本實驗探討荔枝花經過不同極性之溶劑萃取後,此些萃取物之酚類化合物含量及其抗氧化效果。荔枝花在經熱風乾燥後,由三種不同極性之溶劑萃取(丙酮、甲醇及熱水迴流),所得之荔枝花萃取物藉由不同的抗氧化活性評估實驗,包括DPPH自由基清除能力、還原能力、總抗氧化能力、抑制β-carotene 的清除及抑制銅離子誘導低密度脂蛋白氧化。實驗結果顯示: 荔枝花丙酮萃取物在各種抗氧化實驗中都均表現出較佳之抗氧化活性,其次為甲醇萃取物及熱水萃取物。 實驗分析不同溶劑的荔枝花萃取物之抗氧化成分,包括總酚類化合物、總類黃酮及縮合單寧,結果顯示此三種成分均以丙酮萃取物含量為最高,其次為甲醇萃取物,而熱水萃取物相較之下含量較少。實驗進一步以HPLC分析類黃酮及酚酸化合物之組成與含量,發現 epicathchin 和 rutin 為主要的類黃酮化合物,而主要的酚酸類化合物為gentisic acid 和 ferulic acid。荔枝花萃取物之抗氧化成分含量與抗氧化效果有顯著的相關性。
The antioxidant capacities of the acetone, methanol and water extracts of hot-air dried lychee (Litchi chinenesis Sonn.) flowers were estimated with 2,2-diphenyl-2-picrylhydrazyl hydrate (DPPH) radical-scavenging assay, reducing power, Trolox equivalent antioxidant capacity (TEAC) assay, Inhibition of β-carotene bleaching assay and inhibition of Cu2+-induced human low density lipoprotein (LDL) oxidation assay. Results showed that the acetone extracts had the best effects in all assays, followed by methanol extracts and hot water extracts. The acetone extracts had the highest contents of phenols, flavonoids and condensed tannins, and the methanol extracts next. The water extracts also showed the lowest amounts for the three components. Flavonoids and phenolic acids in these extracts were determined by HPLC further. Epicatechin and rutin were the major flavonoids, and genitisic acid and ferulic acid were the major phenolic acids. The contents of antioxidant components in these extracts were correlated with antioxidant activities.