Candida species is the fourth common cause of blood stream infections all over the world which is life threatening. Invasive candidiasis leads to increased mortality and morbidity especially in immunosuppressed. The antifungal resistance pattern in high-risk patients is major concern.

The present study was to access the anticandidal activity of leaves, bark and seeds of Cassia fistula against fluconazole resistant Candida species, C. albicans, C. glabrata, C. krusei, C. tropicalis, C. kefyr and C. parapsilosis isolated from HIV patients. The predominant phytochemical component responsible for fungicidal activity was to be accessed.

Ethanol, chloroform, petroleum ether and aqueous extracts of leaves, bark and seeds of C. fistula linn. was evaluated against Microbial type culture collection (MTCC) Candida strains and 21 fluconazole resistant clinical isolates. Antifungal activity was evaluated by agar diffusion and broth dilution techniques. The active phytochemical component present in the ethanol extract of seeds was accessed by high performance thin layer chromatography. The docking study was done with lanosterol 14-alpha demethylase, the azole drug target with the predominant phytochemical from the extract having antifungal activity.

All the extracts of C. fistula showed excellent anticandidal activity. Ethanol extract of C. fistula seed exhibited the most inhibitory activity. C. krusei and C. parapsilosis were the most inhibited and C. kefyr was the least inhibited species. The predominant phytochemical active component of the ethanol extract of seed was gallic acid. Gallic acid showed excellent binding with lanosterol 14-alpha demethylase.

The present study reports the antifungal activity of various extracts of Cassia fistula for the first time against fluconazole resistant Candida isolates. We can conclude that the polyphenolic compound gallic acid is a potent natural antifungal agent. Further research is needed to assess the pharmacokinetic property.