Prenylated flavonols are known as phytoestrogen and have good bioactivties. However, their abundances in nature are pretty low. It is required to find an efficient synthesis technique. Icariin is a prenylated flavonol glycoside with low cost. It can be used to synthesize different prenylated flavonols. A combination of cellulase and trifluoacetic acid hydrolysis could effectively remove rhamnose and glucose from icariin. Icaritin, anhydroicaritin and wushanicaritin were the leading prenylated flavonol products. Their affinities to estrogen receptors α and β were predicted by docking study. The weak affinity of wushanicaritin indicated that prenyl hydroxylation impaired its affinity to estrogen receptor β. The prenyl cyclization led to a loss of affinity to both receptors. The interactions between icaritin and ligand binding cavity of estrogen receptor β were simulated. π-π stacking and hydrophobic forces were predicted to be the dominant interactions positioning icaritin, which induced the helix (H12) forming an activated conformation.

We investigated the constituents of Leucaena leucocephala foliage collected from Guangdong province in China and isolated 17 diverse flavonoids (1-17), including flavones (5-9, 11, and 12), flavonols (1, 10, and 16), flavanone 4, flavanonol 15, and flavonol glycosides (2, 3, 13, 14, and 17). Flavonoids quercetin (1), quercetin-3- O-α-rhamnopyranoside (2), and myricetin-3- O-α-rhamnopyranoside (17) were the major flavonoids components in L. leucocephala leaves, at a total concentration of about 2.5% of dry matter. pHRE-Luc inductive activity to mimic the activation of erythropoietin (EPO) gene, anti-inflammatory, antidiabetic, and antioxidant activities of isolated flavonoids (1-17) were evaluated. Flavonoids 7, 10, and 13 could strongly induce the transcriptional activity of pHRE-Luc, which indicated their potential to induce the expression of EPO. Flavonoids 7, 10, 13, and 17 displayed strong anti-inflammatory activity, relatively equal to the positive control dexamethasone. Flavonoids 1, 2, 3, 11, 12, 16, and 17 showed stronger antioxidant activities of DPPH radical scavenging capacity than ascorbic acid. Flavonoids 1, 2, and 10 showed weak cellular antioxidant activities against tert-butyl hydroperoxide (tBHP) induced ROS formation. Flavonoid rhamnoside 2 and arabinoside 3 undergone deglycosylation to the aglycone quercetin under anaerobic incubation with cattle rumen microorganisms. Furthermore, the potential health benefits for ruminant of flavonoids, which was rich in L. leucocephala foliage, was also discussed.