Avenanthramide Aglycones and Glucosides in Oat Bran: Chemical Profile, Levels in Commercial Oat Products, and Cytotoxicity to Human Colon Cancer Cells

Design, Synthesis, Anti-TMV Activity, and Structure-Activity Relationships of Seco-pregnane C21 Steroids and Their Derivatives

seco-pregnane C21 steroids exhibit high antiviral activity against the tobacco mosaic virus (TMV). However, the structural modification of seco-pregnane C21 steroids and the structure-activity relationship (SAR) of the modified compounds remain unevaluated. Hence, the present study investigated how variations in the original skeletons of natural seco-pregnane C21 steroids affect their antiviral activity. A series of glaucogenin C and A derivatives were designed and synthesized for the first time, and their anti-TMV activity was evaluated. Bioassay results showed that most of the newly designed derivatives exhibited good to excellent antiviral activity; among these derivatives, 5g, 5j, and 5l with higher antiviral activity than that of ningnanmycin emerged as new antiviral candidates. Reverse transcription-polymerase chain reaction and Western blotting assay revealed reduced levels of TMV coat protein (TMV-CP) gene transcription and TMV-CP protein expression, which confirmed the antiviral activity of these derivatives. These compounds also downregulated the expression of NtHsp70-1 and NtHsp70-061. Computational simulations indicated that 5l displayed strong van der Waals energy and electrostatic with the TMV coat protein, affording a lower binding energy (ΔGbind = -56.2 kcal/mol) compared with Ribavirin (ΔGbind = -47.6 kcal/mol). The SAR of these compounds was also evaluated, which demonstrated for the first time that substitutions at C-3 and double bonds of C-5/C-6 and C-13/C-18 are crucial for maintaining high anti-TMV activity.

Comprehensive study of the effect of oat grain germination on the content of avenanthramides

The chemical profile and the levels of AVNs in oat varieties after germination have been examinated. In the present study, 12 distinct oat varieties were germinated for 0-192 h and a total of 28 AVNs and 3 AVN-hexosides were determined in these samples. Among them, three novel AVNs were synthesized (AVN 1a, AVN 2a, and AVN 2ad), characterized using NMR techniques (1D- and 2D-NMR), and assessed in real samples for the first time. The most abundant AVNs in the samples were AVN 2c, AVN 2p, AVN 2f, and their long-chained analogues AVN 2 cd, AVN 2pd, AVN 2fd, together representing 75-85 % of the total AVNs content. The highest total AVN level was observed on average after 48-72 h of germination time and it reached a value 1-1.2 mg/g. Out of 12 investigated oat varieties, CDC Boyer, Diadem, and Rozmar have proved to be the most suitable genotypes for germination.

Identification of natural Rutaecarpine as a potent tobacco mosaic virus (TMV) helicase candidate for managing intractable plant viral diseases

BACKGROUND

Naturally occurring alkaloids are particularly suitable for use as pesticide precursors and further modifications due to their cost-effectiveness, unique mechanism of action, tolerable degradation, and environmental friendliness. The famous tobacco mosaic virus (TMV) is a persistent plant pathogenic virus that can parasitize many plants and severely reduce crop production. To treat TMV disease, TMV helicase acts as a crucial target by hydrolyzing adenosine triphosphate (ATP) to provide energy for double-stranded RNA unwinding.

RESULTS

To seek novel framework alkaloid leads targeting TMV helicase, this work successfully established an efficient screening platform for TMV helicase inhibitors based on natural alkaloids. In vivo activity screening, enzyme activity detection, and binding assays showed that Rutaecarpine from Evodia rutaecarpa (Juss.) Benth exhibited excellent TMV helicase inhibitory properties [dissociation constant (Kd ) = 1.1 μm, half maximal inhibitory concentration (IC50 ) = 227.24 μm] and excellent anti-TMV ability. Molecular docking and dynamic simulations depicted that Rutaecarpine could stably bind in active pockets of helicase with low binding energy (ΔGbind  = -17.8 kcal/mol) driven by hydrogen bonding and hydrophobic interactions.

CONCLUSION

Given Rutaecarpine's laudable bioactivity and structural modifiability, it can serve as a privileged building block for further pesticide discovery.

Intake of polyphenols from cereal foods and colorectal cancer risk in the Melbourne Collaborative Cohort Study

BACKGROUND

Cereal-derived polyphenols have demonstrated protective mechanisms in colorectal cancer (CRC) models; however, confirmation in human studies is lacking. Therefore, this study examined the association between cereal polyphenol intakes and CRC risk in the Melbourne Collaborative Cohort Study (MCCS), a prospective cohort study in Melbourne, Australia that recruited participants between 1990 and 1994 to investigate diet-disease relationships.

METHODS

Using food frequency questionnaire diet data matched to polyphenol data, dietary intakes of alkylresorcinols, phenolic acids, lignans, and total polyphenols from cereals were estimated. Hazard ratios (HRs) and 95% confidence intervals for CRC risk were estimated for quintiles of intake with the lowest quintile as the comparison category, using multivariable adjusted Cox proportional hazards models with age as the time axis adjusted for sex, socio-economic status, alcohol consumption, fibre intake, country of birth, total energy intake, physical activity and smoking status.

RESULTS

From 35,245 eligible adults, mean (SD) age 54.7 (8.6) years, mostly female (61%) and Australian-born (69%), there were 1394 incident cases of CRC (946 colon cancers and 448 rectal cancers). Results for total cereal polyphenol intake showed reduced HRs in Q2 (HR: 0.80; 95% CI, 0.68-0.95) and Q4 (HR: 0.75; 95% CI, 0.62-0.90), and similar for phenolic acids. Alkylresorcinol intake showed reduced HR in Q3 (HR: 0.80; 95% CI, 0.67-0.95) and Q4 (HR: 0.79; 95% CI, 0.66-0.95).

