Induction of flavonoid production by UV-B radiation in Passiflora quadrangularis callus cultures

OsbZIP18 Is a Positive Regulator of Phenylpropanoid and Flavonoid Biosynthesis under UV-B Radiation in Rice

In plants exposed to ultraviolet B radiation (UV-B; 280-315 nm), metabolic responses are activated, which reduce the damage caused by UV-B. Although several metabolites responding to UV-B stress have been identified in plants, the accumulation of these metabolites at different time points under UV-B stress remains largely unclear, and the transcription factors regulating these metabolites have not been well characterized. Here, we explored the changes in metabolites in rice after UV-B treatment for 0 h, 6 h, 12 h, and 24 h and identified six patterns of metabolic change. We show that the rice transcription factor OsbZIP18 plays an important role in regulating phenylpropanoid and flavonoid biosynthesis under UV-B stress in rice. Metabolic profiling revealed that the contents of phenylpropanoid and flavonoid were significantly reduced in osbzip18 mutants compared with the wild-type plants (WT) under UV-B stress. Further analysis showed that the expression of many genes involved in the phenylpropanoid and flavonoid biosynthesis pathways was lower in osbzip18 mutants than in WT plants, including OsPAL5, OsC4H, Os4CL, OsCHS, OsCHIL2, and OsF3H. Electrophoretic mobility shift assays (EMSA) revealed that OsbZIP18 bind to the promoters of these genes, suggesting that OsbZIP18 function is an important positive regulator of phenylpropanoid and flavonoid biosynthesis under UV-B stress. In conclusion, our findings revealed that OsbZIP18 is an essential regulator for phenylpropanoid and flavonoid biosynthesis and plays a crucial role in regulating UV-B stress responses in rice.

Genome-Wide Identification and Expression Analysis of LBD Transcription Factor Genes in Passion Fruit (Passiflora edulis)

The lateral organ boundary domain (LBD) gene is a plant-specific transcription factor that plays a crucial role in plant growth and development, including the development of lateral vegetative organs such as leaf and root development, as well as floral organs such as sepal, petal, and pollen development. Passion fruit is a tropical fruit with important agricultural, economic and ornamental value. However, there is no systematic research report available on the LBD gene family of passion fruit. In this study, a genome-wide analysis of passion fruit LBD genes identified 33 PeLBDs that were unevenly distributed across nine chromosomes. According to phylogenetic and gene structure analysis, PeLBDs were divided into two categories: Class I (27) and Class II (6). Homologous protein modeling results showed that the gene members of the two subfamilies were structurally and functionally similar. Cis-acting element and target gene prediction analysis suggested that PeLBDs might participate in various biological processes by regulating diverse target genes involved in growth and development, metabolism, hormones and stress response. Collinearity analysis indicated that the expansion of the PeLBD gene family likely took place mainly by segmental duplication, and some duplicated gene pairs such as PeLBD13/15 might show functional redundancy, while most duplicated gene pairs such as PeLBD8/12 showed different expression profiles indicating their functional diversification. After filtering low expressed genes, all Class Id PeLBDs were more highly expressed during pollen development. At the same, all Class Ic and many other PeLBDs were relatively highly expressed during ovule development, similar with their homologous LBD genes in Arabidopsis, indicating their potential regulatory roles in reproductive tissue development in passion fruit. PeLBDs that were highly expressed in floral tissues were also expressed at a higher level in tendrils with some differences, indicating the close relationships of tendrils to floral tissues. Some genes such as PeLBD23/25 might be simultaneously related to floral development and leaf early formation in passion fruit, while other PeLBDs showed a strong tissue-specific expression. For example, PeLBD17/27/29 were specifically expressed in floral tissues, while PeLBD11 were only highly expressed in fruit, suggesting their specific function in the development of certain tissues. A qRT-PCR was conducted to verify the expression levels of six PeLBDs in different tissues. Our analysis provides a basis for the functional analysis of LBD genes and new insights into their regulatory roles in floral and vegetative tissue development.

