葡萄皮渣中结合态及游离态酚类物质及其抗氧化活性

Bound and Free Phenolics and Its Antioxidant Activity in Grape Pomace

摘要: 酿酒后的葡萄皮渣(GP)中含有丰富的酚类物质，大量文献报道了关于葡萄皮渣中游离态酚类物质的提取和分析，但少有关于皮渣中结合态酚类物质的分析。本研究探讨了葡萄皮渣和葡萄籽中结合态酚类的提取方法；定性和定量分析各提取物中游离态和结合态酚类物质并对其抗氧化活性进行测定和比较。以50%的乙醇分别提取葡萄皮渣和葡萄籽中游离态酚类物质；经乙醇提取后的皮渣和籽采用6M的HCL和2M的NaOH分别进行水解，然后以乙酸乙酯提取水解物中的结合态酚类成分；分别测定各葡萄皮渣提取物(GPEs)的总酚含量；采用高效液相色谱法分析GPEs中主要酚类物质种类及含量；测定GPEs对ABTS+和DPPH自由基的清除作用。结果表明经碱水解的葡萄皮渣中的总酚含量最高(14.6 mg/g)，其次为经酸水解的葡萄籽(13.4 mg/g)。经分析GPEs中主要酚类有儿茶素、儿茶酸、表儿茶素和阿魏酸。葡萄籽乙醇提取物中儿茶素和表儿茶素含量较多，分别为0.347mg/ml和0.335mg/ml，其抗氧化能力也最强，对ABTS+及DPPH自由基离子的半数抑制率分别为29.7 µg/ml和69.5 µg/ml。研究明确了酸碱水解可有效促进结合态酚类物质从葡萄皮渣中被水解出来，并显著增加葡萄皮渣中多酚类物质的提取率。

Abstract: Grape pomace (GP) provides a rich source of phenolic which has the capacity to act as powerful antioxidant. In this study, aqueous ethanol (50%) was used to the extraction of free phenolic in grape skin and seeds. HCl (6 M) and NaOH (2 M) were used to the hydrolysis of bound phenolic in the pomace after extracted with 50% aqueous ethanol. The total phenolic content of different grape pomace extracts (GPEs) was determined. And the antioxidant activity of different GPEs was measured further. The phenolic acid profile of the different GPEs was analyzed by High Performance Liquid Chromatography (HPLC). It was showed that the total phenolic content in grape skin hydrolyzed by alkaline and seeds hydrolyzed by acids was higher (14.6 and 13.4 mg/g) than other GPEs. Gallic acid, catechuic acid, catechin, epicatechin, ferulaic acid were the major phenolic acids in the GPEs. Concentration of catechin (0.347 mg/ml) and epicatechin (0.335 mg/ml) in grape seeds extracts by 50% aqueous ethanol was higher than other GPEs. And the antioxidant activity of grape seeds extracts by 50% aqueous ethanol was also the highest. The results showed that acid and alkali hydrolysis could effectively improve the extraction of the bound phenolic compounds in the grape skin.