柚子皮在民俗療法中被認為可用於糖尿病的控制。本研究探討柚子全果皮、中果皮及外果皮水萃物及80%乙醇萃取物之降血糖及抗氧化活性。在試驗的六種樣品中，外果皮乙醇萃取物對α-葡萄糖苷酶的抑制活性最高，而後分別為全果皮乙醇萃取物、中果皮乙醇萃取物、外果皮水萃物、全果皮水萃物及中果皮水萃物。各萃取物間抗氧化活性及多酚類的含量也呈現相同的趨勢。試驗結果分析也顯示萃取物α-葡萄糖苷酶的抑制活性分別與抗氧化活性及多酚類的含量成顯著的正相關。本研究顯示柚子皮可作為天然抗氧化劑及α-葡萄糖苷酶抑制劑的來源，因而具有開發為營養製劑以應用於糖尿病管理的潛力。

Pomelo (Citrus grandis) peel is popular in folklore for managing diabetes. The objective of this study was to determine the hypoglycemic and antioxidative activities of water and 80% ethanol extracts of pomelo whole peel, and flavedo and albedo parts. Among the six studied peel extracts, the hydroethanol flavedo extract possessed the highest α-glucosidase inhibitory activity, followed by the hydroethanol whole-peel extract, hydroethanol albedo extract, aqueous flavedo extract, aqueous whole-peel extract, and finally the aqueous albedo extract. The antioxidative activities and polyphenol contents of the six extracts showed the same trend as the α-glucosidase inhibitory activity. In addition, significant positive correlations of the α-glucosidase inhibitory activity with the total polyphenol content and antioxidant activities were observed. Results of this work therefore indicated the potential of the non-consumed parts of pomelo possibly being exploited as natural sources of potent antioxidants and α-glucosidase inhibitors and could be used as nutraceuticals for managing diabetes.