ANTIOXIDANT ACTIVITY OF Plectranthus amboinicus (KAPPARAWALLIYA) PLANT AQUEOUS EXTRACTS

Plectranthus amboinicus Lour. (Sinhala Kapparawalliya) is a semi-succulentperennial plant found in the tropical regions of Africa, Asia, and Australia. Since ancienttimes, this plant has been widely used in Ayurvedic medicine, with over 50 recipes in theAyurvedic pharmacopeia featuring it as a major ingredient. Studies conducted to date haveidentified several phytoconstituents, including phenolics, terpenoids, phenolic acids,flavonoids, flavones, and tannins. This present study was conducted to evaluate the in vitroantioxidant activity of Plectranthus amboinicus plant extracts using two distinct assays: 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging and Ferric Reducing AntioxidantPower (FRAP). Healthy P. amboinicus Lour plants were collected from Kuliyapitiya in theKurunegala district. The collected plants were washed, dried, ground, and subjected toaqueous extraction by simple maceration. The antioxidant activity was assessed using theDPPH and FRAP assays for a concentration series ranging from 20 µg/mL to 120 µg/mL,and triplicated. Results of the DPPH radical scavenging assay revealed that the halfmaximal inhibitory concentration (IC50) of P. amboinicus plant extract was 83.88 ± 0.18 µg/mL. This result was compared to the positive control, ascorbic acid (IC50 6.31 ±0.11 µg/mL). In the FRAP assay, P. amboinicus plant extract exhibited an IC50 of 125.31 ± 0.46 µg/mL, while the ascorbic acid positive control exhibited an IC50 of 7.72 ±0.16 µg/mL. In conclusion, the P. amboinicus plant extract demonstrated strong in vitroantioxidant activities in DPPH and FRAP assays. These findings justify the traditionalmedicinal uses of P. amboinicus and highlight its potential as a valuable natural source ofantioxidants for various health applications.