Plant Regeneration Protocol for Recalcitrant Passionflower (Passiflora quadrangularis L.)

This research was designed to provide the first protocol to establish an efficient solution for direct organogenesis regeneration in Passiflora quadrangularis using nodal explants from young shoots. Passifloraceae tissue culture has been associated with problems such as recalcitrance, sensitivity to ethylene accumulation and browning of explants due to the presence of phenols in the tissues. Due to the high rate of endogenous contamination of the explants, a preliminary experiment was performed. The best results of surface sterilization were obtained using the pretreatment with 70% EtOH, 1 min and 50% NaOCl, 10 min along with the treatment of Rifampicin 15 µg/mL and Benomyl 2 g/L. The effects of plant growth regulators on the induction of direct organogenesis, multiplication of shoots in subcultures and in vitro rooting were evaluated. Additional compounds such as AgNO3 and Pluronic F-68 were added to the culture media in order to reduce the effects of phenols and the sudden browning of the explants. Shoot proliferation increased to the sixth subculture after which it decreased. A maximum of 7.17 shoots were obtained from one shoot on Murashige and Skoog (MS) medium supplemented with 2 mg/L 6-benzylaminopurine and 1 mg/L thidiazuron. Supplementation of ½ MS medium with 1 mg/L 1-naphthaleneacetic acid was conducing to root formation in 61.11% of shoots. After acclimatization, the plants showed vigorous growth, green leaves, and well-developed roots. Although this species has previously shown difficulty in in vitro propagation, this protocol established based on the results proved to be efficient and reproducible.

Identification of Fungal Pathogens to Control Postharvest Passion Fruit (Passiflora edulis) Decays and Multi-Omics Comparative Pathway Analysis Reveals Purple Is More Resistant to Pathogens than a Yellow Cultivar

Production of passion fruit (Passiflora edulis) is restricted by postharvest decay, which limits the storage period. We isolated, identified, and characterized fungal pathogens causing decay in two passion fruit cultivars during two fruit seasons in China. Morphological characteristics and nucleotide sequences of ITS-rDNA regions identified eighteen isolates, which were pathogenic on yellow and purple fruit. Fusarium kyushuense, Fusarium concentricum, Colletotrichum truncatum, and Alternaria alternata were the most aggressive species. Visible inspections and comparative analysis of the disease incidences demonstrated that wounded and non-wounded yellow fruit were more susceptible to the pathogens than the purple fruit. Purple cultivar showed higher expression levels of defense-related genes through expression and metabolic profiling, as well as significantly higher levels of their biosynthesis pathways. We also found fungi with potential beneficial features for the quality of fruits. Our transcriptomic and metabolomics data provide a basis to identify potential targets to improve the pathogen resistance of the susceptible yellow cultivar. The identified fungi and affected features of the fruit of both cultivars provide important information for the control of pathogens in passion fruit industry and postharvest storage.

Biotechnological processes to obtain bioactive secondary metabolites from some Mexican medicinal plants

The consumption of medicinal plants has increased in recent decades due to the fact that they biosynthesize compounds with many biological activities; thus, some plant species with biological potential are being utilized as raw material by the industries for preparation of drugs, phytodrugs, or food supplements. This has the consequence of overexploitation and deforestation, which endangers plant species-of-interest. In recent years, alternatives have been sought to eradicate this problem. A solution that was given and is maintained is plant biotechnology, which favors the production of secondary metabolites (SMt) with important biological activity. Plant biotechnology allows us to increase the yield of a compound-of-interest, reduces its production times and costs, and allows constant and controlled production of the raw material, while aiding in the protection of medicinal plants that are found in danger of extinction. In the scientific literature, procuring the SMt by means of biotechnological processes is described, highlighting the study of five species from Mexican traditional medicine (Lopezia racemosa, Galphimia glauca, Cnidoscolus chayamansa, and Buddleja cordata), and the main biological activities are as follows: anti-inflammatory, hepatoprotector, neuroprotector, anxiolytic, antitumoral, antibacterial, and antioxidant, among others. KEY POINTS: • Secondary metabolites produce by biotechnology processes • Active secondary metabolites isolated from Mexican medicinal plants • Recent advances on the production of some bioactive secondary metabolites.

