Chemical Constituents From Melodinus Cochinchinensis (Lour.) Merr. And Their Chemotaxonomic Significance

A phytochemical investigation on the twigs and leaves of Melodinus cochinchinensis (Lour.) Merr. resulted in the isolation and identification of 22 compounds, including seven sesamin-type lignans (1-7), three pentacyclic triterpenes (8-10), one anthraquinone (11), one flavanone (12), two phenolic compounds (13 and 14), five aspidosperma-type indole alkaloids (15-19), and three eburnan-type indole alkaloids (20-22). The structures of these compounds were elucidated by means of spectroscopic analysis, including HREIMS together with 1D and 2D NMR experiments, and comparison with reported data. Among them, compounds 1/4, 2/5, and 3/6 are three pairs epimers at C-7 ''. Compounds 1-6, 8 and 11 were firstly isolated from the family Apocynaceae, whereas 17 was isolated from Melodinus species for the first time. Compound 8 was only found in Juglans hopeiensis, while 11 was only found in roots of Rubia cordifolia. Compounds 1-6, 8, 11 and 15-22 could be considered as chemotaxonomic markers for M. cochinchinensis. Furthermore, the chemo-taxonomic significance and distribution of these isolates in Melodinus genus are discussed in detail.