A comprehensive review on ethnobotanical,phytochemical and pharmacological aspects of the genus Dorema

The genus Dorema (Apiaceae) comprises 12 accepted species, mainly growing in Asia and, particularly, in Iran, where D. ammoniacum and D. aucheri are the most used species in cuisine and folk medicine. The Dorema species are traditionally applied in the treatment of catarrh, asthma, chronic bronchitis, as carminative, mild diuretic and anthelmintic agents. In general, 42 non-volatile secondary metabolites were isolated from the 6 studied species, namely D. aitchisonii, D. ammoniacum, D. aucheri, D. glabrum, D. hyrcanum, and D. kopetdaghense. Among them, phenolic acid, flavonoid, acetophenone, coumarin, and sesquiterpene derivatives were identified as the predominant phytoconstituents. The leaves are characterized by the highest volatile content, and the sesquiterpenes in both hydrocarbon and oxygenated forms were reported as the most abundant compounds. Most of the studied pharmacological activities were assessed in vivo. Nevertheless, in vitro antiradical and antimicrobial potentials were the main investigated activities. Overall, the evaluation of bioactivities confirmed the ethnopharmacological use of the Dorema species, particularly their anti-inflammatory, antibacterial, and hypolipidemic properties. This study comprehensively overviewed, for the first time, the literature relating to the folk medicinal use and to the available phytochemical and pharmacological data. Considering the genus application and the rare clinical trials, the study of the efficacy and safety of the uninvestigated Dorema species might be an interesting and promising approach for further researches.

     

Chitosan antitranspirant activity is due to abscisic acid-dependent stomatal closure

Chitosan (CHT) is a natural compound able to activate the plant own defence machinery against pathogen attacks and to reduce both transpiration and stomatal opening when applied as foliar spray. The data here reported show that CHT-induced antitranspirant activity in bean plants is mediated by ABA, whose level raised over threefold in treated leaves, 24 h after foliar spraying. This is thought to induce partial stomatal closure via a H₂O₂-mediated process, as confirmed by scanning electron microscopy (SEM) and histo-cytochemistry, and, in turn, a decrease of stomatal conductance to water vapor (G_w) and transpiration rate (E), assessed by gas exchange measurements. The relatively high internal CO₂ concentration (C_i) values, suggest the occurrence of a slight decrease in carboxylation efficiency after CHT treatment, which however did not prevail over stomatal limitations. The intrinsic water use efficiency (WUE_i) of CHT treated plants was not statistically different from controls and the maximal photochemical efficiency (F_v/F_m) of PSII was not affected. Moreover, CHT determined a stimulation of the xanthophyll cycle towards de-epoxidation state. On the whole, these results, besides confirming the effectiveness of CHT in reducing plant transpiration, prove that the mechanism underlying this activity differs from that showed by the commercial antitranspirant Vapor Gard^® (VP). In fact, the efficacy of the latter is based on the formation of a thin antitranspirant film over the leaf and not on the reduction of stomatal opening. Finally, suggestions for possible use of the two antitranspirants in different environmental conditions are discussed.     

Primula spectabilis Tratt. aerial parts: morphology, volatile compounds and flavonoids

The vacuolar and epicuticular flavonoids and the volatiles of the leaves and parts of flower of P. spectabilis Tratt., an endemic species in the Italian Oriental Alps, were investigated. From a MeOH extract of the leaves two flavone glycosides, 8-C-β-glucopyranosylluteolin 7-O-α-arabinofuranoside (1) and 6-C-α-arabinofuranosylapigenin (2) were isolated, in addition to a flavone and three flavonols already known from species of Primula. From an EtOH extract of leaf exudates, 7,3',4'-tri-O-methylquercetin was obtained. The structures were elucidated on the basis of their 1D 1H- and 13C NMR data and 2D NMR techniques, as well as of HPLC-MS. The volatiles emitted by the leaves were mainly constituted by non-terpene derivatives, followed by comparable proportions of hemiterpens, oxygenated monoterpenes and sesquiterpene hydrocarbons. In flowers, monoterpene hydrocarbons were the most represented chemical class followed by non-terpene derivatives. Different proportions of compounds were found when individual parts of flowers were examined separately; calyx produced a greater proportion (approx. 49.5%) of non-terpenes as its volatile metabolites. P. spectabilis has glandular trichomes in the hyaline margins of the epidermal depressions, distributed on the adaxial leaf blade. Glandular hairs were also present on the corolla. Correlations of phytochemical data with the morphological features of leaf, flower and glandular hair are discussed, and a hypothesis is proposed on the ecological roles of the flavonoids and volatile compounds on the general fitness of the species and cross-pollination strategies.     

