Isolation of Unstable Isomers of Lucilactaene and Evaluation of Anti-Inflammatory Activity of Secondary Metabolites Produced by the Endophytic Fungus Fusarium sp. QF001 from the Roots of Scutellaria baicalensis

Abstract

The filamentous fungal pathogen Fusarium sp. causes several crop diseases. Some Fusarium sp. are endophytes that produce diverse valuable bioactive secondary metabolites. Here, extensive chemical investigation of the endophytic fungus, Fusarium sp. QF001, isolated from the inner rotten part of old roots of Scutellariae baicalensis resulted in the isolation of two new photosensitive geometrical isomers of lucilactaene (compounds 2 and 3) along with lucilactaene (6) and six other known compounds (fusarubin (1), (+)-solaniol (4), javanicin (5), 9-desmethylherbarine (7), NG391 (8) and NG393 (9)). Newly isolated isomers and lucilactaene were unstable under light at room temperature and tended to be a mixture in equilibrium state when exposed to a polar protic solvent during reversed phase chromatography. Normal phase chromatography under dim light conditions with an aprotic mobile phase led to the successful isolation of the relatively unstable isomers 2 and 3. Their structures were elucidated as 8(Z)-lucilactaene (2) and 4(Z)-lucilactaene (3) based on spectroscopic data. The absolute configuration of 4 was speculated to be R by computer-assisted specific rotation analysis. The isolated compounds could inhibit NO production and suppress pro-inflammatory cytokines expression in LPS-stimulated macrophage cells. These properties of the isolated compounds indicate their potential use as anti-inflammatory drugs.