6-sulfonic acid) (ABTS), 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging ability, and ferric ion reducing power. Technique for order preference by similarity to ideal solution (TOPSIS) mathematical model was adopted to comprehensively assess the functional phytochemicals of the different treatments. The results showed that the accumulation patterns of phytochemicals under abiotic stress were complex and not always upregulated or downregulated. The antioxidant activity and functional phytochemicals content of wheatgrass were significantly affected by both the stress treatments and seedling age, while the latter affected the chemicals more efficiently. The top five highest functional phytochemicals were observed in the 200 mM NaCl treated group on the 21st and 27th day, 25% PEG treated group on the 24th day, 200 mM NaCl treated group on the 24th day, and the group of 40 min/day ultraviolet exposure on 27th day.

Short term UV-B radiation mediated modulation of physiological traits and withanolides production in Withania coagulans (L.) Dunal under in-vitro condition

Accumulation of secondary metabolites is a key process in the growth and development of plants under different biotic/abiotic constraints. Many studies highlighted the regulatory potential of UV-B treatment towards the secondary metabolism of plants. In the present study, we examined the impact of UV-B on the physiology and secondary metabolism of Withania coagulans, which is an important ayurvedic plant with high anti-diabetic potential. Results showed that in-vitro UV-B exposure negatively influenced chlorophyll content and photosynthetic machinery. However, Fv/Fm ratio was found non-significantly altered up to 3 h UV-B exposure. The maximum lipid peroxidation level was recorded with 46.8% higher malondialdehyde content in the plants supplemented with 5 h UV-B radiation, that was indicated the oxidative stress in W. coagulans. Conversely, UV-B treatment significantly increased the plant's stress protective compounds like carotenoids, anthocyanin, phenol and proline, in W. coagulans. Free radical scavenging activity was also significantly increased ~ 18% than the control with 3 h UV-B treatment. The maximum antioxidative enzymes activities were observed with the short-term (up to 3 h) UV-B treatment. Specifically, UV-B radiation exposure significantly increased the content of withaferin A and withanolide A in W. coagulans with maximum 1.38 and 3.42-folds, respectively. Additionally, withanolides biosynthesis related genes transcript levels were found over-expressed under the response of UV-B elicitation. The acquired results suggested that short-term UV-B supplementation triggers secondary metabolism along with combating oxidative stress via improving the antioxidative defense system in W. coagulans. Also, UV-B can be used as an efficient abiotic elicitor to increase pharmaceutical compounds (withanolides) production.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s12298-021-01046-7.

In-vitro cytotoxicity in relation to chemotypic diversity in diploid and tetraploid populations of Gentiana kurroo Royle

ETHNOPHARMACOLOGICAL RELEVANCE

Gentiana kurroo is a multipurpose critically endangered medicinal herb prescribed as medicine in Ayurveda in India and exhibits various pharmacological properties including anti-cancer activity. The species is rich repository of pharmacologically active secondary metabolites together with secoiridoidal glycosides.

AIM OF THE STUDY

The study aimed to investigate the chemical diversity in different populations/cytotypes prevailing in G. kurroo to identify elite genetic stocks in terms of optimum accumulation/biosynthesis of desired metabolites and having higher in-vitro cytotoxicity potential in relation to chemotypic diversity.

MATERIAL AND METHODS

The wild plants of the species were collected from different ranges of altitudes from the Kashmir Himalayas. For cytological evaluation, the standard meiotic analysis was performed. The standard LC-MS/MS technique was employed for phytochemical analysis based on different marker compounds viz. sweroside, swertiamarin, and gentiopicroside. Different tissues such as root-stock, aerial parts, and flowers were used for chemo-profiling. Further, the methanolic extracts of diploid and tetraploid cytotypes were assessed for cytotoxic activity by using MTT assay against four different human cancer cell lines.

