| 摘要: | 本研究目的是探討不同乾燥方式對銀杏葉(Ginkgo biloba leaf)抗氧化能力及酪胺酸酶活性之影響。研究結果顯示，銀杏葉之一般成分，水分為74.15%，粗蛋白為3.80%，粗脂肪為2.41%，灰分為3.15%及碳水化合物為16.49%，每克銀杏葉中含有抗氧化營養素維生素C 1.08毫克、維生素E 2.29毫克、硒 76.20微克及鋅 4.15微克。不同乾燥方式處理銀杏葉之乙醇萃取物及銀杏葉水萃取物產率為5.67-25.40%及6.20-26.93%。有效成分方面，銀杏葉乙醇萃取物每毫克之總酚含量為24.07-60.00微克；不同乙醇萃取銀杏葉時間，以乙醇萃取12小時之總酚含量較高；不同乾燥方式處理銀杏葉乙醇萃取物，以室溫乾燥銀杏葉乙醇萃取物總酚含量較高；銀杏葉乙醇萃取物之類黃酮含量(檞皮素、異鼠李素及堪非黃酮醇)為每毫克萃取物中含8.00-26.56微克。銀杏葉水萃取物每毫克之總酚含量為10.69-39.07微克；不同溫度水萃取銀杏葉，以60℃水萃取銀杏葉之總酚含量較高；不同乾燥方式處理銀杏葉水萃取物以室溫乾燥銀杏葉水萃取物總酚含量較高；銀杏葉水萃取物之類黃酮含量(檞皮素、異鼠李素及堪非黃酮醇)為每毫克萃取物中含2.60-12.95微克。在抗氧化能力方面，商業配方(60毫克銀杏葉萃取物中包含14.4毫克黃酮糖苷及3.6毫克類萜類三內酯)、銀杏葉乙醇萃取物及銀杏葉水萃取物之DPPH自由基半數清除劑量分別為每毫升76.48微克、574.80-902.95微克及244.17-375.89微克；不同乾燥方式處理銀杏葉之DPPH自由基半數清除能力均以新鮮銀杏葉乙醇萃取物或新鮮銀杏葉水萃取物較佳。每毫克商業配方、銀杏葉乙醇萃取物及銀杏葉水萃取物之還原力分別相當91.21微克、20.00-28.63微克及19.29-28.09微克之維生素C含量；乾燥方式以室溫、熱風及冷凍乾燥銀杏葉乙醇萃取物或新鮮銀杏葉水萃取物及室溫乾燥銀杏葉水萃取物之還原力較佳。商業配方、銀杏葉乙醇萃取物及銀杏葉水萃取物之Trolox能力分別為每毫克80.56微克、5.90-13.73微克及7.95-12.21微克；乾燥方式以室溫乾燥銀杏葉乙醇萃取物及冷凍乾燥銀杏葉水萃取物之Trolox能力較佳。商業配方及銀杏葉乙醇萃取物之螯合亞鐵離子能力為相當36.91微克EDTA (ethylenediaminetetraacetic acid)及60.28-88.72微克EDTA；螯合亞鐵離子能力以銀杏葉乙醇萃取物高於商業配方。銀杏葉水萃取物之酪胺酸酶半數抑制劑量為每毫升19.34-38.98毫克；乾燥方式以新鮮銀杏葉水萃取物較佳。整體而言，以室溫乾燥方式處理銀杏葉能保留較多的有效成分，亦呈現較佳的抗氧化能力；酪胺酸酶之抑制能力則以新鮮銀杏葉抑制能力較佳。
The objective of the present study was to investigate the effect of drying methods on antioxidant capacity and tyrosinase activity of Ginkgo biloba leaf. The proximate composition of Ginkgo biloba leaf were 74.60%, 3.80%, 2.41%, 3.15% and 16.40%, respectively, for moisture, protein, fat, ash and carbohydrate. The leaves contained antioxidant nutrients for 1.8mg vitamin C, 2.29 mg vitamin E, 76.20 μg Se and 4.15 μg Zn per gram of homogenate. The total yields of ethanol or water Ginkgo biloba extracts by different drying methods were 5.67-25.40% or 6.20-26.93%. Total phenol contents of ethanol extracts were 24.07-60.00 μg per mg, and showed higher (p<0.05) phenolic compounds obtained from Ginkgo biloba leaves by ethanol extracted for 12 hours, the other by room temperature drying. The flavonoids (i.e. quercetin, isorharmnetin and kaempferol) concentrations from ethanol Ginkgo biloba extracts were 8.00-26.56 μg per mg. Total phenol contents of water extracts were 10.69-39.07 μg per mg, and showed higher phenolic compounds obtained from Ginkgo biloba leaves by 60℃ water extracted, the other by room temperature drying. The flavonoids (i.e. quercetin, isorharmnetin and kaempferol) concentrations were 2.60-12.95 μg per mg from water Ginkgo biloba extracts. Helf DPPH radical cation scavenging concentrations of commercial tablet (each 60 mg ginkgo leaf extract contain 14.4 mg flavone glycosides and 3.6 mg terpene lactones), ethanol or water Ginkgo biloba extracts were 76.48 μg, 574.80-902.95 μg or 244.17-375.89 μg per ml, there was significantly higher DPPH radical cation scavenging capacity in ethanol or water fresh Ginkgo biloba extracts. The reducing power concentrations were 91.21 μg, 20.00-28.63 μg or 19.29-28.09 μg vitamin C equivalent per mg, respectively, for commercial tablet, ethanol or water Ginkgo biloba extracts, there were higher reducing power in ethanol Ginkgo biloba extracts by room temperature, oven or freeze drying or water Ginkgo biloba extracts by fresh or oven drying. The equivalent antioxidant Trolox capacity were 80.56μg, 5.90-13.73 μg or 7.95-12.21 μg per mg, respectively, for commercial tablet, ethanol or water Ginkgo biloba extracts, there were higher Trolox capacity in ethanol Ginkgo biloba extracts by room temperature drying or water Ginkgo biloba extracts by freeze drying. The ferrous ions chelating activity of commercial tablet or ethanol Ginkgo biloba extracts were 36.91μg or 60.28-88.72 μg per mg, there was higher ferrous ions chelating activity in ethanol Ginkgo biloba extracts than in commercial tablet. Half inhibitory concentrations of tyrosinase activity of water Ginkgo biloba extract were 19.34-38.98 mg per ml and higher inhibitory capacity in fresh Ginkgo biloba extracts. Conclusion: While room temperature drying usually preserved more flavonoids and antioxidant activity of Ginkgo biloba extract, further, higher inhibitory capacity in fresh Ginkgo biloba extracts. |