Chromosome-level reference genome assembly provides insights into aroma biosynthesis in passion fruit (Passiflora edulis)

Passion fruit, native to tropical America, is an agriculturally, economically and ornamentally important fruit plant that is well known for its acid pulp, rich aroma and distinctive flavour. Here, we present a chromosome-level genome assembly of passion fruit by incorporating PacBio long HiFi reads and Hi-C technology. The assembled reference genome is 1.28 Gb size with a scaffold N50 of 126.4 Mb and 99.22% sequences anchored onto nine pseudochromosomes. This genome is highly repetitive, accounting for 86.61% of the assembled genome. A total of 39,309 protein-coding genes were predicted with 93.48% of those being functionally annotated in the public databases. Genome evolution analysis revealed a core eudicot-common γ whole-genome triplication event and a more recent whole-genome duplication event, possibly contributing to the expansion of certain gene families. The 33 rapidly expanded gene families were significantly enriched in the pathways of isoflavone biosynthesis, galactose metabolism, diterpene biosynthesis and fatty acid metabolism, which might be responsible for the formation of featured flavours in the passion fruit. Transcriptome analysis revealed that genes related to ester and ethylene biosynthesis were significantly upregulated in the mature fruit and the expression levels of those genes were consistent with the accumulation of volatile lipid compounds. The passion fruit genome analysis improves our understanding of the genome evolution of this species and sheds new lights into the molecular mechanism of aroma biosynthesis in passion fruit.

The Callus of Phaseolus coccineus and Glycine max Biotransform Flavanones into the Corresponding Flavones

In vitro plant cultures are gaining in industrial importance, especially as biocatalysts and as sources of secondary metabolites used in pharmacy. The idea that guided us in our research was to evaluate the biocatalytic potential of newly obtained callus tissue towards flavonoid compounds. In this publication, we describe new ways of using callus cultures in the biotransformations. In the first method, the callus cultures grown on a solid medium are transferred to the water, the reaction medium into which the substrate is introduced. In the second method, biotransformation is carried out on a solid medium by growing callus cultures. In the course of the research, we have shown that the callus obtained from Phaseolus coccineus and Glycine max is capable of converting flavanone, 5-methoxyflavanone and 6-methoxyflavanone into the corresponding flavones.

Anthocyanins, multi-functional natural products of industrial relevance: Recent biotechnological advances

Anthocyanins, the color compounds of plants, are known for their wide applications in food, nutraceuticals and cosmetic industry. The biosynthetic pathway of anthocyanins is well established with the identification of potential key regulatory genes, which makes it possible to modulate its production by biotechnological means. Various biotechnological systems, including use of in vitro plant cell or tissue cultures as well as microorganisms have been used for the production of anthocyanins under controlled conditions, however, a wide range of factors affects their production. In addition, metabolic engineering technologies have also used the heterologous production of anthocyanins in recombinant plants and microorganisms. However, these approaches have mostly been tested at the lab- and pilot-scales, while very few up-scaling studies have been undertaken. Various challenges and ways of investigation are proposed here to improve anthocyanin production by using the in vitro plant cell or tissue culture and metabolic engineering of plants and microbial culture systems. All these methods are capable of modulating the production of anthocyanins , which can be further utilized for pharmaceutical, cosmetics and food applications.

