红薯叶不同溶剂提取物抗氧化性及活性成分鉴定

研究不同极性溶剂对红薯叶中酚类化合物的提取以及提取物抗氧化性的影响，并鉴定提取物中的主要抗氧化成分组成。分别采用极性不同的7 种溶剂（蒸馏水、甲醇、无水乙醇、丙酮、正丁醇、乙酸乙酯和氯仿）从红薯叶中提取多酚，并评价提取物中总酚、总黄酮和花青素的含量，以及对1,1-二苯基-2-三硝基苯肼（1,1-diphenyl-2-picrylhydrazyl，DPPH）自由基清除能力和还原能力，最后运用高效液相色谱-串联质谱（high performance liquidchromatography tandem mass spectroscopy，HPLC-MS/MS）技术分析抗氧化活性最好的提取物中多酚的主要组成成分。结果表明：提取溶剂的极性对红薯叶中多酚类化合物的提取效率和提取物抗氧化活性有很大的影响，水提物具有最高的粗提物得率（（37.13±1.60）%），而甲醇提取物中总酚含量（13.80 mg GAE/g）和总黄酮含量（（5.68±0.35）mg QE/g）最高，且具有最好的DPPH自由基清除能力（IC50为0.32 mg/mL）与还原能力（ρ0.5为0.95 mg/mL）。采用HPLC-MS/MS从红薯叶甲醇提取物中鉴定9 种、初步鉴定3 种酚类化合物，鉴定的化合物为咖啡酸、对羟基苯甲酸、1-咖啡酸奎宁酸、3-咖啡酸奎宁酸、异绿原酸A、异绿原酸B、异绿原酸C、3,4,5-三咖啡酰奎尼酸和金丝桃苷。

Comparison of Antioxidant Activities of Various Solvent Extracts of Sweet Potato (Ipomoea batatas (L.) Lam.) Leaves and Identification of Antioxidant Constituents of the Merthanol Extract

This study aimed to investigate the effects of solvents with different polarities on the extraction of phenolic
compounds from sweet potato leaves, to compare antioxidant activities of the extracts, and to identify the main antioxidants
of the extract with the highest antioxidant activity. Seven solvents, namely distilled water, methanol, ethanol, acetone,
n-butanol, ethyl acetate and chloroform, were used to extract polyphenols from sweet potato leaves. The contents of total
phenolics, total flavonoids and anthocyanins, as well as in vitro antioxidant activities of these extracts were compared.
The major antioxidant compounds in the extract with the highest antioxidant activity were identified by high performance
liquid chromatography tandem mass spectroscopy (HPLC-MS/MS). Results indicated that solvent polarity had a
substantial influence on the extraction efficiency of polyphenols from sweet potato leaves and the antioxidant activities
of the extracts. The water extract had the highest crude extract yield of (37.13 ± 1.60)%, but the highest total phenolic
content (13.80 mg GAE/g) and total flavonoid content ((5.68 ± 0.35) mg QE/g) were observed in the methanol extract and
it exhibited the strongest DPPH (1,1-diphenyl-2-picryl-hydrazyl-hydrate) radical scavenging activity with IC50 value of
0.32 mg/mL and reducing power of ρ0.5 value of 0.95 mg/mL. A total of 9 phenolic compounds, namely caffeic acid,
chlorogenic acid, 3,4-dicaffeoylquinic acid, 3,5-dicaffeoylquinic acid, 4,5-dicaffeoylquinic acid and 3,4,5-tricaffeoylquinic
acid, were identified from the methanol extract, including 3 phenolic compounds.