Abstract

Seven new polycyclic-fused cytochalasins (CYTs), harziachalasins A–G ( 1 – 7 ), together with three known analogues ( 8 – 10 ) were isolated from the solid culture of the endophytic fungus Trichoderma harzianum MLJ-4, which was originally isolated from the leaves of Asclepias curassavica . The planar and absolute structures of all new compounds were determined on the basis of extensive spectroscopic data (1D, 2D NMR and HR-ESI–MS), NMR calculations with DP4 + probability analysis, and theoretical simulations of ECD spectra. Compound 1 represents the first example of 5/6/6 tricyclic CYT featuring a 2-methyl-4-oxopentyl side chain at the C-14 position. This novel architecture originates from a 5/6/6/7 tetracyclic CYT precursor through sequential oxidative cleavage of the C-19–C-20 bond followed by decarboxylative elimination of C-19. Compound 2 features an unprecedented 5/6/6/6/7 pentacyclic scaffold incorporating a 1,3-dioxane moiety, may be constructed by the acetalization of the 7-OH and 13-OH on a 5/6/6/7 tetracyclic CYT with acetaldehyde. Compounds 1 – 10 were screened for HIV latency reversal activity using J-Lat A72 and J-Lat 10.6 cell models. Compound 4 showed strong activity, with half-maximal effective concentrations (EC 50 ) values of 2.68 μM (J-Lat A72 cells) and 2.99 μM (J-Lat 10.6 cells), demonstrating consistent potency. Mechanistic studies revealed 4 activated the NF- κ B pathway to reverse HIV latency, offering insights for new therapeutic strategies targeting this pathway. Graphic