臺灣鄉土紫葉蔬菜萃取物的抗氧化能力

The Antioxidant Capacity of Extracts from Taiwan Indigenous Purple-leaved Vegetables

The aim of this study was to evaluate the antioxidant components and activity of Taiwan indigenous purple-leaved vegetables, including gynura (Gynura bicolor DC.), sweet potato [Ipomoea batatas (L.) Lamark], celosia (Celosia argentea L.), edible amaranth (Amaranthus tricolor L.), perilla (purple-leaved and bicolored-leaved) [Perilla frutescents (L.) Britton], and heartleaf houttuynia (Houttuynia cordata Thumb.). The same vegetables with green leaves were used as controls. The items analyzed were the antioxidant components including polyphenol, flavonoids, anthocyanidins, and porphyrins. The antioxidant activity including reducing power, chelating Fe^(2+) ion, and scavenging of 1,1-disphenyl-2-picryl-hydrazyl (DPPH) radical and superoxide anion, the inhibition of conjugated diene formation, and malondialdehyde (MDA) formation, and lag phase of low density lipoprotein (LDL). The results showed that purple-leaved sweet potato was rich in polyphenol, flavonoids and porphyrins. Both purple- and bicolored-leaved perilla (lines 1 and 2) contained relative high levels of anthocyanidins and porphyrins. Purple-leaved perilla line 1 and green-leaved sweet potato had highest reducing power in aqueous extract. Aqueous extract of light green-leaved edible amaranth and methanolic extract of heartleaf houttuynia exhibited the highest scavenging superoxide capacity. The aqueous extracts of all vegetables showed very low DPPH scavenging activities. The inhibitions of MDA formation in LDL system of purple and green-leaved sweet potato were higher than other aqueous extracts. In methanolic extracts, welwet plant, Taiwan welwet plant, purple and green-leaved sweet potato, heartleaf houttuynia, and purple-, bicolored- and green-leaved perilla (lines 1, 2 and 3) had much higher activity to prolong the lag phase of LDL oxidation (P ＜ 0.05). In the above three tested antioxidant activity assays (the inhibition of conjugated diene formation, the inhibition of MDA formation, and the lag phase of LDL oxidation), purple-leaved sweet potato exhibited higher antioxidative capacity compared to other vegetables. 本研究以臺灣紫葉鄉土蔬菜為原材料，包括紅鳳菜（Gynura bicolor DC.）、紫甘藷葉[Ipomoea batatas(L.) Lamark]、紫葉青葙（Celosia argentea L.）、紫葉莧菜（Amaranthus tricolor L.）、紫蘇[Perilla frutescens(L.) Britton]品系1與芳香雙色品系2及蕺菜（Houttuynia cordata Thumb.），並以各蔬菜之綠葉型為對照組。測定抗氧化成份包括：多酚類、類黃酮、花青素與吡啉類；測定抗氧化活性包括：還原力、螯合亞鐵離子、清除DPPH自由基與清除超氧陰離子；亞麻油酸乳化自氧化系統共軛雙烯生成抑制性、LDL系統丙二醛生成抑制百分比與LDL遲滯期變化。結果顯示紫甘藷葉含有最豐富多酚類、類黃酮與吡啉類含量。同時紫蘇與芳香雙色紫蘇亦含豐富花青素與吡啉類含量。還原力以紫蘇與綠甘藷葉的效力最高；清除超氧陰離子在水相以白莧菜效力最高，甲醇萃取則以蕺菜效果最佳；水相萃取物之清除DPPH自由基能力低弱。在三種萃取溶液系統中，以紫甘藷葉具有最佳共軛雙烯生成抑制性。LDL系統抑制丙二醛生成以紫甘藷葉與綠甘藷葉的水相萃取抑制性最高。在甲醇萃取相中具有較高抗氧化活性，紅鳳菜與白鳳菜、紫與綠甘藷葉、蕺菜、紫蘇、芳香雙色紫蘇與綠紫蘇較可延長LDL氧化遲滯期（P<0.05）。綜合以上三種抗氧化力分析（抑制共軛雙烯生成、抑制丙二醛生成與LDL氧化遲滯期），具有強抗氧化力者為紫甘藷葉。