Possible ways of fagopyrin biosynthesis and production in buckwheat plants

Advancements in multi-omics for nutraceutical enhancement and traits improvement in buckwheat

Buckwheat (Fagopyrum spp.) is a typical pseudocereal, valued for its extensive nutraceutical potential as well as its centuries-old cultivation. Tartary buckwheat and common buckwheat have been used globally and become well-known nutritious foods due to their high quantities of: proteins, flavonoids, and minerals. Moreover, its increasing demand makes it critical to improve nutraceutical, traits and yield. In this review, bioactive compounds accumulated in buckwheat were comprehensively evaluated according to their chemical structure, properties, and physiological function. Biosynthetic pathways of flavonoids, phenolic acids, and fagopyrin were methodically summarized, with the regulation of flavonoid biosynthesis. Although there are classic synthesis pathways presented in the previous research, the metabolic flow of how these certain compounds are being synthesized in buckwheat still remains uncovered. The functional genes involved in the biosynthesis of flavonols, stress response, and plant development were identified based on multi-omics research. Furthermore, it delves into the applications of multi-omics in improving buckwheat's agronomic traits, including: yield, nutritional content, stress resilience, and bioactive compounds biosynthesis. While pangenomics combined with other omics to mine elite genes, the regulatory network and mechanism of specific agronomic traits and biosynthetic of bioactive components, and developing a more efficient genetic transformation system for genetic engineering require further investigation for the execution of breeding designs aimed at enhancing desirable traits in buckwheat. This critical review will provide a comprehensive understanding of multi-omics for nutraceutical enhancement and traits improvement in buckwheat.

Phytochemistry, Bioactivities of Metabolites, and Traditional Uses of Fagopyrum tataricum

In Tartary buckwheat (Fagopyrum tataricum), the edible parts are mainly grain and sprouts. Tartary buckwheat contains protecting substances, which make it possible for plants to survive on high altitudes and under strong natural ultraviolet radiation. The diversity and high content of phenolic substances are important for Tartary buckwheat to grow and reproduce under unfriendly environmental effects, diseases, and grazing. These substances are mainly flavonoids (rutin, quercetin, quercitrin, vitexin, catechin, epicatechin and epicatechin gallate), phenolic acids, fagopyrins, and emodin. Synthesis of protecting substances depends on genetic layout and on the environmental conditions, mainly UV radiation and temperature. Flavonoids and their glycosides are among Tartary buckwheat plants bioactive metabolites. Flavonoids are compounds of special interest due to their antioxidant properties and potential in preventing tiredness, diabetes mellitus, oxidative stress, and neurodegenerative disorders such as Parkinson's disease. During the processing and production of food items, Tartary buckwheat metabolites are subjected to molecular transformations. The main Tartary buckwheat traditional food products are bread, groats, and sprouts.

Molecular Shield for Protection of Buckwheat Plants from UV-B Radiation

Tartary buckwheat (Fagopyrum tataricum (L.) Gaertn.) and common buckwheat (Fagopyrum esculentum Moench) are adapted to growing in harsh conditions of high altitudes. Ultraviolet radiation at high altitudes strongly impacts plant growth and development. Under the influence of ultraviolet radiation, protecting substances are synthesized in plants. The synthesis of UV-B defense metabolites is genetically conditioned, and their quantity depends on the intensity of the ultraviolet radiation to which the plants and plant parts are exposed. These substances include flavonoids, and especially rutin. Other substances with aromatic rings of six carbon atoms have a similar function, including fagopyrin, the metabolite specific for buckwheat. Defensive substances are formed in the leaves and flowers of common and Tartary buckwheat, up to about the same concentration in both species. In comparison, the concentration of rutin in the grain of Tartary buckwheat is much higher than in common buckwheat. Flavonoids also have other functions in plants so that they can protect them from pests and diseases. After crushing the grains, rutin is exposed to contact with the molecules of rutin-degrading enzymes. In an environment with the necessary humidity, rutin is turned into bitter quercetin under the action of rutin-degrading enzymes. This bitterness has a deterrent effect against pests. Moreover, flavonoids have important functions in human nutrition to prevent several chronic diseases, including obesity, cardiovascular diseases, gallstone formation, and hypertension.

Theoretical Studies on the Structure and Intramolecular Interactions of Fagopyrins-Natural Photosensitizers of Fagopyrum

Simple Summary

The study determines the spatial structure and intramolecular interactions of fagopyrins—natural photosensitizers of Fagopyrum species. In silico calculations show many fagopyrin conformers characterized by the formation of strong intramolecular interactions.

Abstract

Compounds characterized by a double-anthrone moiety are found in many plant species. One of them are fagopyrins—naturally occurring photosensitizers of Fagopyrum. The photosensitizing properties of fagopyrins are related to the selective absorption of light, which is a direct result of their spatial and electronic structure and many intramolecular interactions. The nature of the interactions varies in different parts of the molecule. The aim of this study is to determine the structure and intramolecular interactions of fagopyrin molecules. For this purpose, in silico calculations were used to perform geometry optimization in the gas phase. QTAIM and NCI analysis suggest the formation of the possible conformers in the fagopyrin molecules. The presence of a strong OHO hydrogen bond was shown in the anthrone moiety of fagopyrin. The minimum energy difference for selected conformers of fagopyrins was 1.1 kcal∙mol⁻¹, which suggested that the fagopyrin structure may exist in a different conformation in plant material. Similar interactions were observed in previously studied structures of hypericin and sennidin; however, only fagopyrin showed the possibility of brake the strong OHO hydrogen bond in favor of forming a new OHN hydrogen bond.

