Anti-yeast activity of endophytic fungi isolated from medicinal herb Ocimum sanctum with emphasis on Candida albicans

Abstract

Endophytic fungi, Lasiodiplodia pseudotheobromae IBRL OS-64 and Muscodor sp. IBRL OS-94 were previously isolated from the leaf of medicinal plant, Ocimum sanctum was screened for their anti-yeast activity against pathogenic yeast. Both fungal isolates were cultivated in submerged fermentation using yeast extract sucrose broth as culture medium enriched with plant water extract and incubated for 20 d at 30°C with an agitation speed of 120 rpm. Preliminary study via agar plug diffusion assay revealed that both fungal isolates possess a fair anti-yeast activity against three out of four test yeast including Candida albicans, C. utilis and Rhodotorula rubra. On the disk diffusion assay, the ethyl acetate extract of L. pseudotheobromae IBRL OS-64 and Muscodor sp. IBRL OS-94 showed significant anti-yeast activity with the size of the inhibition zone ranging in between 9.6±0.5 - 21.3±0.5 mm and 14.4±0.5 - 20.2±0.7 mm respectively. As for ethyl acetate extract from L. pseudotheobromae OS-64, the MIC and MYC values were in the range of 500 – 1000 μg/mL and 2000 – 8000 μg/mL respectively. On the other hand, the MIC and MYC values of ethyl acetate extract of Muscodor sp. OS-94 ranged between 250 – 500 μg/mL and 1000 – 4000 μg/mL respectively. The time-kill assay demonstrated that the growth of C. albicans cell was dose-dependent in which the extract concentration was lower and higher than the MIC value showing yeastostatic and yeastocidal effects respectively. The scanning and transmission electron microscopes observation revealed that the candidal cells expose to extract experienced severity of morphological deterioration which led to cell death beyond repair and thus suggesting that the fungal extract could be a potential anti-candidal agent.