Antioxidant Activity and its Interaction Effect on Polyherbal Formulations of Nephrodium inophyllum, Polygonum minus Annona squamosal L. and Stevia rebaudiana

Antioxidant activities have a great potential on various plant extracts due to the complexity of the composition of bioactive compounds present in the plants. Besides that, various combinations of plants can give possible interactions such that synergistic, antagonistic and indifferent between particular compounds which is importance in development of food products. Therefore, the objective of this study is to determine and evaluate the antioxidant activity and the possible interaction effect on aqueous extracts of leaves of Nephrodium inophyllum (pakis merah), Polygonum minus (kesum), Annona squamosal L. (nona) and Stevia rebaudiana through in-vitro assay. In this study, the antioxidant activity of the extracts individually and their different combinations were analyzed by total phenolic content (TPC), total flavonoid content (TFC), 2, 2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity and lipid peroxidation inhibition (LPI) assay. Meanwhile, the interaction effect was evaluated by comparing the experimental antioxidant activity of the mixtures with calculated theoretical values and the interactions of the compounds were determined. The results depicted that individual extract of N. inophyllum had significant flavonoid content and lipid peroxidation inhibition while P. minus has the highest phenolic content and percentage inhibition DPPH compared to other plant extracts. For the interaction effect, synergism was exhibited on only four combinations of plant extracts for all assays conducted with the highest one was shown on DPPH assay for combination of N. inophyllum and A. squamosal L. This proved that there was a little molecular interaction between particular phenolics or flavonoids compound found in plant extracts. Out of all studied plant extracts, there was only one antagonistic interaction between P. minus and A. squamosal L on DPPH assay. However, indifferent effect on other compounds was revealed in the majority of all plant extract combinations for all assays. Hence, this present study justifies the aqueous extracts have significant antioxidant properties individually thus it gave possible interaction effects that could contribute for future design in food industries.