Phenolic content and antioxidant capacity of infusions herbs: Optimization of phenolic extraction and HPLC-DAD method

Abstract The aim of this work was to investigate the phenolic content and antioxidant capacity of infusions of commercial herb samples (fennel, anise, peppermint, lemon grass and lemon balm) popularly consumed in Brazil. The infusion preparation for phenolic extraction was optimized using multivariate planning. Spectrophotometric methods were used to determine in vitro antioxidant activity and total phenolic and flavonoid content. Peppermint infusions had higher phenolic content and antioxidant potential. It was developed and validated a method by HPLC-DAD for the determination of caffeine, phenolic acids and flavonoids and applied for the analysis of the composition of the infusions. Higher concentrations were obtained for chlorogenic and p-coumaric phenolic acids and for flavonoids rutin and catechin. Principal Components Analysis and Hierarchical Cluster Analysis were applied for the comparative evaluation of the phenolic composition of the infusions. The multivariate analyzes indicate that the phenolic profile for the samples of the same species tend to present greater similarities in relation to other herbs and one of the analyzed samples, commercialized as anise, does not belong to the P. anisum species.摘要 本研究旨在探究巴西民众日常饮用的5款商业在售草本浸液样品（小茴香、洋茴香、薄荷、香茅及柠檬香蜂草）的总酚含量与抗氧化能力。本研究采用多变量试验设计优化了用于酚类物质提取的草本浸液制备工艺。采用分光光度法测定了样品的体外抗氧化活性、总酚含量与总黄酮含量。结果显示，薄荷浸液的总酚含量与抗氧化潜能均为最高。本研究建立并验证了一种基于高效液相色谱-二极管阵列检测器（HPLC-DAD）的分析方法，用于测定咖啡因、酚酸与黄酮类物质，并将其应用于草本浸液的成分分析。受试样品中，绿原酸、对香豆酸两种酚酸以及芦丁、儿茶素两种黄酮类物质的含量较高。本研究采用主成分分析（Principal Components Analysis）与分层聚类分析（Hierarchical Cluster Analysis）对各草本浸液的酚类组成开展对比评价。多变量分析结果表明，同种受试样品的酚类物质谱相较于其他草本样品往往具有更高的相似性；另有1份以洋茴香名义售卖的分析样品并不属于P. anisum物种。