RESULTS

The quantification of major bioactive compounds based on tissue- and location-specific comparison, as well as in-vitro cytotoxic potential among extant cytotypes, was evaluated. The comprehensive cytomorphological studies of the populations from NW Himalayas revealed the occurrence of different chromosomal races viz. n = 13, 26. The tetraploid cytotype was hitherto unreported. The tissue-specific chemo-profiling revealed relative dominance of different phytoconstituents in root-stock. There was a noticeable increase in the quantity of the analyzed compounds in relation to increasing ploidy status along the increasing altitudes. The MTT assay of methanolic extracts of diploid and tetraploid cytotypes displayed significant cytotoxicity potential in tetraploids. The root-stock extracts of tetraploids were highly active extracts with IC₅₀ value ranges from 5.65 to 8.53 μg/mL against HCT-116 colon cancer.

CONCLUSION

The chemical evaluation of major bioactive compounds in diverse cytotypes from different plant parts along different altitudes presented an appreciable variability in sweroside, swertiamarin, and gentiopicroside contents. Additionally, the concentrations of these phytoconstituents varied for cytotoxicity potential among different screened cytotypes. This quantitative difference of active bio-constituents was in correspondence with the growth inhibition percentage of different tested cancer cell lines. Thus, the present investigation strongly alludes towards a prognostic approach for the identification of elite cytotypes/chemotypes with significant pharmacological potential.

Optimization of Tabersonine Methoxylation to Increase Vindoline Precursor Synthesis in Yeast Cell Factories

Plant specialized metabolites are widely used in the pharmaceutical industry, including the monoterpene indole alkaloids (MIAs) vinblastine and vincristine, which both display anticancer activity. Both compounds can be obtained through the chemical condensation of their precursors vindoline and catharanthine extracted from leaves of the Madagascar periwinkle. However, the extensive use of these molecules in chemotherapy increases precursor demand and results in recurrent shortages, explaining why the development of alternative production approaches, such microbial cell factories, is mandatory. In this context, the precursor-directed biosynthesis of vindoline from tabersonine in yeast-expressing heterologous biosynthetic genes is of particular interest but has not reached high production scales to date. To circumvent production bottlenecks, the metabolic flux was channeled towards the MIA of interest by modulating the copy number of the first two genes of the vindoline biosynthetic pathway, namely tabersonine 16-hydroxylase and tabersonine-16-O-methyltransferase. Increasing gene copies resulted in an optimized methoxylation of tabersonine and overcame the competition for tabersonine access with the third enzyme of the pathway, tabersonine 3-oxygenase, which exhibits a high substrate promiscuity. Through this approach, we successfully created a yeast strain that produces the fourth biosynthetic intermediate of vindoline without accumulation of other intermediates or undesired side-products. This optimization will probably pave the way towards the future development of yeast cell factories to produce vindoline at an industrial scale.

Transcriptomic analysis reveals the parallel transcriptional regulation of UV-B-induced artemisinin and flavonoid accumulation in Artemisia annua L

UV-B radiation is a pivotal photomorphogenic signal and positively regulates plant growth and metabolite biosynthesis. In order to elucidate the transcriptional regulation mechanism underlying UV-B-induced artemisinin and flavonoid biosynthesis in Artemisia annua, the transcriptional responses of A. annua L. leaves to UV-B radiation were analyzed using the Illumina transcriptome sequencing. A total of 10705 differentially expressed genes (DEGs) including 533 transcription factors (TFs), were identified. Based on the expression trends of the differentially expressed TFs as well as artemisinin and flavonoid biosynthesis genes, we speculated that TFs belonging to 6 clusters were most likely to be involved in the regulation of artemisinin and/or flavonoid biosynthesis. The regulatory relationship between TFs and artemisinin/flavonoid biosynthetic genes was further studied. Dual-LUC assays results showed that AaMYB6 is a positive regulator of AaLDOX which belongs to flavonoid biosynthesis pathway. In addition, we identified an R2R3 MYB TF, AaMYB4 which potentially mediated both artemisinin and flavonoid biosynthesis pathways by activating the expression of AaADS and AaDBR2 in artemisinin biosynthesis pathway and AaUFGT in flavonoid biosynthesis pathway. Overall, our findings would provide an insight into the elucidation of the parallel transcriptional regulation of artemisinin and flavonoid biosynthesis in A. annua L. under UV-B radiation.