CONCLUSIONS

Overall, the present study showed little evidence of association between intakes of cereal polyphenols and CRC risk. Future investigations may be useful to understand associations between cereal-derived polyphenols and additional cancers in different populations.

Estimated dietary intake of polyphenols from cereal foods and associated lifestyle and demographic factors in the Melbourne Collaborative Cohort Study

Cereal foods are consumed globally and are important sources of polyphenols with potential health benefits, yet dietary intakes are unclear. We aimed to calculate the dietary intakes of polyphenols from cereal foods in the Melbourne Collaborative Cohort Study (MCCS), and describe intakes by demographic and lifestyle factors. We estimated intakes of alkylresorcinols, lignans and phenolic acids in n = 39,892 eligible MCCS participants, using baseline dietary data (1990-1994) from a 121-item FFQ containing 17 cereal foods, matched to a polyphenol database developed from published literature and Phenol-Explorer Database. Intakes were estimated within groups according to lifestyle and demographic factors. The median (25th-75th percentile) intake of total polyphenols from cereal foods was 86.9 mg/day (51.4-155.8). The most consumed compounds were phenolic acids, with a median intake of 67.1 mg (39.5-118.8), followed by alkylresorcinols of 19.7 mg (10.8-34.6). Lignans made the smallest contribution of 0.50 mg (0.13-0.87). Higher polyphenol intakes were associated with higher relative socio-economic advantage and prudent lifestyles, including lower body mass index (BMI), non-smoking and higher physical activity scores. The findings based on polyphenol data specifically matched to the FFQ provide new information on intakes of cereal polyphenols, and how they might vary according to lifestyle and demographic factors.

Avenanthramides, Distinctive Hydroxycinnamoyl Conjugates of Oat, Avena sativa L.: An Update on the Biosynthesis, Chemistry, and Bioactivities

Avenanthramides are a group of N-cinnamoylanthranilic acids (phenolic alkaloid compounds) that are produced in oat plants as phytoalexins, in response to pathogen attack and elicitation. The enzyme catalysing the cinnamamide-generating reaction is hydroxycinnamoyl-CoA: hydroxyanthranilate N-hydroxycinnamoyltransferase (HHT, a member of the super family of BAHD acyltransferases). HHT from oat appears to have a narrow range of substrate usage, with preferred use of 5-hydroxyanthranilic acid (and to a lesser extent, other hydroxylated and methoxylated derivatives) as acceptor molecules, but is able to use both substituted cinnamoyl-CoA and avenalumoyl-CoA thioesters as donor molecules. Avenanthramides thus combine carbon skeletons from both the stress-inducible shikimic acid and phenylpropanoid pathways. These features contribute to the chemical characteristics of avenanthramides as multifunctional plant defence compounds, as antimicrobial agents and anti-oxidants. Although avenanthramides are naturally and uniquely synthesised in oat plants, these molecules also exhibit medicinal and pharmaceutical uses important for human health, prompting research into utilisation of biotechnology to enhance agriculture and value-added production.

Effect of Germination on the Avenanthramide Content of Oats and Their in Vitro Antisensitivity Activities

In this study, a method, based on an ultraperformance liquid chromatography coupled with high-field quadrupole orbitrap high-resolution mass spectrometry (UHPLC-QE-HF-HRMS) platform, was established for the trace determination of three major avenanthramides (AVNs). The MS conditions for determining the AVNs were optimized, and the cracking methods of avenanthramides were analyzed. The linear range of the results and the correlation coefficient were 1−2000 μg/L and >0.996, respectively. Further, the established method was employed for the determination of the AVN contents of oats at different germination times, and the results indicated that the AVN contents of Zaohua and Bayou oats increased 19.26 and 6.09 times, respectively, after germination. The total AVN content of both oat varieties reached a maximum on the fifth day of germination (153.51 ± 4.08 and 126.30 ± 3.33 μg/g for the Zaohua and Bayou oats, respectively). Furthermore, this study investigated the antiallergic and antioxidant activities of the germinated oats via hyaluronidase inhibition and 2,2-diphenyl-1-picrylhydrazyl (DPPH)-scavenging assays. The antiallergic and DPPH-scavenging abilities of the ungerminated forms of both oat varieties were weaker. However, on the fifth day of germination, the inhibition rate of anthranilamide hyaluronidase reached 72.7% and 67.3% for the Zaohua and Bayou oat varieties, respectively. The antiallergic abilities of the oats increased significantly on the fifth day of germination in terms of their antiallergic capacities and DPPH clearance (82.67% and 77.64% for the Zaohua and Bayou oats, respectively), and the two indicators exhibited similar trends. These findings demonstrated that AVNs exhibit good antisensitivity and antioxidation properties, and the antisensitivity effect correlated positively with the AVN content.

In vitro and in vivo anti-lymphoma effects of Ophiorrhiza pumila extract

Background: Current therapeutic strategies on patients with lymphomas remains limited. Previously we found the suppressive effect of Ophiorrhiza pumila (OPE) on hepatocarcinoma. In present study, the effect of OPE on lymphoma in vitro and in vivo were investigated.

Methods: CCK-8 assay was applied to detect the effect of OPE on cell proliferation. Flow cytometry was used to analyze the effect of OPE on cell cycle distribution and apoptosis. Xenograft mouse model was conducted to determine the anti-tumor activity of OPE. TNUEL assay was performed to detect the apoptosis in tumor tissues. Western blot and immuno-histochemistry were used to determine protein expression.

Results: In vitro tests indicate that OPE suppressed A20 cell proliferation in a dose- and time-dependent manner. OPE treatment induced cell cycle arrest at S phase and elevated apoptosis in A20 cells. OPE displayed a significant inhibition in tumor growth in a mouse xenograft model. OPE promoted apoptosis of tumor cell in the mouse model Cleaved caspase 3 expression and Bax/Bcl2 ratio were also enhanced. In addition, OPE suppressed A20 cell viability partially by reducing phosphorylation of EGFR.

