Isoflavonoids in non-leguminous families: an update

Biosynthesis and metabolic engineering of isoflavonoids in model plants and crops: a review

Isoflavonoids, the major secondary metabolites within the flavonoid biosynthetic pathway, play important roles in plant defense and exhibit free radical scavenging properties in mammals. Recent advancements in understanding the synthesis, transport, and regulation of isoflavonoids have identified their biosynthetic pathways as promising targets for metabolic engineering, offering potential benefits such as enhanced plant resistance, improved biomass, and restoration of soil fertility. This review provides an overview of recent breakthroughs in isoflavonoid biosynthesis, encompassing key enzymes in the biosynthetic pathway, transporters influencing their subcellular localization, molecular mechanisms regulating the metabolic pathway (including transcriptional and post-transcriptional regulation, as well as epigenetic modifications). Metabolic engineering strategies aimed at boosting isoflavonoid content in both leguminous and non-leguminous plants. Additionally, we discuss emerging technologies and resources for precise isoflavonoid regulation. This comprehensive review primarily focuses on model plants and crops, offering insights for more effective and sustainable metabolic engineering approaches to enhance nutritional quality and stress tolerance.

Chemical diversity of Brittonodoxa subpinnata, a Brazilian native species of moss

Plants should be probably thought of as the most formidable chemical laboratory that can be exploited for the production of an incredible number of molecules with remarkable structural and chemical diversity that cannot be matched by any synthetic libraries of small molecules. The bryophytes chemistry has been neglected for too long, but in the last ten years, this scenery is changing, with several studies being made using extracts from bryophytes, aimed at the characterization of interesting metabolites, with their metabolome screened. The main objective of this study was to analyze the metabolome of Brittonodoxa subpinnata, a native Brazilian moss species, which occurs in the two Brazilian hotspots. GC-MS and LC-MS2 were performed. All extracts were analyzed using the molecular networking approach. The four extracts of B. subpinnata (polar, non-polar, soluble, and insoluble) resulted in 928 features detected within the established parameters. 189 (20.4%) compounds were annotated, with sugars, fatty acids, flavonoids, and biflavonoids as the major constituents. Sucrose was the sugar with the highest quantity; palmitic acid the major fatty acid but with great presence of very long-chain fatty acids rarely found in higher plants, glycosylated flavonoids were the major flavonoids, and biflavonoids majorly composed by units of flavones and flavanones, exclusively found in the cell wall. Despite the high percentage, this work leaves a significant gap for future works using other structure elucidation techniques, such as NMR.

Isoflavonoid metabolism in leguminous plants: an update and perspectives

Isoflavonoids constitute a well-investigated category of phenylpropanoid-derived specialized metabolites primarily found in leguminous plants. They play a crucial role in legume development and interactions with the environment. Isoflavonoids usually function as phytoalexins, acting against pathogenic microbes in nature. Additionally, they serve as signaling molecules in rhizobial symbiosis. Notably, owing to their molecular structure resembling human estrogen, they are recognized as phytoestrogens, imparting positive effects on human health. This review comprehensively outlines recent advancements in research pertaining to isoflavonoid biosynthesis, transcriptional regulation, transport, and physiological functions, with a particular emphasis on soybean plants. Additionally, we pose several questions to encourage exploration into novel contributors to isoflavonoid metabolism and their potential roles in plant-microbe interactions.

Discovery of isoflavone phytoalexins in wheat reveals an alternative route to isoflavonoid biosynthesis

Isoflavones are a group of phenolic compounds mostly restricted to plants of the legume family, where they mediate important interactions with plant-associated microbes, including in defense from pathogens and in nodulation. Their well-studied health promoting attributes have made them a prime target for metabolic engineering, both for bioproduction of isoflavones as high-value molecules, and in biofortification of food crops. A key gene in their biosynthesis, isoflavone synthase, was identified in legumes over two decades ago, but little is known about formation of isoflavones outside of this family. Here we identify a specialized wheat-specific isoflavone synthase, TaCYP71F53, which catalyzes a different reaction from the leguminous isoflavone synthases, thus revealing an alternative path to isoflavonoid biosynthesis and providing a non-transgenic route for engineering isoflavone production in wheat. TaCYP71F53 forms part of a biosynthetic gene cluster that produces a naringenin-derived O-methylated isoflavone, 5-hydroxy-2',4',7-trimethoxyisoflavone, triticein. Pathogen-induced production and in vitro antimicrobial activity of triticein suggest a defense-related role for this molecule in wheat. Genomic and metabolic analyses of wheat ancestral grasses further show that the triticein gene cluster was introduced into domesticated emmer wheat through natural hybridization ~9000 years ago, and encodes a pathogen-responsive metabolic pathway that is conserved in modern bread wheat varieties.

