Phenylphenalenones (PPs) are phytoalexins protecting
banana plants
(Musaceae) against various pathogens. However, how plants synthesize
PPs is still poorly understood. In this work, we investigated the
major secondary metabolites of developing seed coats ofMusella
lasiocarpato determine if this species might be a good model
system to study the biosynthesis of PPs. We found that PPs are major
components ofM. lasiocarpaseed coats at middle
and late developmental stages. Two previously undescribed PP dimers
(M-4andM-6) and a group of unreported
diarylheptanoid (DH) derivatives named musellins A–F (B-7,B-9,B-10,B-12,B-14, andB-15) were isolated along with
14 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 by
spectroscopic data, including NMR, HRESIMS, and ECD analysis. Plausible
biosynthetic pathways for the formation of PPs and DHs are proposed.