Studies On The Extraction And Antineoplastic Activities Of The Flavonoids From Ginkgo Biloba Leaves

There are many constituents in Ginkgo biloba leaves, includingflavonoids, terpene lactones, alkaloids, polysaccharides,hydroxybenzenes, amino acids and microelements. Among these components,the content of flavonoids is higher, which mainly composed of glycosidesof quercetin, kaempferol and isorhamnetin. Many researches haveidentified that quercetin possesses vasodilatation, antiflammation,antioxidation, antivirus, immunomodulation and other importanttherapeutic activities. In this paper total flavonoids were extractedfrom Ginkgo biloba leaves and the primary determination of the content,antitumor and immunomodulatory effects of total flavonoids and quercetinwere studied.Total flavonoids were obtained after four solvents( water,methanol,ethanol and acetone) with ultrasonic wave treatment and petroleum etherextraction. The single wavelength ultraviolet spectrophotometry was usedto determine the content of total flavonoids. The extraction efficienciesof acetone(1.6247%), methanol(1.3363%) and ethanol(1.2451%)are higherthan that of water(1.1702%). In addition, the content of quercetin inthe flavonoids extracted by ethanol solvent determined by HPLC is 0.20153%,so the content of quercetin in the Ginkgo biloba leaves is 0.3947mg/g.The growth inhibitory effects of the flavonoids from Ginkgo bilobaleaves and quercetin on cancer cells were observed by MTT assay. Theresults show that the flavonoids have antitumor activity on humanhepatocellular carcinoma cell line HepG2. Quercetin also have antitumoreffects on HepG2 and gastric cancer cell line BGC823 by inhibitingproliferation of tumor cells in time and dose dependent manners.The shapes of cancer cells treated with quercetin were detected withacridine orange fluorescence staining and the results reveal that the twocell lines show obvious apoptosis bodies, indicating quercetin can inducecell apoptosis. DNA extracted from cells treated with quercetin exhibitsDNA ladder by electrophoresis. Moreover, flow cytometry (FCM) indicatethat cell cycle progressions are delayed at GO/G1 phase by quercetin andthe apoptosis rate also increases as compared to controls.In vitro the flavonoids from Ginkgo biloba leaves and quercetin showno obviously effects on the unactivated spleen cells but inhibitoryeffects on the over-proliferation of spleen cells from natural micetogether with ConA or LPS. The inhibition rate of quercetin on the growthof hypostatic tumor S-180 in the body of Kunming mice is 23.39% at doseof 100mg/kg body weight with i.p. injection. Both thymus index and spleenindex decrease compared to controls. The results suggest that quercetinmaybe inhibit S-180 hypostatic tumor through direct cytotoxicity effectbut not immunocytes.All above results suggest that both the flavonoids from Ginkgo bilobaleaves and quercetin have antitumor activities. Therefore it can providesome references for making further exploitation of ginkgo biloba leaves.