Toxicity and Anti-Inflammatory Activity of Phenolic-Rich Extract from Nopalea cochenillifera (Cactaceae): A Preclinical Study on the Prevention of Inflammatory Bowel Diseases

Phenolic compounds have been scientifically recognized as beneficial to intestinal health. The cactus Nopalea cochenillifera, used as anti-inflammatory in traditional medicine, is a rich source of these bioactive compounds. The present study aimed to investigate the phytochemical profile of N. cochenillifera extract and evaluate its acute toxicity and anti-inflammatory effect on 2,4-dinitrobenzenesulfonic acid (DNBS)-induced colitis in rats. The total phenolic content per gram of dry extract was 67.85 mg. Through HPLC-IES-MSⁿ, a total of 25 compounds such as saccharides, organic acids, phenolic acids and flavonoids were characterized. The dose of 2000 mg/kg of extract by an oral route showed no signs of toxicity, mortality or significant changes in biochemical and hematological parameters. Regarding intestinal anti-inflammatory effects, animals were treated with three different doses of extract or sulfasalazine. Macroscopic analysis of the colon indicated that the extract decreased the disease activity index. Levels of IL-1β and TNF-α decreased, IL-10 increased and MDA and MPO enzyme levels decreased when compared with the control group. In addition, a down-regulation of MAPK1/ERK2 and NF-κB p65 pathway markers in colon tissue was observed. The epithelial integrity was improved according to histopathological and immunohistological analysis. Thus, the extract provided strong preclinical evidence of being effective in maintaining the remission of colitis.

Millettia isoflavonoids: a comprehensive review of structural diversity, extraction, isolation, and pharmacological properties

There are approximately 260 known species in the genus Millettia, many of which are used in traditional medicine to treat human and other animal ailments in various parts of the world. Being in the Leguminosae (Fabaceae) family, Millettia species are rich sources of isoflavonoids. In the past three decades alone, several isoflavonoids originating from Millettia have been isolated, and their pharmacological activities have been evaluated against major diseases, such as cancer, inflammation, and diabetes. Despite such extensive research, no recent and comprehensive review of the phytochemistry and pharmacology of Millettia isoflavonoids is available. Furthermore, the structural diversity of isoflavonoids in Millettia species has rarely been reported. In this review, we comprehensively summarized the structural diversity of Millettia isoflavonoids, the methods used for their extraction and isolation protocols, and their pharmacological properties. According to the literature, 154 structurally diverse isoflavonoids were isolated and reported from the various tissues of nine well-known Millettia species. Prenylated isoflavonoids and rotenoids were the most dominant subclasses of isoflavonoids reported. Other subclasses of reported isoflavonoids include isoflavans, aglycone isoflavones, glycosylated isoflavones, geranylated isoflavonoids, phenylcoumarins, pterocarpans and coumaronochromenes. Although some isolated molecules showed promising pharmacological properties, such as anticancer, anti-inflammatory, estrogenic, and antibacterial activities, others remained untested. In general, this review highlights the potential of Millettia isoflavonoids and could improve their utilization in drug discovery and medicinal use processes.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s11101-022-09845-w.

Therapeutic Potential and Mechanisms of Novel Simple O-Substituted Isoflavones against Cerebral Ischemia Reperfusion

Isoflavones have been widely studied and have attracted extensive attention in fields ranging from chemotaxonomy and plant physiology to human nutrition and medicine. Isoflavones are often divided into three subgroups: simple O-substituted derivatives, prenylated derivatives, and glycosides. Simple O-substituted isoflavones and their glycosides, such as daidzein (daidzin), genistein (genistin), glycitein (glycitin), biochanin A (astroside), and formononetin (ononin), are the most common ingredients in legumes and are considered as phytoestrogens for daily dietary hormone replacement therapy due to their structural similarity to 17-β-estradiol. On the basis of the known estrogen-like potency, these above isoflavones possess multiple pharmacological activities such as antioxidant, anti-inflammatory, anticancer, anti-angiogenetic, hepatoprotective, antidiabetic, antilipidemic, anti-osteoporotic, and neuroprotective activities. However, there are very few review studies on the protective effects of these novel isoflavones and their related compounds in cerebral ischemia reperfusion. This review primarily focuses on the biosynthesis, metabolism, and neuroprotective mechanism of these aforementioned novel isoflavones in cerebral ischemia reperfusion. From these published works in in vitro and in vivo studies, simple O-substituted isoflavones could serve as promising therapeutic compounds for the prevention and treatment of cerebral ischemia reperfusion via their estrogenic receptor properties and neuron-modulatory, antioxidant, anti-inflammatory, and anti-apoptotic effects. The detailed mechanism of the protective effects of simple O-substituted isoflavones against cerebral ischemia reperfusion might be related to the PI3K/AKT/ERK/mTOR or GSK-3β pathway, eNOS/Keap1/Nrf-2/HO-1 pathway, TLRs/TIRAP/MyD88/NFκ-B pathway, and Bcl-2-regulated anti-apoptotic pathway. However, clinical trials are needed to verify their potential on cerebral ischemia reperfusion because past studies were conducted with rodents and prophylactic administration.

