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The genus Primula is the largest among the Primulaceae and is widespread mainly in the cold and temperate regions of the Northern Hemisphere. Since the beginning of the Twentieth century, several studies on the phytochemical composition of different species of Primula have been carried out. The main constituents examined were tissue and epicuticular flavonoids and saponins, which are of therapeutic significance. Only in recent years studies of the volatiles emitted by leaves and flowers have been carried out as well, but they are restricted to a small number of species. Only a few authors have documented the morphology and function of glandular trichomes in relation to the production of flavonoids and volatile organic compounds (VOCs). The use of Primula in folk medicine is described in the literature. Investigation of the biological and pharmacological activities of Primula are reported. This study aims at providing a collection of publications on the genus Primula along with a critical revision of literature data. It focuses on the possible taxonomic significance of the secondary metabolites and on their ecological role as attractors for pollinators and deterrents against herbivores and parasites, in order to build the base for further studies., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

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., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

The vacuolar and epicuticular flavonoids and the volatiles of the leaves and parts of flower of P. spectabilis Tratt., an endemic species in the Italian Oriental Alps, were investigated. From a MeOH extract of the leaves two flavone glycosides, 8-C-β-glucopyranosylluteolin 7-O-α-arabinofuranoside (1) and 6-C-α-arabinofuranosylapigenin (2) were isolated, in addition to a flavone and three flavonols already known from species of Primula. From an EtOH extract of leaf exudates, 7,3',4'-tri-O-methylquercetin was obtained. The structures were elucidated on the basis of their 1D ¹H- and ¹³C NMR data and 2D NMR techniques, as well as of HPLC-MS. The volatiles emitted by the leaves were mainly constituted by non-terpene derivatives, followed by comparable proportions of hemiterpens, oxygenated monoterpenes and sesquiterpene hydrocarbons. In flowers, monoterpene hydrocarbons were the most represented chemical class followed by non-terpene derivatives. Different proportions of compounds were found when individual parts of flowers were examined separately; calyx produced a greater proportion (approx. 49.5%) of non-terpenes as its volatile metabolites. P. spectabilis has glandular trichomes in the hyaline margins of the epidermal depressions, distributed on the adaxial leaf blade. Glandular hairs were also present on the corolla. Correlations of phytochemical data with the morphological features of leaf, flower and glandular hair are discussed, and a hypothesis is proposed on the ecological roles of the flavonoids and volatile compounds on the general fitness of the species and cross-pollination strategies., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

The taxonomy of alpine Primula species has long been in dispute because of high morphologic variability and several hybridisations. In Primula species, the trichome height and the colour of hair-tips are usually indicated as diacritic characters, but in our experience this is not adequate. The present study, focused on Primula auricula, Primula daonensis and Primula hirsuta, therefore proposes the use of other morphologic trichome parameters (size and dimensional ratio of stalk, neck and gland head). Phytochemical investigations about the flavonoid composition (epicuticular and vacuolar) of leaves, as taxonomic markers, have also been performed. We report the isolation and identification of two new flavonol glycosides, isorhamnetin 3-O-(2,6-di-O-beta-D-glucopyranosyl-beta-D-glucopyranoside) (1) and kaempferol 3-O-(2-O-alpha-L-rhamnopyranosyl-6-O-beta-D-xylopyranosyl-beta-D-glucopyranoside) (2) and of eight known flavonoids. Size and dimensional ratio of the three trichome elements (stalk, neck and glandular head) are typical for each species analysed. The flavonoid profile well characterise the entities under study. Three different profiles have been obtained with both vacuolar and epicuticular flavonoids. The morphologic and phytochemical markers proposed in this work seem to be parameters which significatively discriminate the species under study.