Extraction of bioactive compounds from Senecio brasiliensis using emergent technologies

Several plant species synthesize biologically active secondary metabolites. Pyrrolizidine alkaloids are a large group of biotoxins produced by thousands of plant species to protect against the attack of insects and herbivores, but they are highly toxic for humans and animals. In this study, extracts from the aerial part of Senecio brasiliensis were obtained using different technologies: ultrasound-assisted extraction (UAE), pressurized liquid extraction (PLE), and microwave hydrodiffusion and gravity (MHG). The study aimed to evaluate the effectiveness of these technologies for the extraction of chemical compounds found in this plant, focusing on two pyrrolizidine alkaloids: integerrimine and senecionine. Influential parameters on yield and chemical composition were also evaluated: for UAE and MHG, temperature and pressure; for PLE, temperature, and percentage of ethanol. All the extraction techniques were efficient for the extraction of integerrimine and senecionine. The UAE and PLE stood out for the higher yields and number of compounds. The PLE presented a maximum yield of 18.63% for the matrix leaf and the UAE a maximum yield of 11.82% for the same matrix. These two techniques also stood out in terms of the number of compounds, once 36 different compounds were found via PLE and 17 via UAE.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s13205-021-02845-1.

Pathological Impact on the Phyllosphere Microbiota of Artemisia argyi by Haze

The pathological impact of haze upon the phyllosphere microbiota awaits investigation. A moderate degree of haze environment and a clean control were selected in Chengdu, China. Artemisia argyi, a ubiquitously distributed and extensively applied Chinese herb, was also chosen for experiment. Total genome DNA was extracted from leaf samples, and for metagenome sequencing, an Illumina HiSeq 2500 platform was applied. The results showed that the gene numbers of phyllosphere microbiota derived from haze leaves were lower than those of the clean control. The phyllosphere microbiota derived from both haze and clean groups shared the same top ten phyla; the abundances of Proteobacteria, Actinomycetes and Anorthococcuso of the haze group were substantially increased, while Ascomycetes and Basidiomycetes decreased. At the genus level, the abundances of Nocardia, Paracoccus, Marmoricola and Knoelia from haze leaves were markedly increased, while the yeasts were statistically decreased. KEGG retrieval demonstrated that the functional genes were most annotated to metabolism. An interesting find of this work is that the phyllosphere microbiota responsible for the synthesis of primary and secondary metabolites in A. argyi were significantly increased under a haze environment. Relatively enriched genes annotated by eggNOG belong to replication, recombination and repair, and genes classified into the glycoside hydrolase and glycosyltransferase enzymes were significantly increased. In summary, we found that both structure and function of phyllosphere microbiota are globally impacted by haze, while primary and secondary metabolites responsible for haze tolerance were considerably increased. These results suggest an adaptive strategy of plants for tolerating and confronting haze damage.

Quality and yield of Pseudostellaria heterophylla treated with GGBS as pH adjuster against the toxicity of Cd and Cu

The contamination of Cd and Cu in soil is a great threat to medicinal plant. Ground granulated blast furnace slag (GGBS) is a potential soil pH adjuster to reduce metal toxicity. However, how GGBS affects the quality and yield of herbal plants under the stress of Cd and Cu is not clear. This study aims to investigate the quality and yield of a medicinal plant (Pseudostellaria heterophylla) responding to GGBS treatment in Cd and Cu contaminated soil. GGBS with three mass percentages (0%, 3%, 5%) was added into contaminated lateritic soils for planting. Each condition had 21 replicated seedlings. The concentrations of Cd and Cu in plant, amounts of active ingredients (polysaccarides and saponins) in medicinal organ, and tuber properties were measured after harvest. The results showed that under 3% and 5% GGBS treatments, Cd and Cu accumulations in all plant organs (leaf, stem, root and tuber) were reduced by 69.4-86.0% and 10.3-30.1%, respectively. They were below the permissible limits (World Health Organization, WHO). Even though the concentrations of active ingredients in P. heterophylla tuber decreased by up to 35.8%, they still met Hong Kong Chinese Materia Medica standard. Besides, the biomass of root tuber increased by 9.8% and 46%, due to 3% and 5% GGBS treatments, respectively. The recommended 5% GGBS treatment in practice can balance the reduction of active ingredients and the increase of plant yield when minimizing Cd and Cu accumulation in tuber.

