杜仲是一種傳統中藥材，其樹皮經炮製與其他中藥材同時使用，具有補肝腎強筋骨安胎等作用。由於採取杜仲樹皮會造成杜仲樹的乾枯，而杜仲葉也具有類似樹皮的成份，因此近年來杜仲的樹葉經曬乾加工後，做成杜仲茶包，在日本與台灣當作保健食品銷售。本計畫第一階段定量杜仲茶萃取液之quercetin含量，並以體外實驗及細胞實驗評估杜仲茶之抗氧化作用及安全性。我們以Ames test strain TA100測試其致突變性時發現，杜仲葉各種萃取液均不具有致突變性。我們以高效液相層析法及質譜儀確定杜仲葉的水萃取液中含有quercetin，並估計每克杜仲葉(乾重)之水萃取液含有106.4微克quercetin。接著我們評估杜仲葉萃取液之抗氧化性。在鐵離子存在下，杜仲葉各種萃取液對完整紅血球及紅血球細胞膜具有抗氧化作用。接著最後我們利用流質細胞計數法再次證實杜仲葉的水萃取液在人類肝癌細胞HepG2中具有抗氧化作用。杜仲葉各種萃取液在Ames test strain TA100，SOS/Umu無致突變性，對肺細胞DNA及外周血網織紅細胞無基因毒性，但我們以杜仲葉水萃取液處理小鼠周邊淋巴細胞之後，以彗星試驗偵測到細胞發生DNA斷裂的現象。因此杜仲葉萃取液的安全性需要進一步評估。 Tochu, which is the dry stem bark of Eucommia ulmoides Oliv, is one of the oldest herbs in traditional Chinese medicine. Since Cortex Eucommiae is difficult to obtain, its leaves which contain same components as the cortex, have been used for medical research. Recently Tochu tea, an aqueous extract of Eucommia ulmoides Oliv leaves, has become a popular beverage in Japan and Taiwan. The objective of this project is to evaluate the antioxidant activity of aqueous extract of Tochu leave and its genotoxicity. We found that tochu-leaf extract was not mutagenic in Ames' test (TA100 strain). Later, we identified quercetin in tochu-leaf with HPLC-MASS and estimate 106.4mg quercetin /g of dried tochu-leaf. Antioxidant effect of tochu-leaf extract was evaluated in intact RBC, RBC-gost, and human hepatoma HepG2 cells. We found that tochu-leaf extact reduced-butyl hydroperoxide-induced lipid peroxidation in intact RBC and RBC-gost system, and oxidative stress in HepG2 cells. We further evaluate the genotoxicity of tochu-leaf extract in vitro and in vivo. We found that tochu-leaf extract was negative in Umu test, DNA cross-linking assay, micronuclei assay. However, it caused DNA stand breaks as measured with the Comet assay.
