Microbial transformation of the triterpene nigranoic acid in Trichoderma sp.

► Two new metabolites, 15α, 16α-dihydroxy-3,4-secocycloarta-4 (28), 17 (20), 17 (E), 24 (E)-triene-3,26-dioic acid (2) and 16α, 20α-dihydroxy-18 (13 → 17β) abeo-3,4-secocycloarta-4 (28), 12 (13), 24 (Z)-triene-3,26-dioic acid (3) were isolated and identified from the co-cultures of nigranoic acid (1) and Trichoderma sp. JY-1. ► Compound 2 was found to possess an unusual 17(20), 17 (E)-ene structure and compound 3 featured an unprecedented 18(13 → 17β)-abeo-secocyloarta skeleton. ► Both biotransformation products, compound 2 and compound 3 showed anti-HIV-1 activity with EC50 values of less than 10.5 μg/mL, superior to that of nigranoic acid (1).