Epimeric Macrolactin Analogs From a Marine-Derived Bacillus velezensis Against Herpesvirus

Two new glycosylated macrolides (1, 2), along with five known compounds (3-7) were isolated from an endophytic bacterium of Bacillus velezensis inhabiting the mangrove plant Acanthus ilicifolius L. Compound 1 is a 24-membered macrolide featuring a 7-OH glycosylation and a 6'-succinate ester, the C-7 epimer of macrolactin D, while compound 2 is the 7-position epimer of macrolactin B, as determined through comprehensive analysis of one-dimensional and two-dimensional nuclear magnetic resonance, and high-resolution electrospray ionization mass spectra spectroscopic data, as well as chemical transformation. In addition, compounds 1 and 2 exhibit significant antiviral activity against herpesvirus as determined by quantitative real-time polymerase chain reaction and Western Blot assay. At the messenger RNA level, compounds 1 and 2 achieved about 85% inhibition at 5 µg/mL, almost equivalent to the positive control of acyclovir.