Flavonol glycosides acylated with 3-hydroxy-3-methylglutaric acid as systematic characters in Rosa

LC-UV-MS/MS analysis of leaf extracts from 146 accessions of 71 species of Rosa revealed that some taxa accumulated flavonol O-glycosides acylated with 3-hydroxy-3-methylglutaric acid, which are relatively uncommon in plants. The structures of two previously unrecorded examples isolated from Rosa spinosissima L. (syn. Rosa pimpinellifolia L.) were elucidated using spectroscopic and chemical methods as the 3-O-α-L-rhamnopyranosyl-(1→2)-[6-O-(3-hydroxy-3-methylglutaryl)-β-D-galactopyranosides] of kaempferol (3,5,7,4'-tetrahydroxyflavone) and quercetin (3,5,7,3',4'-pentahydroxyflavone). The corresponding 3-O-[6-O-(3-hydroxy-3-methylglutaryl)-β-D-galactopyranoside] of quercetin was also present in R. spinosissima, but at lower levels, together with 17 other flavonol O-glycosides for which structures were assigned using LC-UV-MS/MS. The distribution of flavonol 3-hydroxy-3-methylglutarylgalactosides in Rosa was limited to some species of subgenus Rosa section Pimpinellifoliae and Rosa roxburghii Sw. of the monotypic subgenus Platyrhodon, indicating that this character could be of value in phylogenetic analyses of the genus.