Raistrickiones A−E from a Highly Productive Strain of Penicillium raistrickii Generated through Thermo Change

Abstract

Three new diastereomers of polyketides (PKs), raistrickiones A−C ( 1– 3), together with two new analogues, raistrickiones D and E ( 4 and 5), were isolated from a highly productive strain of Penicillium raistrickii, which was subjected to an experimental thermo-change strategy to tap its potential of producing new secondary metabolites. Metabolites 1 and 2 existed in a diastereomeric mixture in the crystal packing according to the X-ray data, and were laboriously separated by semi-preparative HPLC on a chiral column. The structures of 1– 5 were determined on the basis of the detailed analyses of the spectroscopic data (UV, IR, HRESIMS, 1D, and 2D NMR), single-crystal X-ray diffractions, and comparison of the experimental and calculated electronic circular dichroism spectra. Compounds 1– 5 represented the first case of 3,5-dihydroxy-4-methylbenzoyl derivatives of natural products. Compounds 1– 5 exhibited moderate radical scavenging activities against 1,1-diphenyl-2-picrylhydrazyl radical 2,2-diphenyl-1-(2,4,6-trinitrophenyl) hydrazyl (DPPH).