Bioactivity of medicinal plant extracts against human fungal pathogens and evaluation of toxicity using Vero cells

Medicinal plants are a potential source of new antifungal agents to combat the development of drug-resistant fungi. This study aims to investigate the aerial parts of Alternanthera sessilis (Amaranthaceae) and Ipomoea aquatica (Convolvulaceae), and the leaves of Catunaregam spinosa (Rubiaceae) and Tradescantia spathacea (Commelinaceae) for antifungal activity and cytotoxicity. The plant materials were extracted sequentially using hexane, chloroform, ethyl acetate, ethanol, methanol, and distilled water. The antifungal activity was evaluated against four species of yeasts and two species of filamentous fungi using a colorimetric broth microdilution method. The toxicity of the extracts was assessed using African monkey kidney epithelial (Vero) cells. All 24 extracts from the four medicinal plants showed inhibitory activity against all fungal species, except Aspergillus fumigatus, with a minimum inhibitory concentration range of 0.04-2.50 mg/mL. The antifungal activity of these plants was more prominent on the yeasts than the filamentous fungi. Generally, the less polar extracts (hexane, chloroform, and ethyl acetate) of the plants had stronger antifungal activity than the more polar extracts (ethanol, methanol, and water). In contrast, toxicity assessment revealed that the less polar extracts showed relatively higher toxicity towards the Vero cells than the more polar extracts. The lowest median cytotoxic concentration was shown by the chloroform extract of A. sessilis (17.4 ± 0.4 μg/mL). All water extracts, the methanol extract of I. aquatica, and the ethyl acetate, ethanol, and methanol extracts of T. spathacea did not show significant toxicity (P>0.05) towards the Vero cells. The results suggested that Tradescantia spathacea has the most promising potential for pharmaceutical developments due to its broad spectrum and selective activity against human fungal pathogens.