Quantitative Analysis of UV-B Radiation Interception in 3D Plant Structures and Intraindividual Distribution of Phenolic Contents

Ultraviolet-B (UV-B) acts as a regulatory stimulus, inducing the dose-dependent biosynthesis of phenolic compounds such as flavonoids at the leaf level. However, the heterogeneity of biosynthesis activation generated within a whole plant is not fully understood until now and cannot be interpreted without quantification of UV-B radiation interception. In this study, we analyzed the spatial UV-B radiation interception of kales (Brassica oleracea L. var. Acephala) grown under supplemental UV-B LED using ray-tracing simulation with 3-dimension-scanned models and leaf optical properties. The UV-B-induced phenolic compounds and flavonoids accumulated more, with higher UV-B interception and younger leaves. To distinguish the effects of UV-B energy and leaf developmental age, the contents were regressed separately and simultaneously. The effect of intercepted UV-B on flavonoid content was 4.9-fold that of leaf age, but the effects on phenolic compound biosynthesis were similar. This study confirmed the feasibility and relevance of UV-B radiation interception analysis and paves the way to explore the physical and physiological base determining the intraindividual distribution of phenolic compound in controlled environments.

Ultraviolet-B mediated biochemical and metabolic responses of a medicinal plant Adhatoda vasica Nees. at different growth stages

In the present study, the effects of elevated UV-B (eUVB; ambient ± 7.2 kJ m^-2 day^-1) were evaluated on the biochemical and metabolic profile of Adhatoda vasica Nees. (an indigenous medicinal plant) at different growth stages. The results showed reduction in superoxide radical production rate, whereas increase in the content of hydrogen peroxide which was also substantiated by the histochemical localization. Malondialdehyde content, which is a measure of oxidative stress, did not show significant changes at any of the growth stages however photosynthetic rate and chlorophyll content showed reduction at all growth stages under eUV-B exposure. Increased activities of the enzymatic and non-enzymatic antioxidants were noticed except ascorbic acid, which was reduced under eUV-B exposure. The metabolic profile of A. vasica revealed 43 major compounds (assigned under different classes) at different growth stages. Triterpenes, phytosterols, unsaturated fatty acids, diterpenes, tocopherols, and alkaloids showed increment, whereas reduction in saturated fatty acids and sesquiterpenes were observed under eUV-B treatment. Vasicinone and vasicoline, the two important alkaloids of A. vasica, showed significant induction under eUV-B exposure as compared to control. Treatment of eUV-B leads to the synthesis of some new compounds, such as oridonin oxide (diterpene) and α-Bisabolol oxide-B (sesquiterpene), which possess potent anti-inflammatory and anticancerous activities. The study displayed that differential crosstalk between antioxidants and secondary metabolites at different growth stages, were responsible for providing protection to A. vasica against eUV-B induced oxidative stress and enhancing its medicinal properties.

Nano-Structured Lignin as Green Antioxidant and UV Shielding Ingredient for Sunscreen Applications

Green, biocompatible, and biodegradable antioxidants represent a milestone in cosmetic and cosmeceutical applications. Lignin is the most abundant polyphenol in nature, recovered as a low-cost waste from the pulp and paper industry and biorefinery. This polymer is characterized by beneficial physical and chemical properties which are improved at the nanoscale level due to the emergence of antioxidant and UV shielding activities. Here we review the use of lignin nanoparticles in cosmetic and cosmeceutical applications, focusing on sunscreen and antiaging formulations. Advances in the technology for the preparation of lignin nanoparticles are described highlighting structure activity relationships.

Seasonal Variations of Polyphenols Content, Sun Protection Factor and Antioxidant Activity of Two Lamiaceae Species

Secondary metabolite production by plants is influenced by external environmental factors that can change depending on the seasons, which makes it important to know how the plant, through its metabolism, is able to adapt to these variations. Mentha x villosa and Plectranthus amboinicus present in their chemical composition polyphenols, and through previous studies, it has been seen that these two species present promising in vitro photoprotective activity. The aim of this study was to evaluate seasonal alterations in photoprotective and antioxidant activities and the influence of factors such as precipitation levels and sun radiation incidence. Thus, polyphenol quantification, cromatographics (HPLC-DAD) and multivariate (PCA) analyses of extracts of the two species through twelve months were done. It was observed that the best months for photoprotective and antioxidant activities were September for M. villosa and July for P. amboinicus (SPF = 14.79). It was possible to conclude that solar radiation more clearly influences the production of phenolics and the increase of SPF in M. villosa, in addition to favoring the antioxidant activity of the two species, while precipitation seems to have no influence.

