Striking Diversification of Exudate Profiles in Selected Primula Lineages.

In continuation of previous studies on glandular exudates of Primula, we analyzed eleven so far unstudied species and several populations for exudate composition. Unsubstituted flavone and unusually substituted flavones, normally predominant in Primula exudates, were not detected in all of the analyzed samples. Instead, some species exhibited regular substituted flavonoids, and in some cases, no flavonoids could be detected at all. The detection of a diterpene (1) in P. minima exudates is new to Primula. On basis of MS and NMR, 1 was structurally characterized as ent-kaur-16-en-19-oic acid. Comparative profiling of exudates as performed by HPLC and TLC against authentic markers indicated further the presence of the benzoquinone primin and derivatives in some exudates. Thus, exudates of newly studied species contrast markedly with those analyzed so far. The significance of observed exudate diversification is discussed in view of the phylogeny of derived lineages in European alpine regions.

Orphan flavonoids and dihydrochalcones from Primula exudates.

Two orphan flavonoids containing an oxepin structure in ring A and named as Primcortusin (1) and 3'-OH-Primcortusin (2) were isolated from leaf exudates of Primula cortusoides, while P. glutinosa exudates yielded two dihydrochalcone derivatives (3,4). These novel structures have not been detected in other species of Primula so far. Chemical structures were elucidated by 2D NMR and mas spectrometry. The nature of compounds 1 and 2 is discussed, and ideas about their possible origin and that of unsubstituted flavone and other irregular substituted Primula flavones are presented.

Diversification of exudate flavonoid profiles in further Primula spp.

In continuation of previous work, exudate flavonoid profiles of 22 new accessions of the genus Primula L. aligned to different subgenera were studied for the first time. Profiling was done by comparative TLC and UV-HPLC against authentic marker compounds. Most of the studied species accumulated the typical Primula flavonoids, comprising derivatives of unsubstituted flavone, of 5,8- or 5,6-hydroxyflavones including partly highly oxygenated flavones, together with 2,2'-diOH-chalcone in their exudate. The profile of P. edelbergii belonging to subgen. Sphondylia differed largely from the majority of Primula species studied so far, showing accumulation tendencies similar to those observed earlier for the closely related genus Dionysia. The phylogenetic significance of this diversification is shortly addressed.

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.

Unusual compounds from exudates of Dionysia diapensifolia and D. gaubae var. megalantha (Primulaceae).

Exudates of Dionysia diapensifolia yielded (R)-(+)-3-acetoxy-3-phenyl-propiophenone as a new natural product with a basic dihydrochalcone structure, which was elucidated unequivocally by mass spectrometry and NMR spectroscopy. The sesquiterpenoidcarissone was found as the major compound in the exudate of D. gaubae var. megalantha. Sesquiterpenoids have so far not been described as exudate constituents of Primula and Dionysia. Structural identifications are discussed in detail, and the significance of the occurrence of these unusual compounds in exudates of Primulaceae is shortly addressed.

Xanthones, biflavanones and triterpenes from Pentadesma grandifolia (Clusiaceae): structural determination and bioactivity.

Stem bark, roots, leaves and fruits of Pentadesma grandifolia Baker f. (Clusiaceae) have been analyzed for the presence of xanthones, biflavonoids and triterpenoids. Isolated and identified structures include the xanthones cowagarcinone B (1) and alpha-mangostin (2), further the two biflavanones 3,8"-binaringenin (3) and the corresponding 3,6"-binaringenin (4), which is here reported as natural constituent for the first time. Structures were determined by NMR and mass spectrometry, as well as by 13C-NMR CSEARCH and SPECINFO database systems. The triterpenes lupeol (5), beta-amyrin (6) and betulin (7) were also encountered. Compounds 2 - 4 exhibited antifungal activity against Cladosporium sphaerospermum. Results are discussed in context to organ-specific accumulation and to other bioactivities that may relate to the ethnomedicinal uses of this species.

Chemodiversity of exudate flavonoids in Dionysia (Primulaceae): a comparative study.

More than 60 accessions of various Dionysia spp. were analysed for their exudate flavonoid composition. Many Dionysia spp. accumulate the typical Primula flavonoids with irregular substitution (unsubstituted flavone, its 2',5'-substituted derivatives and corresponding 5-OH-flavones), but flavones, flavonols and flavanones with regular 5,7-diOH-substitution are also encountered in their exudates. The formation of both types of flavonoids is not mutually exclusive. This paper analyses the chemodiversity of Dionysia exudates with respect to infraspecific variability, infrageneric distribution, patterns in hybrid taxa, and comparisons of biogenetic tendencies between Dionysia and closest related species of Primula. The uniqueness of occurrence of Primula-type flavonoids in the family Primulaceae, and their presumed different biosynthetic origin, suggest significance as further character in the Primula-Dionysia assemblage. Principal component analysis was applied to test the significance of variation of flavonoid composition across Dionysia. Comparative analysis of flavonoid profiles against the current taxonomic views yielded correlations, confined to the level of smaller groups, and only in parts at level of the current infrageneric concept. Flavonoid data are further discussed against the background of morphological and biogeographic differentiation of the genus. Increased diversification of flavonoid profiles may be interpreted as a derived status in Dionysia, which agrees with current views on the phylogeny of Dionysia as a specialised group within Primula. Functional aspects of exudate flavonoid formation are shortly addressed.

Exudate flavonoids of Primula spp: 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.

Chemodiversity of exudate flavonoids in seven tribes of Cichorioideae and Asteroideae (Asteraceae).

Members of several genera of Asteraceae, belonging to the tribes Mutisieae, Cardueae, Lactuceae (all subfamily Cichorioideae), and of Astereae, Senecioneae, Helenieae and Heliantheae (all subfamily Asteroideae) have been analyzed for chemodiversity of their exudate flavonoid profiles. The majority of structures found were flavones and flavonols, sometimes with 6- and/or 8-substitution, and with a varying degree of oxidation and methylation. Flavanones were observed in exudates of some genera, and, in some cases, also flavonol- and flavone glycosides were detected. This was mostly the case when exudates were poor both in yield and chemical complexity. Structurally diverse profiles are found particularly within Astereae and Heliantheae. The tribes in the subfamily Cichorioideae exhibited less complex flavonoid profiles. Current results are compared to literature data, and botanical information is included on the studied taxa.

Chemodiversity of surface flavonoids in Solanaceae.

Several species of Nicotiana and Solanum and further members of the Solanaceae have been examined for their exudate flavonoids. Most of the aglycones are widespread flavonols, but rare and unusual flavonols were also found, e.g. in exudates of Physalis and Solanum species. Flavones occur throughout the family, but flavanones are rare. Our data are presented in comparison to previous results. The chemodiversity of the observed structures is discussed in relation to literature reports. Morphological and systematic aspects are briefly addressed.