Phytosterols and flavonoids in Ginkgo biloba L. and Quercus L. and the anti-HIV effect of ginkgo leaf extract
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7 Plant sterols (²-sitosterol, campesterol, and -avenasterol) were found in Ginkgo biloba L. (leaves and nuts) and their content was demonstrated to change during the maturation process. 77Plant sterols (²-sitosterol, campesterol, -Stigmasterol, and -avenasterol were found in five species of Quercus L. (oak leaves and acorns) in significant amounts. Three major flavonoids (quercetin, kaempferol, and isorhamnetin) were investigated in ginkgo and oak leaves. The flavonoid content in ginkgo leaves was affected by maturation changes. Yellowish green ginkgo leaves were found to have maximum total flavonoid content. Oak leaves (five species) were found to have similar flavonoid profile as ginkgo leaves although isorhamnetin was said to be found only in ginkgo leaves before. This study demonstrated that the antioxidant capacity (ORACROO.) of ginkgo leaves decreases with maturity. A synergistic effect on antioxidant capacity appeared to exist when flavonoids (quercetin, kaempferol, and isorhamnetin) were mixed together. Ginkgo nuts, oak leaves and acorns were found to have good antioxidant activity. In bioassays, the flavonoid standards and the mixture were demonstrated to have significant inhibitory effect on TNF- . induced HIV LTR (NF- B) activation. Ginkgo leaves were demonstrated to have strong inhibitory effect on HIV, however, the effect decreases with leaf maturation. Antioxidant capacity of ginkgo leaf extract was found to be correlated to the inhibitory effect on TNF- . induced HIV LTR (NF- B) activation. Mixture of flavonoids displayed a greater anti-HIV effect than individual flavonoid.