A comparative study of phytoconstituents and antibacterial activity of in vitro derived materials of four Passiflora species

Passiflora species are well known for their common use in popular medicine for the treatment of several diseases, such as insomnia, anxiety, and hysteria, in addition to their anti-inflammatory, antioxidant, analgesic and antibacterial potential. However, few data about the chemical composition and the medicinal potential of in vitro derived materials are available. Therefore, the goal of this work was to compare, for the first time, the phytoconstituents of in vitro derived materials of four Passiflora species, and evaluate the antibacterial potential of their extracts against 20 Gram-positive and negative strains. Chromatographic analysis indicated the presence of saponins in roots extracts from all studied species, whereas leaf extracts presented both saponins and flavonoids. Extracts from leaves and roots of P. alata and P. foetida exhibited a selective inhibitory activity against B. thuringiensis and S. pyogenes, which might be related to the presence of a high concentration of secondary metabolites, including flavonoids and saponins.

A rich source of potential bioactive compounds with anticancer activities by Catharanthus roseus cambium meristematic stem cell cultures

ETHNOPHARMACOLOGICAL IMPORTANCE

Catharanthus roseus (L.) G. Don. is an important medicinal plant with rich sources of remarkable health benefits consisting more than 100 alkaloids and significant amounts of bioactive compounds, which have been widely used as a folk medicine for treatment of several pathologies.

THE AIM OF THE STUDY

In the present study, we isolated and cultured innately undifferentiated cambium meristematic cells (CMCs), which were observed stable cell growth, enhancement of bioactive compounds from C.roseus.

MATERIALS AND METHODS

We attempted to determine the effect of association between time-course growth rates, bioactive compounds and terpenoids indole alkaloid (TIA) contents as well as antioxidant and anticancer efficacies of C. roseus CMC suspension culture treated by UV-C.

RESULTS

The bioactive compounds, vincristine contents, and antioxidant power were noticed significantly higher in 60 min exposure at 5 cm distances and with the directly collected sample (T7). A similar trend has also been noticed from the anticancer activity. Demonstration of TIA accumulation was found higher at 5 min exposure, at 20 cm distances and 48 h of incubation (T21) and the result of TIA contents had the highest correlation effects of anticancer activities.

CONCLUSION

In the current study, we demonstrated that UV-C light could enhance the production of the essential compounds and bioactivities in the CMCs of C. roseus, and thus, C. roseus CMCs have the potential to serve as an industrial platform for the production of bioactive alkaloids and antioxidant, anticancer activity. Moreover, additional efforts should be made to irradiate CMC suspension cultures from C. roseus with UV-C to achieve better pharmacological profiles.

Histological characterization of Passiflora pohlii Mast. root tips cryopreserved using the V-Cryo-plate technique

Cryopreservation stands out as the main strategy to ensure safe and cost efficient long-term conservation of plant germplasm, especially for biotechnological materials. However, the injuries associated with the procedure may result in structural damage and low recovery rates after cooling. Histological analysis provides useful information on the effects of osmotic dehydration, LN exposure, and recovery conditions on cellular integrity and tissue organization, allowing the determination of the critical steps of the cryopreservation protocol and, thus, the use of optimized treatments. Passiflora pohlii Mast. (Passifloraceae) is a native species from Brazil with potential agronomic interest. Recent studies showed the presence of saponins in its roots, which presented antioxidant activity. The goal of this work was to develop a cryopreservation technique for root tips of in vitro-derived plants of P. pohlii using the V-Cryo-plate technique and to characterize the anatomical alterations that occurred during the successive steps of the protocol. Root tips were excised from in vitro plants and precultured before adhesion to cryo-plates and then treated for different periods with the plant vitrification solutions PVS2 or PVS3. Treatment with PVS2 for 45 min resulted in higher recovery (79%) when compared with PVS3 (43%). The greatest number of adventitious roots per cryopreserved explant was also observed after a 45-min exposure to PVS2. Plasmolysis levels were higher in cortical cells of cryopreserved explants treated with PVS2, while pericycle and central cylinder cells were not damaged after this treatment. Thirty days after rewarming, no plasmolysis could be detected, regardless of the experimental conditions.