Conclusions: Our data showed that OPE suppressed the proliferation of lymphoma cells and promoted apoptosis in vitro and in vivo, which might be partially mediated by inactivating EGFR signaling.

The Progress of Nomenclature, Structure, Metabolism, and Bioactivities of Oat Novel Phytochemical: Avenanthramides

Oats are among the most commonly consumed whole grains and are widely grown worldwide, and they contain numerous nutrients, including proteins, lipids, vitamins, minerals, β-glucan, and unique phytochemical polyphenol avenanthramides (Avns). Recent studies have indicated that Avns play essential roles in mediating the health benefits of oats. This review systemically summarized the nomenclature and structures of Avns, effect of germination on promoting Avns production, and in vivo metabolites produced after Avns consumption. The classical functions and novel potential bioactivities of Avns were further elucidated. The classical functions of Avns in cancer prevention, antioxidative response, anti-inflammatory reaction, and maintaining muscle health were expounded, and the internal mechanisms of these functions were analyzed. The potential novel bioactivities of Avns in modulating gut microbiota, alleviating obesity, and preventing chronic diseases, such as atherosclerosis and osteoporosis, were further revealed. This review may provide new prospects and directions for the development and utilization of oat Avns.

A Review of Health-Beneficial Properties of Oats

Oat is among the food crops and ancient grains cultivated and consumed worldwide. It is gaining in popularity owing to its nutritional composition and multifunctional benefits of select bioactive compounds. Beta-glucan is an important component of dietary fiber found in oat grains. It is the major active compound in oats with proven cholesterol-lowering and antidiabetic effects. Oats also provide substantial levels of other bioactive compounds such as phenolic acids, tocols, sterols, avenacosides, and avenanthramides. The consumption of oats has been determined to be beneficial for human health by promoting immunomodulation and improving gut microbiota. In addition, oat consumption assists in preventing diseases such as atherosclerosis, dermatitis, and some forms of cancer. While much has been published in relation to oat nutrients and oat fibers and their impact on major diseases, the oat industries and consumers may benefit from greater knowledge and understanding of clinical effects, range of occurrence, distribution, therapeutic doses and food functional attributes of other oat bioactives such as avenanthramides and saponins as well as other anti-inflammatory agents found in the cereal. This review focuses on the various studies relevant to the contribution of the consumption of oats and oat-based products in preventing human diseases and promoting human health.

Metabolite Profiling of Meridianin C In Vivo of Rat by UHPLC/Q-TOF MS

Meridianin C (MC), as a marine alkaloid, is a potent protein kinase inhibitor which exhibits good anticancer activity. However, the in vivo metabolism of MC has not been described to date. In this study, an ultra-high performance liquid chromatography/quadrupole time-of-flight mass spectrometry (UHPLC/Q-TOF MS) method is employed to investigate the in vivo metabolites of MC in rats. Plasma, bile, urine, and feces are collected after a single oral dose of MC. Protein precipitation, solid phase extraction (SPE), and ultrasonic extraction methods are used to prepare samples. Based on the mass spectral fragmentation patterns, elution order, and retrieving literatures, a total of 13 metabolites of MC were detected and tentatively identified, utilizing MetaboLynx software. The metabolic pathways of MC in rats include N- or O-glucuronidation, O-sulfation, N-hydroxylation, dihydroxylation, and trihydroxylation. The relative content of the metabolites in each kinds of biological samples is also evaluated. This study will help to understand the in vivo properties of MC for the future usage.

Pityriacitrin marine alkaloids as novel antiviral and anti-phytopathogenic-fungus agents

BACKGROUND

Plant diseases have been gripping agricultural production, seriously affecting the growth and yields of crops. Marine natural products are an important source for novel drugs discovery. In this work, pityriacitrin marine alkaloids were selected as the parent structures. A series of pityriacitrin alkaloid analogues were rationally designed, synthesized and evaluated for their antiviral activities and fungicidal activities.

RESULT

Most of these compounds were demonstrated to have higher antiviral activities than ribavirin. Particularly, compounds 3a, 3e, 8f, 8g, and 9g displayed higher anti-TMV activities than ningnanmycin at 500 μg·mL^-1 . Mechanism research revealed that 3a could bind to TMV CP with an excellent affinity (K_a  = 8.67 × 10⁶  L·mol^-1 ), thus interfere with the assembly of virus particles. These alkaloids also showed broad-spectrum fungicidal activities against eight kinds of phytopathogenic fungi. Compound 5f with 1.43-3.84 μg·mL^-1 EC₅₀ value against three fungi emerged as a new fungicidal candidate.

CONCLUSION

Pityriacitrin alkaloids and their derivatives were synthesized and evaluated for anti-TMV and fungicidal activities for the first time. Compounds 3a and 5f with excellent activities emerged as new candidates for antiviral research and fungicidal research, respectively. Current work provided a new idea for the molecular design and development of novel plant virus and fungi inhibitors in the future. © 2021 Society of Chemical Industry.

Multiple Antioxidative and Bioactive Molecules of Oats (Avena sativa L.) in Human Health

Oats (Avena sativa L.) are rich in protein, fiber, calcium, vitamins (B, C, E, and K), amino acids, and antioxidants (beta-carotene, polyphenols, chlorophyll, and flavonoids). β-glucan and avenanthramides improve the immune system, eliminate harmful substances from the body, reduce blood cholesterol, and help with dietary weight loss by enhancing the lipid profile and breaking down fat in the body. β-glucan regulates insulin secretion, preventing diabetes. Progladins also lower cholesterol levels, suppress the accumulation of triglycerides, reduce blood sugar levels, suppress inflammation, and improve skin health. Saponin-based avanacosidase and functional substances of flavone glycoside improve the immune function, control inflammation, and prevent infiltration in the skin. Moreover, lignin and phytoestrogen prevent hormone-related cancer and improve the quality of life of postmenopausal women. Sprouted oats are rich in saponarin in detoxifying the liver. The literatures have been reviewed and the recent concepts and prospects have been summarized with figures and tables. This review discusses recent trends in research on the functionality of oats rather than their nutritional value with individual immunity for self-medication. The oat and its acting components have been revisited for the future prospect and development of human healthy and functional sources.

