New naturally occurring phenolic derivatives from marine Nocardiopsis sp. AS23C: Structural elucidation and in silico computational studies

Abstract

In our persistent research for new bioactive secondary metabolites from marine actinomycetes, Nocardiopsis sp. AS23C strain was isolated from the marine Alga Sargassum arnaudianum coltected in the Red Sea at Hurghada coast, Egypt. A large-scale fermentation of the strain on M₂ medium containing 50% sea water, followed by fractionation and purification of the obtained extract afforded a new phenolic acid derivative, 4-amino-6-methylsalicylic acid (1a), together with 5-methylresorcinol (2) and linoleic acid (3). Their molecular structures were proved through the sophisticated spectroscopic analyses including exhaustive 1D and 2D NMR (1 and 2-Dimensional Nuclear Magnetic Resonance) as well mass spectroscopy techniques. The extract exhibited antibacterial activity against the Gram-positive Staphylococcus aureus, Bacillus subtilis ATCC6051, and Streptomyces viridochromogenes Tu 57. An in vitro cytotoxicity assaying of 1a and 2 against the human cervix carcinoma cell line (KB-3-1), prohounced no obvious activity. Additionally, in silico predictions of physicochemical properties, ADME (absorption, distribution, metabolism and excretion) parameters, acute oral toxicity and indication of toxicity targets were performed for 1a and 2 in comparison with the antioxidant agent orsellinic acid.