In the current study, the extraction of bioactive secondary metabolites from the macroalgae Padina pavonica with different organic solvents were examined. The influence of three different solvents, i.e. ethyl acetate, acetone, and ethanol on the extraction of P. pavonica extracts were analyzed for major phenolic sub-groups, i.e. total phenolics, flavonoids, and tannins as well as total sulfated polysaccharide and carotenoids using spectrometric methods. Meanwhile, the total bioactive secondary metabolites were measured by GC -MS. The antioxidant activities were evaluated using 2,2-diphenyl-1-picrylhydrazyl (DPPH), and the antimicrobial activities were assessed against different pathogenic bacterial and fungal strains (Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, Enterococcus faecalis, and Candida albicans.). The aim of the study was also to find the correlation between the chemical constituents of the extracts and their biological activities. The current study revealed that these extracts exhibit a good antioxidant activity, especially acetone extract, with high reducing capacity (80.58%). Also, the antimicrobial activities for acetone extract was higher than either the ethanol and ethyl acetate organic solvents due to their higher contents in bioactive compounds as reflected from their phytochemical screening and GC-MC. The GC-MS analysis revealed the presence of different phytochemical compounds resulted in 20 peaks for acetone, 14 for ethanol, and 12 for ethyl acetate. The results of this investigation could be interesting for future studies dealing with the application of P. pavonica in marine biotechnology, textile industry, nutrition, and pharmaceuticals for their higher antioxidant as well as antimicrobial activities.
