Isolation and Identification of Flavonoids Accumulated in Proanthocyanidin-free Barley

Flavonoids accumulated in proanthocyanidin-free near-isOgenic lines iso ant.13, iso ant 17, and iso ant 22 of IVishinohoshi, developed by backcross breeding using a leading cultivar, Nishincihoslii, as a recurrent parent and a proanthocyanidinfree mutant as a nonrecurrent parent in Japan, were examined. A new flavanone, (2RS)-dihydrotricin 7-043-n-glucopyranoside (1), known flavanones (2RS)-dihydrotricin (2) and (2RS)-homoeriodictyol (3),_an,41<noWn.flavones chrysoerio17-0-[a-L-rhamnopyranosyl(1-6)13-D-glucopyranoside] (4), chrysoeriol 7-0-13-D-glucopyranoside_(5)4Fitn (6), and chryioeriol (7) were isolated from iso ant 17 of Nishinohoshi. The structures and stereochernistries of the isirilateii.flaVdUoi& (14-7) were elucidated on the basis of spectroscopic analyses The concentrations of the isolated flavonoids (1.-7-).1tis6.200 13, isd.ant.,17; and iso ant 22 of Nishinohoshi were similar to each other, whereas the flavonoids 1-5 and 7 were not detectaidNishinohoshi,,an Old Japanese cultivar, Amaginijo, and North American cultivar Harrington. The concentration of tricin (6) in N;AShinolioshi was a half those in iso ant 13, iso ant 17, and iso ant 22 of Nishinohoshi. Except for iso ant 13, iso ant 17, and iso ant. 22'61-N4hinohoshi,'`the' concentration of tricin (6) was highest in Nishinohoshi, followed by Amaginijo and Harrington. Thus,.44eiti:,(6), its precursor dihydrotricin (2), and its glucopyranosicle, dihydrotricin 7-0-fi-n-glucopyranoside (1), as well as chryidei7ol(7) and homoeriodictyol (3) were accumulated in iso ant 13, iso ant 17, and iso ant 22 of Nishinohoshi probably by blockingrafqi.step of flavanone 3-hydroxylase in the procyanidin biogenetic pathway, resulting in enhancement of the alternative biogenetic pathway.