Formation of structured polymers upon controlled denaturation of beta-lactoglobulin with different chaotropes

Prolonged exposure (>90 days) of bovine beta-lactoglobulin (BLG) to subdenaturing concentrations of either urea or potassium thiocyanate resulted in the formation of ordered polymers in the form of fibrils. The fibrils obtained with each chaotrope showed major differences in morphology, surface properties, thiol accessibility, and stability to dissociating agents as a consequence of the different chemical bonds involved in their stabilization. Hydrophobic interactions between BLG monomers are predominant in thiocyanate-formed fibrils, whereas urea-formed fibrils are stabilized by intermolecular disulfides generated through a thiol-disulfide exchange reaction. The different features of fibrils obtained with each chaotrope relate to the peculiar structural features and chemical properties of the "active" monomers generated by subdenaturing chaotrope concentrations in the early phases of the polymerization process, as detected by spectroscopic and limited proteolysis/mass spectrometry studies in the earliest stages of the action of individual chaotropes. The chaotrope-specific features of these early intermediates in turn affect the polymerization mechanism, whose intermediates were studied by size-exclusion chromatography on the soluble fraction at different times of fibril formation. The potential of these findings for the production of protein-derived nanostructures having different and controlled geometries and chemical properties is also discussed.     

Chemical-induced resistance against powdery mildew in barley: the effects of chitosan and benzothiadiazole

Chitosan (CHT), a deacetylated chitin derivative, and benzo-(1,2,3)-thiadiazole-7-carbothioic acid S-methyl ester (BTH), a non toxic synthetic functional analogue of salicylic acid, were applied as foliar spray to barley plants (Hordeum vulgare L.), to compare their effectiveness in inducing resistance against Blumeria graminis f. sp. hordei and to investigate the underlying defence response. After an induction phase of 3 days (IP, time elapsed between treatment and fungal inoculation) both compounds reduced significantly the infection on the primary leaf, namely of 55.5% for CHT and of 68.9% for BTH, showing the induction of a good level of local resistance (LAR). A 5-day IP further reduced the infected areas in BTH treated plants (−77.2%) but not in CHT treated ones (−47.1%). Furthermore, both CHT and BTH also induced SAR, being the infection in the second non treated leaves reduced of 57% and 76.2%, respectively, as evaluated at 10-day IP. Both BTH and CHT induced oxidative burst and phenolic compound deposition in treated leaves, creating an hostile environment that slowed down the fungal spreading by impairing haustorium development. However, the greater efficacy of BTH was possibly due to: i) a greater reinforcement of papilla; ii) a higher level and the more homogeneous diffusion of H₂O₂ in the treated leaf tissues and iii) an induced hypersensitive-like response in many penetrated cells.     

Abscisic acid is involved in chitosan-induced resistance to tobacco necrosis virus (TNV)

Chitosan (CHT) antiviral activity has been further investigated in the pathosystem Phaseolus vulgaris - tobacco necrosis virus (TNV). CHT application elicited both callose apposition and ABA accumulation in leaf tissues, at 12 and 24h after treatment, respectively, and induced a high level of resistance against TNV. Besides, treatment with the ABA inhibitor nordihydroguaiaretic acid (NDGA), before CHT application, reduced both callose deposition and plant resistance to the virus, thus indicating the involvement of ABA in these processes. Exogenous application of ABA also induced a significant resistance to TNV, though this resistance was abolished by NDGA pre-treatment. These results, overall, indicate that the rise of ABA synthesis induced by chitosan plays an important role in enhancing callose deposition but the latter has only a partial effect on virus spreading, which must be constraint by other resistance mechanisms.     

