New Primula-type Flavones from Exudates of Selected Dionysia spp. (Primulaceae)

Hitherto unstudied Dionysia leucotricha and D. denticulata as well as new accessions of already studied species were analyzed for their exudate flavonoid profile. Results were compared with those of closely related species by HPLC-reinvestigation of existing exudate solutions. In addition to already known compounds typical of the Primula assemblage, three compounds were isolated from D. bryoides and identified as 2’-hydroxy-3’-methoxyflavone (1), 2’,3’-dimethoxyflavone (2) and 3’,5’-dimethoxyflavone (3), respectively, by HPLC and NMR. All compounds are new for the genus Dionysia, with compound 3 being novel and yet only described from synthesis. The occurrence of Primula-type flavones in Dionysia and the rare reports from genera outside Primulaceae are commented briefly.

Flavonoids in Selected Primula Spp.: Bridging Micromorphology with Chemodiversity

A combined study was carried out on the micromorphology and chemistry of glandular trichomes with focus on Primula vialii and P. vulgaris, respectively. Epifluorescence microscopy was applied to study the auto-fluorescent properties of flavonoids and their localization in glandular trichomes. Both species differed in the morphology of the glandular trichomes and in the exudate flavonoid composition. Leaf glands from P. vialii and from some species of subgen. Primula exhibited uniform glandular fluorescence, but notable differentiation was observed within a single leaf of P. vulgaris. Our observations indicate that exudate flavonoids are not transported from the tissue to the glandular hairs. Conversely, only the newly isolated glycoside 1 (kaempferol 3- O-(2″’-rhamnosyl)-robinobioside) was obtained from leaf tissue of P. vialii after removal of the exudate. Its structure was confirmed by NMR and mass spectrometry. This glycoside was not detected in tissue extracts of P. vulgaris after similar treatment. The observed chemical diversity is discussed, with focus on possible correlation with glandular structures and tissue differentiation in Primula, and also against other studied species. Aspects of biosynthesis in relation to tissue-specific flavonoid diversification are shortly addressed.

Exudate Flavonoids ofPrimulaSpp: Structural and Biogenetic Chemodiversity

Several new accessions of the genus Primula and of the closely related Cortusa matthioli have been studied for their exudate flavonoid profiles. Unsubstituted flavone, 5-hydroxy-, 2′-hydroxyflavone and 5,2′-dihydroxyflavone were found as main components. Several other rather unusual substitution patterns were also found. 8- O-Substituted flavones appear to be accumulated more often than 6- O-substituted products. Chalcones with corresponding substitution patterns were of scattered occurrence, while flavanones could so far not be detected in exudates of Primula species. The distribution of externally accumulated flavonoids, including literature data, is related to current taxonomic views on the infrageneric grouping of Primula and related taxa. Organ-specific accumulation, biosynthetic and chemosystematic aspects are briefly addressed.