Kaempferol

Kaempferol is a natural flavonol widely distributed in fruits, vegetables, and herbs, including grapes, tomatoes, broccoli, tea, and Ginkgo biloba leaves. This biologically active compound exhibits many pharmacological activities including antioxidant, antiinflammatory, antimicrobial, antidiabetic, and anticancer activities.
The pharmacokinetics of kaempferol has been studied in vitro and in vivo, both in rats and humans. Flavonols such as kaempferol are commonly ingested as glycosides. The types and attachments of saccharide impact bioavailability, and also bioactivity. Glycosides are highly polar compounds, a property that greatly impacts their absorption, whereas the intermediate polarity of aglycones facilitates it. For some types of glycosides, previous hydrolysis to absorbable aglycones is needed, and others can be absorbed without hydrolysis. Like other flavonoids, kaempferol is mainly absorbed in the small intestine. The lipophilicity of aglycone kaempferol facilitates its absorption by passive diffusion, but evidence suggests that it can also be absorbed by facilitated diffusion or active transport.The nature of sugar linking will influence the compound uptake, as enterocytes have a preference for glucose, as membrane-bound beta-glucosidase breaks down the glucoside before absorption. Kaempferol glucosides with many sugar units in their structure travel to the large intestine, where gut microbiota will remove terminal saccharides exposing the glucose, and then absorption by enterocytes occurs . Studies have shown that kaempferol-O-glycosides decomposition can be extended to a breakdown process known as C-ring fission (C-ring is the central ring of the flavonoid structure) to form simple phenolic compounds such as 4-hydroxyphenylacetic acid, phloroglucinol and 4- methylphenol, which can either be absorbed or excreted in feces. After absorption, conjugated forms of kaempferol, some phenolic compounds produced by the colon microflora, kaempferol, and some kaempferol glycosides can reach systemic circulation and tissues and are transported along with intestinal metabolites to the liver, where a part of them are metabolized (mainly compounds with poor hydro solubility). In the liver, and also in enterocytes, metabolism involves the phase I (oxidation and O-demethylation) and the phase II pathway (sulfation, glucuronidation, and methylation) followed by distribution to body tissues and urine excretion .