Comparative Antifungal Efficacy of Persea americana, Azadirachta indica Extracts and Synthetic Drugs against Candida Species

Abstract

There is an urgent need for new therapeutic options due to the rising incidence of antifungal resistance, especially among Candida species. Although medicinal plants such as Azadirachta indica (neem) and Persea americana (avocado) have long been used to treat infections, a thorough assessment of their relative effectiveness against modern clinical fungal isolates is necessary. Clinical Candida isolates were characterized using phenotypic and molecular techniques. Their susceptibility to fluconazole, ketoconazole, and amphotericin B was determined by agar well diffusion. Methanolic leaf extracts of P. americana and A. indica were prepared, and their phytochemical constituents identified using Gas Chromatography-Mass Spectrometry (GC-MS). The antifungal activity of the extracts was evaluated and compared to the conventional drugs using agar well diffusion and agar dilution methods to determine the Minimum Inhibitory Concentration (MIC) and Minimum Fungicidal Concentration (MFC). Molecular identification confirmed the isolates as Candida albicans, C. parapsilosis, and C. tropicalis. All isolates (100%) were resistant to fluconazole, while varying resistance pattern was observed for ketoconazole (44.4%) and amphotericin B (44.4%). GC-MS analysis revealed diverse bioactive compounds in both extracts, including fatty acids, terpenoids, and phenolics. P. americana extract showed broad-spectrum activity, inhibiting all isolates at 100 mg/ml, including those resistant to all synthetic drugs, with an MIC of 20 mg/ml and an MFC of 20-30 mg/ml. In contrast, A. indica extract showed minimal activity in diffusion assays, although it shared a similar MIC (20 mg/ml), and MFC (30 mg/ml) when subjected to dilution assays. This study confirms high rates of antifungal resistance among clinical Candida isolates, with both plant extracts demonstrating inhibitory potential. Persea americana leaf extract showed better efficacy, comparable to amphotericin B and fluconazole. These findings validate its ethnomedicinal use and strongly advocate for its further development as a promising source of novel antifungal agents against drug-resistant candidiasis.