Diarylheptanoid Derivatives (Musellins A-F) and Dimeric Phenylphenalenones from Seed Coats of Musella lasiocarpa, the Chinese Dwarf Banana

Phenylphenalenones (PPs) are phytoalexins protectingbanana plants(Musaceae) against various pathogens. However, how plants synthesizePPs is still poorly understood. In this work, we investigated themajor secondary metabolites of developing seed coats of Musellalasiocarpa to determine if this species might be a good modelsystem to study the biosynthesis of PPs. We found that PPs are majorcomponents of M. lasiocarpa seed coats at middleand late developmental stages. Two previously undescribed PP dimers(M-4 and M-6) and a group of unreporteddiarylheptanoid (DH) derivatives named musellins A-F (B-7, B-9, B-10, B-12, B-14, and B-15) were isolated along with14 known compounds. Musellin D (B-12) and musellin F(B-15) contain the first reported furo[3,2-c]pyran ring and represent a previously undescribed carbon skeleton.The chemical structures of all new compounds were characterized byspectroscopic data, including NMR, HRESIMS, and ECD analysis. Plausiblebiosynthetic pathways for the formation of PPs and DHs are proposed.

Automated summary

In this study, we discovered that Phenylphenalenones (PPs) are major components of the seed coats of Musella lasiocarpa. We also identified two previously unknown PP dimers (M-4 and M-6) and a group of unreported diarylheptanoid derivatives (musellins A-F), which provide a good system for studying the biosynthesis of PPs.