The interaction effect and optimal formulation of selected polyherbal extracts towards antioxidant activity
Past study showed that lemongrass (Cymbopogon citratus), curry leaves (Murrya koenigii), turmeric (Curcuma longa) and ginger (Zingiber officinale) contain phytochemicals associated with antioxidant properties. However, all the herbs are tested individually and rarely mix together. This study was conducted to examine the antioxidant properties and interaction effect when combined. The plants studied were decocted with distilled water. Eighteen formulations of aqueous extracts were established using simplex lattice mixture design that was generated by Design Expert software. The antioxidant properties were analyzed by 2-diphenyl-2-picryl hydrazyl radical scavenging (DPPH), ferric reducing antioxidant power (FRAP), total phenolic content (TPC) and total flavonoid content (TFC) assays. The result showed that the mixture of lemongrass and curry leaves extracts gave the highest reading in DPPH assay (91.14%), FRAP assay (215.66 mM) and TFC (22.62 µg Rutin/mL). In the DPPH assay, the ratio of one to one (1:1) mixture of lemongrass with other plants extracts showed antagonistic interaction. There were five (5) formulations that showed synergistic interaction in all assays. However, there were two (2) formulations that showed antagonistic interactions on both DPPH and FRAP assays. No additive effect was observed in all formulations. The suggested optimum formulation contains 53.7% lemongrass, 43.4% curry leaves, 2.9% ginger and 0.0% turmeric. Most of the mixtures presented synergistic interactions. This indicated the potential of plant extract mixtures to be developed into nutraceutical products in the future by conducting in-vivo study.