Chemical Composition and Antimicrobial Activity of the Essential Oil of Juniperus excelsa M.Bieb. Growing Wild in Lebanon

The essential oils (EOs) isolated from the leaves and twigs of Juniperus excelsa M.Bieb . growing wild in Lebanon were characterized, and their antimicrobial activity and antiradical capacity were evaluated. The EOs were obtained by hydrodistillation using a Clevenger‐type apparatus and characterized by GC and GC/MS analyses. The antimicrobial activity was evaluated by determining minimal inhibitory concentrations (MICs) against a Gram‐positive and a Gram‐negative bacterium, a yeast, and a dermatophyte with the broth microdilution technique. A total of 28 constituents was identified and accounted for 90.1 and 95.6% of the twig and leaf EO composition, respectively. Both EOs were essentially composed of monoterpene hydrocarbons (46.7 and 59.6% for twig and leaf EOs, resp.) and sesquiterpenes (39.4 and 32.1%, resp.). The main components were α‐pinene, α‐cedrol, and δ‐car‐3‐ene. The J. excelsa EOs did not show any antiradical potential, but revealed interesting in vitro antimicrobial activities against Staphylococcus aureus and Trichophyton rubrum (MICs of 64 and 128 μg/ml, resp.). The three major compounds were tested separately and in combination according to their respective amounts in the oil. δ‐Car‐3‐ene was the most active component and is undoubtedly one of the constituents driving the antifungal activity of J. excelsa essential oil, even though synergies are probably involved.     

A chimeric Potato virus X encoding a heterologous peptide affects Nicotiana benthamiana chloroplast structure

Abstract

The cytopathology of a Potato virus X (PVX) recombinant variant (encoding as fusion of an epitope of immunological interest with the N‐terminus of the coat protein, PVXSmaP18DD) has been compared with that induced by the wild‐type virus (PVX wt) in Nicotiana benthamiana plants. Both PVX wt and PVXSmaP18DD caused similar ultrastructural alterations, characterized by the presence of laminated inclusion components and bulk virus accumulations in mesophyll cells. However, some striking differences were observed not only in the morphology of these accumulations (typically ordered in PVX wt infection and disordered in PVXSmaP18DD infection) but also because the chimeric virus caused peculiar alterations in chloroplasts structure.

Abbreviations: CP, coat protein; d.p.i., days post inoculation; LIC, laminated inclusion components; PVX, Potato virus X     

Phenolic compounds from Achillea millefolium L. and their bioactivity

Since antiquity, Achillea millefolium L. (Asteraceae) has been used in traditional medicine of several cultures, from Europe to Asia. Its richness in bioactive compounds contributes to a wide range of medicinal properties. In this study, we assessed A. millefolium methanolic extract and its isolated components for free radical scavenging activity against 2,2-diphenyl-pycrilhydrazyl, total antioxidant capacity (based on the reduction of Cu(++) to Cu(+)), and ability to inhibit lipid peroxidation. The activity against chloroquine-sensitive and chloroquine-resistant strains of Plasmodium falciparum was also tested. Chlorogenic acid, its derivatives and some flavonoids isolated by semipreparative HPLC and identified by NMR and spectrometric techniques were the major bioactive constituents of the methanolic extract. The latter exhibited significant antioxidant properties, as well as its flavonol glycosides and chlorogenic acids. With regard to the antiplasmodial activity, apigenin 7-glucoside was the most effective compound, followed by luteolin 7-glucoside, whereas chlorogenic acids were completely inactive. On the whole, our results confirmed A. millefolium as an important source of bioactive metabolites, justifying its pharmaceutical and ethnobotanical use.