飲食中天然的抗氧化成分已經確定可藉由保護重要的生命分子如DNA及細胞膜上脂質的氧化而在人類健康上扮演角色；火龍果為台灣少數不需噴農藥的水果，已知火龍果果肉與果皮中富含類黃酮（flavonoids）。本研究以紅肉火龍果（Red pitaya, Hylocereus polyrhizus）和白肉火龍果（white pitaya, Hylocereus undatus）之果肉（flesh）及果皮（peel）為材料，以乙醇萃取後，共分為四組，進行總酚含量測定，另外，抗氧化活性則包括DPPH（1,1-diphenyl-2-picrylhydrazyl）自由基清除能力、ABTS（2,2-azinobis（3-ethylbenz-thiazoline）-6-sulfonic acid）自由基清除能力及還原力測定，比較不同品種及部位火龍果之乙醇萃取物其抗氧化能力之差異。在總酚化合物含量測定，以白肉火龍果果皮組含量最高且明顯高於其他組別。比較各組之抗氧化能力，在DPPH及ABTS自由基清除能力中，EC_(50)表現上皆以白肉火龍果果皮組表現最佳，分別為0.61 mg／mL及0.65 mg／mL，其次為紅肉火龍果果皮組，白肉火龍果果肉組，而紅肉火龍果果肉組表現最差；在還原力表現上，四組隨濃度增加其還原力能力逐升，不論品種果皮組在所有濃度中皆較果肉組有較佳還原力。由本研究結果得知，火龍果不可食用之果皮部位比經常食用之果肉有較高抗氧化成份及活性，在未來機能性成分之發展上具有相當之潛能。
Hylocereus polyrhizus (red pitaya) and H. undatus (white pitaya) are belongs to the vine cacti from the Cactaceae family. The antioxidant activities of ethanoilic extract of fleshes and peels of two species of Hylocereus were studied. The sudy has four extracts groups, fleshes and peels of red and white of pitaya, respectively. The total phenol contents of peels of white pitaya were higher than other groups. Comparison of fleshes and peels of two species of Hylocereus of antioxidant capacity, the EC_(50) values of peels of white pitaya exhibited 0.61 mg/mL and 0.65 mg/mL scavenging capacity on DPPH and ABTS free radical, respectively. The reducing power, four extracts associated with the concentration of reducing power capacity gradually increased. Regardless of the species, the peels of pitaya than fleshes of pitaya had better reducing power. These results demonstrated that the ethanolic extracts of peels of pitaya have excellent antioxidant activities, indicating its potential applications are worthy of further investigations.
