About this Research Topic
Flavonoids comprise a diverse and ubiquitous group of polyphenolic plant secondary metabolites. They are constituted by flavonol, flavan-3-ol, anthocyanin, flavanone, flavone, isoflavone and proanthocyanidin subclasses. In the last decades over 10,000 flavonoids have been characterized. They have diverse functions in biological processes, including UV protection, auxin transport inhibition, allelopathy, flower and fruit coloring, fertility, and disease resistance. Flavonoids have been related to plant defense against pathogens and environmental stress. In an evolutionary context, stress-related oxidative damage may have been a significant trigger for the distribution and abundance of flavonoids. In the last years several studies have been made to achieve better knowledge about flavonoids biosynthesis and their cellular targets. The knowledge of biosynthesis pathways has enabled metabolic engineering of flavonoids, which can be produced, accumulated and extracted from living systems.
Flavonoid research has not been restricted to plant research, since they are present in a great range of fruits and vegetables, research has widely extended to the fields of human diet, health benefits and drug research. Flavonoids have considerable antioxidant in vitro activity, which is related to their biological properties. Epidemiological studies have detected the benefit of their intake to prevent the development of some cancers, hepatoxicity, cardiovascular diseases, obesity, diabetes and other diseases. Additionally, studies highlight the antimicrobial activity of flavonoids and influence of glycosylation of on human health. However, more in-depth and well-controlled clinical and experimental assays are indispensable to better determine their potential pharmacological therapeutic value and their health effects in these diseases. The principal factors that have made it difficult to obtain clear results on flavonoids health effects are (i) a dearth of information on their bioavailability and metabolism, (ii) lack of validated in vivo biomarkers, and (iii) lack of long-term assays.
Flavonoids have promoted notable attention as a result of their important functions in plants, their structural diversity and biological activities.The study in all these fields is based decisively on precise analytical data. The LC-MS constitutes an essential tool to provide new advances in the natural flavonoids chemodiversity, evolution throughout the plant kingdom, and human bioavailability and metabolization. This technique allows fast identification and accurate quantification of low levels flavonoids in different matrices. Nowadays, ultra high pressure LC (UHP-LC), and comprehensive two-dimensional LC (LC x LC), are the methodologies which provide improved LC separation of flavonoids. Other powerful analytical techniques have emerged in the last years, which may also be useful for the analysis of flavonoids.
This Research Topic is devoted to the latest new insights, in the form of Reviews and Original Research articles, as well as Opinion and Perspective papers covering several aspects of plant flavonoids including:
1) Flavonoid biosynthesis and their cellular targets: how plants regulate the types and amounts of flavonoids that are produced in response to different signals; identification of genes and enzyme involved in flavonoid biosynthesis; and correlations between primary metabolism and flavonoid biosynthesis.
2) Chemistry/Analytical methods of flavonoids: extraction, separation and purification analytical methods of flavonoids from plant and other matrices, such as food or human samples; structural elucidation.
3) Biological activities of flavonoids: in vitro laboratory experiments, especially antioxidant and antimicrobial assays; human bioavailability and metabolism studies; potential mechanisms of action and biological targets for drug development, therapeutic value in human diseases. Note that studies carried out only with crude extracts will not be considered for review.
Keywords: Flavonoids, Biosynthesis, Antioxidant, Health effects, Chromatography
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