Antibacterial Activity of Ketapang Leaf Extract (Terminalia catappa) Against Streptococcus pneumoniae In Vitro

Abstract

Background: Streptococcus pneumoniae is a Gram-positive bacterium typically residing as normal flora in the respiratory tract, which can transform into a pathogen causing severe infections such as pneumonia and meningitis. Although amoxicillin is widely utilized as the primary therapy, its effectiveness has progressively declined due to the rising incidence of antibiotic resistance. Consequently, exploring the antibacterial potential of natural resources, such as ketapang leaves (Terminalia catappa), has become crucial as a viable alternative solution. Objectives: . This study aimed to determine the antibacterial activity of ketapang leaf extract (T. catappa) against S. pneumoniae isolates in vitro. This experimental study used a post-test group only method with ketapang leaf extract obtained through maceration. Methods: The antibacterial activity test was conducted using the disc diffusion method (Kirby-Bauer) on Mueller-Hinton agar media against S. pneumoniae bacteria collected from the Microbiology Laboratory of the Faculty of Medicine, Unsoed. This experimental consisted of seven groups, namely the treatment group (T. catappa leaf extract) at concentrations of 10%, 20%, 40%, and 80%; the positive control group (amoxicillin); the negative control group (distilled water); and the solvent group (10% DMSO) with four replicates. The inhibition zone diameter was measured and analyzed using Shapiro-Wilk, Kruskal-Wallis, and post hoc Bonferroni test to determine its antibacterial activity.  Key findings: The results showed that ketapang leaf extract at concentrations of 10%, 20%, 40%, and 80% was unable to form an inhibition zone against the growth of S. pneumoniae. This finding contrasted with the positive control, amoxicillin (25 µg/disk), which produced an inhibition zone with an average diameter of 12.5 mm. The absence of inhibitory activity by the extract is suspected to be related to physical factors, such as molecular size and extract viscosity that hinder diffusion, or suboptimal bacterial growth. Conclusions: Ketapang leaf extract shows no antibacterial activity against S. pneumoniae in vitro.