Response of Plant Secondary Metabolites to Environmental Factors

Plant secondary metabolites (SMs) are not only a useful array of natural products but also an important part of plant defense system against pathogenic attacks and environmental stresses. With remarkable biological activities, plant SMs are increasingly used as medicine ingredients and food additives for therapeutic, aromatic and culinary purposes. Various genetic, ontogenic, morphogenetic and environmental factors can influence the biosynthesis and accumulation of SMs. According to the literature reports, for example, SMs accumulation is strongly dependent on a variety of environmental factors such as light, temperature, soil water, soil fertility and salinity, and for most plants, a change in an individual factor may alter the content of SMs even if other factors remain constant. Here, we review with emphasis how each of single factors to affect the accumulation of plant secondary metabolites, and conduct a comparative analysis of relevant natural products in the stressed and unstressed plants. Expectantly, this documentary review will outline a general picture of environmental factors responsible for fluctuation in plant SMs, provide a practical way to obtain consistent quality and high quantity of bioactive compounds in vegetation, and present some suggestions for future research and development.

Picroside I and Picroside II from Tissue Cultures of Picrorhiza kurroa

Background:

Picrorhiza kurroa (PK) belongs to Scrophulariaceae family and is a representative endemic, medicinal herb, widely distributed throughout the higher altitudes of alpine Himalayas from west to east, between 3000 and 4500 m above mean sea level.

Objective:

The objective of the present study is to assess the production of picroside I and picroside II from tissue cultures of PK.

Materials and Methods:

Auxiliary shoot tips of PK were incubated in Murashige and Skoog medium supplemented with indole-3-butyric acid and kinetin phytohormones. The callus produced was collected at different time intervals and was processed for extraction of picroside I and picroside II followed by thin layer chromatography and high-performance liquid chromatography HPLC analysis.

Results:

The maximum growth index was found to be 5.109 ± 0.159 at 16-week-old callus culture. The estimation of picroside-I and picroside-II was carried out by (HPLC) analysis; quantity of secondary metabolite found to be 16.37 ± 0.0007 mg/g for PK-I and 6.34 ± 0.0012 mg/g for PK-II.

Conclusion:

This is the first attempt to produce the Picroside-I and II in large amount by the tissue culture technique. It can be observed that the method of callus culture can be used in production of secondary metabolites Picroside-I and II from PK

SUMMARY

Picrorhiza kurroa is a high value medicinal herb due to rich source of hepatoprotective metabolites, Picroside-I and Picroside-II. The medicinal importance of P. kurroa is due to its pharmacological properties like hepatoprotective, antioxidant (particularly in liver), antiallergic and antiasthamatic, anticancer activity particularly in liver and immunomodulatory. Shoot apices which were produced a good response was inoculated on selected medium i.e., on MS medium containing 2, 4 D (mg/l) + KN (1mg/l) for induction of callus. The initiation of callus was observed after 4weeks and it was light green and fragile Maximum growth was observed with 3% w/v of sucrose supplement. The callus culture was maintained and growth index was recorded after every subculture. The growth index was calculated from the obtained final dried weight divided by initial weight.

Abbreviations Used: PK-Picrorhizakurroa, IBA-Indole-3-butyricacid, KN-Kinetin, 2,4D-2,4Dichlorophenoxy acetic acid.

A systematic review on phenolic compounds in Passiflora plants: Exploring biodiversity for food, nutrition, and popular medicine

Passiflora plants are strategic in the context of biodiversity for food and nutrition. We applied the procedures of a systematic review protocol to study the state of the art on identification of phenolic compounds from Passiflora plants. An automated literature search was conducted using six databases and a combination of seven keywords. All the analytical, chromatographic, and spectroscopic methods were included. The studies were classified according to their method of identification, phenolic classes, and method of extraction. In total, 8,592 abstracts were found, from which 122 studies were selected for complete reading and 82 were selected for further analysis. Techniques of extraction, evaluated parts of the plant and methods of identification were systematized. Studies with leaves were most conspicuous (54.4%), 34 species of Passiflora were evaluated and orientin, isoorientin, vitexin, isovitexin were commonly found structures. A High Performance Liquid Chromatography-diode array detector was the technique most applied, with which the same structures were identified all through the studies, although other unknown structures were detected, but not elucidated. The use of Nuclear Magnetic Resonance and Mass Spectrometry, which are more sensitive techniques, needs to be intensified, to identify other unconventional compounds detected in Passiflora, to enhance the comprehension of the bioactive compounds in these plants.