Effects of Light on Secondary Metabolite Biosynthesis in Medicinal Plants

Secondary metabolites (SMs) found in medicinal plants are one of main sources of drugs, cosmetics, and health products. With the increase in demand for these bioactive compounds, improving the content and yield of SMs in medicinal plants has become increasingly important. The content and distribution of SMs in medicinal plants are closely related to environmental factors, especially light. In recent years, artificial light sources have been used in controlled environments for the production and conservation of medicinal germplasm. Therefore, it is essential to elucidate how light affects the accumulation of SMs in different plant species. Here, we systematically summarize recent advances in our understanding of the regulatory roles of light quality, light intensity, and photoperiod in the biosynthesis of three main types of SMs (polyphenols, alkaloids, and terpenoids), and the underlying mechanisms. This article provides a detailed overview of the role of light signaling pathways in SM biosynthesis, which will further promote the application of artificial light sources in medicinal plant production.

Environmental effects of stratospheric ozone depletion, UV radiation, and interactions with climate change: UNEP Environmental Effects Assessment Panel, Update 2020

This assessment by the Environmental Effects Assessment Panel (EEAP) of the United Nations Environment Programme (UNEP) provides the latest scientific update since our most recent comprehensive assessment (Photochemical and Photobiological Sciences, 2019, 18, 595-828). The interactive effects between the stratospheric ozone layer, solar ultraviolet (UV) radiation, and climate change are presented within the framework of the Montreal Protocol and the United Nations Sustainable Development Goals. We address how these global environmental changes affect the atmosphere and air quality; human health; terrestrial and aquatic ecosystems; biogeochemical cycles; and materials used in outdoor construction, solar energy technologies, and fabrics. In many cases, there is a growing influence from changes in seasonality and extreme events due to climate change. Additionally, we assess the transmission and environmental effects of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which is responsible for the COVID-19 pandemic, in the context of linkages with solar UV radiation and the Montreal Protocol.

Combined ultraviolet and darkness regulation of medicinal metabolites in Mahonia bealei revealed by proteomics and metabolomics

Roots of Mahonia bealei have been used as traditional Chinese medicine with antibacterial, antioxidant and anti-inflammatory properties due to its high alkaloid content. Previously, we reported that alkaloid and flavonoid contents in the M. bealei leaves could be increased by the combined ultraviolet B and dark treatment (UV+D). To explore the underlying metabolic pathways and networks, proteomic and metabolomic analyses of the M. bealei leaves were conducted. Proteins related to tricarboxylic acid cycle, transport and signaling varied greatly under the UV + D. Among them, calmodulin involved in calcium signaling and ATP-binding cassette transporter involved in transport of berberine were increased. Significantly changed metabolites were overrepresented in phenylalanine metabolism, nitrogen metabolism, phenylpropanoid, flavonoid and alkaloid biosynthesis. In addition, the levels of salicylic acid and gibberellin decreased in the UV group and increased in the UV + D group. These results indicate that multi-hormone crosstalk may regulate the biosynthesis of flavonoids and alkaloids to alleviate oxidative stress caused by the UV + D treatment. Furthermore, protoberberine alkaloids may be induced through calcium signaling crosstalk with reaction oxygen species and transported to leaves. SIGNIFICANCE: Mahonia bealei root and stem, not leaf, were used as traditional medicine for a long history because of the high contents of active components. In the present study, UV-B combined with dark treatments induced the production of alkaloids and flavonoids in the M. bealei leaf, especially protoberberine alkaloids such as berberine. Multi-omics analyses indicated that multi-hormone crosstalk, enhanced tricarboxylic acid cycle and active calcium signaling were involved. The study informs a strategy for utilization of the leaves, and improves understanding of the functions of secondary metabolites in M. bealei.