Biosynthetic glycosylation as a critical structural determinant of antifungal activity in venturicidin A.

Venturicidin A (1) constitutes a glycosylated macrolide endowed with potent antifungal activity; however, the discrete contributions of its post-polyketide synthase modifications to bioactivity have remained elusive. Here we systematically deconvolute the structure-activity relationships of venturicidin A (1), its glycosylated congener venturicidin B (2), and the aglycon derivative venturicidin X (3). The latter was generated through targeted disruption of the glycosyltransferase-encoding gene vtdG. Across a panel of eight phytopathogenic fungal species, the glycosylated congeners exhibit markedly superior antifungal activity relative to the aglycon, with 1 outperforming the commercial fungicide carbendazim against Alternaria alstroemeriae CGMCC 3.1640. Mechanistically, glycosylation critically dictates the extent of plasma membrane disruption and mitochondrial impairment, whereas the carbamoyl moiety contributes negligibly to these phenotypes. Collectively, these findings establish the glycosyl moiety as an indispensable structural determinant of antifungal potency, furnishing a strategic blueprint for the rational optimization of venturicidin analogues.