The discovery of antioxidants in marine microorganisms and their protective effects on the hepatic cells from chemical-induced oxidative stress.

The marine environment is emerging as a biodiversity resource for the discovery of natural molecules or chemical scaffolds with pharmaceutical activity. Marine microbes have a tremendous ability to sense and respond to their surroundings to survive in a stressful environment by producing different molecules. As oxidative stress is directly or indirectly involved in various pathological conditions in humans, we believe that marine-derived antioxidant molecules will have a great prospect as a novel antioxidant molecule. We, in this work, explored the marine microbial resources from the Gulf of Mannar, Bay of Bengal, India. High-throughput screening of antioxidant molecule producing marine microbes has revealed that extract from Kocuria marina CDMP 10, can effectively reduce the DPPH free radical. Methanolic crude extract obtained by the freeze-thawing was fractionated and purified by using activity guided purification with the help of reverse phase HPLC and analysed through UPLC-MS. Chemical analysis, as well as MS-spectra, indicated that marine bacteria K. marina CDMP 10 derived antioxidant fraction contains the short peptides. The antioxidant activity of the three highly hydrophobic peptides, (Ser-Ser-Gln, Phe-Glu, Asp-Ile and Leu-Glu) was confirmed by in vitro as well as a cell-based assay. These small peptide molecules are noncytotoxic and can prevent the human cells from chemical-induced oxidative stress. Ser-Ser-Gln peptide demonstrated a potent free radical scavenging activity in Hepatocellular carcinoma cell lines. This study suggests that these short peptides from K. marina CDMP 10 may serve as a potential pharmaceutical candidate with antioxidant activity.