Antimicrobial activity and cytotoxicity of endophytic fungi associated with four medicinal plants from Sudan

Abstract

In this study four medicinal plants, used in Sudan to cure different types of health problems, were selected for isolation of endophytic fungi, fungi reside within the plant host tissues without causing disease symptoms. A total of 20 distinct endophytic fungi species were isolated from surface- sterilized parts of the plants, Kigelia africana, Cymbopogon proximus, Balanites egyptiaca and Solenostemma argel. Nine of the isolated fungi were identified according to their microscopic and macroscopic characteristics. The remaining strains which did not have spores or have sterile mycelium were given codes as unidentified species (UID). The ethyl acetate extracts of the pure isolated endophytic fungi were prepared from fungal material and culture media. Antimicrobial activity using agar diffusion well against different pathogenic microbes at 500 µg/ml concentration and MTT cytotoxicity bioassay using African green monkey kidney normal cell line (vero cell line) were performed for all extracts. The extracts were then screened for the presence of Taxol, a diterpene anticancer drug, using different chromatographic and spectroscopic techniques. The antimicrobial activity against the most common pathogenic bacteria and fungi revealed significant activity with inhibition zone range between 14- 37 mm compare to antimicrobial controls 17- 26 mm at 40µg/ml. The cytotoxicity assay results showed that the IC50 values were quite diverse, ranging from 3.5 μg/ml to more than 1000 μg/ml, whereas that of the positive control podophyllotoxin, a wellknown cytotoxic lignan, was 2.72 μg/ml. Taxol was detected in reference to standard one from the extract of unidentified fungi No. 10 of Kigelia africana,. Future work will focus on the bioassay guidedfractionation of potent bioactive extracts to isolate the active compounds responsible for their activities. Improvement of culture techniques and the application of genetic engineering to increase taxol production will be carried out, followed by isolation of pure Taxol from the active crude extract.