Kuwanon O is a flavonoid derivative with a fused dihydrochalcone partial moiety, that can be isolated from the root bark of Morus lhou (set.) Koidz.
[1]. Hano Y, et al. Components of root bark of morus lhou1 1. Structures of two new natural diels-alder adducts, kuwanons N and o. Planta Med. 1984 Apr;50(2):127-30.