A species-specific flavonoid from Pyrus ussuriensis Max. and Pyrus aromatica Nakai et Kikuchi, and its geographical distribution in Japan.

Abstract

To clarify the taxonomical status and the geographical differentiation of pear cultivars in Japan, the occurrence of a species-specific flavonoid in leaf extracts was surveyed on 31 Pyrus species, 171 East Asian pear cultivars, and several uncultivated wild clones located in Japan and other places using paper chromatography. A brilliant yellow spot under UV Iight, with small Rf values 0.04 in BXA (n-BuOH/xylene/HOAc/H20 (6:4: 2:8)) and 0.02 in 2% HOAc (acetic acid) solvent was found in the extracts from the Ussurian pear (Pyrus ussuriensis Max.), native to northern China and northern-central Korea, from Iwateyamanashi (P.aromatica Nakai et Kikuchi) native to Tohoku region in Japan, and from their cultivars, but not from other East Asian Pyrus species, nor from European and Mediterranean species and their cultivars. This spot was confirmed to contain the flavonol aglycone (F-Ar), which seems to be a specific flavonold for the above species, and a useful chemotaxonomical marker in the genus Pyrus. In Japan, the occurrence of F-Ar was restricted to the old native cultivars originating in the Tohoku region and to the wild clones originating in the Kanto and Chubu regions and in Iwate prefecture. It was not contained in the old cultivars native to Kanto, Hokuriku and Kyushu regions. The distribution of cultivars and clones containing F-Ar nearly covered the native area of the Iwateyamanashi (P.aromatica). Most of the recent cultivars lacked F-Ar except for 5 cultivars including Nijisseik-i.