Antioxidant and Antibacterial Activities of Ethanol Extract of Kesambi Leaves ( Schleichera oleosa ) from Alor District, Indonesia

Abstract

Human health is increasingly threatened by oxidative stress and microbial infections, emphasizing the need for effective antioxidant and antibacterial agents. Schleichera oleosa (Kesambi), a tropical plant native to South and Southeast Asia, is rich in bioactive secondary metabolites such as alkaloids, phenolics, tannins, and flavonoids. This study investigated the antioxidant and antibacterial activities of ethanol extracts from Kesambi leaves collected in highland and lowland areas of Alor Regency, Indonesia. Antioxidant activity was assessed using the DPPH assay, while antibacterial activity was evaluated against Pseudomonas aeruginosa and Bacillus subtilis through the well diffusion method. The highland extract displayed stronger antibacterial activity, particularly against P. aeruginosa , whereas the lowland extract showed higher antioxidant potency. Both extracts produced larger inhibition zones against P. aeruginosa than B. subtilis , indicating species-specific susceptibility. In the antioxidant assay, the lowland extract exhibited an IC₅₀ value of 4.81 ± 1.00 ppm, surpassing the positive control ascorbic acid (IC₅₀ 6.07 ± 1.03 ppm), while the highland extract showed an IC₅₀ of 7.16 ± 0.61 ppm. These findings suggest that Kesambi leaves hold significant potential as natural therapeutic agents, with lowland samples as strong antioxidants and highland samples as promising antibacterial candidates, warranting further investigation for pharmaceutical and biomedical applications.