Identification and characterization of unique 5-hydroxyisoflavonoid biosynthetic key enzyme genes in Lupinus albus

5-Hydroxyisoflavonoids, no 5-deoxyisoflavonoids, in Lupinus species, are due to lack of CHRs and Type II CHIs, and the key enzymes of isoflavonoid biosynthetic pathway in white lupin were identified. White lupin (Lupinus albus) is used as food ingredients owing to rich protein, low starch, and rich bioactive compounds such as isoflavonoids. The isoflavonoids biosynthetic pathway in white lupin still remains unclear. In this study, only 5-hydroxyisoflavonoids, but no 5-deoxyisoflavonoids, were detected in white lupin and other Lupinus species. No 5-deoxyisoflavonoids in Lupinus species are due to lack of CHRs and Type II CHIs. We further found that the CHI gene cluster containing both Type I and Type II CHIs possibly arose after the divergence of Lupinus with other legume clade. LaCHI1 and LaCHI2 identified from white lupin metabolized naringenin chalcone to naringenin in yeast and tobacco (Nicotiana benthamiana), and were bona fide Type I CHIs. We further identified two isoflavone synthases (LaIFS1 and LaIFS2), catalyzing flavanone naringenin into isoflavone genistein and also catalyzing liquiritigenin into daidzein in yeast and tobacco. In addition, LaG6DT1 and LaG6DT2 prenylated genistein at the C-6 position into wighteone. Two glucosyltransferases LaUGT1 and LaUGT2 metabolized genistein and wighteone into its 7-O-glucosides. Taken together, our study not only revealed that exclusive 5-hydroxyisoflavonoids do exist in Lupinus species, but also identified key enzymes in the isoflavonoid biosynthetic pathway in white lupin.

Antiparasitic Effects of Selected Isoflavones on Flatworms

Medicinal plants have been successfully used in the ethno medicine for a wide range of diseases since ancient times. The research on natural products has allowed the discovery of biologically relevant compounds inspired by plant secondary metabolites, what contributed to the development of many chemotherapeutic drugs. Flavonoids represent a group of therapeutically very effective plant secondary metabolites and selected molecules were shown to exert also antiparasitic activity. This work summarizes the recent knowledge generated within past three decades about potential parasitocidal activities of several flavonoids with different chemical structures, particularly on medically important flatworms such as Schistosoma spp., Fasciola spp., Echinococcus spp., Raillietina spp., and model cestode Mesocestoides vogae. Here we focus on curcumin, genistein, quercetin and silymarin complex of flavonolignans. All of them possess a whole spectrum of biological activities on eukaryotic cells which have multi-therapeutic effects in various diseases. In vitro they can induce profound alterations in the tegumental architecture and its functions as well as their activity can significantly modulate or damage worm´s metabolism directly by interaction with enzymes or signaling molecules in dose-dependent manner. Moreover, they seem to differentially regulate the RNA activity in numbers of worm´s genes. This review suggests that examined flavonoids and their derivates are promising molecules for antiparasitic drug research. Due to lack of toxicity, isoflavons could be used directly for therapy, or as adjuvant therapy for diseases caused by medically important cestodes and trematodes.

Metabolic Engineering of Isoflavones: An Updated Overview

Isoflavones are ecophysiologically active secondary metabolites derived from the phenylpropanoid pathway. They were mostly found in leguminous plants, especially in the pea family. Isoflavones play a key role in plant-environment interactions and act as phytoalexins also having an array of health benefits to the humans. According to epidemiological studies, a high intake of isoflavones-rich diets linked to a lower risk of hormone-related cancers, osteoporosis, menopausal symptoms, and cardiovascular diseases. These characteristics lead to the significant advancement in the studies on genetic and metabolic engineering of isoflavones in plants. As a result, a number of structural and regulatory genes involved in isoflavone biosynthesis in plants have been identified and characterized. Subsequently, they were engineered in various crop plants for the increased production of isoflavones. Furthermore, with the advent of high-throughput technologies, the regulation of isoflavone biosynthesis gains attention to increase or decrease the level of isoflavones in the crop plants. In the review, we begin with the role of isoflavones in plants, environment, and its benefits in human health. Besides, the main theme is to discuss the updated research progress in metabolic engineering of isoflavones in other plants species and regulation of production of isoflavones in soybeans.

Naturally Occurring Flavonoids and Isoflavonoids and Their Microbial Transformation: A Review

Flavonoids and isoflavonoids are polyphenolic secondary metabolites usually produced by plants adapting to changing ecological environments over a long period of time. Therefore, their biosynthesis pathways are considered as the most distinctive natural product pathway in plants. Seemingly, the flavonoids and isoflavones from fungi and actinomycetes have been relatively overlooked. In this review, we summarized and classified the isoflavones and flavonoids derived from fungi and actinomycetes and described their biological activities. Increasing attention has been paid to bioactive substances derived from microorganism whole-cell biotransformation. Additionally, we described the utilization of isoflavones and flavonoids as substrates by fungi and actinomycetes for biotransformation through hydroxylation, methylation, halogenation, glycosylation, dehydrogenation, cyclisation, and hydrogenation reactions to obtain rare and highly active biofunctional derivatives. Overall, among all microorganisms, actinomycetes are the main producers of flavonoids. In our review, we also summarized the functional genes involved in flavonoid biosynthesis.

Polyhalogenation of Isoflavonoids by the Termite-Associated Actinomadura sp. RB99

Based on high-resolution tandem mass spectrometry (HR-MS²) and global natural products social molecular networking (GNPS), we found that plant-derived daidzein and genistein derivatives are polyhalogenated by termite-associated Actinomadura species RB99. MS-guided purification from extracts of bacteria grown under optimized conditions led to the isolation of eight polychlorinated isoflavones, including six unreported derivatives, and seven novel polybrominated derivatives, two of which showed antimicrobial activity.

