Farinose alpine Primula species: phytochemical and morphological investigations

This work investigated the epicuticular and tissue flavonoids, the volatiles and the glandular trichome structure of the leaves of four species of Primula L. that grow in the Italian Eastern Alps. Primula albenensis Banfi and Ferlinghetti, P. auricula L., P. farinosa L., P. halleri Gmelin produce farinose exudates that are deposited on the leaf surface as filamentous crystalloids. In addition to compounds already known, a new flavone, the 3,5-dihydroxyflavone, was isolated from the acetone extract of leaf farinas and three new flavonol glycosides, 3'-O-(β-galactopyranosyl)-2'-hydroxyflavone, isorhamnetin 3-O-α-rhamnopyranosyl-(1→3)-O-[α-rhamnopyranosyl-(1→6)]-O-β-galactopyranoside, quercetin 3-O-α-rhamnopyranosyl-(1→3)-O-[α-rhamnopyranosyl-(1→6)]-O-β-galactopyranoside, were isolated from the MeOH extract of the leaves. All the structures were elucidated on the basis of their (1)H and (13)C NMR data and 2D NMR techniques, as well as on HPLC-MS. The leaf-volatiles emitted by these Primula species were mainly sesquiterpene hydrocarbons, with the exception of P. albenensis, which produced almost exclusively a non-terpene derivative; P. halleri flowers were also examined and the volatiles emitted by the flower parts (corolla and calyx) were compared with the corresponding leaves.