Diaporindenes A–D: Four Unusual 2,3-Dihydro‑1H‑indene Analogues with Anti-inflammatory Activities from the Mangrove Endophytic Fungus Diaporthe sp. SYSU-HQ3

Diaporindenes A–D (1–4), four unusual 2,3-dihydro-1H-indene isomers, a novel isoprenylisobenzofuran A (5), two new isoprenylisoindole alkaloids diaporisoindoles D and E (6 and 7), and a new benzophenone derivative tenellone D (11), together with four known biogenetic agents (8–10 and 12), were all separated from the endophytic fungus Diaporthe sp. SYSU-HQ3 guided by ultraperformance liquid chromatography high-resolution mass spectrometry. The absolute configurations of 1–7 and 11 were defined by X-ray diffraction, quantum chemical calculations, and spectroscopic analysis. Diaporindenes A–D (1–4) possessed an unprecedented chemical skeleton featuring a 2,3-dihydro-1H-indene ring and a 1,4-benzodioxan moiety. All of the isolates (1–12) were tested for their inhibitory effects on the production of nitric oxide in lipopolysaccharide-induced microglial cells (RAW 264.7 cells). Compounds 1–5, 8, and 9 were found to exhibit significant inhibitory effects against nitric oxide production with IC50 values from 4.2 to 9.0 μM and SI values from 3.5 to 6.9. In addition, the structure–activity relationships of all compounds were summarized.