Constituents of twig bark of pear cultivars (Pyrus species).

Organic solvent extracts from fresh twig bark of Japanese pear cultivars (Pyrus serotina) Shinko and Nijisseiki, and European pear cultivar (P. communis) Le Lectier were obtained by maceration with n-hexane and EtOAc, and analyzed in GC-EIMS experiments. In these two Japanese cultivars, the lupeol, betulin, epifriedelinol, friedelin and arbutin contents of Nijisseiki were higher than those of Shinko. In the case of the lupane-type triterpenes, lupeol and betulin, the lupeol content of Japanese pears Shinko and Nijisseiki was higher than that of European pear Le Lectier. The betulin content of Le Lectier was higher than those of Shinko and Nijisseiki. Friedelane-type triterpenes, epifriedelinol and friedelin, were not detected in twig bark of Le Lectier. Quantitative and qualitative differences in the constituents of these three pear cultivars were observed.