Toad Alkaloid for Pesticide Discovery: Dehydrobufotenine Derivatives as Novel Agents against Plant Virus and Fungi

Plant viruses and fungi are a serious threat to food security and natural ecosystems. The efficient and environment-friendly control methods are urgently needed to help safeguard such resources. Here, we achieved the efficient synthesis of toad alkaloid dehydrobufotenine in eight steps with an overall yield of 8% from 5-methoxyindole. A series of dehydrobufotenine derivatives were designed, synthesized, and evaluated for their antiviral and fungicidal activities systematically. It was found for the first time that these compounds have good anti-plant virus activities and anti-plant pathogen activities. The antiviral activities of 21 compounds were similar to or better than those of ribavirin. Compounds 12 and 17 displayed better antiviral activities than ningnanmycin which is perhaps the most effective anti-plant virus agent. The antiviral mechanism research study of 12 revealed that it could make 20S CP disk fusion and aggregation. Further molecular docking results showed that there are hydrogen bonds between compounds 12, 17, and tobacco mosaic virus CP. The docking results are consistent with the antiviral activity. These compounds also displayed broad-spectrum fungicidal activities against 14 kinds of fungi, especially for Sclerotinia sclerotiorum. In this work, the synthesis, structure optimization, structure-activity relationship studies, and mode of action research of dehydrobufotenine alkaloids were carried out. It provides a reference for the development of the anti-plant virus agent and anti-plant pathogen agent from toad alkaloids.

Oat polyphenol avenanthramide-2c confers protection from oxidative stress by regulating the Nrf2-ARE signaling pathway in PC12 cells

Accumulating evidence has demonstrated that cellular antioxidant systems play essential roles in retarding oxidative stress-related diseases, such as Parkinson's disease. Because nuclear factor erythroid 2-related factor 2 (Nrf2) is a chief regulator of cellular antioxidant systems, small molecules with Nrf2-activating ability may be promising neuroprotective agents. Avenanthramide-2c (Aven-2c), avenanthramide-2f (Aven-2f) and avenanthramide-2p (Aven-2p) are the most abundant avenanthramides in oats, and they have been documented to possess multiple pharmacological benefits. In this work, we synthesized these three compounds and evaluated their cytoprotective effect against oxidative stress-induced PC12 cell injuries. Aven-2c displayed the best protective potency among them. Aven-2c conferred protection on PC12 cells by scavenging free radicals and activating the Nrf2-ARE signaling pathway. Pretreatment of PC12 cells with Aven-2c efficiently enhanced Nrf2 nuclear accumulation and evoked the expression of a set of cytoprotective molecules. The mechanistic study also supports that Nrf2 activation is the molecular basis for the cellular action of Aven-2c. Collectively, this study demonstrates that Aven-2c is a potent Nrf2 agonist, shedding light on the potential usage of Aven-2c in the treatment of neuroprotective diseases.

Avenanthramide Metabotype from Whole-Grain Oat Intake is Influenced by Faecalibacterium prausnitzii in Healthy Adults

BACKGROUND

Oat has been widely accepted as a key food for human health. It is becoming increasingly evident that individual differences in metabolism determine how different individuals benefit from diet. Both host genetics and the gut microbiota play important roles on the metabolism and function of dietary compounds.

OBJECTIVES

To investigate the mechanism of individual variations in response to whole-grain (WG) oat intake.

METHODS

We used the combination of in vitro incubation assays with human gut microbiota, mouse and human S9 fractions, chemical analyses, germ-free (GF) mice, 16S rRNA sequencing, gnotobiotic techniques, and a human feeding study.

RESULTS

Avenanthramides (AVAs), the signature bioactive polyphenols of WG oat, were not metabolized into their dihydro forms, dihydro-AVAs (DH-AVAs), by both human and mouse S9 fractions. DH-AVAs were detected in the colon and the distal regions but not in the proximal and middle regions of the perfused mouse intestine, and were in specific pathogen-free (SPF) mice but not in GF mice. A kinetic study of humans fed oat bran showed that DH-AVAs reached their maximal concentrations at much later time points than their corresponding AVAs (10.0-15.0 hours vs. 4.0-4.5 hours, respectively). We observed interindividual variations in the metabolism of AVAs to DH-AVAs in humans. Faecalibacterium prausnitzii was identified as the individual bacterium to metabolize AVAs to DH-AVAs by 16S rRNA sequencing analysis. Moreover, as opposed to GF mice, F. prausnitzii-monocolonized mice were able to metabolize AVAs to DH-AVAs.

CONCLUSIONS

These findings demonstrate that the presence of intestinal F. prausnitzii is indispensable for proper metabolism of AVAs in both humans and mice. We propose that the abundance of F. prausnitzii can be used to subcategorize individuals into AVA metabolizers and nonmetabolizers after WG oat intake. This study was registered at clinicaltrials.gov as NCT04335435.