Improvement in Flavonoids and Phenolic Acids Production and Pharmaceutical Quality of Sweet Basil (Ocimum basilicum L.) by Ultraviolet-B Irradiation

Sweet basil (Ocimum basilicum Linnaeus) is aromatic herb that has been utilized in traditional medicine. To improve the phytochemical constituents and pharmaceutical quality of sweet basil leaves, ultraviolet (UV)-B irradiation at different intensities (2.30, 3.60, and 4.80 W/m²) and durations (4, 6, 8, and 10-h) was applied at the post-harvest stage. Total flavonoid content (TFC) and total phenolic content (TPC) were measured using spectrophotometric method, and individual flavonoids and phenolic acids were identified using ultra-high performance liquid chromatography. As a key enzyme for the metabolism of flavonoids, chalcone synthase (CHS) activity, was measured using a CHS assay. Antioxidant activity and antiproliferative activity of extracts against a breast cancer cell line (MCF-7) were evaluated using 1,1-diphenyl-2-picrylhydrazyl (DPPH) assays and MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assays, respectively. UV-B irradiation at an intensity of 3.60 W/m² increased TFC approximately 0.85-fold and also increased quercetin (0.41-fold), catechin (0.85-fold), kaempferol (0.65-fold) rutin (0.68-fold) and luteolin (1.00-fold) content. The highest TPC and individual phenolic acid (gallic acid, cinnamic acid and ferulic acid) was observed in the 3.60 W/m² of UV-B treatment. Cinnamic acid and luteolin were not detected in the control plants, production being induced by UV-B irradiation. Production of these secondary metabolites was also significantly influenced by the duration of UV-B irradiation. Irradiation for 8-h led to higher TFC, TPC and individual flavonoids and phenolic acids than for the other durations (4, 8, and 10-h) except for cinnamic acid, which was detected at higher concentration when irradiated for 6-h. Irradiation for 10-h significantly decreased the secondary metabolite production in sweet basil leaves. CHS activity was induced by UV-B irradiation and highest activity was observed at 3.60 W/m² of UV-B irradiation. UV-B treated leaves presented the highest DPPH activity and antiproliferative activity with a half-maximal inhibitory concentration (IC50) value of 56.0 and 40.8 µg/mL, respectively, over that of the control plants (78.0 and 58.2 µg/mL, respectively). These observations suggest that post-harvest irradiation with UV-B can be considered a promising technique to improve the healthy-nutritional and pharmaceutical properties of sweet basil leaves.

In Vitro Culture and Phytochemical Analysis of Passiflora tenuifila Killip and Passiflora setacea DC (Passifloraceae)

We have developed reproducible micropropagation, callus culture, phytochemical, and antioxidant analysis protocols for the wild passion fruit species P. tenuifila, and P. setacea, native to the Brazilian endangered biomes Atlantic Forest, Cerrado, and Caatinga, by using seeds and explants from seedlings and adult plants. Genotype and explant origin-linked differences are visible amongst the Passiflora species concerning callus production, total phenolics, and antioxidant activity. The protocols developed for screening phytochemicals and antioxidants in P. tenuifila and P. setacea callus extracts have shown their potential for phenolic production and antioxidant activity. The high level of phenolic compounds seems to account for the antioxidant activity of methanolic extracts of P. tenuifila derived from 45-day-old immature seed callus. The methanolic extracts of callus derived from P. setacea seedling leaf node and cotyledonary node explants have shown the highest antioxidant activity despite their lower content of phenolics, as compared to cotyledon callus extracts. The optimized micropropagation and callus culture protocols have great potential to use cell culture techniques for further vegetative propagation, in vitro germplasm conservation, and secondary metabolite production using biotic and abiotic elicitors.

