الفهرس 
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Abstract
Endophytes are endosymbiotic groups of microorganisms that colonize their host plant tissues and act as reservoirs of novel bioactive secondary metabolites that constitute an important source for drug discovery. In this work, two medicinal plants were selected as potential candidates for the isolation of bacterial endophytes, Solanum nigrum and Withania somnifera. The selection is based on their long history of usage in folk medicine and a variety of therapeutic benefits, in particular the anticancer potential of their secondary metabolites. A single bacterial kind is recovered from fruits of each of them after proper surface sterilization. Analysis of endophytes’ 16SrDNA nucleotide sequences showed that Solanum nigrum harbor Staphylococcus warneri while Withania somnifera fruits harbor Staphylococcus hominis. Secondary metabolites in endophytes’ culture filtrate are extracted by three organic solvents (hexan, ethyl acetate, and butanol). These crude extracts were tested for their anticancer effect against DU-145, HepG2 and MCF-7 human cancer cell lines by the SRB (Sulforhodamine B) assay.
The best cytotoxic impact of endophytes’ secondary metabolites was seen for that of Staphylococcus warneri hexan crude extract for all tested cancer cell lines (DU-145, HepG2 and MCF-7) as determined by the inhibitory concentration (IC50) to be at 52.6 μg/mL, 65.5 μg/mL and 61 μg/mL, respectively, and also that of Staphylococcus hominis to be at 68.85 μg/mL, 64.18 μg/mL and 51.42 μg/mL, respectively. Butanol crude extract of Staphylococcus warneri induces cell death of tested human cancer cell lines with IC50 values of 54.58 μg/mL, 75.18 μg/mL and 85.61 μg/mL respectively while that of Staphylococcus hominis was not highly effective. Also, ethyl acetate crude extract of Staphylococcus hominis showed very low efficacy, while that of Staphylococcus warneri was not effective. It can be concluded that Staphylococcus warneri and Staphylococcus hominis hexan crude extract could be used as renewable bioresources of biosynthesis of anticancer drugs.