Quantitative Analysis and Anti-inflammatory Activity Evaluation of the A-Type Avenanthramides in Commercial Sprouted Oat Products

Avenanthramides (AVAs) are unique phytochemicals in oat that contain two distinct groups of compounds. The first group is constituted by N-cinnamoylanthranilic acids with a single double bond (referred to as C type), and the other group is constituted by N-avenalumoylanthranilic acids with two double bonds (referred to as A type). C-type AVAs have been reported with their chemical profiles and levels in commercial oat products as well as their bioactivities. However, the accurate levels of A-type AVAs in commercial sprouted oat products and their bioactivity are still unknown. In this study, we purified seven A-type AVAs from sprouted oat bran and characterized their structures with corresponding mass spectrometry and nuclear magnetic resonance data. Among them, five compounds were isolated from oat bran for the first time. The purified A-type AVAs were used as authentic standards to establish the chemical profile of A-type AVAs in oat and to quantify the levels of all individual A-type AVAs in six commercial sprouted oat products using ultra-high-performance liquid chromatography with tandem mass spectrometry. The total A-type AVA contents in the various oat products ranged from 7.85 to 133.3 μg/g. Furthermore, the inhibition of lipopolysaccharide-induced nitric oxide production and inducible nitric oxide synthase expression by A- and C-type AVAs in macrophages were compared. The most abundant A-type AVAs (2p_d, 2c_d, and 2f_d) have similar anti-inflammatory activity to the major C-type AVAs (2p, 2c, and 2f). To the best of our knowledge, this is the first report on the bioactivity of A-type AVAs.

Characterization and antioxidant activity of avenanthramides from selected oat lines developed by mutagenesis technique

From a mutagenized oat population, produced by ethyl methanesulfonate mutagenesis, hulled grains from 17 lines with elevated avenanthramide (AVN) content were selected and their AVN structures, concentrations and antioxidant potentials were determined by HPLC-MS² and HPLC equipped with an on-line ABTS⁺ antioxidant detection system. The data obtained showed qualitative and quantitative differences in the synthesis of AVNs in the different lines, with a total AVN concentration up to 227.5 µg/g oat seed flour in the highest line, compared with 78.2 µg/g seed in the commercial line, SW Belinda. In total, 25 different AVNs were identified with avenanthramide B structures being among the most abundant, and AVN C structures having the highest antioxidant activity. The findings indicate the potential of oat mutagenesis in combination with a high precision biochemical selection method for the generation of stable mutagenized lines with a high concentration of total and/or individual AVNs in the oat seed grain.

Marine Natural Product for Pesticide Candidate: Pulmonarin Alkaloids as Novel Antiviral and Anti-Phytopathogenic-Fungus Agents

Plant diseases are seriously endangering agricultural production. The emergence of drug resistance has brought great challenges to the prevention and control of plant diseases. There is an urgent need for the emergence of new drug candidates. In this work, we achieved the efficient synthesis of pulmonarins A and B in 64% and 59% overall yield, respectively. Pulmonarins A and B were found to have good antiviral activities against tobacco mosaic virus (TMV) for the first time. A series of pulmonarin derivatives were designed, synthesized, and evaluated for their antiviral and fungicidal activities systematically. Most compounds displayed higher anti-TMV activities than commercial ribavirin. Compounds 6a, 6c, and 6n with better inactivation effects than ningnanmycin emerged as new antiviral candidates. We selected 6c for further antiviral mechanism research, which revealed that it could inhibit virus assembly by interacting with TMV coat protein (CP). The molecular docking results further confirmed that these compounds could interact with CP through hydrogen bonding. These compounds also displayed broad spectrum fungicidal activities. Especially compound 6u with prominent antifungal activity emerged as a new fungicidal candidate for further research. The current work provides a reference for understanding the application of pulmonarin alkaloids in plant protection.

Marine-natural-products for biocides development: first discovery of meridianin alkaloids as antiviral and anti-phytopathogenic-fungus agents

BACKGROUND

Food is an important strategic material related to national economy and people's livelihood. Plant diseases seriously affect crop yield and quality. Marine natural products are an important source for novel drugs discovery. In this work, meridianin alkaloids were selected as the parent structure. A series of meridianin alkaloid analogues were rationally designed, synthesized and evaluated for their antiviral activities and fungicidal activities.

RESULT

These compounds were found to have good antiviral and fungicidal activities for the first time. The structure-activity relationship (SAR) research revealed that introducing bromine atom at the 5-position of indole ring is beneficial to antiviral activity, but introducing methoxy group is not conducive. Introducing bromine atom at the 6-position of indole ring or nitrogen atom at the 7-position of the indole ring resulted in lower antiviral activity. Most of the meridianin derivatives showed higher anti-TMV activities at 500 μg mL^-1 than Ribavirin, especially for compounds 6c, 8a and 10a. All of the compounds also displayed broad spectrum fungicidal activities against 14 kinds of phytopathogenic fungi at 50 μg mL^-1 .

CONCLUSION

Compound 6c with relatively simple structure and excellent antiviral activity, which is similar to that of Ningnanmycin, emerged as novel anti-TMV lead compound. Compound 5d with broad spectrum and high effect fungicidal activity emerged as a new fungicidal lead compound. Current research lays a solid foundation for the application of meridianin alkaloids in crop protection. © 2019 Society of Chemical Industry.

Phenolamides: Plant specialized metabolites with a wide range of promising pharmacological and health-promoting interests

Phenolamides constitute a family of metabolites, widely represented in the plant kingdom, that can be found in all plant organs with a predominance in flowers and pollen grains. They represent a large and structurally diverse family, resulting from the association of phenolic acids with aliphatic or aromatic amines. Initially revealed as active compounds in several medicinal plant extracts, phenolamides have been extensively studied for their health-promoting and pharmacological properties. Indeed, phenolamides have been shown to exhibit antioxidant, anti-inflammatory, anti-cancer and antimicrobial properties, but also protective effects against metabolic syndrome and neurodegenerative diseases. The purpose of this review is to summarise this large body of literature, including in vitro and in vivo studies, by describing the diversity of their biological properties and our actual knowledge of the molecular mechanisms behind them. With regard to their considerable pharmacological interest, the question of industrial production is also tackled through chemical and biological syntheses in engineered microorganisms. The diversity of biological activities already described, together with the active discovery of the broad structural diversity of this metabolite family, make phenolamides a promising source of new active compounds on which future studies should be focused.

