Biological Activity Of Endophytic Fungi Associated With Medicinal Plants From Sudan

Abstract

The microorganisms which colonize healthy plant tissues without causing any obvious symptoms and noticeable damage to the host are called endophytes. They encompass a heterogenous group of organisms including bacteria, fungi and actinomycetes. Endophytes with unique ecological niches exhibit unique physiological and biochemical characteristics leading to the production of niche specific secondary metabolites which may have pharmacological potential. In this study endophytic fungi associated to medicinal plants growing in Sudan were identified and their bioactive potential was evaluated. Thirty eight endophytic fungal strains were recovered from the leaves and stems of Datura stramonium L, Moringa oleifera Lam., Prosopis chilensis (Molina) Stuntz, Calotropis procera Ait., Catharanthus roseus L., Euphorbia prostrata Ait., Trigonella foenum-graecum L., and Vernonia amygdalina Del.. The ethyl acetate extracts obtained from the isolated fungal endophytes were screened for evaluation of their antimicrobial, antioxidant and anticancer activity. The antimicrobial activity of extracts was determined using the disc diffusion and microdilution methods. Endophytic fungi crude extracts isolated from of P. chilensis showed the highest antibacterial activity compared to other isolates. They all inhibited Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumonia, Salmonella Typhi and and Staphylococcus aureus with minimum inhibitory concentration value of 25 μg/mL. The antioxidant activity was determined using the 1, 1-diphenyl-2-picrylhydrazyl (DPPH) assay. A remarkable scavenging activity was obtained from endophytic fungi Aspergillus sp. and Emericella bicolor isolated from D. stramonium and M. oleifera respectively where they possessed activity higher than that obtained from the standard control ascorbic acid. Moreover, a positive correlation between the phenolic content of the extracts with their antioxidant activity was also observed. Cytotoxicity studies were performed by the MTT assay using three cancer cells type; Human breast carcinoma (MCF7), and Colon adenocarcinoma (HT29, HCT116). Results of the studied samples showed that, the endophytic fungi Paecilomyces sp. displayed very high cytotoxicity (IC50 value of 1.51 MCF7 ± 0.2 μg/mL) followed by Cladosporium sp. (IC50 value of 10.5 MCF7 ± 1.5 μg/mL). Astonishingly, these two cytotoxic fungi were isolated from E. prostrata leaves and stems which showed no cytotoxic activity (IC50 value > 100 μg/mL). However, the endophytes isolated from the high cytotoxic Catharanthus roseus leaves (IC50 7.00 HT29 ± 0.43 and 7.83 HCT116 ± 1.28) showed very weak or no activity. In conclusion, the endophytic flora associated within these widely used medicinal plants could be a potential source of novel products of great importance in medicine and industry.