A Pharmacological Overview of Alpinumisoflavone, a Natural Prenylated Isoflavonoid

Over the last decade, several studies demonstrated that prenylation of flavonoids enhances various biological activities as compared to the respective nonprenylated compounds. In line with this, the natural prenylated isoflavonoid alpinumisoflavone (AIF) has been explored for a number of biological and pharmacological effects (therapeutic potential). In this review, we summarize the current information on health-promoting properties of AIF. Reported data evidenced that AIF has a multitherapeutic potential with antiosteoporotic, antioxidant and anti-inflammatory, antimicrobial, anticancer, estrogenic and antiestrogenic, antidiabetic, and neuroprotective properties. However, research on these aspects of AIF is not sufficient and needs to be reevaluated using more appropriate methods and methodology. Further series of studies are needed to confirm these pharmacological effects, and this review should lay the basis for the design of respective investigations. Overall, despite the drawbacks of studies recorded, AIF exhibits a potential as drug candidate.

Isolation of Tryptanthrin and Reassessment of Evidence for Its Isobaric Isostere Wrightiadione in Plants of the Wrightia Genus

A series of Wrightia hanleyi extracts was screened for activity against Mycobacterium tuberculosis H37Rv. One active fraction contained a compound that initially appeared to be either the isoflavonoid wrightiadione or the alkaloid tryptanthrin, both of which have been previously reported in other Wrightia species. Characterization by NMR and MS, as well as evaluation of the literature describing these compounds, led to the conclusion that wrightiadione (1) was misidentified in the first report of its isolation from W. tomentosa in 1992 and again in 2015 when reported in W. pubescens and W. religiosa. Instead, the molecule described in these reports and in the present work is almost certainly the isobaric (same nominal mass) and isosteric (same number of atoms, valency, and shape) tryptanthrin (2), a well-known quinazolinone alkaloid found in a variety of plants including Wrightia species. Tryptanthrin (2) is also accessible synthetically via several routes and has been thoroughly characterized. Wrightiadione (1) has been synthesized and characterized and may have useful biological activity; however, this compound can no longer be said to be known to exist in Nature. To our knowledge, this misidentification of wrightiadione (1) has heretofore been unrecognized.

Isolation of naturally occurring novel isoflavonoids: an update

This review covers the literature concerning the isolation and identification of new naturally occurring isoflavonoids from Leguminosae and non-Leguminous species between 2012–2017.

Legume isoflavone synthase genes have evolved by whole-genome and local duplications yielding transcriptionally active paralogs

Isoflavone synthase (IFS) is the key enzyme of isoflavonoid biosynthesis. IFS genes were identified in numerous species, although their evolutionary patterns have not yet been reconstructed. To address this issue, we performed structural and functional genomic analysis. Narrow leafed lupin, Lupinus angustifolius L., was used as a reference species for the genus, because it has the most developed molecular tools available. Nuclear genome BAC library clones carrying IFS homologs were localized by linkage mapping and fluorescence in situ hybridization in three chromosome pairs. Annotation of BAC, scaffold and transcriptome sequences confirmed the presence of three full-length IFS genes in the genome. Microsynteny analysis and Bayesian inference provided clear evidence that IFS genes in legumes have evolved by lineage-specific whole-genome and tandem duplications. Gene expression profiling and RNA-seq data mining showed that the vast majority of legume IFS copies have maintained their transcriptional activity. L. angustifolius IFS homologs exhibited organ-specific expression patterns similar to those observed in other Papilionoideae. Duplicated lupin IFS homologs retained non-negligible levels of substitutions in conserved motifs, putatively due to positive selection acting during early evolution of the genus, before the whole-genome duplication. Strong purifying selection preserved newly arisen IFS duplicates from further nonsynonymous changes.

Polysubstituted Isoflavonoids from Spatholobus suberectus, Flemingia macrophylla, and Cudrania cochinchinensis

Four hitherto unknown polysubstituted isoflavonoids, including three isoflavans: 7,4'-dihydroxy-8,2',3'-trimethoxyisoflavan (1), 7,2',4'-trihydroxy-8,3'-dimethoxyisoflavan (2), and 7,2',4'-trihydroxy-5-methoxyisoflavan (3), and one prenylated isoflavone cudraisoflavone M (4) were isolated from the ethanol extracts of Spatholobus suberectus (for 1 and 2), Flemingia macrophylla (for 3), and Cudrania cochinchinensis (for 4), respectively. Their structures were established on the basis of extensive spectroscopic analysis. Compounds 1 and 4 exhibited weak cytotoxic activity against five human cancer cell lines (HL-60, A-549, SMMC-7721, MCF-7, and SW-480).

