白柿萃取物抗氧化能力及抑制生理活性酵素之研究

白柿( Casimiroa edulis)屬於芸香科( Rutaceae )香肉果屬( Casimiroa )之果樹植物。在西班牙、墨西哥的傳統醫學中具有抗發炎、抗高血壓、抗焦慮之功效，具潛在的藥理開發價值。然而，目前關於白柿之抗氧化能力與酵素活性抑制研究極少，因此，本研究旨在選用樹葉與莖部，使用不同濃度乙醇(25%、50%、75%、95%)、甲醇與95℃熱水進行萃取，比較兩者之生物活性成分(總酚與總類黃酮含量)、抗氧化能力(DPPH·自由基清除能力與總抗氧化能力(Trolox equivalent antioxidant capacity, TEAC)、螯合亞鐵離子能力、還原力)以及酵素活性抑制能力(α-葡萄糖苷酶、黃嘌呤氧化酶、酪胺酸酶)，並以高效能液相層析儀(High performance liquid chromatography, HPLC)分析生物活性成分。實驗數據顯示，白柿之莖與樹葉75%乙醇萃取物，其總酚與總類黃酮含量最高，總酚含量分別為178.92 mg Gallic acid equivalent/g 乾重與230.07 mg Gallic acid equivalent /g 乾重，而總類黃酮分別為97.08 mg Quercetin equivalent/g 乾重與218.34 mg Quercetin equivalent/g 乾重。利用HPLC分析，並與標準品比對，發現咖啡酸、兒茶素、阿魏酸為莖之萃取物的主要酚類化合物，而樹葉萃取物則以兒茶素、木犀草素之含量最豐富。於DPPH·自由基清除能力與TEAC方面，皆以樹葉50%乙醇萃取物具有最佳之自由基清除效果，EC50數值分別為27.39 µg/mL與247.97 µg/mL；莖之50%乙醇萃取物呈現出最佳之亞鐵離子螯合效果，EC50為435.61 µg/mL；還原力方面，莖之25%與75%乙醇萃取物表現出最高之吸光值，顯示較佳之還原效果，EC50數值分別為147.87 µg/mL與149.51 µg/mL。於酵素活性抑制實驗中，樹葉95%與25%乙醇萃取物分別在α-葡萄糖苷酶以及黃嘌呤氧化酶活性抑制方面呈現出較佳之效果，IC50分別為817.05 µg/mL與424.15 µg/mL；莖之95%乙醇萃取物具有最佳之酪胺酸酶活性抑制效果，IC50數值為1751.99 µg/mL。綜上所述，白柿之莖與樹葉萃取物富含多種植化素，具有抗氧化與酵素抑制之功效，此結果有助於未來保健食品開發之參考。

關鍵字

白柿( Casimiroa edulis) ；抗氧化；酵素

並列摘要

Casimiroa edulis belongs to the Rutaceae family of the Casimiroa genus, which grows as a fruit tree. In Mexican and Spanish traditional medicine, the stem bark and leaf of Casimiroa edulis are known for their anti-inflammatory, anti-hypertensive and anti-anxiety properties. However, there is little research on its antioxidant and enzyme inhibitory activities. In the light of the preliminary narrative, the stem bark and leaf were selected to be extracted with different concentrations of ethanol (25%, 50%, 75%, 95%), methanol and 95℃ hot water and compared the functional components (total phenolic content, total flavonoid content), antioxidant activities (DPPH· scavenging ability, Trolox equivalent antioxidant capacity (TEAC), Ferrous ion chelating ability, Reducing power) and enzyme inhibition test (α-glucosidase, Xanthine oxidase, Tyrosinase). The HPLC method was employed for analyzing bioactive ingredients of our sample extracts. Experimental data showed that the 75% ethanol extract of stem bark and leaf exhibited the highest content of total phenolics and total flavonoids content. The total phenolic content is 178.92 mg Gallic acid equivalent/g dried weight (DW) and 230.07 mg Gallic acid equivalent/g DW respectively, while the total flavonoid content is 97.08 mg Quercetin equivalent/g DW and 218.34 mg Quercetin equivalent/g DW respectively. HPLC results indicated that caffeic acid, catechin and ferulic acid were the major phenolic compounds in the stem bark extract, while catechin and luteolin were the most abundant in the leaf extract. In terms of DPPH· free radical scavenging ability and TEAC, the 50% ethanol extract of the leaf demonstrated the best free radical scavenging ability, with EC50 values of 27.39 µg/ml and 247.97 µg/ml respectively. With an EC50 of 435.61 µg/mL, the 50% ethanol extract of the stem bark illustrated the best ferrous ion chelating ability. Regarding the reducing power, the 25% and 75% ethanol extracts of the stem bark depicted the highest absorbance values, indicating superior reducing effects, with EC50 values of 147.87 µg/mL and 149.51 µg/mL, respectively. In the experiment to inhibit enzyme activity, the extracts of leaf in 95% and 25% ethanol showed better results in inhibiting α-glucosidase and xanthine oxidase activities, with IC50 values of 817.05 µg/mL and 424.15 µg/mL respectively. The 95% ethanol extract of the stem bark suggested the most effective inhibition of tyrosinase activity, with an IC50 value of 1751.99 µg/mL. In summary, the extracts from Casimiroa edulis stem bark and leaf contain a variety of phytochemicals that have antioxidant and enzyme inhibitory effects. Our results provide another alternative from natural botanical for developing new nutraceuticals.