Kalina Danova

Influence of vitamins on polyphenolic content, morphological development, and stress response in shoot cultures of Hypericum spp

Hypericin is a widely studied phytopharmaceutical produced by the more developed representatives of the Hypericum genus. We established that Gamborg’s (G5) vitamins significantly raised hypericins levels in H. rumeliacum and H. tetrapterum shoot cultures in comparison with the Murashige and Skoog’s (MS) vitamin supplementation. To elucidate this effect, we further examined the impact of the two vitamin formulations on the polyphenolic compounds, morphological development, hydrogen peroxide (H2O2) and malondialdehyde (MDA) levels in the two species, as well as in hypericin non-producing H. calycinum. It was found that in all three species Gamborg vitamins decreased the polyphenolic compounds content, stimulated multiplication, decreased leaf compactness and increased dark glands density per square millimeter (for the two hypericin producing species) as compared to MS vitamins. In addition, the raised levels of hypericins in H. rumeliacum and H. tetrapterum, were also connected to increased content of H2O2 and MDA in vitro. Moreover, the values of these two parameters were considerably lower in hypericin non-producing H. calycinum, implying that oxidative stress either by increased metabolic activity, connected with higher hypericin production, or by a possible auto-toxic effect of the high amounts of pro-oxidant hypericin itself could be induced in Hypericum in vitro.

Highly oxygenated sesquiterpenes in Artemisia alba Turra

Ten new sesquiterpene alcohols of which seven germacranes, a eudesmane, a guaiane and an oplopane were isolated from the aerial parts of Artemisia alba Turra. Their structures and relative stereochemistry were elucidated by spectral methods ((1)H and (13)C NMR, COSY, HSQC, HMBC, NOESY, and MS). In addition, the known 7-hydroxycadin-4-en-3-one, centaureidin and axillarin were found for the first time in the studied species.

Essential oil composition of Inula britannica L. from Bulgaria

Abstract The separately distilled flowers (F) and leaves’ (L) essential oils of Inula britannica L. were investigated using capillary gas chromatography–flame ionization detector (GC–FID) and gas chromatography–mass spectrometry (GC–MS). A total of 83 constituents, representing 96.91% (F) and 96.73% (L) of the total oils, were registered. The oils were rich in terpenoids (57.85% and 77.28%), of which sesquiterpenoids dominated. The main constituents of the essential oils were viridiflorol (7.17%–8.20%) and himachalol (3.45%–8.71%) followed by 6,10,14-trimethyl-2-pentadecanone (5.43%–2.95%), 13-tetradecanolide (3.93%–4.87%) and 3-methyl-4-propyl-2,5-furandione (4.06%–0.29%).

Effect of Cytokinin and Auxin Treatments on Morphogenesis, Terpenoid Biosynthesis, Photosystem Structural Organization, and Endogenous Isoprenoid Cytokinin Profile in Artemisia alba Turra In Vitro

Developmental pattern modification in essential oil bearing Artemisia alba Turra was obtained by exogenous plant growth regulator (PGRs) treatments in vitro. Enhanced rooting (in PGR-free and auxin-treated plants) led to elevation of the monoterpenoid/sesquiterpenoid ratio in the essential oils of aerials. On the contrary, root inhibition and intensive callusogenesis [combined cytokinin (CK) and auxin treatments] reduced this ratio more than twice, significantly enhancing sesquiterpenoid production. Both morphogenic types displayed sesquiterpenoid domination in the underground tissues, which however differed qualitatively from the sesquiterpenoids of the aerials, excluding the hypothesis of their shoot-to-root translocation and implying the possible role of another signaling factor, affecting terpenoid biosynthesis. Inhibited rooting also resulted in a significant drop of endogenous isoprenoid CK bioactive-free bases and ribosides as well as CK N-glycoconjugates and in decreased trans-zeatin (transZ):cis-zeatin (cisZ) ratio in the aerials. Marked impairment of the structural organization of the photosynthetic apparatus and chloroplast architecture were also observed in samples with suppressed rooting. It is well known that in the plant cell monoterpenoid and transZ-type CKs biogenesis are spatially bound to plastids, while sesquiterpenoid and cisZ production are compartmented in the cytosol. In the present work, interplay between the biosynthesis of terpenoids and CK bioactive free bases and ribosides in A. alba in vitro via possible moderation of chloroplast structure has been hypothesized.

Relations between photosynthetic performance and polyphenolics productivity of Artemisia alba Turra in in vitro tissue cultures

Establishing optimal growth conditions for secondary metabolites production in vitro is vital for the biotechnological development of medicinal plants. In the present work we investigate the relations between the supplementation of plant growth regulators (benzyl adenine and indole-3-butyric acid) to in vitro shoot cultures of the medicinal plant Artemisia alba Turra, the productivity of antioxidant polyphenolic compounds and the structural and functional characteristics of the photosynthetic apparatus. We assayed the structural characteristics of isolated thylakoid membranes from the aerial parts by means of circular dichroism spectroscopy and atomic force microscopy, and the photosynthetic performance by pulse amplitude fluorescence modulated imaging. Although a complex relationship between benzyl adenine and indole-3-butyric acid supplementation, the polyphenolic levels and the architecture and functionality of the photosynthetic thylakoid membranes was revealed, a clear correlation was established between the concentration of the produced polyphenolic compounds and the quantum yield of photosystem II. Our data demonstrate that there is an optimal combination of the applied plant growth regulators that triggers efficient photosynthesis and high phenolics production.

Phenolic profile of Artemisia alba Turra

The aim of this study was to evaluate flower and leaf methanol extracts of Artemisia alba Turra for their total phenolic and flavonoid contents, antioxidant capacity and to investigate their phenolic composition. The flower extract was richer in total phenolics and flavonoids and possessed higher antioxidant activity through DPPH and ABTS assays. The UHPLC‐PDA‐MS analysis of the flower and leaf methanol extracts revealed similar phenolic profile and allowed identification of 31 phenolic compounds (flavonoids, coumarins, and phenolic acids) by comparison with the respective reference compounds or tentatively characterized by their chromatographic behavior, UV patterns, and MS fragmentations. The presence of hispidulin, jaceosidin, desmethoxycentaureidin, and dicaffeoyl esters of quinic acid in A. alba is reported herein for the first time. The distribution of flavonoids in A. alba from different origins was discussed from chemotaxonomic point of view.