Total Phenolic and Flavonoid Content and In Vitro Antioxidant Activity of Selected Herbal Products Using Oxygen Radical Absorbance Capacity, Multi-radical (ORAC MR5) Assays.

Reactive oxygen and nitrogen species (ROS/RNS) are known to cause oxidative damage to cells and macromolecules. Intake of antioxidant-rich fruits and vegetables has been touted as a strategy to mitigate oxidative stress, but this is not always accommodated in modern diets. Augmentation with antioxidant-rich herbal supplements may be a preventive measure against the negative effects of ROS/RNS. In this study, we verify and compare the antioxidant claims of herbal supplements by measuring their phytochemical content and antioxidant capacities through the oxygen radical absorption capacity-multi-radical (ORAC MR5) assays. ORAC MR5 measures antioxidant activity against five biologically relevant ROS/RNS (peroxyl and hydroxyl radical, superoxide anion, singlet oxygen, and peroxynitrite). Four products were tested: two multi-herbal capsules (INT and Oxxy), a mangosteen fruit pulp powder capsule (MPC), and a mixed herbal drink (MHD). Phytochemical content was quantified through total phenolic and flavonoid content assays. Oxxy had the highest flavonoid content per serving (106.4 mg catechin eq/450 mg capsule) and ORAC MR5 value (37,503 μmol Trolox eq/450 mg capsule), followed by INT (53.5 mg catechin eq and 17,298 μmol Trolox eq/200 mg capsule), MPC (48.1 mg catechin eq and 7,675 μmol Trolox eq/500 mg capsule), and then MHD (7.4 mg catechin eq and 146.7 μmol Trolox eq/30 mL drink). Significant antioxidant activities against peroxyl radicals and singlet oxygen were observed for INT and Oxxy, whereas the antioxidant activity of MPC and MHD were mostly towards peroxyl radicals. A strong correlation was found between phenolic and flavonoid contents and ORAC MR5 values, and we confirmed supplier claims on standardized phenolic content or antioxidant activity of INT and Oxxy. This study demonstrated the utility of ORAC MR5 as a measure of in vitro antioxidant activity of herbal supplements against biologically relevant ROS/RNS and may be used for the development and quality control of herbal supplements. [ABSTRACT FROM AUTHOR]