The present study investigates the effect of varying pH on the antimicrobial activity of Aloe vera L. extracts derived from both in vivo grown and in vitro regenerated plants. Ethyl acetate extracts of whole leaf and inner gel were evaluated against a wide range of clinically significant microorganisms, including bacterial species such as Escherichia coli, Staphylococcus aureus, Salmonella typhi, fungal species like Aspergillus spp., and yeasts including Candida albicans. The extracts were adjusted to different pH levels (3.0, 6.0, and 9.0) to assess their stability and efficacy under varying acidic and alkaline conditions. Antimicrobial activity was determined using the disc diffusion method, and results were statistically analysed using ANOVA. The findings revealed that the antimicrobial activity of Aloe vera L. extracts was significantly influenced by pH. Maximum inhibitory effects were observed under acidic conditions (pH 3.0), where the activity was slightly higher than the control. At neutral pH (6.0), a marginal reduction in antimicrobial activity was noted, whereas at alkaline pH (9.0), a significant decline in inhibitory effects was observed across most tested microorganisms. Importantly, control solutions adjusted to similar pH levels did not exhibit antimicrobial activity, confirming that the observed effects were due to the plant extracts rather than pH alone. The results suggest that the bioactive compounds in Aloe vera L. are more stable and effective in acidic environments, possibly due to their cationic nature, which enhances interaction with negatively charged microbial cell surfaces. This study highlights the potential application of Aloe vera L. extracts as natural antimicrobial agents, particularly in acidic conditions, and supports their use in pharmaceutical and food preservation industries.
Neelofar Khanam*1,2,3, G. K. Sharma3 (Fri,) studied this question.