Chemical Constituents from a Mangrove‐Derived Actinobacteria Isoptericola chiayiensis BCRC 16888 and Evaluation of Their Anti‐NO Activity

Cultivation of the actinobacteria strain Isoptericola chiayiensis, a mangrove‐derived actinobacteria that was isolated from a mangrove soil collected in Chiayi County, resulted in the isolation of one new 2‐furanone derivative, isopterfuranone (1), one new sesquiterpenoid, isopterchiayione (2), one new benzenoid derivative, isopterinoid (3), five new flavonoids, chiayiflavans A−E (4–8), and 4 metabolites isolated for the first time from nature source, methyl 3‐(4‐methyl‐2,5‐dioxopyrrolidin‐3‐yl)propanoate (9), 3‐ethyl‐4‐methylpyrrolidine‐2,5‐dione (10), chiayiensol (11) and chiayiensic acid (12). Their structures were determined through in‐depth spectroscopic and mass‐spectrometric analyses. Most of the isolates showed potent inhibitory effects on NO production in LPS‐stimulated RAW 264.7 murine macrophages cells with IC50 values ranging from 9.36 to 40.02 μM. Of these isolates, 4 and 5 showed NO inhibitory activity with IC50 values of 17.14 and 9.36 μM, stronger than the positive control quercetin (IC50=36.95 μM). This is the first report on flavan metabolites from the genus Isoptericola.