Bioactive Sesquiterpenes from the Edible Mushroom Flammulina velutipes and Their Biosynthetic Pathway Confirmed by Genome Analysis and Chemical Evidence

Abstract

Twelve putative sesquiterpene synthases genes were found in clades along with enzymes with 1,6-, 1,10-, and 1,11-cyclase activities in the genome of Flammulina velutipes. Chemistry investigation of F. velutipes led to the identification of two seco-cuparane sesquiterpenes, flammufuranone A (1) and B (2); 13 new sesquiterpenes with nor-eudesmane, spiroaxane, cadinane, and cuparane skeletons (3-14, 16); as well as two new ergosterol derivatives (17 and 18). Sesquiterpenes (3-14) derived from 1,10-cyclizing enzyme were first reported from this mushroom. The absolute configurations in 1 (3R,7S) and 2 (3R,7R) were assigned by electronic circular dichroism (ECD) calculation. The absolute configuration in 3 was confirmed by X-ray diffraction analysis. The absolute configurations in the 1,2-diol moiety of 13, and in the 1,3-diol moiety of 17 and 18 were determined using Snatzke's method. Among these compounds, 3, 5, 13, and 14 were found to inhibit the HMG-CoA reductase with IC50 of 114.7, 77.6, 55.5, and 87.1 μM, respectively. Compounds 5, 6, 7, 10, 13, and 14 showed DPP-4 inhibitory activity with IC50 of 75.9, 83.7, 70.9, 79.7, 80.5, and 74.8 μM, respectively. The biosynthesis for sesquiterpenes in F. velutipes was also discussed.