Antimicrobial and Antioxidant Potentials of Aqueous Extracts of Ocimum gratissimum Leaves

Abstract

Ocimum gratissimum, commonly known as scent leaf, is a medicinal plant with a long history of use in traditional medicine due to its therapeutic properties. This study evaluates the antimicrobial and antioxidant potentials of aqueous extracts of O. gratissimum leaves. The antimicrobial activity was assessed using the agar well diffusion assay, and the antioxidant activity was determined using 2,2-Diphenyl-1-Picrylhydrazy (DPPH), nitric oxide scavenging assay (NOSA), ascorbic acid content, and total phenolic content assays. The results revealed that the O. gratissimum leaf extract exhibited significant antimicrobial activity against both gram-positive and gram-negative bacteria, with the highest inhibition observed against Staphylococcus aureus and Pseudomonas aeruginosa. In the antioxidant assays, the extract demonstrated moderate DPPH free radical scavenging activity, with a half-maximal inhibitory concentration (IC₅₀) of 40.21 ± 0.01 µg/mL, and high nitric oxide scavenging activity, with an IC₅₀ of 47.62 ± 0.02 µg/mL. The extract also contained a notable amount of ascorbic acid (15.20 ± 2.20 mg/100 g) and phenolic compounds (0.80 ± 0.01 mg/100 g). These findings highlight the dual therapeutic potential of O. gratissimum in both animal and human health. The antimicrobial properties suggest its use as a natural alternative to synthetic antibiotics, especially in the management of bacterial infections in livestock. The antioxidant activity indicates the potential of the plant to mitigate oxidative stress, thereby improving overall animal health, productivity, and resistance to diseases. Moreover, the consumption of animal products derived from animals fed with antioxidant-rich plants like O. gratissimum could contribute to human health by reducing the risk of oxidative stress-related diseases.