PHYTOCHEMICAL AND ANTIMICROBIAL ACTIVITY IN SOME MEDICINAL PLANT (AZIDIRACHTA INDICA AND PSIDIUM GUAJAVA) LEAVES EXTRACT.

Abstract This study investigated the phytochemical composition and antimicrobial properties of Azadirachta indica (neem) and Psidium guajava (guava) leaf extracts against selected pathogenic bacteria. Fresh neem and guava leaves were collected, air-dried, and extracted using methanol and aqueous solvents. Qualitative phytochemical screening was conducted to identify secondary metabolites including alkaloids, flavonoids, saponins, tannins, steroids, and terpenoids. Antimicrobial activity was evaluated using the disc diffusion method against Staphylococcus aureus, Escherichia coli, and Salmonella typhi at concentrations of 500, 250, 125, and 62.5 mg/mL. Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) were determined for each extract. Results revealed that both plant extracts contained alkaloids and flavonoids in both solvent systems, while saponins, steroids, and terpenoids showed solvent-dependent distribution. Neem leaf aqueous extract demonstrated broad-spectrum antimicrobial activity against all tested organisms, with zones of inhibition ranging from 9-19 mm. The extract showed particularly high efficacy against S. typhi (19 mm at 500 mg/mL), which exceeded the gentamicin control (20 mm). The MIC values for neem extract were 62.5 mg/mL for E. coli, 250 mg/mL for S. aureus, and 500 mg/mL for S. typhi. In contrast, guava leaf aqueous extract exhibited limited antimicrobial activity, showing inhibition only against S. aureus (11 mm) at the highest concentration tested (500 mg/mL), with no activity against E. coli or S. typhi. The study concludes that neem leaf extract possesses significant broad-spectrum antimicrobial properties, supporting its traditional use in treating bacterial infections. The limited activity of guava aqueous extract suggests the need for alternative extraction methods to optimize bioactive compound recovery. These findings provide scientific validation for the traditional medicinal use of neem leaves and highlight the importance of extraction methodology in harnessing the therapeutic potential of medicinal plants.