西藏芜菁和玛咖低极性组分的化学组成及其抗氧化活性比较研究

Comparative Studies of Chemical Compositions and Antioxidant Capacity of Low-Polarity Components from Tibetan turnip(Brassica rapa var L. ) and Maca(Lepidium meyenii Walp)

比较来源于西藏的芜菁（Brassica rapa var L.）和玛咖（Lepidium meyenii Walp）块茎中低极性挥发组分的化学组成及其抗氧化性能的差异。采用超临界二氧化碳萃取（SCFE）获得低极性组分,并运用响应面分析法对SCFE工艺参数进行优化。采用GC-MS联用技术分析两种低极性组分的化学组成,采用UPLC-PDA法针对性地比较其中4种植物甾醇的含量;最后,采用体外抗氧化评价方法（ABTS和FRAP）对两者的抗氧化活性进行比较。结果表明,芜菁和玛咖块茎中SCFE低极性组分产率分别为（4.190±0.169）mg/g物料（干基）和（4.378±0.356）mg/g物料（干基）,共同含有的主要成分是亚油酸、棕榈酸和棕榈酸甲酯,占总量的74.73%~80.40%;芜菁低极性组分中所含的化合物种类较玛咖丰富,其甾醇含量（711.87μg/g）为玛咖（254.82μg/g）的2.79倍。抗氧化法评价结果表明,芜菁低极性组分的抗氧化活性显著高于玛咖（P〈0.05）。表明同一产地的芜菁块茎中低极性组分较玛咖具有更强的抗氧化活性。

The aim of this study was to compare low-polarity components and its anfioxidant activities from Tibetan turnip （Brassica rapa L. ） and Maca （Lepidium meyenii Walp）. The supercritical CO2 fluid extraction （SCFE） conditions for low-polarlty components were optimized by response surface methodology. GC-MS was applied for qualitative analysis of SCFE extracts. UPLC-PDA method was employed to quantify four major phytosterels. Furthermore, ABTS and FRAP assays were used to assess the antioxldant activities of SCFE extracts. As a result, the low-polarity components yields were （4. 190±0. 169） mg/g dry Turnip and （4. 378 ± 0.356） mg/g dry Maca,respoctively. The major components in both plants were linoleic acid,palmitic acid and methyl palmitate ,which account for 74.73% to 80.40% of the total compo- nents. The total phytosterols of Turnip （711.87 μg/g） was 2.79 times of that in Maca （254.82 μg/g）. Moreover,Turnip showed stronger antioxidant activities than Maca both in the ABTS and FRAP assays （P 〈0.05）.