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Nepetalactones are accumulated as the main secondary metabolites in the majority of Nepeta species; however, their biosynthetic pathway remains to a great extent unknown, as well as their relationship to the overall physiology of these plants. Nepetalactones most certainly arise through general iridoid biosynthetic pathway leading to nepetalactol, a common precursor of all plant-derived iridoids that is formed in a reaction catalysed by iridoid synthase ( IS , EC 1.3.1.99). In this paper, we aimed to localize the sites of nepetalactone biosynthesis and accumulation by comparatively analysing the nepetalactones content and the expression of putative iridoid synthase ( NrIS ) in leaves of Nepeta rtanjensis Diklić & Milojević, a trans,cis -nepetalactone and dehydronepetalactone rich species. Another aim was to give an insight into the developmental regulation of nepetalactone biosynthesis in leaves of cultivated N. rtanjensis plants. Knowledge on the spatial-, and developmental- regulation of nepetalactone metabolism could greatly benefit potential growers by enabling them to adequately plan and manage plant cultivation, harvesting, and handling and thus increase yield of bioactive compounds. The expression profile of putative NrIS1 is highly correlated with trans,cis -nepetalactone and dehydronepetalactone content/ratio in leaves of different developmental stages. The results strongly indicate that developmental regulation of nepetalactone biosynthesis in leaves resides largely at the level of gene expression, and suggest an important role of NrIS1 . Young leaves exhibited the most intensive nepetalactone biosynthesis and accumulation, but also its conversion to dehydronepetalactone. Thus, the pattern of NL accumulation in leaves can be explained by both the rate of its biosynthesis and metabolic degradation. The gene expression patterns of NrIS1 and NrIS2 transcripts in trichomes and abraded leaves revealed trichomes as the main site of their activity. UHPLC/qqqMS profiling of nepetalactones in trichomes and abraded leaves, complemented with Raman spectroscopy and dichloromethane dipping experiment, supported glandular trichome-specific localization of nepetalactone biosynthesis and accumulation. [ABSTRACT FROM AUTHOR]

Species within the genus Centaurium readily hybridize and polyploid complexes are often seen in natural populations. We describe phytochemical profiles of newly discovered allohexaploid hybrid, here named Centaurium pannonicum , and its parental tetraploid species C. erythraea and rare C. littorale ssp . compressum. Our aim was to examine chemodiversity of these taxa in the area of Vojvodina (North Serbia) and to perform metabolomics search for chemical classifiers which would provide high resolution discrimination of parental and hybrid individuals. In sum, UHPLC - MS/MS Orbitrap metabolomics fingerprinting revealed seventy compounds in methanol extracts. Despite the lack of qualitative chemical novelty in hybrid plants, UHPLC-qqqMS targeted metabolomics approach, aimed at three secoiridoid compounds and seventeen phenolics, pointed to considerable differences in quantitative composition of these dominant compounds among the plant taxa studied. In addition to the difference in the ploidy levels, the hybrid taxon was well distinguished from both parental species based on metabolite profiles, and, for most individuals, positioned intermediately to the parental taxa in both PCA and hierarchical clustering. After optimizing and comparing several statistical learning methods, it was possible to narrow the number of taxonomic classifiers to five (three xanthones, one secoiridoid glycoside, and one phenolic acid), while increasing the differentiation resolution. The presented metabolomics approach will certainly, along with morphometrics and molecular genetics studies, have high impact on further elucidation of complex relationships among taxa within the genus Centaurium. [ABSTRACT FROM AUTHOR]

Highlights: [•] Centauries are an appreciative source of biologically active compounds. [•] Phenolics, flavonoids, xanthones and secoiridoid glycosides were quantified. [•] Considerable antioxidant activities and ferric reducing capacity was recorded. [•] Appreciative antibacterial and strong antifungal activities were demonstrated. [•] Centauries could be recommended as food preservation additives. [ABSTRACT FROM AUTHOR]

Highlights: [•] Centaurium maritimum contains a considerable amount of bioactive compounds. [•] Hairy roots of C. maritimum were induced by A. rhizogenes strain A40M70GUS. [•] Hairy roots were grown in low-cost bioreactor systems RITA® TIBs. [•] High biomass and secoiridoid glycosides production were achieved in bioreactors. [ABSTRACT FROM AUTHOR]

Abstract: The content of secoiridoid glycosides in the aerial parts and roots of in vitro grown centaury (Centaurium erythraea Rafn) plants, originating from 52 Balkan Peninsula populations was analyzed. The results of this study give insight into the infraspecific variability of centaury, based on the yield of secoiridoid glycosides as chemical markers of phenotypic variation. According to the cluster analysis, existence of two basic chemotypes is suggested. Moreover, the impact of prevailing environmental gradients in natural habitats on chemotype differentiation was assessed. The precipitation rate of the warmest quarter of year significantly affects the accumulation of secondary metabolites. These results will enable the selection of particular populations which are characterized by enhanced accumulation of secondary metabolites of interest, thus making it possible to realize the commercial field cultivation and upscale production and of this threatened and pharmacologically important species. [Copyright &y& Elsevier]

Abstract: A heterotrophic model system was established in our studies in order to differentiate the effect of high salt concentrations in external medium on growth and sugar metabolism in roots from the effect of reduced sugar availability resulting from decreased photosynthesis under salinity. Soluble sugar content and the activity of acid invertase in root cultures of salt-tolerant (ST) and salt-sensitive (SS) Schenkia spicata (L.) Mansion genotypes were investigated during exposure to different NaCl concentrations (0–200mM). Their response to severe salinity was characterized by a metabolic adjustment that led to the accumulation of sucrose (Suc) in root tissues. There was clear evidence that cell wall invertase (CW-Inv) is the major contributor to the Suc/hexose ratio in roots during exposure to elevated salinity. The results of CW-Inv activity and immunodetection assays in our study suggest that the regulation of CW-Inv expression is most likely achieved in a salt stress dependent manner. Also, NaCl modulated soluble acid invertase (SA-Inv) expression differentially in SS and ST genotypes of S. spicata. Regardless of the salt treatment, genotype, or the amount of enzyme, SA-Inv activity was generally low, indicating regulation at the posttranslational level. The results suggest no direct role of SA-Inv in the regulation of the root tissue carbohydrate pool and therefore in the control of the availability of glucose and fructose for the primary metabolism and/or osmotic adjustment in the present heterotrophic model system. [Copyright &y& Elsevier]