Abstract
The endophytic fungus Fusarium equiseti was isolated from the brown alga Padina pavonica, collected from the Red Sea. The fungus was identified by its morphology and 18S rDNA. Cultivation of this fungal strain in biomalt-peptone medium led to isolation of 12 known metabolites of diketopeprazines and anthraquinones. The organic extract and isolated compounds were screened for their inhibition of hepatitis C virus NS3/4A protease (HCV PR). As a result, the fungal metabolites showed inhibition of HCV protease (IC(50) from 19 to 77 μM), and the fungus was subjected to culture on Czapek's (Cz) media, with a yield of nine metabolites with potent HCV protease inhibition ranging from IC(50) 10 to 37 μM. The Cz culture extract exhibited high-level inhibition of HCV protease (IC(50) 27.6 μg/mL) compared to the biomalt culture extract (IC(50) 56 μg/mL), and the most potent HCV PR isolated compound (Griseoxanthone C, IC(50) 19.8 μM) from the bio-malt culture extract showed less of an inhibitory effect compared to isolated ω-hydroxyemodin (IC(50) 10.7 μM) from the optimized Cz culture extract. Both HCV PR active inhibitors ω-hydroxyemodin and griseoxanthone C were considered as the lowest selective safe constituents against Trypsin inhibitory effect with IC(50) 48.5 and 51.3 μM, respectively.