Retracted Article: The synthesis and biological activity of marine alkaloid derivatives and analogues

The ocean is the origin of life, with a unique ecological environment, which has given birth to a wealth of marine organisms. The ocean is an important source of biological resources and tens of thousands of monomeric compounds have been separated from marine organisms using modern separation technology. Most of these monomeric compounds have some kind of biological activity that has attracted extensive attention from researchers. Marine alkaloids are a kind of compound that can be separated from marine organisms. They have complex and special chemical structures, but at the same time, they can show diversity in biological activities. The biological activities of marine alkaloids mainly manifest in the form of anti-tumor, anti-fungus, anti-viral, anti-malaria, and anti-osteoporosis properties. Many marine alkaloids have good medicinal prospects and can possibly be used as anti-tumor, anti-viral, and anti-fungal clinical drugs or as lead compounds. The limited amounts of marine alkaloids that can be obtained by separation, coupled with the high cytotoxicity and low selectivity of these lead compounds, has restricted the clinical research and industrial development of marine alkaloids. Marine alkaloid derivatives and analogues have been obtained via rational drug design and chemical synthesis, to make up for the shortcomings of marine alkaloids; this has become an urgent subject for research and development. This work systematically reviews the recent developments relating to marine alkaloid derivatives and analogues in the field of medical chemistry over the last 10 years (2010-2019). We divide marine alkaloid derivatives and analogues into five types from the point-of-view of biological activity and elaborated on these activities. We also briefly discuss the optimization process, chemical synthesis, biological activity evaluation, and structure-activity relationship (SAR) of each of these compounds. The abundant SAR data provides reasonable approaches for the design and development of new biologically active marine alkaloid derivatives and analogues.

Luotonin A and Its Derivatives as Novel Antiviral and Antiphytopathogenic Fungus Agents

Plant diseases caused by viruses and fungi have posed a serious threat to global agricultural production. The discovery of new leads based on natural products is an important way to innovate pesticides. In this work, natural product luotonin A was found to have good antiviral activity against tobacco mosaic virus (TMV) for the first time. A series of luotonin A derivatives were designed, synthesized, and evaluated for their antiviral activities and fungicidal activities systematically. Most compounds displayed better antiviral activities against TMV than commercial ribavirin. Compounds 9k, 12b, and 12d displayed about similar inhibitory effects as ningnanmycin (inhibitory rates of 55, 57, and 59% at 500 μg/mL for inactivation, curative, and protection activities in vivo, respectively), the best antiviral agent at present, and emerged as novel antiviral leads for further research. We selected 9k for further antiviral mechanism research via transmission electron microscopy and molecular docking, which revealed that compound 9k can interact with TMV coat protein through the hydrogen bond, leading to its polymerization, thus preventing virus assembly. Further fungicidal activity tests showed that these compounds also showed broad-spectrum fungicidal activities against 14 kinds of phytopathogenic fungi. Especially, compound 14 with a 100% antifungal effect against Botrytis cinereal emerged as a lead for further research. This work provides a reference for the development of agricultural active ingredients based on Chinese medicine plants.

Streptindole and Its Derivatives as Novel Antiviral and Anti-Phytopathogenic Fungus Agents

Plant diseases caused by plant viruses and pathogens seriously affect the production and storage of food crops. With the emergence of drug resistance, it is very difficult to control. Natural products are the source of new drug discovery. Here, the natural product streptindole was found to have good antiviral activity against tobacco mosaic virus (TMV) and fungicidal activities against 14 kinds of phytopathogenic fungi. A series of derivatives of streptindole were designed, synthesized, and evaluated for their antiviral and fungicidal activities. Compounds 4, 5, 11, 12c, 12d, 13d, and 13i-13l showed higher anti-TMV activities than ribavirin (inhibitory rate: 38, 37, and 40% at 500 μg/mL for inactivation, curative, and protection activity in vivo, respectively), among which compound 12d (inhibitory rate: 57, 55, and 53% at 500 μg/mL for inactivation, curative, and protection activity in vivo, respectively) with excellent antiviral activity was further evaluated for the mode of action. The mechanism research revealed that 12d can break the three-dimensional structure of TMV coat protein (CP) through hydrogen bonds, thus inhibiting the assembly of virus particles. The molecular docking result showed that compound 12d did exhibit strong interaction with TMV CP. The derivatives of streptindole also displayed broad-spectrum fungicidal activities. The current study provided valuable insights into the antiviral and fungicidal activities of streptindole derivatives.

Triterpenoid Saponins in Oat Bran and Their Levels in Commercial Oat Products

Oats are commonly consumed as whole grains and generally considered as a healthy food. However, the bioactive compounds in oats have not been fully investigated. In this study, we reported for the first time the purification, structure elucidation, and chemical profile of the major triterpenoid saponins in oat bran as well as the quantification of the major triterpenoid saponins in commercial oat products. Thirteen triterpenoid saponins (1-13) were purified from oat bran. Their structures were characterized by analyzing their high-resolution mass spectrometry (MS), one-dimensional (1-D), and two-dimensional (2-D) NMR spectra. All of the purified triterpenoid saponins have been reported from oat bran for the first time, in which compounds (1-8) are newly discovered compounds and compound (9) is a new natural product. Using ultra-high-performance liquid chromatography with tandem mass spectrometry techniques, a complete profile of oat triterpenoid saponins was established, and the contents of the 13 purified triterpenoid saponins were quantitated in 19 different commercial oat products. The total levels of the 13 triterpenoid saponins varied from 1.77 to 18.20 μg/g in these 19 products, in which oat bran (11 samples) and oatmeal (three samples) had higher levels than cold oat cereal (five samples). Among the 11 commercial oat bran samples, the average total levels of the 13 triterpenoid saponins in the five sprouted oat samples are slightly higher than those in the regular oat bran products.

