Isolation and identification of novel terpene lactones from quince fruit (Cydonia oblonga Mill., Marmelo).

The fruit of the quince (Cydonia oblonga Mill.) has a powerful and characteristic sweet odor, however, it is not edible due to its very hard, tough and fibrous texture. Most of the fruit is used for marmalade and jelly. In Japan, the fruit is called the Japanese quince or marmelo. A number of chemical constituents of quince fruit, such as organic acids, amino acids , sugars, flavonols, etc., have been reported, while only few volatile constituents have been studied.1) Recently, Shimizu and Yoshihara2) and Schreyen et al.3) reported some of the volatile constituents of the fruit, but no com pound responsible for the odor of the marmelo was isolated. Now, as described below, two compounds have been isolated from the vo latiles of the fruit as the main components responsible for the characteristic odor of the marmelo and identified to be the 2,4-cisand 2,4-trans-stereoisomers of 2,7-dimethyl-4hydroxy-5E,7-octadienoic acid lactone (I). This is the first time these lactones have been isolated from a natural source.