STRUCTURE DETERMINATION OF A NEW SAPONIN FROM THE PLANT ALPHITONIA-ZIZYPHOIDES BY NMR-SPECTROSCOPY

High-field NMR experiments, including the 2D INADEQUATE technique coup led with a computerized spectral analysis, were used to determine the full structure of a new saponin extracted from a plant (Alphitonia ziz yphoides) found in the Samoan rain forests. The saponin, which shows s ignificant pharmacological activity, consists of an aglycone framework of six rings (three saturated six-membered rings, two oxygen-containi ng five-membered rings and a five-membered carbon ring) to which are a ttached four sugar units and a six-carbon side-chain. The INADEQUATE e xperiment, which was carried out on 60 mg of sample, provided absolute confirmation of the assignments for 35 of the possible 53 C-C bonds f rom the C-13-C-13 connectivities.