New Caledonia: A 'Hot Spot' for Valuable Chemodiversity. Part 1: Gymnosperms

The flora of New Caledonia encompasses more than 3,000 species and almost 80% of them are endemic. New Caledonia is considered as a 'hot spot' for biodiversity. With the current global loss of biodiversity, and the fact that several drugs and pesticides are becoming obsolete, there is an urgent need to increase sampling and research on new natural products. In this context, we review the chemical information available on New Caledonian native flora from economical perspectives. We expect that a better knowledge of the economic potential will encourage the plantation of native plants for the development of a sustainable economy which will participate in the conservation of biodiversity. In the first part of this review, we discuss the results reported in 18 scientific articles on the chemicals isolated from 23 endemic conifers of New Caledonia. Several bioactive and original products, such as neocallitropsene or libocedrins, have been isolated from these conifers. This review also highlights several groups, such as Podocarpus spp., that are unexplored in New Caledonia despite the fact that they have been described in other countries to contain a wide range of original bioactive compounds. Those plants are considered as priority for future chemical investigations.

Role of quercetin as an alternative for obesity treatment: you are what you eat!

Obesity is one of the most serious global health problems, which increases the risk of other different chronic diseases. The crucial role of oxidative stress in the initiation and progression of obesity leads to the hypothesis that antioxidants can be used as therapeutic agents for obesity treatment. Among antioxidants, much attention has been paid to polyphenols due to their negligible adverse effects. Among them, quercetin is one of the most common dietary antioxidants widely distributed in different plant materials, such as fruits, vegetables and cereals. Quercetin shows a wide range of biological and health-promoting effects, such as anticancer, hepatoprotective, antidiabetic, anti-inflammatory and antibacterial activities. Furthermore, quercetin has anti-obesity activity through mitogen-activated protein kinase and adenine monophosphate-activated protein kinase signaling pathways. In this study, we reviewed the available scientific reports concerning the beneficial role of quercetin against obesity with emphasis on its mechanisms of action.

When plants produce not enough or at all: metabolic engineering of flavonoids in microbial hosts

As a result of the discovery that flavonoids are directly or indirectly connected to health, flavonoid metabolism and its fascinating molecules that are natural products in plants, have attracted the attention of both the industry and researchers involved in plant science, nutrition, bio/chemistry, chemical bioengineering, pharmacy, medicine, etc. Subsequently, in the past few years, flavonoids became a top story in the pharmaceutical industry, which is continually seeking novel ways to produce safe and efficient drugs. Microbial cell cultures can act as workhorse bio-factories by offering their metabolic machinery for the purpose of optimizing the conditions and increasing the productivity of a selective flavonoid. Furthermore, metabolic engineering methodology is used to reinforce what nature does best by correcting the inadequacies and dead-ends of a metabolic pathway. Combinatorial biosynthesis techniques led to the discovery of novel ways of producing natural and even unnatural plant flavonoids, while, in addition, metabolic engineering provided the industry with the opportunity to invest in synthetic biology in order to overcome the currently existing restricted diversification and productivity issues in synthetic chemistry protocols. In this review, is presented an update on the rationalized approaches to the production of natural or unnatural flavonoids through biotechnology, analyzing the significance of combinatorial biosynthesis of agricultural/pharmaceutical compounds produced in heterologous organisms. Also mentioned are strategies and achievements that have so far thrived in the area of synthetic biology, with an emphasis on metabolic engineering targeting the cellular optimization of microorganisms and plants that produce flavonoids, while stressing the advances in flux dynamic control and optimization. Finally, the involvement of the rapidly increasing numbers of assembled genomes that contribute to the gene- or pathway-mining in order to identify the gene(s) responsible for producing species-specific secondary metabolites is also considered herein.

Glycosylation and subsequent malonylation of isoflavonoids in E. coli: strain development, production and insights into future metabolic perspectives

Genistin and daidzein exhibit a protective effect on DNA damage and inhibit cell proliferation. Glycosylation and malonylation of the compounds increase water solubility and stability. Constructed pET15b-GmIF7GT and pET28a-GmIF7MAT were used for the transformation of Escherichia coli and bioconversion of genistein and daidzein. To increase the availability of malonyl-CoA, a critical precursor of GmIF7MAT, genes for the acyl-CoA carboxylase α and β subunits (nfa9890 and nfa9940), biotin ligase (nfa9950), and acetyl-CoA synthetase (nfa3550) from Nocardia farcinia were also introduced. Thus, the isoflavonoids were glycosylated at position 7 by 7-O-glycosyltranferase and were further malonylated at position 6(″) of glucose by malonyl-CoA: isoflavone 7-O-glucoside-6(″)-O-malonyltransferase both from Glycine max. Engineered E. coli produced 175.7 µM (75.90 mg/L) of genistin and 14.2 µM (7.37 mg/L) genistin 6''-O-malonate. Similar conditions produced 162.2 µM (67.65 mg/L) daidzin and 12.4 µM (6.23 mg/L) daidzin 6''-O-malonate when 200 µM of each substrate was supplemented in the culture. Based on our findings, we speculate that isoflavonoids and their glycosides may prove useful as anticancer drugs with added advantage of increased solubility, stability and bioavailability.

