Several plant bioactive compounds have exhibited functional activities that suggest they could play a remarkable role in preventing a wide range of chronic diseases. The largest group of naturally-occurring polyphenols are the flavonoids, including apigenin. The present work is an updated overview of apigenin, focusing on its health-promoting effects/therapeutic functions and, in particular, results of in vivo research. In addition to an introduction to its chemistry, nutraceutical features have also been described. The main key findings from in vivo research, including animal models and human studies, are summarized. The beneficial indications are reported and discussed in detail, including effects in diabetes, amnesia and Alzheimer’s disease, depression and insomnia, cancer, etc. Finally, data on flavonoids from the main public databases are gathered to highlight the apigenin’s key role in dietary assessment and in the evaluation of a formulated diet, to determine exposure and to investigate its health effects in vivo.

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The Therapeutic Potential of Apigenin.

This review gives an updated picture of each class of phenolic compounds and their properties. The most common classification implies the subdivision of phenolics in two main groups: flavonoids (e.g., anthocyanins, flavanols, flavanones, flavonols, flavonones, and isoflavones) and non-flavonoids (e.g., phenolic acids, xanthones, stilbens, lignans, and tannins) polyphenols. The great interest in polyphenols is associated with their high potential application for food preservation and for therapeutic beneficial use. The relationship between polyphenol intake and human health has been exploited with special reference to cardiovascular diseases, hypertension, diabetes, metabolic syndrome, obesity, and cancer. The use of current existing databases of bioactive compounds including polyphenols is described as key tools for human health research.

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Polyphenols: A concise overview on the chemistry, occurrence, and human health

The dietary flavonoids, especially their glycosides, are the most vital phytochemicals in diets and are of great general interest due to their diverse bioactivity. The natural flavonoids almost all exist as their O-glycoside or C-glycoside forms in plants. In this review, we summarized the existing knowledge on the different biological benefits and pharmacokinetic behaviors between flavonoid aglycones and their glycosides. Due to various conclusions from different flavonoid types and health/disease conditions, it is very difficult to draw general or universally applicable comments regarding the impact of glycosylation on the biological benefits of flavonoids. It seems as though O-glycosylation generally reduces the bioactivity of these compounds - this has been observed for diverse properties including antioxidant activity, antidiabetes activity, anti-inflammation activity, antibacterial, antifungal activity, antitumor activity, anticoagulant activity, antiplatelet activity, antidegranulating activity, antitrypanosomal activity, influenza virus neuraminidase inhibition, aldehyde oxidase inhibition, immunomodulatory, and antitubercular activity. However, O-glycosylation can enhance certain types of biological benefits including anti-HIV activity, tyrosinase inhibition, antirotavirus activity, antistress activity, antiobesity activity, anticholinesterase potential, antiadipogenic activity, and antiallergic activity. However, there is a lack of data for most flavonoids, and their structures vary widely. There is also a profound lack of data on the impact of C-glycosylation on flavonoid biological benefits, although it has been demonstrated that in at least some cases C-glycosylation has positive effects on properties that may be useful in human healthcare such as antioxidant and antidiabetes activity. Furthermore, there is a lack of in vivo data that would make it possible to make broad generalizations concerning the influence of glycosylation on the benefits of flavonoids for human health. It is possible that the effects of glycosylation on flavonoid bioactivity in vitro may differ from that seen in vivo. With in vivo (oral) treatment, flavonoid glycosides showed similar or even higher antidiabetes, anti-inflammatory, antidegranulating, antistress, and antiallergic activity than their flavonoid aglycones. Flavonoid glycosides keep higher plasma levels and have a longer mean residence time than those of aglycones. We should pay more attention to in vivo benefits of flavonoid glycosides, especially C-glycosides.

Dietary flavonoid aglycones and their glycosides: Which show better biological significance?

