A chemical investigation of the marine-derived fungal strain Penicillium glabrum (SF-7123) revealed a new citromycetin (polyketide) derivative (1) and four known secondary fungal metabolites, i.e, neuchromenin (2), asterric acid (3), myxotrichin C (4), and deoxyfunicone (5). The structures of these metabolites were identified primarily by extensive analysis of their spectroscopic data, including NMR and MS data. Results from the initial screening of anti-inflammatory effects showed that 2, 4, and 5 possessed inhibitory activity against the excessive production of nitric oxide (NO) in lipopolysaccharide (LPS)-stimulated BV2 microglial cells, with IC50 values of 2.7 µM, 28.1 µM, and 10.6 µM, respectively. Compounds 2, 4, and 5 also inhibited the excessive production of NO, with IC50 values of 4.7 µM, 41.5 µM, and 40.1 µM, respectively, in LPS-stimulated RAW264.7 macrophage cells. In addition, these compounds inhibited LPS-induced overproduction of prostaglandin E2 in both cellular models. Further investigation of the most active compound (2) revealed that these anti-inflammatory effects were associated with a suppressive effect on the over-expression of inducible nitric oxide synthase and cyclooxygenase-2. Finally, we showed that the anti-inflammatory effects of compound 2 were mediated via the downregulation of inflammation-related pathways such as those dependent on nuclear factor kappa B and p38 mitogen-activated protein kinase in LPS-stimulated BV2 and RAW264.7 cells. In the evaluation of the inhibitory effects of the isolated compounds on protein tyrosine phosphate 1B (PTP1B) activity, compound 4 was identified as a noncompetitive inhibitor of PTP1B, with an IC50 value of 19.2 µM, and compound 5 was shown to inhibit the activity of PTP1B, with an IC50 value of 24.3 µM, by binding to the active site of the enzyme. Taken together, this study demonstrates the potential value of marine-derived fungal isolates as a bioresource for bioactive compounds.
Keywords: PTP1B; anti-inflammation; anti-neuroinflammation; marine-derived fungi.