Efficacy and safety of Stephania glabra: an alkaloid-rich traditional medicinal plant

Stephania glabra (Roxb.) Miers (Menispermaceae) has long been used for the treatment of asthma, tuberculosis, dysentery, hyperglycaemia, cancer, fever, intestinal complaints, sleep disturbances and inflammation in many Asian countries. It mainly contains alkaloids and, until now, over 30 alkaloids such as bisbenzylisoquinolines, hasubanalactams, berberines and aporphines have been isolated from its tuber. Most of its traditional medicinal activities are scientifically approved by various in vitro and in vivo studies. It shows remarkable anti-psychotic, anti-diabetic, antipyretic, analgesic, antimicrobial and anti-hypertensive activities. This work includes comprehensive information on the ethnobotany, chemistry and pharmacology of S. glabra. This review also focuses on the future perspectives with main emphasis on the establishment of therapeutic index and safety index of the plant. This review concludes that S. glabra has a great potential to treat various diseases, and could be used as a source for novel healthcare products in the near future, which needs further studies.

Adulteration of Ginkgo biloba products and a simple method to improve its detection

Extracts of ginkgo (Ginkgo biloba) leaf are widely available worldwide in herbal medicinal products, dietary supplements, botanicals and complementary medicines, and several pharmacopoeias contain monographs for ginkgo leaf, leaf extract and finished products. Being a high-value botanical commodity, ginkgo extracts may be the subject of economically motivated adulteration. We analysed eight ginkgo leaf retail products purchased in Australia and Denmark and found compelling evidence of adulteration with flavonol aglycones in three of these. The same three products also contained genistein, an isoflavone that does not occur in ginkgo leaf. Although the United States Pharmacopeia - National Formulary (USP-NF) and the British and European Pharmacopoeias stipulate a required range for flavonol glycosides in ginkgo extract, the prescribed assays quantify flavonol aglycones. This means that these pharmacopoeial methods are not capable of detecting adulteration of ginkgo extract with free flavonol aglycones. We propose a simple modification of the USP-NF method that addresses this problem: by assaying for flavonol aglycones pre and post hydrolysis the content of flavonol glycosides can be accurately estimated via a simple calculation. We also recommend a maximum limit be set for free flavonol aglycones in ginkgo extract.

Isoflavonoids in the Amaryllidaceae family

Plants of the Amaryllidaceae family are known as producers of biologically active alkaloids. Besides these a variety of flavonoids, including flavones, chalcones and chromones, have been detected in the Amaryllidaceous plants. In this study, we have analysed 16 representatives of the family for the presence of isoflavonoids. The water/ethanolic extracts were analysed with HPLC-ESI-MS both without any pre-treatment and after immunoaffinity chromatography as a clean-up step. Four individual immunosorbents specific for biochanin A, daidzein and genistein were used. In addition, five enzyme-linked immunosorbent assays specific for the above-mentioned isoflavonoids and their derivatives have been used for the analysis of the extracts after fractionation by semi-preparative HPLC. Fifteen selected isoflavonoids were detected in the studied samples, and the amount of individual compounds ranged between ca. 0.8 and 400 ng/g of dry weight. This study extends the number of known isoflavonoid-producing families within the monocotyledonous plants.

On the radical scavenging activity of isoflavones: thermodynamics of O-H bond cleavage

We have performed Density Functional Theory B3LYP/6-311++G** calculations of reaction enthalpies of antioxidant action mechanisms for nine isoflavones. O-H bond dissociation enthalpies, ionization potentials, proton dissociation enthalpies, proton affinities and electron transfer enthalpies related to Hydrogen Atom Transfer (HAT), Single Electron Transfer-Proton Transfer (SET-PT) and Sequential Proton-Loss Electron-Transfer (SPLET) mechanisms were investigated in gas- and solution-phases. Studies on the radical scavenging ability of isoflavones, contrary to various flavonoids, are still scarce. Thus, understanding of its thermodynamics can be considered beneficial. The selection of isoflavones (daidzein, formononetin, genistein, biochanin A, prunetin, 6-hydroxydaidzein, glycitein, orobol and santal) enables us to evaluate the effects of various structural features, such as the presence of methoxy (4'-OMe, 6-OMe, 7-OMe) and hydroxy (3'-OH, 5-OH, 6-OH) groups, on studied reaction enthalpies. The obtained results show that HAT can be attributed predominantly to the B ring, while SPLET takes place preferentially in the A ring, as was also indicated in experimental works.

Distribution of isoflavones and coumestrol in neglected tropical and subtropical legumes

BACKGROUND

Isoflavones and coumestrol from dietary legumes are plant constituents showing multiple beneficial effects on humans. Owing to their ability to bind with mammalian estrogenic receptors and thereby intervention in several kinds of hormone-related cancers, they have received much attention. Soybean (Glycine max) is currently the major source of isoflavonoids in human diet. However, dozens of tropical and subtropical leguminous species remain unexplored for their isoflavonoids content.

RESULTS

We have analyzed 55 extracts from 41 tropical and subtropical legume species used either in human or animal diet by high-performance liquid chromatography for the content of soy isoflavones, biochanin A, daidzein, daidzin, formononetin, genistein, genistin, sissotrin, ononin and the coumestan coumestrol. Genistein and biochanin A were the most abundant compounds. The highest content of genistein was found in aerial parts of Andira macrothyrsa, seeds of Pachyrhizus tuberosus and aerial parts of Calopogonium mucunoides (598, 250 and 184 µg g(-1), respectively) and biochanin A in aerial parts of Cratylia argentea, C. mucunoides and flowers of A. macrothyrsa (76, 53 and 40 µg g(-1), respectively).