Flavones: Food Sources, Bioavailability, Metabolism, and Bioactivity

Advances in the biotechnological glycosylation of valuable flavonoids

Scope: Flavones have reported anti-inflammatory activities, but the ability of flavone-rich foods to reduce inflammation is unclear. Here, we report the effect of flavone glycosylation in the regulation of inflammatory mediators in vitro and the absorption of dietary flavones in vivo. Methods and results: The anti-inflammatory activities of celery extracts, some rich in flavone aglycones and others rich in flavone glycosides, were tested on the inflammatory mediators tumor necrosis factor (TNF-) and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-B) in lipopolysaccharide-stimulated macrophages. Pure flavone aglycones and aglycone-rich extracts effectively reduced TNF- production and inhibited the transcriptional activity of NF-B, while glycoside-rich extracts showed no significant effects. Deglycosylation of flavones increased cellular uptake and cytoplasmic localization as shown by high-performance liquid chromatography (HPLC) and microscopy using the flavonoid fluorescent dye diphenylboric acid 2-aminoethyl ester (DPBA). Celery diets with different glycoside or aglycone contents were formulated and absorption was evaluated in mice fed with 5 or 10% celery diets. Relative absorption in vivo was significantly higher in mice fed with aglycone-rich diets as determined by HPLC-MS/MS (where MS/MS is tandem mass spectrometry). Conclusion: These results demonstrate that deglycosylation increases absorption of dietary flavones in vivo and modulates inflammation by reducing TNF- and NF-B, suggesting the potential use of functional foods rich in flavones for the treatment and prevention of inflammatory diseases.

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Flavone deglycosylation increases their anti-inflammatory activity and absorption

Effects of food formulation and thermal processing on flavones in celery and chamomile

Three vineyard floor management strategies—reflective (white) geotextile mulch, black geotextile mulch, and an herbicide strip in vine rows—were evaluated with regard to canopy light and temperature, vine growth, and fruit composition of Cabernet franc. Using a randomized complete block design, two trials were conducted at commercial vineyards in the Finger Lakes Region of New York during 2004 to 2005. Black and white geotextiles in 2-m-wide or 5-m-wide strips almost doubled vine size after two years, but did not affect overwinter primary bud survival compared with mowed sod row middles with undervine herbicide control treatment. In both experiments, the white geotextile mulch significantly increased sunlight reflected from the vineyard floor into the vine cluster zone, especially early in the growing season. Vines mulched with white geotextile had greater yields, but there were no significant differences in fruit ripening time or fruit chemical composition at harvest, and minimal differences in vine nutrient status among the floor management systems. The increased yield values in reflective geotextile plots were not sufficient to compensate for the substantially greater costs of geotextiles relative to the standard practices of mowed sod row middles with undervine herbicide weed control.

Influence of Geotextile Mulches on Canopy Microclimate, Yield, and Fruit Composition of Cabernet franc

Four undervine floor management techniques—composted bark mulch, reflective (white) and black geotextile mulches, and mechanical soil cultivation—were evaluated with regard to weed suppression, canopy sunlight regimes, soil temperatures, vine growth, and fruit composition of Pinot noir at an organically managed vineyard in the Finger Lakes Region of New York during 2004 and 2005. Composted bark mulch and black or white geotextiles significantly reduced weed biomass compared with cultivation, but did not affect vine vigor or overwintering primary bud survival in either year. Vines mulched with white geotextile had significantly greater yields, but there were few differences among treatments in ripening time or fruit composition at harvest. The white geotextile increased yields in one year of this experiment, but those yield increases did not compensate for the higher costs of geotextiles compared with the grower’s standard practice of mechanical soil cultivation.

Gregory L. Hostetler

Papers

Flavones: Food Sources, Bioavailability, Metabolism, and Bioactivity

Flavone deglycosylation increases their anti-inflammatory activity and absorption

Effects of food formulation and thermal processing on flavones in celery and chamomile

Influence of Geotextile Mulches on Canopy Microclimate, Yield, and Fruit Composition of Cabernet franc

Influence of undervine floor management on weed competition, vine nutrition, and yields of Pinot noir.