β-SitosteryI-D-glucoside from the Olive Tree(Olea europaea LINNE; Oleaceae) as a Feeding Stimulant toward the Olive Weevil (Dyscerus perforatus)

The olive weevil [Dyscerus perforatus (ROELOFS); Coleopetera; Curculionidae] is a native species in Japan and now the most serious pest of the olive trees. Originally, this weevil seemed to colonise Ligustrum japonicum Thumb. and L. obtusifolium Sieb. et Zucc, both of which belong to the same oleacea family as olive. However, when olive trees were introduced to Japan in 1908, the weevils immediately attacked the plants and soon preferred them to the former hosts. Unlike in the former hosts, where the weevils live in a low population density, it is extraordinary high in the case of olive trees and the subsequent assault becomes seriously damaging for the host plant. During the course of our study on the relationship between olive trees and olive weevils, we came to be interested in the possible chemical constituents that are responsible for host selection and attraction of the olive weevil to this plant. Previously, we reported that a secoiridoid gluconside, oleuropein, and some lignans, (-)-olivil and (+)-l-acetoxypinoresinol, from the olive tree stimulated the feeding habit of the weevil. In this study, we found a steroidal glucoside as another feeding stimulant component in the olive tree. Here, we describe the isolation, characterization and activity of this feeding stimulant.

オリーブアナアキゾウムシは，モクセイ科のオリーブに多数寄生し甚大な被害を与えるため，オリーブ栽培上の深刻な問題となっている．我々は，これまでオリーブのメタノール抽出物から，オリーブアナアキゾウムシの摂食刺激成分として，雌雄に活性を示すセコイリドイド配糖体1種と，雌に特異的に活性を持つ2種のリグナン類を得た．さらに今回，同じメタノール抽出物から，活性物質としてステロイド配糖体であるβ-sitosteryl-D-glucosideを得た．この成分は雌雄に対してほぼ同等の摂食刺激活性を示した．