CONCLUSION

None of the samples tested was richer overall source of soy isoflavones and coumestrol than soybean; nevertheless several species (C. mucunoides or A. macrothyrsa) may serve as a promising source of individual compounds.

Estrogenic plant consumption predicts red colobus monkey (Procolobus rufomitratus) hormonal state and behavior

Numerous studies have examined the effects of anthropogenic endocrine disrupting compounds; however, very little is known about the effects of naturally occurring plant-produced estrogenic compounds (i.e., phytoestrogens) on vertebrates. To examine the seasonal pattern of phytoestrogen consumption and its relationship to hormone levels (407 fecal samples analyzed for estradiol and cortisol) and social behavior (aggression, mating, and grooming) in a primate, we conducted an 11-month field study of red colobus (Procolobus rufomitratus) in Kibale National Park, Uganda. The percent of diet from estrogenic plants averaged 10.7% (n=45 weeks; range: 0.7-32.4%). Red colobus fed more heavily on estrogenic Millettia dura young leaves during weeks of higher rainfall, and the consumption of this estrogenic item was positively correlated to both their fecal estradiol and cortisol levels. Social behaviors were related to estradiol and cortisol levels, as well as the consumption of estrogenic plants and rainfall. The more the red colobus consumed estrogenic plants the higher their rates of aggression and copulation and the lower their time spent grooming. Our results suggest that the consumption of estrogenic plants has important implications for primate health and fitness through interactions with the endocrine system and changes in hormone levels and social behaviors.

Phytotoxic effect, uptake, and transformation of biochanin A in selected weed species

Certain isoflavones are plant growth inhibitors, and biochanin A is a major isoflavone in clover species used for weed management. The effect of biochanin A on the monocot weed species Echinochloa crus-galli L. and Lolium perenne L. and dicot species Silene noctiflora L., Geranium molle L., and Amaranthus caudatus L. was evaluated in agar medium bioassays. S. noctiflora and G. molle root growth was progressively inhibited with increasing concentrations of biochanin A, whereas the monocot species were unaffected. With regard to the dicot species, S. noctiflora (EC(50) = 35.80 μM and EC(25) = 5.20 μM) was more susceptible than G. molle (EC(50), EC(25) > 400 μM). S. noctiflora, G. molle, and E. crus-galli root and shoot samples, representing a susceptible, a less susceptible, and a nonsusceptible species, respectively, were analyzed by LC-MS to quantify biochanin A and its transformation products. Biochanin A and its known transformation products genistein, dihydrobiochanin A, pratensein, and p-coumaric acid were quantified. Sissotrin was identified and quantified while assigning unknown peaks. The treated root samples contained more biochanin A, genistein, pratensein, and dihydrobiochanin A than shoot samples.

Prediction of molecular targets of cancer preventing flavonoid compounds using computational methods

Plant-based polyphenols (i.e., phytochemicals) have been used as treatments for human ailments for centuries. The mechanisms of action of these plant-derived compounds are now a major area of investigation. Thousands of phytochemicals have been isolated, and a large number of them have shown protective activities or effects in different disease models. Using conventional approaches to select the best single or group of best chemicals for studying the effectiveness in treating or preventing disease is extremely challenging. We have developed and used computational-based methodologies that provide efficient and inexpensive tools to gain further understanding of the anticancer and therapeutic effects exerted by phytochemicals. Computational methods involving virtual screening, shape and pharmacophore analysis and molecular docking have been used to select chemicals that target a particular protein or enzyme and to determine potential protein targets for well-characterized as well as for novel phytochemicals.

Estrogenic plant foods of red colobus monkeys and mountain gorillas in Uganda

Phytoestrogens, or naturally occurring estrogen-mimicking compounds, are found in many human plant foods, such as soybeans (Glycine max) and other legumes. Because the consumption of phytoestrogens may result in both health benefits of protecting against estrogen-dependent cancers and reproductive costs of disrupting the developing endocrine system, considerable biomedical research has been focused on the physiological and behavioral effects of these compounds. Despite this interest, little is known about the occurrence of phytoestrogens in the diets of wild primates, nor their likely evolutionary importance. We investigated the prevalence of estrogenic plant foods in the diets of two folivorous primate species, the red colobus monkey (Procolobus rufomitratus) of Kibale National Park and mountain gorilla (Gorilla beringei) of Bwindi Impenetrable National Park, both in Uganda. To examine plant foods for estrogenic activity, we screened 44 plant items (species and part) comprising 78.4% of the diet of red colobus monkeys and 53 plant items comprising 85.2% of the diet of mountain gorillas using transient transfection assays. At least 10.6% of the red colobus diet and 8.8% of the gorilla diet had estrogenic activity. This was mainly the result of the red colobus eating three estrogenic staple foods and the gorillas eating one estrogenic staple food. All estrogenic plants exhibited estrogen receptor (ER) subtype selectivity, as their phytoestrogens activated ERβ, but not ERα. These results demonstrate that estrogenic plant foods are routinely consumed by two folivorous primate species. Phytoestrogens in the wild plant foods of these two species and many other wild primates may have important implications for understanding primate reproductive ecology.