Metabolomics integrated with transcriptomics reveals the changes during developmental stages in Shiraia bambusicola

Shiraia bambusicola is a fungus with high economic value widely used in medicine, agriculture, and food. We wished to understand the genes and metabolites changes involved in the different developmental stages of S. bambusicola. So, to reveal key genes and metabolites in the main active metabolite, the  were analyzed in different developmental stages of S. bambusicola fruiting body. A total of 29,137 Unigenes were annotated. In the whole growth process, differentially expressed genes were involved in the pathways of cytochrome P450, transcription factors, transporters, and so on, while in the early stage of growth, genes enriching to synthesis pathways of basic substances. In the middle stage of growth, genes with more prominent changes were involved in the pathways of the cell cycle, cancer mechanisms, and aminobenzoate degradation; in the later stage of growth, differentially expressed genes that enriched synthesis pathways of secondary metabolites. A total of 612 metabolites were detected from different growth stages of S. bambusicola. Among them, coumarins, alkaloids, rutin, liquiritigenin, quercetin, and other medically relevant metabolites were detected for the first time. We have identified 31 secondary metabolites,  relevantly only accumulated in the early and middle stage, but not detected in the later stage, such as flavonols, coumarins, nucleotides and its derivates and hydroxycinnamoyl derivatives. The differential genes and metabolites of the same group were enriched in 127 pathways, and more significantly in ubiquinone and other terpenoid quinone biosynthesis, phenylalanine metabolism, phenylalanine, tyrosine and tryptophan biosynthesis, and phenylpropanoid biosynthesis. The correlation networks of several significantly enriched pathways were analyzed, and the relationships within and between these pathways, genes, and metabolites, were analyzed. The synthetic pathway of hypocrellin has been speculated upon. We believe that hypocrellin is synthesized in S. bambusicola via the shikimic acid pathway followed by phenylalanine, tyrosine, and tryptophan biosynthesis pathway, then the ubiquinone and other terpenoid quinone biosynthesis pathway, and finally a series of polymerization and modification reactions. Several genes and metabolites involved in the biosynthesis of hypocrellin have been identified. This study provides a reference for further research on S. bambusicola, by providing a basis for its use and development.

Implications of Fagopyrin Formation In Vitro by UV Spectroscopic Analysis

The present work aims at studying the possible biosynthesis of fagopyrin in buckwheat plants with an attempt to address the existing gaps. The developed method of differential spectrophotometry can be used for identification of naphthodianthrones fagopyrins. It was found that in the vegetative mass of buckwheat plants, fagopyrin precursor-2-(piperidine-2-yl)-emodindianthron could be present. As fagopyrin can be produced by light effect, the temperature factor may influence the formation of protofagopyrin in vitro. An optimum temperature range was estimated for protofagopyrin formation. A possible fagopyrin biosynthesis under in vitro conditions was suggested.

The Therapeutic Potential of the Labdane Diterpenoid Forskolin

Forskolin is mainly found in the root of a plant called Coleus forskohlii (Willd.) Briq., which has been used in the traditional medicine of Indian Ayurvedic and Southeast Asia since ancient times. Forskolin is responsible for the pharmacological activity of this species. Forskolin is a labdane diterpenoid with a wide biological effect. Several studies suggested a positive role of forskolin on heart complications, respiratory disorders, high blood pressure, obesity, and asthma. There are numerous clinical and pre-clinical studies representing the effect of forskolin on the above-mentioned disorders but more clinical studies need to be performed to support its efficacy.

Fagopyrins and Protofagopyrins: Detection, Analysis, and Potential Phototoxicity in Buckwheat

Buckwheat contains many healthy nutrients, and its consumption is therefore increasing. Buckwheat also contains fluorescent phototoxic fagopyrins. A systematic review of fagopyrins and the phototoxicity of buckwheat found that reliable quantitative data on fagopyrin toxicity are not yet available. Generally, buckwheat seeds, flour, and teas are safe in normal amounts. Diets extensively composed of buckwheat sprouts, herbs, and particularly flowers or of fagopyrin-rich buckwheat extracts may cause fagopyrism. A reference standard is needed, as it would enable the accurate evaluation of fagopyrin content in buckwheat products and would allow proper testing of their as yet unknown physical, chemical, and biological characteristics.

Comparative analysis of flavonoids and polar metabolite profiling of Tanno-original and Tanno-high rutin buckwheat

Rutin is an important indicator for evaluating the quality of buckwheat. In this study, flavonoid biosynthesis was compared between two common cultivars (an original and a high-rutin line) of buckwheat, Fagopyrum esculentum Moench. Transcriptional levels of the main flavonoid biosynthetic genes were analyzed by real-time PCR, and main flavonoid metabolites were detected by high-performance liquid chromatography (HPLC); levels of gene expression varied among organs of the two cultivars. Significantly higher transcription levels of most flavonoid biosynthetic genes, except FeFLS1, were detected in stems of the high-rutin line than in stems of the original line. FeCHI and FeFLS2 genes also showed higher expression levels in seeds of the high-rutin cultivar. In contrast, FePAL, FeC4H, Fe4CL1, FeCHS, FeF3H, FeF3'H, FeFLS2, and FeDFR were highly detected in the roots of the original line. The HPLC results indicated 1.73-, 1.62-, and 1.77-fold higher accumulation of rutin (the primary flavonoid compound) in leaves, stems, and mature seeds of the high-rutin cultivar (24.86, 1.46, and 1.36 μg/mg, respectively) compared with the original cultivar (14.40, 0.90, and 0.77 μg/mg, respectively). A total of 46 metabolites were identified from seeds by gas chromatography-time-of-flight mass spectrometry. The metabolite profiles were subjected to principal component analysis (PCA). PCA could clearly differentiate the original and high-rutin cultivars. Our results indicate that the high-rutin cultivar could be an excellent alternative for buckwheat culture, and we provide useful information for obtaining this cultivar.