Changing trends in biotechnology of secondary metabolism in medicinal and aromatic plants

Medicinal and aromatic plants are known to produce secondary metabolites that find uses as flavoring agents, fragrances, insecticides, dyes and drugs. Biotechnology offers several choices through which secondary metabolism in medicinal plants can be altered in innovative ways, to overproduce phytochemicals of interest, to reduce the content of toxic compounds or even to produce novel chemicals. Detailed investigation of chromatin organization and microRNAs affecting biosynthesis of secondary metabolites as well as exploring cryptic biosynthetic clusters and synthetic biology options, may provide additional ways to harness this resource. Plant secondary metabolites are a fascinating class of phytochemicals exhibiting immense chemical diversity. Considerable enigma regarding their natural biological functions and the vast array of pharmacological activities, amongst other uses, make secondary metabolites interesting and important candidates for research. Here, we present an update on changing trends in the biotechnological approaches that are used to understand and exploit the secondary metabolism in medicinal and aromatic plants. Bioprocessing in the form of suspension culture, organ culture or transformed hairy roots has been successful in scaling up secondary metabolite production in many cases. Pathway elucidation and metabolic engineering have been useful to get enhanced yield of the metabolite of interest; or, for producing novel metabolites. Heterologous expression of putative plant secondary metabolite biosynthesis genes in a microbe is useful to validate their functions, and in some cases, also, to produce plant metabolites in microbes. Endophytes, the microbes that normally colonize plant tissues, may also produce the phytochemicals produced by the host plant. The review also provides perspectives on future research in the field.

Induction of secondary metabolite production by UV-C radiation in Vitis vinifera L. Öküzgözü callus cultures

Background

The aim of the present work was to examine the role of UV-C irradiation on the production of secondary metabolites (total phenolic, total flavanols, total flavonols, catechin, ferulic acid and trans-resveratrol in phenolic compounds and α-, β-, γ- δ-tocopherols) in callus cultures. Studies on the effects of UV-C treatment on callus culture are seldom and generally focused on UV-B. However UV-C radiation play an important role in accumule secondary metabolites.

Results

In this study, callus cultures from Öküzgözü grape cultivar were initiated from leaf petiole explants. Calli formed after 6 weeks on the medium supplemented with 0.5 mg L^-1 benzylaminopurine (BA), 0.5 mg L^-1 indole acetic acid (IAA) on B5 media. Callus tissues were exposed to UV-C irradiation at 10, 20 and 30 cm distances from the UV source for 5 and 10 minutes and samples were collected at hours 0, 24 and 48.

Conclusions

The greatest total phenolic content (155.14 mg 100 g^-1) was detected in calli exposed to UV-C for 5 min from 30 cm distance and sampled after 24 h. 24 h and 48 h incubation times, 30 cm and 5 min were the most appropriate combination of UV-C application in total flavanol content. Maximum total flavonol content (7.12 mg 100 g^-1) was obtained on 0 h, 5 min and 20 cm combination. The highest (+)- catechin accumulation (8.89 mg g^-1) was found in calli with 10 min UV-C application from 30 cm distance and sampled after 48 h. Ferulic acid content increased 6 fold in Öküzgözü callus cultures (31.37 μg g^-1) compared to the control group. The greatest trans-resveratrol content (8.43 μg g^-1) was detected in calli exposed to UV-C for 5 min from 30 cm distance and sampled after 24 h. The highest α-tocopherol concentration was found in calli exposed to UV-C for 10 min from 30 cm distance and sampled after 24 h. As a conclusion, it was showed that UV-C radiation had remarkable promoting effects on the accumulation of secondary metabolites in the calli of Öküzgözü grape cultivar.

