ISOLATION AND CHARACTERIZATION OF PENTACYCLIC TRITERPENE OVIPOSITIONAL STIMULANT FOR THE SWEET-POTATO WEEVIL FROM IPOMOEA-BATATAS (L) LAM

A methylene chloride extract from the surface of sweet potato storage roots (cultivar Centennial) was fractionated on silicic acid and eluted with hexane, 1: 3 methylene chloride-hexane, and 1: 1 methylene chloride-hexane. The 1: 3 methylene chloride-hexane fraction yielded compound I: >96% purity, the most dominant compound present; mp 238-239. 5 °C; IR, 1730, 1250 cm-1. The mass spectrum of compound I displayed a molecular ion at m/z 468 with a molecular formula of C32H52O2. The fragmentation pattern was indicative of a pentacyclic triterpene with isopropyl and acetate moieties. Compound II, which could be produced by the hydrolysis of compound I, was present in the 1: 1 methylene chloride-hexane fraction: mp 214-215. 5 °C; IR, 3400 cm-1; molecular ion, m/z 426; molecular formula, C30H50O. The alcohol of compound I (compound II) was identified as boehmerol. Based on 13C NMR and GC-MS data and physical evidence, the structure of compound I was established and tentatively named boehmeryl acetate. Boehmeryl acetate extracted from the surface of sweet potato storage roots appears to act as an ovipositional stimulant for the sweet potato weevil, Cylas formicarius elegantulus Summers. © 1990, American Chemical Society. All rights reserved.