Abstract:
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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. |