龍眼核萃取物之抗氧化活性研究

Study on Antioxidative Activities in Dimocarpus longan Seed Extracts

本研究以熱迴流方式，利用不同溶劑（水、甲醇、50％乙醇、乙酸乙酯）萃取新鮮與曬乾龍眼核，探討不同溶劑對萃取率、總多酚化合物含量、類黃酮化合物含量及抗氧化活性（清除DPPH自由基能力、螯合亞鐵離子能力、清除ABTS陽離子能力、相對還原力及清除超氧陰離子能力）之影響。新鮮與曬乾龍眼核以50％乙醇溶劑萃取之萃取率最高。新鮮龍眼核萃取物試驗結果顯示，以50％乙醇萃取物之總多酚化合物含量最高；乙酸乙酯萃取物之類黃酮化合物含量最高；乙酸乙酯萃取物在濃度1.0 mg／mL時，清除DPPH自由基能力達99％；清除ABTS自由基能力的效果均很高，除乙酸乙酯萃取物外，在濃度0.5 mg／mL時高達99％；50％乙醇萃取物於濃度2.0 mg／mL時，相對還原力與標準品（BHA）比較達110.8％；清除超氧陰離子能力在濃度2.0 mg／mL時，以50％乙醇萃取物最高。曬乾龍眼核萃取物試驗結果顯示，50％乙醇與乙酸乙酯萃取物之總多酚化合物含量最高；以乙酸乙酯萃取物之類黃酮化合物含量最高；亞鐵離子螯合能力，水萃取物在濃度1.0 mg／mL時達85.2％；清除超氧陰離子能力在濃度2.0 mg／mL時，以50％乙醇萃取物最高。不同溶劑萃取物對大腸桿菌、金黃色葡萄球菌、枯草桿菌都有抑菌的效果。龍眼核含有豐富之多酚類和類黃酮化合物，具有清除DPPH自由基、ABTS陽離子能力和超氧陰離子之抗氧化活性，且具極佳之相對還原力和亞鐵離子螯合能力，有助益於增進人體抗氧化能力，具應用發展潛能。

In this study, different solvents (water, methanol, 50% ethanol, and ethyl acetate) were used to extract from fresh and dried longan seeds using the hot reflux method. The extraction rate, total polyphenolic content, total flavonoid content, and antioxidative activities (such as scavenging capacity of 2,2-diphenyl-1-picrylhydrazyl [DPPH] free radicals, chelating capacity of ferrous ions, scavenging capacity of 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) cations, relative reducing power, and scavenging capacity of superoxide anions) were investigated. The extraction rate for fresh and dried longan seeds was highest using 50% ethanol. The fresh longan seed extracts obtained using 50% ethanol and ethyl acetate had the highest total polyphenolic content and highest flavonoid content, respectively. The fresh longan seed extract obtained using ethyl acetate had a scavenging capacity of 99% in DPPH free radical at a concentration of 1.0 mg/mL. The effect of fresh longan seed extract on the scavenging capacity of ABTS cations was as high as 99% at a concentration of 0.5 mg/mL, except with ethyl acetate extract. The 2.0 mg/mL ethanol extract of fresh longan seeds had a relative reducing power of 110.8% compared with the standard (BHA). The fresh longan seed extract using 50% ethanol had highest scavenging capacity in superoxide anions at a concentration of 2.0 mg/mL. For the dried longan seed extract obtained using 50% ethanol and ethyl acetate, the total polyphenolic content was highest. For the dried longan seed extract obtained using ethyl acetate, the total flavonoid content was highest. The dried longan seed extract using water had a chelating capacity in ferrous ion of 85.2% at a concentration of 1.0 mg/mL. The dried longan seed extract obtained using 50% ethanol extract had the highest scavenging capacity in superoxide anions at a concentration of 2.0 mg/mL. Different solvent extracts have antibacterial effects against Escherichia coli, Staphylococcus aureus, and Bacillus subtilis.