Mulberry leaf extract components, especially
flavonoids (ie, quercetin, rutin, and isoquercitrin), possess
the free radical scavenging effect, showing the possibility of
antioxidant activity [23]. The antioxidant compounds in
mulberry leaf ethanol extract are able to pass from the small
intestine into the blood circulation with their intact
antioxidant activity in the rat [14]. For quercetin, its
metabolites produced by microbial in the gut are absorbed
and still retain systemic antioxidant activity[24]. Anthocyanin is another antioxidant found in wild mulberry fruit and is
absorbed from gastrointestinal tract, even at the small
amount, giving antioxidant activity in plasma[25]. It has
also been demonstrated that synthetic quercetin administration to diabetic rats restored the vascular function [26,27].
Moreover, the clinical effectiveness of a flavonoid-rich
dietary supplement in alleviating the vascular complication
in diabetic patients has been reported