Diarylheptanoids are a group of secondary metabolites widely distributed in the Betulaceae family and characteristic for Alnus species. In this study, the chemotaxonomic power of diarylheptanoids, such as hirsutanonol-5-O-β-d-glucopyranoside, rubranoside A, oregonin, platyphylloside, alnuside A and hirsutanonol, has been investigated in combination with principal component analysis (PCA) for differentiation of Alnus species. Concentrations of six diarylheptanoids in the bark extracts of two natural populations of Alnus glutinosa (black alder) and Alnus incana (gray alder) were determined by ultraperformance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). PCA clearly shows the separation of three groups. Populations I (A. glutinosa) and II (A. incana) both consisted of individuals of the corresponding species. Four individuals from both sampled populations formed a separate group (population III), which possibly represents a hybrid group. Accordingly, diarylheptanoids may serve in combination with PCA as chemotaxonomic markers at the species level, which may also reveal hybrid species.
The aerial parts of Amphoricarpos neumayeri ssp. murbeckii afforded eleven guaianolides with the same relative (1αH,4β H,5αH,7αH) configuration of the basic skeleton. All of them contained a CH2OX (X = H, acetyl or isovaleroyl) group in 4α-position, typical for amphoricarpolides. Four compounds (1 - 4) were isolated before from the same species, originating from different localities. Guaianolides 5 - 11 are new compounds. Compounds 7 and 8 were epoxidized at the 10α(14)-position. Instead of the Δ11(13)-double bond, observed in all previously isolated guaianolides from the same species, the four lactones contained 11α,13-diol (8 - 10) or 11α-OH,13-chloro (11) moieties respectively.
In this paper, examination of the aerial parts of seven Senecio species from Serbia and Montenegro is reported. Phytochemical investigation of Senecio erucifolius led to the isolation and characterization of semiquinol butyl 2-(1-hydroxy-4-oxocyclohexa-2,5-dienyl)acetate (I), along with methyl 2-(1-hydroxy-4-oxocyclohexa-2,5-dienyl)acetate (jacaranone, II), and methyl 2-(4-hidroxyphenyl)acetate (III). The structure of I was established based on spectroscopic studies (1H- and 13C-NMR, IR, and CI-MS). Compound II was also isolated from S. carpathicus and S. subalpinus. The presence of jacaranone in the methanol extracts of S. wagneri, S. othonnae, and S. paludosus was confirmed by LC/ESI-TOF MS.
The reliability of diarylheptanoids as chemotaxonomic markers at inter- and intraspecific levels has been investigated. Six diarylheptanoids were quantified in bark ethanol extracts of four Alnus spp. populations by ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The populations described here as locus classicus Alnus glutinosa (I) and locus classicus Alnus incana (III) are clearly differentiated. Compared to population I, individuals in population III have higher extract yields and hirsutanonol-5-O-β-D-glucopyranoside content and lower contents of hirsutanonol, rubranoside A and oregonin. Individuals from neighboring populations of A. glutinosa (II) and A. incana (IV) share similar contents of hirsutanonol. All the studied populations exhibit a high intrapopulation variability of the selected diarylheptanoids; they have a heterogeneous chemotype and they partially overlap. The geographical proximity of populations II and IV increases their chemical similarity. Principal component analysis (PCA) clearly shows that the biggest dispersion of individuals lies within population IV. The reason for its heterogeneity might be its physical proximity to population II, i.e. the appearance of hybrids. Also, geometric morphometrics of leaves was performed as a screening criterion for spontaneous hybrids.