Mantidisflavin A: A Riboflavin Derivative Featuring a 6/6/6/5/5 Skeleton from the Egg Cases of the Insect Tenodera sinensisSaussure and Its Anti-Renal Fibrosis Activity

Mantidisflavin A (1) was isolated from the egg cases of the Tenodera sinensisSaussure. It exhibits an unprecedented 6/6/6/5/5 skeleton, accompanied by the formation of two additional fused heterocycles through a novel C–C bond and an oxygen bridge on riboflavin backbone. The structure of 1was identified by spectroscopic and computational methods. To assess the inhibitory effect against renal fibrosis, compound 1was evaluated in TGF-β1-induced rat kidney epithelial cells, and the results were compared to those of its precursor, riboflavin.