Isolation and characterization of bioactive compounds with antibacterial, antioxidant and enzyme inhibitory activities from marine-derived rare actinobacteria, Nocardiopsis sp. SCA21

Abstract

A rare actinobacteria strain designated SCA21, producing bioactive metabolites was isolated from marine sediment of Havelock Island, Andaman and Nicobar Islands, India. Analysis of 16S rRNA sequences suggested that the strain SCA21 belonged to the genus Nocardiopsis. Chemical investigation of the fermentation broth led to the isolation of two pure bioactive compounds (1-2). Compound 1: 4-bromophenol, a bromophenol derivative; Compound 2: Bis (2-ethylhexyl) phthalate, a phthalate ester. The structure of compound 1 and 2 were elucidated by the detailed analysis of FT-IR, HR-ESI-MS, 1D and 2D NMR, along with literature data analysis. The isolated metabolites were evaluated for enzyme inhibition activity against α-glucosidase and α-amylase, free radical scavenging activity against DPPH and ABTS radicals, metal chelating and antibacterial activity against clinical pathogens. 1 and 2 exhibited remarkable enzyme inhibitory activities against α-glucosidase. However, Compound 2 was found less active against α-amylase. They showed significant free radical scavenging activity against DPPH and ABTS radicals. In addition, except the strain Salmonella typhi ATCC 25241 and Listeria cytogens ATCC 13932, 1 and 2 showed broad spectrum inhibitory activity against MRSA ATCC NR-46171, MRSA ATCC-46071, Klebsiella pneumonia ATCC 13883, Bacillus subtilis ATCC 6633, Staphylococcus aureus ATCC 12600. In conclusion, to best of our knowledge these findings are the first report of isolation of 4-bromophenol and Bis (2-ethylhexyl) phthalate from genus Nocardiopsis, thus suggesting that rare actinomycetes are promising source of therapeutically important bioactive metabolites.

Keywords: Antibacterial; Antioxidants; Bioactive compounds; Enzyme inhibitors; Marine organisms; Nocardiopsis.