FUNGICIDAL EFFICACY AND VALIDATION OF NEEM (AZADIRACHTA INDICA) AND LEMON (CITRUS LIMON) BASED HERBAL SURFACE CLEANER AGAINST ASPERGILLUS NIGER: A NEUTRALIZATION AND LOG REDUCTION KINETICS STUDY

Abstract

With increasing concerns about antimicrobial resistance and the environmental impact of synthetic disinfectants, there is growing interest in plant-derived alternatives for surface sanitation. In this study, the fungicidal effectiveness of a newly developed herbal surface cleaner containing neem (Azadirachta indica) and lemon (Citrus limon) extracts was investigated against Aspergillus niger ATCC 16404. The formulation was evaluated using neutralization validation, appropriate positive and negative controls, and quantitative suspension testing. Concentrations ranging from 3% to 7% were assessed at contact times of 10, 20, 30, and 40 minutes, with all tests performed in triplicate. The neutralization study confirmed that the neutralizer effectively quenched the antimicrobial activity of the formulation without affecting fungal recovery, yielding inoculum counts between 1.40 × 10⁷ and 1.52 × 10⁷ CFU/mL. Positive control results demonstrated stable fungal populations, with initial counts ranging from 1.48 × 10⁷ to 1.55 × 10⁷ CFU/mL (log₁₀ 7.17 7.19), confirming the reliability of the test system. The herbal cleaner exhibited strong antifungal activity across all tested concentrations. Complete elimination of A. niger was observed with the 3% and 7% formulations at every contact time examined, corresponding to a log reduction of 7.18. Although the 4% and 6% formulations showed slightly lower activity after 10 minutes of exposure (mean log reduction 6.88), complete fungal inactivation was achieved within 20 minutes. Statistical analysis using one-way ANOVA demonstrated significant differences among the tested concentrations and exposure times (p < 0.05), highlighting the influence of both factors on fungicidal performance. Overall, the results indicate that the neem–lemon herbal surface cleaner possesses potent antifungal properties and can serve as an effective, environmentally friendly alternative to conventional chemical disinfectants for routine surface hygiene applications.