There has been increasing interest in the research on flavonoids from plant sources because of their versatile health benefits reported in various epidemiological studies. Since flavonoids are directly associated with human dietary ingredients and health, there is need to evaluate structure and function relationship. The bioavailability, metabolism, and biological activity of flavonoids depend upon the configuration, total number of hydroxyl groups, and substitution of functional groups about their nuclear structure. Fruits and vegetables are the main dietary sources of flavonoids for humans, along with tea and wine. Most recent researches have focused on the health aspects of flavonoids for humans. Many flavonoids are shown to have antioxidative activity, free radical scavenging capacity, coronary heart disease prevention, hepatoprotective, anti-inflammatory, and anticancer activities, while some flavonoids exhibit potential antiviral activities. In plant systems, flavonoids help in combating oxidative stress and act as growth regulators. For pharmaceutical purposes cost-effective bulk production of different types of flavonoids has been made possible with the help of microbial biotechnology. This review highlights the structural features of flavonoids, their beneficial roles in human health, and significance in plants as well as their microbial production.

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Chemistry and Biological Activities of Flavonoids: An Overview

There has been increasing interest in the research of flavonoids from dietary sources, due to growing evidence of the versatile health benefits of flavonoids through epidemiological studies. As occurrence of flavonoids is directly associated with human daily dietary intake of antioxidants, it is important to evaluate flavonoid sources in food. Fruits and vegetables are the main dietary sources of flavonoids for humans, along with tea and wine. However, there is still difficulty in accurately measuring the daily intake of flavonoids because of the complexity of existence of flavonoids from various food sources, the diversity of dietary culture, and the occurrence of a large amount of flavonoids itself in nature. Nevertheless, research on the health aspects of flavonoids for humans is expanding rapidly. Many flavonoids are shown to have antioxidative activity, free-radical scavenging capacity, coronary heart disease prevention, and anticancer activity, while some flavonoids exhibit potential for anti-human immunodeficiency virus functions. As such research progresses. further achievements will undoubtedly lead to a new era of flavonoids in either foods or pharmaceutical supplements. Accordingly, an appropriate model for a precise assessment of intake of flavonoids needs to be developed. Most recent research has focused on the health aspects of flavonoids from food sources for humans. This paper reviews the current advances in flavonoids in food, with emphasis on health aspects on the basis of the published literature, which may provide some guidance for researchers in further investigations and for industries in developing practical health agents.

Flavonoids in Food and Their Health Benefits

Plant phenolic antioxidant and prooxidant activities: phenolics-induced oxidative damage mediated by metals in plants.

https://nph.onlinelibrary.wiley.com/doi/pdf/10.1111/j.1469-8137.2010.03269.x

Multiple functional roles of flavonoids in photoprotection.

The process of polar auxin transport, central to a plant's auxin relations, can be inhibited by a group of synthetic compounds that apparently act by binding to a plasma membrane protein known as the naphthylphthalamic acid (NPA) receptor No endogenous ligand to the NPA receptor, capable of affecting polar auxin transport in plants, has yet been found It is now shown that a group of flavonoids-including quercetin, apigenin, and kaempferol-can specifically compete with [(3)H]NPA for binding to its receptor and can perturb auxin transport in a variety of plant tissues and transport systems in a manner closely paralleling the action of synthetic transport inhibitors Because the active flavonoids are widely distributed in the plant kingdom and exert their effects at micromolar concentrations approximating likely endogenous levels, they may act as natural auxin transport regulators in plants

https://science.sciencemag.org/content/sci/241/4863/346.full.pdf

Naturally occurring auxin transport regulators.

Occurrence and distribution of free flavonoid aglycones in plants

Flavonoids from chemotypes of the goldback fern, Pityrogramma triangularis

Flavonoid patterns in the farina of goldenback and silverback ferns

Abstract Pityrogramma triangularis var. viscosa is one of the clearly defined varieties within the Pityrogramma triangularis complex. The flavonoid constituents of its frond exudate show a pattern characteristic for this taxon. The major component of the exudate could now be isolated. By spectroscopic methods it has been shown to be 2′,6′,4-trihydroxy,4′-m ethoxy,3′-m ethyl dihydrochalcone, a novel natural compound.

Volker H. Dietz

Papers

Occurrence and distribution of free flavonoid aglycones in plants

Flavonoids from chemotypes of the goldback fern, Pityrogramma triangularis

Flavonoid patterns in the farina of goldenback and silverback ferns

A Novel C-Methylated Dihydrochalcone from Pityrogramma triangularis var. viscosa

The occurrence of aurentiacin and flavokawin B on Pityrogramma triangularis var. pallida and Didymocarpus species