Antioxidant and Antimicrobial Properties of Different Solvent Extracts of Malaysian Plectranthus Amboinicus and Ocimum Sanctum Plants

Vasu, Kirthna Rubine (2023) Antioxidant and Antimicrobial Properties of Different Solvent Extracts of Malaysian Plectranthus Amboinicus and Ocimum Sanctum Plants. Final Year Project (Bachelor), Tunku Abdul Rahman University College.

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Abstract

Plant-based remedies have long been used as part of the cultural heritage and their benefits are supported by chemical and pharmacological studies. Many synthetic drugs are often modelled on the chemical constituents of medicinal plants. The benefits of using plants as pharmaceuticals in phytotherapy can be justified from studies of various scientific disciplines. Indian borage, the common name for the medicinal herb Plectranthus ambonicus (Lour.), which is widely used in South East Asia and India. Ocimum sanctum referred as Tulsi, is a member of the Lamiaceae family. This plant is widely grown throughout Southeast Asia's tropical regions and is renowned for its medicinal properties. In this research, Ocimum sanctum and Plectranthus amboinicus were extracted with three different solvents: 99.9% ethanol, 80% ethanol, and ethyl acetate. The antioxidant and antibacterial activities of these plants were assessed. Using the maceration procedure, the plants were processed and extracted. Two analyses, including antioxidant testing and antimicrobial activity, were performed on two different plants. The DPPH radical scavenging activity, ABTS assay, total phenolic compound (TPC), total flavonoid content (TFC), and ferric reducing antioxidant power (FRAP) assays were used in the antioxidant analysis. Antimicrobial properties of plants were evaluated by disc diffusion method to determine the minimum inhibitory concentration against Bacillus spp., Klebsiella spp., Escherichia coli, and Staphylococcus aureus Ethyl acetate was the most efficient solvent in extracting phytochemical compounds from Plectranthus amboinicus and Ocimum sanctum had the highest total phenolic content (5.34 ± 0.02, 7.56 ± 0.01mg GAE/g extract), total flavonoid content (8.54 ± 0.17, 8.10 ± 0.23mg QE/g extract), FRAP assays (3.66 mg ± 0.01, 3.70 ± 0.18 FE/g of extract. The ethyl acetate extract also had the highest DPPH free radical scavenging activity value (64.23 ± 0.33, 55.98 ± 0.97 mg AA/g extract), followed by ABTS (66.67 ± 0.43, 63.00 ± 2.29 mg AA/g extract). In the antimicrobial studies, gram-positive bacteria have a bigger zone of inhibition than gram-negative bacteria. The minimum inhibitory concentration of Plectranthus amboinicus and Ocimum sanctum ethyl acetate extracts had highest inhibition zone at 1.0 mg/ml of the ethyl acetate extracts and were able to inhibit gram-positive bacteria and gram-negative bacteria. The findings of this study suggested that Plectranthus amboinicus and Ocimum sanctum extracts may contain phytochemical sources that can function as antioxidant and antibacterial agents