Asymmetric Methods for the Synthesis of Flavanones, Chromanones, and Azaflavanones

Flavanones, chromanones, and related structures are privileged natural products that display a wide variety of biological activities. Although flavanoids are abundant in nature, there are a limited number of available general and efficient synthetic methods for accessing molecules of this class in a stereoselective manner. Their structurally simple architectures belie the difficulties involved in installation and maintenance of the stereogenic configuration at the C2 position, which can be sensitive and can undergo epimerization under mildly acidic, basic, and thermal reaction conditions. This review presents the methods currently used to access these related structures. The synthetic methods include manipulation of the flavone/flavanone core, carbon-carbon bond formation, and carbon-heteroatom bond formation.

Flavonoids from the heartwood of the Thai medicinal plant Dalbergia parviflora and their effects on estrogenic-responsive human breast cancer cells

From the heartwood of Dalbergia parviflora, eight new compounds, khrinones A (1), B (2), C (3), D (4), and E (5), isodarparvinol B (6), dalparvin (7), and (3S)-sativanone (22), along with 32 known compounds, have been isolated and characterized as 17 isoflavones, nine isoflavanones, five flavanones, six isoflavans, and three miscellaneous substances. Isolates were evaluated for their cell proliferation stimulatory activity against the MCF-7 and T47D human breast cancer cell lines, and their luciferase inductive effects using luciferase transiently transfected MCF-7/luc and T47D/luc cells were also determined. Isoflavones such as genistein (10), biochanin A (11), tectorigenin (12), and 2'-methoxyformononetin (13) stimulated the proliferation of both cells, and concentrations of lower than 1 muM of these compounds showed equivalent activity to 10 pM of estradiol (E2). The new isoflavanone (22) also showed activity against both cell types, although it was weaker than that of the corresponding isoflavone (2'-methoxyformononetin, 13). Two optically active isoflavanones (22 and 24: (3S)-violanone) stimulated the proliferation of both cell lines at lower concentrations than three racemates (21: vestitone, 23: 7,3'-dihydroxy-4'-methoxyisoflavanone, and 25: 3-O-methylviolanone). Bowdichione (20), an isoflavone with a quinone structure in its B-ring, showed activity against only one cell line associated with MCF-7 in these assays.

Influence of red clover (Trifolium pratense) isoflavones on gene and protein expression profiles in liver of ovariectomized rats

Isoflavones such as genistein, biochanin A, formononetin, and glycetin are fairly abundant in red clover (Trifolium pratense, Fabaceae) and show estrogenic, antioxidant and hypolipidemic activities. To explore these effects mediated by red clover extract at the gene and protein levels, female ovariectomized rats were treated with an isoflavone rich extract of T. pratense. The experimental rats were divided into 2 groups of five animals each: a) control b) experimental group (red clover extract treated with 450mg/kg/day for four days). The treatment influenced the plasma lipid levels differentially. Plasma LDL concentrations were significantly reduced (p<0.05), whereas triglycerides increased (p<0.05). Plasma HDL and total cholesterol remained unchanged. The rat livers were examined for their differential gene expression by Affymetrix Rae230 DNA microarrays. In addition, the total liver proteins were separated by 2D PAGE and proteins, which showed differences in their intensities were identified by MALDI-TOF-MS. The extract influenced the transcript levels of many novel estrogen and non-estrogen responsive genes as well as other regulatory genes. Functional annotations indicate that genes involved in metabolic pathways, information processing, membrane transport regulation, signal transduction and other cellular processes were regulated. Quantitative reverse transcription analysis with real-time PCR confirmed that red clover extract regulates genes involved in lipid metabolism and antioxidation mechanisms. Proteomic analysis support the potential of red clover extract to modulate the lipid metabolism. In summary isoflavone rich red clover extract mediates numerous genomic and non-genomic effects, which influence besides the lipid metabolism a broad range of cellular functions, including metabolic actions, cell cycle regulation and antioxidant activity.

Alveolar and cystic echinococcosis: towards novel chemotherapeutical treatment options

Echinococcus granulosus and Echinococcus multilocularis are cestode parasites, of which the metacestode (larval) stages cause the neglected diseases cystic echinococcosis (CE) and alveolar echinococcosis (AE), respectively. The benzimidazoles albendazole and mebendazole are presently used for the chemotherapeutical treatment, alone or prior to and after surgery. However, in AE these benzimidazoles do not appear to be parasiticidal in vivo. In addition, failures in drug treatments as well as the occurrence of side-effects have been reported, leading to discontinuation of treatment or to progressive disease. Therefore, new drugs are needed to cure AE and CE. Strategies that are currently employed in order to identify novel chemotherapeutical treatment options include in vitro and in vivo testing of broad-spectrum anti-infective drugs or drugs that interfere with unlimited proliferation of cancer cells. The fact that the genome of E. multilocularis has recently been sequenced has opened other avenues, such as the selection of novel drugs that interfere with the parasite signalling machinery, and the application of in silico approaches by employing the Echinococcus genome information to search for suitable targets for compounds of known mode of action.