Individual and Combined Antioxidant Activities of Desmodium triflorum Linn. and Pogostemon heyneanus Benth.

Abstract

Desmodium triflorum Linn. and Pogostemon heyneanus Benth. are medicinal plants in Sri Lanka. This investigation was conducted to determine the individual and combined antioxidant activities of D. triflorum whole plant and P. heyneanus leaves. Physicochemical properties of the two plants were determined. Individual and combined antioxidant activities of different concentrations (100–700 μg/mL) of aqueous extracts of the plants were evaluated using 2, 2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging and oxygen radical absorbance capacity (ORAC) assay according to the standard protocols and the total antioxidant capacity by ferric reducing antioxidant power (FRAP) method. Total flavonoid content (TFC) and total polyphenolic content (TPC) were quantified. Moisture content, total ash content, water soluble ash content and extractable matter content was higher in P. heyneanus leaves than D. triflorum whole plant. DPPH radical scavenging activity and ORAC exhibited by D. triflorum (IC50, 439.4±20.4 ppm, 0.82±0.54 mg Trolox equivalent/g extract, respectively) were higher than P. heyneanus (IC50,493.6±9.1 ppm, 0.26±0.53 mg Trolox equivalent/g of extract, respectively). Among the combined extracts, combinations of D. triflorum: P. heyneanus 1:1 have exhibited the highest DPPH radical scavenging activity (IC₅₀- 402.5 ± 3.5 ppm) and TFC (52.89±0.88 mg Quercetin per g of sample). Combination of D. triflorum: P. heyneanus 3:1 demonstrated higher ORAC (1.40±0.17 Trolox equivalent/g extract) value than that of individual plants. Highest TPC observed at the combination 3:1(51.99±1.68 mg Trolox per g of sample) may have promoted the synergistic activity. In conclusion, the plants, D. triflorum and P. heyneanus have exhibited concentration dependent individual and combined antioxidant activity. The higher activity shown by D.triflorum: P. heyneanus (3:1) mixture may be due to synergistic effect.