Improvement of friable callus production of Boerhaavia paniculata Rich and the investigation of its lipid profile by GC/MS

In this study, a protocol to induce high amount of friable callus of Boerhaavia paniculata RICH and a lipidomics technique were applied to investigate the profile of lipids to relate to those present in the roots of this plant that presented anti-inflammatory activity in the crude hexane extract. The callus culture was induced from seeds in solidified Murashige and Skoog medium containing different amounts of glucose and different concentrations of 2,4-Dichlorophenoxyacetic acid. The explants were kept in a germination chamber at 30±2°C with a photoperiod of 16 h under light intensity of 27 µmol m–2 s–1 for 4 weeks. The best results for friable callus formation and development of the biomass were obtained in the treatment containing 2.26 µM 2.4-D and glucose (1.5 %; w/v). Lipidomics techniques were applied in hexane fraction showing higher concentrations of the steroids β-sitosterol (3.53 mg/100 g dc–dry cells), and fatty acids, especially 2-hydroxy-tetracosanoic acid (0.34 mg/100 g dc), eicosanoic acid (86.25 mg/100 g dc), stearic acid (420.83 mg/100 g dc), tetradecanoic acid (10.74 mg/100 g dc) and linoleic acid (100.61 mg/100 g dc). The lipid profile of callus versus that found in the roots of wild plant is described in this work.

UV-induced changes of active components and antioxidant activity in postharvest pigeon pea [Cajanus cajan (L.) Millsp.] leaves

In this study, the effect of UV irradiation (UV-A, UV-B, and UV-C) on phytochemicals, total phenolics, and antioxidant activity of postharvest pigeon pea leaves was evaluated. The response of pigeon pea leaves to UV irradiation was phytochemical specific. UV-B and UV-C induced higher levels of phytochemicals, total phenolics, and antioxidant activity in pigeon pea leaves compared with UV-A. Furthermore, UV-B irradiation proved to possess a long-lasting effect on the levels of phenolics and antioxidant activity. After adapting for 48 h at 4 °C following 4 h UV-B irradiation, total phenolics and antioxidant activity were approximately 1.5-fold and 2.2-fold increased from 39.4 mg GAE/g DM and 15.0 μmol GAE/g DM to 59.1 mg GAE/g DM and 32.5 μmol GAE/g DM, respectively. These results indicate that UV irradiation of pigeon pea leaves can be beneficial in terms of increasing active components and antioxidant activity.

Structurally different flavonol glycosides and hydroxycinnamic acid derivatives respond differently to moderate UV-B radiation exposure

The aim of this study was to investigate the modifying influence of moderate ultraviolet-B (UV-B) radiation exposure on structurally different flavonol glycosides and hydroxycinnamic acid derivatives during pre-harvest using kale, a leafy Brassica species with a wide spectrum of different non-acylated and acylated flavonol glycosides. Juvenile kale plants were treated with short-term (1 day), moderate UV-B radiation [0.22-0.88 kJ m⁻² day⁻¹ biologically effective UV-B (UV-B(BE))]. Twenty compounds were quantified, revealing a structure-specific response of flavonol glycosides and hydroxycinnamic acid derivatives to UV-B radiation. A dose- and structure-dependent response of the investigated phenolic compounds to additional UV-B radiation was found. The investigated quercetin glycosides decreased under UV-B; for kaempferol glycosides, however, the amount of sugar moieties and the flavonol glycoside hydoxycinnamic acid residue influenced the response to UV-B. Monoacylated kaempferol tetraglucosides decreased in the investigated UV-B range, whereas the monoacylated kaempferol diglucosides increased strongly with doses of 0.88 kJ m⁻² day⁻¹ UV-B(BE) . The UV-B-induced increase in monoacylated kaempferol triglucosides was dependent on the acylation pattern. Furthermore, the hydroxycinnamic acid glycosides disinapoyl-gentiobiose and sinapoyl-feruloyl-gentiobiose were enhanced in a dose-dependent manner under UV-B. While UV-B radiation treatments often focus on flavonol aglycones or total flavonols, our investigations were extended to structurally different non-acylated and acylated glycosides of quercetin and kaempferol.