The Chemistry and Health Benefits of Dietary Phenolamides

Phenolamides, also known as hydroxycinnamic acid amides or phenylamides, have been reported throughout the plant kingdom, while a few of these amine-conjugated hydroxycinnamic acids are unique in foods. The current knowledge of their specific functions in plant development and defense is readily available as is their biosynthesis; however, their functionality in humans is still largely unknown. Of the currently known phenolamides, the most common are avenanthramides, which are unique in oats and similar to the well-known drug Tranilast, which possess anti-inflammatory, antioxidant, anti-itch, and antiatherogenic activities. While recent data have brought to light more information regarding the other known phenolamides, such as hordatines, dimers of agmatine conjugated to hydroxycinnamic acid, and kukoamines, spermine-derived phenolamides, the information is still severely limited, leaving their potential health benefits to speculation. Herein, to highlight the importance of dietary phenolamides to human health, we review and summarize the four major subgroups of phenolamides, including their chemical structures, dietary sources, and reported health benefits. We believe that the studies on phenolamides are still in the infancy stage and additional health benefits of these phenolamides may yet be identified.

Comprehensive analysis of oat avenanthramides using hybrid quadrupole-Orbitrap mass spectrometry: Possible detection of new compounds

RATIONALE

Avenanthramides (AVNs) are constituents unique to oats and have many outstanding health benefits. AVNs are antioxidants and possess anti-inflammatory, antifungal and antibacterial activity. The number of known AVNs increased recently because of the latest developments in high-resolution tandem mass spectrometry (HRMS/MS) techniques.

METHODS

Oat seed extract from 10 oat cultivars was analysed using ultra-high-performance liquid chromatography (UHPLC) and Q Exactive hybrid quadrupole-Orbitrap mass spectrometry (HRMS/MS) with positive heated electrospray ionization.

RESULTS

Thirty-five AVNs were identified and characterized in seed extracts, and the structures of 10 novel AVNs were tentatively elucidated, among which were AVNs bearing a cinamoyl or sinapoyl moiety. These AVNs are reported in oats for the first time. The method was validated using AVN standards (AVNs 2c, 2f and 2p), with limits of detection and quantitation at low picomole levels. Recovery of AVN standards varied from 83% to 106%, and relative standard deviations ranged from 2% to 9%. The total AVNs in the selected oat varieties ranged from 36.0 to 302.5 μg/g (dry weight), with AVN 2c, AVN 2f and AVN 2p representing approximately 65%-70% of that total.

CONCLUSIONS

Our comprehensive method for detecting the full avenanthramide spectrum can contribute to better understanding the chemical and biological properties of individual AVNs for utilization in developing new oat cultivars and novel functional foods.

Discovery of Tryptanthrins as Novel Antiviral and Anti-Phytopathogenic-Fungus Agents

Plant diseases seriously affect the yield and quality of crops and are difficult to control. Tryptanthrin and its derivatives (tryptanthrins) were synthesized and evaluated for their antiviral activities and fungicidal activities. We found that tryptanthrins have good antiviral activities against tobacco mosaic virus (TMV) for the first time. Most of the tryptanthrins showed higher anti-TMV activities than that of ribavirin (inhibitory rates of 40, 37, and 38% at 500 μg/mL for inactivation, curative, and protection activities in vivo, respectively). Compound 3n (inhibitory rates of 52, 49, and 54% at 500 μg/mL for inactivation, curative, and protection activities in vivo, respectively) and compound 14 (inhibitory rates of 51, 48, and 53% at 500 μg/mL for inactivation, curative, and protection activities in vivo, respectively) emerged as new antiviral lead compounds with excellent antiviral activities. Compound 16 was selected for further antiviral mechanism research, which revealed that compound 16 could inhibit virus assembly by decomposing 20S coat protein (CP) disk. Molecular docking results showed that compounds 3n and 14, which have higher antiviral activities in vivo than that of compound 16, do show stronger interaction with TMV CP. Further fungicidal activity tests showed that tryptanthrins displayed broad-spectrum fungicidal activities, especially for compound 16. These compounds showed good selectivity to Physalospora piricola. In the current study, a small molecular library of tryptanthrin was constructed and the bioactivity spectrum of these compounds was broadened, which lays a foundation for their application in plant protection.

Discovery, Structural Optimization, and Mode of Action of Essramycin Alkaloid and Its Derivatives as Anti-Tobacco Mosaic Virus and Anti-Phytopathogenic Fungus Agents

Plant diseases seriously affect crop yield and quality and are difficult to control. Marine natural products (MNPs) have become an important source of drug candidates with new biological mechanisms. Marine natural product essramycin (1) was found to have good anti-tobacco mosaic virus (TMV) and anti-phytopathogenic fungus activities for the first time. A series of essramycin derivatives were designed, synthesized, and evaluated for their bioactivity. Most of these compounds exhibited antiviral effects that are greater than that of the control ribavirin. Compounds 7e and 8f displayed antiviral activities that are greater than that of ningnanmycin (the most widely used antiviral agent at present), thus emerging as novel antiviral lead compounds. As the lead compound, 7e was selected for further antiviral mechanism research. The results indicated that 7e could inhibit virus assembly and promote 20S disk protein aggregation. Fungicidal activity tests against 14 kinds of phytopathogenic fungi revealed that essramycin analogues displayed broad-spectrum fungicidal activities. Compound 5b displayed more than 50% inhibition rate against most of the 14 kinds of phytopathogenic fungi at 50 μg/mL. The current research lays a solid foundation for the application of essramycin alkaloids in crop protection.

