Antioxidant and anticancer activity of 3,5-dihydroxy-4-isopropylstilbene produced by Bacillus sp. N strain isolated from entomopathogenic nematode.

3,5-Dihydroxy-4-isopropylstilbene is a natural phytoalexin and was first identified as bacterial secondary metabolites. The aim of this study is to investigate in vitro antioxidant and anticancer activity of 3,5-dihydroxy-4-isopropystilbene purified from the cell free culture filtrate of Bacillus sp. N strain associated with rhabditid entomopathogenic nematode. Antioxidant activity was evaluated by five separate methods: free radical scavenging, reducing power assay, chelating effects on ferrous ions, NBT superoxide radical scavenging assay and hydroxyl radical scavenging activity. The stilbene recorded powerful antioxidant activity at various antioxidant systems in vitro. The superoxide radical scavenging (92.1 %) and hydroxyl radical scavenging (83.4 %) activities of the stilbenes at 100 μg/ml were higher than the butylated hydroxyanisole, the known antioxidant agent. Anticancer activity of stilbene was tested against breast cancer (MDAM B-231), cervical cancer (HeLa), lung cancer (A 549), colon cancer (HTL 116) cell lines using MTT method. The induction of apoptosis was studied by morphological analysis, apoptotic cell staining, caspase 3 activation assay and cell cycle analysis using flow cytometry. Stilbene induced significant morphological changes and DNA fragmentation associated with apoptosis in HeLa cells. Acridine orange/ethidium bromide stained cells indicated apoptosis induction by stilbene. Up-regulation of caspase 3 activity was also found in cells treated with stilbene. Flow cytometry analysis showed an increase in the percentage of apoptotic cells in sub G0 phase (2.4 % in control plates to 11.4 % in 25 μg/ml of stilbene) confirming the stilbene induced apoptosis. The results of the present study showed that stilbene demonstrated a strong antioxidant and anticancer effects. These suggest that stilbene may be used as possible natural antioxidant and anticancer agents to control various human diseases.