不同品种龙眼果肉酚类物质的抗氧化活性比较

为研究不同龙眼品种资源中酚类物质、黄酮类化合物含量及其抗氧化性差异,选取广东省农业科学院果树研究所龙眼资源圃的24个龙眼品种,分析其果肉中游离态和结合态总酚、总黄酮物质的含量,采用DPPH自由基清除能力、ABTS总抗氧化能力、FRAP抗氧化能力和氧自由基吸收能力ORAC四种不同方法评价其体外抗氧化能力差异；不同龙眼品种果肉总酚、总黄酮含量与DPPH、ABTS、FRAP、ORAC四种不同方法测定的抗氧化能力的变幅和变异系数较大,呈现出显著的基因型差异；不同品种龙眼果肉的多酚和黄酮的含量分别与ABTS自由基清除能力、FRAP和ORAC呈极显著(p<0.01)正相关关系,而与DPPH自由基清除能力的EC₅₀值呈极显著负相关关系(p<0.01)。采用快速聚类法将24个不同品种的龙眼聚成多酚及总黄酮含量和抗氧化能力差异显著的三大群类。不同品种龙眼果肉游离态和结合态酚类物质含量与其抗氧化活性均呈显著正相关关系,提示酚类物质是龙眼果肉抗氧化活性的主要成分；酚类物质和黄酮类物质在龙眼果肉中主要以游离态存在,其中结合态平均占总酚含量的17.45%。

Comparison of Phenolic Contents and Antioxidant Activity of Fruit Pulp from Different Longan Varieties

The correlation of the in vitro antioxidant activity with contents of total phenol and flavonoid in fruit pulp of 24 longan varieties was analyzed. The contents of free and bound phenolics, total flavonoids and total phenol in 24 varieties of longan pulp from Institute of Pomology of Guangdong Academy of Agricultural Sciences were investigated. The radical scavenging ability (DPPH), total antioxidant capacity (ABTS), antioxidant capacity (FRAP), and absorptive capacity of oxygen free radicals(ORAC) were determined for evaluating their in vitro antioxidant capacity difference.The total polyphenols, flavonoids, DPPH, FRAP, ABTS and ORAC methods were used to determine the antioxidant abilities of phenolic extracts of different longan pulp varieties. Results showed that a significant difference (p<0.01) existed in the capacity of pulp phenolic extracts of different longan varieties and displayed significant genotype differences. The longan varieties with the higher content polyphenol and flavone showed stronger antioxidant activity. The quick clustering method was used to evaluate polyphenols and flavonoids content and antioxidant capacity in 24 varieties of longan pulp, dividing into three group of classes with significant difference. The polyphenols or flavonoids content positively correlated with the ABTS, FRAP , and ORAC analysis while it negatively related with the DPPH radical scavenging capacity (p<0.01). Thus, phenolics and flavonoids exist mainly in the free form in longan pulp. Phenolics of longan pulp had played an important role in antioxidant activity.