Overview of the Anticancer Profile of Avenanthramides from Oat

Cancer represents one of the leading causes of death worldwide. Progresses in treatment of cancer have continued at a rapid pace. However, undesirable side effects and drug resistance remain major challenges for therapeutic success. Natural products represent a valuable starting point to develop new anticancer strategies. Polyphenols, well-known as antioxidant, exert anticancer effects through the modulation of multiple pathways and mechanisms. Oat (Avena sativa L., Poaceae) is a unique source of avenanthramides (AVAs), a group of polyphenolic alkaloids, considered as its signature compounds. The present review aims to offer a comprehensive and critical perspective on the chemopreventive and chemotherapeutic potential of AVAs. AVAs prevent cancer mainly by blocking reactive species. Moreover, they exhibit potential therapeutic activity through the modulation of different pathways including the activation of apoptosis and senescence, the block of cell proliferation, and the inhibition of epithelial mesenchymal transition and metastatization. AVAs are promising chemopreventive and anticancer phytochemicals, which need further clinical trials and toxicological studies to define their efficacy in preventing and reducing the burden of cancer diseases.

Optimization, Structure-Activity Relationship, and Mode of Action of Nortopsentin Analogues Containing Thiazole and Oxazole Moieties

Plant diseases seriously endanger plant health, and it is very difficult to control them. A series of nortopsentin analogues were designed, synthesized, and evaluated for their antiviral activities and fungicidal activities. Most of these compounds displayed higher antiviral activities than ribavirin. Compounds 1d, 1e, and 12a, with excellent antiviral activities, emerged as novel antiviral lead compounds, among which 1e was selected for further antiviral mechanism research. The mechanism research results indicated that these compounds may play an antiviral role by aggregating viral particles to prevent their movement in plants. Further fungicidal activity tests revealed that nortopsentin analogues displayed broad-spectrum fungicidal activities. Compounds 2p and 2f displayed higher antifungal activities against Alternaria solani than the commercial fungicides carbendazim and chlorothalonil. Current research has laid a foundation for the application of nortopsentin analogues in plant protection.

Avenanthramide-C prevents noise- and drug-induced hearing loss while protecting auditory hair cells from oxidative stress

Noise exposure or ototoxic drugs instigate various types of damage to the cochlea, resulting in hearing loss (HL). While the incidence of HL is growing continuously, there are, so far, no adequate drugs to prevent or treat HL. Avenanthramide (AVN), a natural product extracted from oats, has been reported to possess anti-oxidant/inflammatory properties, and protect several types of cells. In this study, we investigated whether AVN-C can protect auditory hair cells, and preserve hearing from noise trauma and ototoxic drugs. Wild-type C57BL/6 mice were used to generate several HL models. Serum and perilymphatic fluid samples were analyzed using mass spectrophotometry to detect AVN-C. AVN-C crossed the blood-labyrinth barrier, and was detected in the perilymph after systemic injection. Pretreatment by AVN-C 24 h before exposure to temporary threshold shift noise contributed to the preserving hearing. Moreover, in the case of permanent threshold shift, AVN-C provided significant protection from noise. AVN-C also strongly protected against deterioration in hearing due to kanamycin and furosemide (K + F). According to the results of our scanning electron microscopy analysis, many outer hair cells (OHCs) were destroyed by noise trauma, while AVN-C prevented these losses. OHC loss due to K + F was even more severe, even affecting the apex. Strikingly, AVN-C treatment maintained OHCs at a level comparable to normal cochlea. AVN-C reduced the dichlorofluorescin (DCF)-positive population in gentamicin-treated HEI-OC1 in vitro. The expressions of TNF-a, BAK, IL-1b, and Bcl-2 were attenuated by AVN-C, revealing its antioxidant effects. The results of this study show that AVN-C crosses the blood-labyrinth barrier and provide a significant protection against noise- and drug-induced ototoxicity. Hence, AVN-C is a good candidate for future therapy aimed at protecting against sensorineural HL.

Avenanthramide A Induces Cellular Senescence via miR-129-3p/Pirh2/p53 Signaling Pathway To Suppress Colon Cancer Growth

Cellular senescence is the state of irreversible cell cycle arrest that provides a blockade during oncogenic transformation and tumor development. Avenanthramide A (AVN A) is an active ingredient exclusively extracted from oats, which possesses antioxidant, anti-inflammatory, and anticancer activities. However, the underlying mechanism(s) of AVN A in the prevention of cancer progression remains unclear. In the current study, we revealed that AVN A notably attenuated tumor formation in an azoxymethane/dextran sulfate sodium (AOM/DSS) mouse model. AVN A treatment triggered cellular senescence in human colon cancer cells, evidenced by enlarging cellular size, upregulating β-galactosidase activity, γ-H2AX positive staining, and G1 phase arrest. Moreover, AVN A treatment significantly increased the expression of miR-129-3p, which markedly repressed the E3 ubiquitin ligase Pirh2 and two other targets, IGF2BP3 and CDK6. The Pirh2 silencing by miR-129-3p led to a significant increase in protein levels of p53 and its downstream target p21, which subsequently induced cell senescence. Taken together, our data indicate that miR-129-3p/Pirh2/p53 is a critical signaling pathway in AVN A induced cellular senescence and AVN A could be a potential chemopreventive strategy for cancer treatment.

Mass spectrometric characterisation of avenanthramides and enhancing their production by germination of oat (Avena sativa)

Avenanthramides are amides, with a phenylalkenoic acid (PA) and an anthranilic acid (AA) subunit, which are secondary metabolites of oat. Oat seeds were germinated, extracted, and the avenanthramides analysed by a combination of UHPLC with ion trap and high resolution ESI-MS. Typical fragmentation pathways with corresponding diagnostic fragments belonging to the PA and AA subunits were identified and summarised in a decision guideline. Based on these findings 28 unique avenanthramides were annotated in the oat seed(ling) extracts, including the new avenanthramide 6f (with a 4/5-methoxy AA subunit). Avenanthramide content increased by 25 times from seed to seedling. Avenanthramides 2p, 2c, and 2f, which are commonly described as the major avenanthramides, represented less than 20% of the total content in the seedlings. Future quantitative analyses should, therefore, include a wider range of avenanthramides to avoid underestimation of the total avenanthramide content.