Thesis (M.Sc.) - Cairo University - Faculty of Science - Department of Microbiology

The discovery and production of novel bioactive compounds from natural sources is the target of several studies to combat the emergence of multidrug resistant pathogens. Calotropis procera plant was collected from petrified forest protected area located at El Qattameya, New Cairo, Egypt. In the present study, 50 endophytic microorganisms (8 fungal isolates and 42 bacterial isolates) isolated from C. procera plant and screened for their antimicrobial and antioxidant activities. The bioactive endophytes were selected for phenotypic and molecular identification. Among all isolated endophytes, Aspergillus ochraceus strain CPE7 showed the highest antimicrobial and antioxidant activities was selected for further investigations.The crude extract of A. ochraceus was subjected to chromatographic and spectroscopic techniques to purify the bioactive compounds and elucidate their chemical structures.This led to identification of butyrolactone 1 (BL-1) as bioactive compound. BL-1 exhibited antibacterial activity against Staphylococcus aureus, Bacillus subtilis and Micrococcus luteus with MICs 32, 128 and 64 og/ml, respectively. But no activity was observed against Escherichia coli and Salmonella typhi. Furthermore, BL-1 exhibited high antioxidant activity against DPPH. In the in vivo study, silkworm larvae were used as model organism, which declared that BL-1 exhibited no cytotoxicity up to concentration 48 mg/ml. It also protected silkworms against the pathogenic bacteria S. aureus. So, bioactive butyrolactone 1 could be a promising candidate in pharmaceutical field

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