Arbuscular mycorrhizal fungi impact the production of alkannin/shikonin and their derivatives in Alkanna tinctoria Tausch. grown in semi-hydroponic and pot cultivation systems

IntroductionAlkanna tinctoria Tausch. is a medicinal plant well-known to produce important therapeutic compounds, such as alkannin/shikonin and their derivatives (A/Sd). It associates with arbuscular mycorrhizal fungi (AMF), which are known, amongst others beneficial effects, to modulate the plant secondary metabolites (SMs) biosynthesis. However, to the best of our knowledge, no study on the effects of AMF strains on the growth and production of A/Sd in A. tinctoria has been reported in the literature.MethodsHere, three experiments were conducted. In Experiment 1, plants were associated with the GINCO strain Rhizophagus irregularis MUCL 41833 and, in Experiment 2, with two strains of GINCO (R. irregularis MUCL 41833 and Rhizophagus aggregatus MUCL 49408) and two native strains isolated from wild growing A. tinctoria (R. irregularis and Septoglomus viscosum) and were grown in a semi-hydroponic (S-H) cultivation system. Plants were harvested after 9 and 37 days in Experiment 1 and 9 days in Experiment 2. In Experiment 3, plants were associated with the two native AMF strains and with R. irregularis MUCL 41833 and were grown for 85 days in pots under greenhouse conditions. Quantification and identification of A/Sd were performed by HPLC-PDA and by HPLC-HRMS/MS, respectively. LePGT1, LePGT2, and GHQH genes involved in the A/Sd biosynthesis were analyzed through RT-qPCR.ResultsIn Experiment 1, no significant differences were noticed in the production of A/Sd. Conversely, in Experiments 2 and 3, plants associated with the native AMF R. irregularis had the highest content of total A/Sd expressed as shikonin equivalent. In Experiment 1, a significantly higher relative expression of both LePGT1 and LePGT2 was observed in plants inoculated with R. irregularis MUCL 41833 compared with control plants after 37 days in the S-H cultivation system. Similarly, a significantly higher relative expression of LePGT2 in plants inoculated with R. irregularis MUCL 41833 was noticed after 9 versus 37 days in the S-H cultivation system. In Experiment 2, a significant lower relative expression of LePGT2 was observed in native AMF R. irregularis inoculated plants compared to the control.DiscussionOverall, our study showed that the native R. irregularis strain increased A/Sd production in A. tinctoria regardless of the growing system used, further suggesting that the inoculation of native/best performing AMF is a promising method to improve the production of important SMs

Pyrazine and Thiazole Structaral Properties and Their Influence on the Recovery of Such Derivatives in Aroma Extraction Procedures

This work aims to provide better knowledge of pyrazine and thiazole structural properties, exploitable in aroma extraction. An optimized extraction method including steam-vacuum distillation and liquid/ liquid extractions of the aqueous distillate followed by gas chromatography-nitrogen-phosphorus detector analysis enabled us to quantify 50 ppt of such heterocycles in a food matrix such as beer. Lipophilicity appears as a determining parameter for vacuum distillation while basicity governs the liquid/liquid extractions

Flavour retention by lipids measured in a fresh cheese matrix

Interactions between lipids and several aroma compounds (aldehydes, methylketones, esters, and dimethyldisulfide) were studied in a real food system composed of fresh cheese, triolein, and water. The concentration of 'free' ligands was measured with a dynamic headspace-gas chromatographic system. From our results, we conclude that retention of all flavouring molecules increases with the amount of triolein. This phenomenon is highly influenced, however, by the structure of the aroma compound, as demonstrated by RP-HPLC lipophilicity determinations. Within the same chemical family there exists a linear relationship between the lipophilicity index k(w) and retention, indicating that this physicochemical property should be taken into account in choosing the best internal analytical standard. (C) 1998 Published by Elsevier Science Ltd. All right reserved

Determination of the lipophilicity of aroma compounds by RP-HPLC

The lipophilicity of aroma compounds was measured by reversed-phase high pressure liquid chromatography (RP-HPLC). The lipophilicity index provided by this technique is the capacity factor, log k(w), obtained by extrapolating series of log k values measured at various proportions of methanol in the methanol-water mobile phase. This article lists the log k(w) capacity factors of 96 flavouring compounds belonging to various families (pyrazines, thiazoles, other heterocyclic compounds, alcohols and phenols, ketones, caters, aldehydes and sulphur compounds). (C) 1998 John Wiley & Sons, Ltd

Affinities of nutty and green-smelling pyrazines and thiazoles to odorant-binding proteins, in relation with their lipophilicity

Thirty-two green- and/or nutty-smelling compounds, most of them pyrazine and thiazole derivatives, were tested in ligand binding assays with purified 19 kDa bovine and 22 kDa porcine olfactive binding proteins (OBPs). Unlike the nutty ones, all the green odorants were found to be good ligands for both proteins. Lipophilicity appears as an interesting discriminating physicochemical parameter, predictive of the affinity for OBPs and of the related odour profile

Effect of gamma and e-beam radiation on the essential oils of Thymus vulgaris thymoliferum, Eucalyptus radiata, and Lavandula angustifolia

The microbiological contamination of raw plant materials is common and may be adequately reduced by radiation processing. This study evaluated the effects of gamma- and e-beam ionizing radiations (25 kGy) on three plants used as food or as medicinal products (Thymus vulgaris L., Eucalyptus radiata D.C., and Lavandula angustifolia Mill.) as well as their effects on extracted or commercial essential oils and pure standard samples. Comparison between irradiated and nonirradiated samples was performed by GC/FID and GC/MS. At the studied doses, gamma and e-beam ionizing radiation did not induce any detectable qualitative or quantitative significant changes in the contents and yields of essential oils immediately after ionizing radiation of plants or commercial essential oils and standards. As the maximum dose tested (25 kGy) is a sterilizing dose (much higher than doses used for decontamination of vegetable drugs), it is likely that even decontamination with lower doses will not modify yields or composition of essential oils of these three plants

Determination of new retention indices for quick identification of essential oils compounds

The classical methods of chromatographic identification of compounds were based on calculation of retention indices by using different stationary phases. The aim of the work was to differentiate essential oils extracted from different plant species by identification of some of their major compounds. The method of identification was based on the calculation of new retention indices of essential oils compounds fractionated on a polar chromatographic column with temperature programming system. Similar chromatograms have been obtained on the same column for one plant family with two different temperature gradients allowing the rapid identification of essential oils of different species, sub-species or chemotypes of Citrus, Mentha and Thymus