Polyphenol content and antioxidant activity of phytoestrogen containing food and dietary supplements: DPPH free radical scavenging activity by HPLC

Soy, red clover, chaste tree, hop and flax have all been found to contain a wide range of phytoestrogenic compounds, and a large number of dietary supplements contain their extracts as principal ingredients. This study is aimed to evaluate the total polyphenolic content and antioxidant activity of phytoestrogen-containing food and formulated dietary supplements. The HPLC-DPPH method was applied for DPPH free radical scavenging activity testing of various phytoestrogen-containing samples. Polyphenol content and antioxidant activity in dietary supplements were higher than in functional food samples; multiple-botanical-source preparations showed higher polyphenol content and antioxidant activity than the mono-botanical counterparts. Furthermore, the correlation between polyphenol content and antioxidant activity was strongly statistically significant, so it might be concluded that antioxidant activity is proportional to the content of these secondary metabolites. The most striking batch-to-batch deviations were represented by one chaste berry-based product (RSD 41.3 %) and one red clover derived product (RSD 57.9 %). The results of this study contribute to a better understanding of the phenolic profile and antioxidant properties of phytoestrogen containing food and dietary supplements