Evaluation of Antimicrobial Potential of Locally Formulated Soap Containing Neem (Azadirachta indica) and Turmeric (Curcuma longa) Powders

Research Article

Abstract

Background: The increasing prevalence of antibiotic-resistant pathogens and consumer preference for natural products has renewed interest in plant-based antimicrobial formulations. This study was undertaken to formulate soaps incorporating neem (Azadirachta indica) and turmeric (Curcuma longa) powders and to evaluate their antibacterial efficacy against Staphylococcus aureus and Escherichia coli, in comparison with selected commercial soaps.

Methods: Antimicrobial activity was assessed using three complementary methods: total viable count (TVC) following simulated hand-washing, disc diffusion assay, and broth microdilution for minimum inhibitory concentration (MIC) determination. The MICs of the formulated soaps were determined via two-fold serial dilutions ranging from 100 to 1.56 µL/200 µL.

Results: In the TVC assay, neem soap achieved a 90% reduction in microbial load post-handwash, whereas turmeric soap and Dettol soap each showed a 70% reduction, followed by Lifebuoy (50%) and Capri (30%). In disc diffusion testing, neem soap produced the largest inhibition zones (20 mm against both S. aureus and E. coli). Turmeric soap exhibited moderate activity (14 mm and 10 mm, respectively), while among commercial soaps, Dettol showed the highest zones (17 mm against S. aureus and 13 mm against E. coli), followed by Lifebuoy (12 mm and 11 mm) and Capri (10 mm and 9 mm). The MIC of neem soap was 12.5 µL/200 µL against S. aureus and 25 µL/200 µL against E. coli; for turmeric soap, MIC values were 25 µL/200 µL and 50 µL/200 µL, respectively.

Conclusion: The formulated neem and turmeric soaps demonstrated potent, dose-dependent antibacterial activity, with neem soap outperforming all commercial products tested. These findings suggest that herbal-based soaps represent a promising, cost-effective alternative to conventional antimicrobial soaps for personal hygiene and infection control.