Discovery and Biosynthesis of Brasilanes G−L: N -Acetylglucosamine-Decorated Sesquiterpenoids with Anti-Inflammatory Activity

Abstract

N-Acetylglucosamine (GlcNAc)-decorated natural products represent a structurally unique class of metabolites that possess diverse biological activities. Through the genome mining of Coccidioides sp. CMB-TN39F, we identified a GlcNAc transferase-encoding terpene synthase gene cluster brc. Heterologous expression of this cluster in Aspergillus nidulans enabled the characterization of seven GlcNAc-adorned brasilane-type sesquiterpene glycosides, including six previously undocumented compounds, brasilane G−L (1−6), and one known compound, brasilane A (7). Functional characterization revealed that the cytochrome P450 BrcC functions as an epoxidase, catalyzing a stereoselective epoxidation of 7 to form 1. Compound 1 can undergo non-enzymatic conversions to generate compounds 2−5 under mildly acidic conditions. Pharmacological evaluation demonstrated that compounds 1−6 effectively downregulate the expression of pro-inflammatory cytokines (IL-6, IL-1β, and TNF-α) in LPS/IFN-γ-stimulated THP-1-derived macrophages. Notably, 1, which features an epoxide moiety, exhibits superior anti-inflammatory activity compared to its biosynthetic precursor 7, with an IC50 value of 30.4 μM against IL-6. This study expands the chemical space of GlcNAc-conjugated terpenoids and showcases a biosynthetic logic in which enzymatic tailoring is coupled with nonenzymatic reactions to amplify both structural diversity and biological properties.