Native and endemic Iranian Nepeta spp.: powerful antimicrobial agents.

Pathogenic microorganisms are more or less successfully treated by synthetic chemical compounds, whose residues often cause serious health problems. Plant specialized metabolites with antimicrobial properties have for a long time been the focus of both medicine and pharmacology. This study was conducted to evaluate the in vitro antimicrobial activity of methanol extracts of selected endemic and native Iranian Nepeta species against some of the most important pathogenic bacteria and fungi. The results indicated that N. kotschyi leaf extract was the most efficient against the tested bacteria, with Pseudomonas aeruginosa being the most sensitive and fungal species were more susceptible to the extracts than bacterial strains. Nepeta spp. extracts showed a strong antifungal activity against micromycetes, except for quite resistant Aspergillus niger. Antibacterial MIC values (mg.mL-1) ranged from 0.01 (N. kotschyi) to 0.20 (N. crassifolia), while antifungal MIC values ranged from 0.02 (N. crassifolia, N. kotschyi, N. menthoides, and N. cataria) to 0.13 (N. crassifolia and N. menthoides). When compared to positive controls, in most cases the extracts performed much better. The recorded antimicrobial activity candidates the selected 4 endemic and native Iranian Nepeta spp. as prospective and promising antimicrobial agents to be used in both pharmacology and biotechnology.

Centaurium erythraea extract improves survival and functionality of pancreatic beta-cells in diabetes through multiple routes of action.

ETHNOPHARMACOLOGICAL RELEVANCE: Centaurium erythraea Rafn (CE) is used as a traditional medicinal plant in Serbia to treat different ailments due to its antidiabetic, antipyretic, antiflatulent and detoxification effects. AIM OF THE STUDY: Elucidation of the mechanisms that underlie the antioxidant and pro-survival effects of the CE extract (CEE) in beta-cells and pancreatic islets from streptozotocin (STZ)-treated diabetic rats. MATERIAL AND METHODS: Diabetes was induced in rats by multiple applications of low doses of STZ (40 mg/kg intraperitoneally (i.p.), for five consecutive days). CEE (100 mg/kg) was administered orally, in the pre-treated group for two weeks before diabetes induction, during the treatments with STZ and for four weeks after diabetes onset, and in the post-treatment group for four weeks after diabetes induction. The impact of CEE on diabetic islets was estimated by histological and immunohistochemical examination of the pancreas. Molecular mechanisms of the effects of CEE were also analyzed in insulinoma Rin-5F cells treated with STZ (12 mM) and CEE (0.25 mg/mL). Oxidative stress was evaluated by assessing the levels of DNA damage, lipid peroxidation, protein S-glutathionylation and enzymatic activities and expression of CAT, MnSOD, CuZnSOD, GPx and GR in beta-cells. The presence and activities of the redox-sensitive and islet-enriched regulatory proteins were also analyzed. RESULTS: Treatment with CEE ameliorated the insulin level and glycemic control in STZ-induced diabetic rats by improving the structural and functional properties of pancreatic islets through multiple routes of action. The disturbance of islet morphology and islet cell contents in diabetes was reduced by the CEE treatment and was associated with a protective effect of CEE on the levels of insulin, GLUT-2 and p-Akt in diabetic islets. The antioxidant effect of CEE on STZ-treated beta-cells was displayed as reduced DNA damage, lipid peroxidation, protein S-glutathionylation and alleviation of STZ-induced disruption in MnSOD, CuZnSOD and CAT enzyme activities. The oxidative stress-induced disturbance of the transcriptional regulation of CAT, MnSOD, CuZnSOD, GPx and GR enzymes in beta-cells was improved after the CEE treatment, and was observed as readjustment of the presence and activities of redox-sensitive NFκB-p65, FOXO3A, Sp1 and Nrf-2 transcription factors. The observed CEE-mediated induction of proliferative and pro-survival pathways and insulin expression/secretion after STZ-induced oxidative stress in beta-cells could be partially attributed to a fine-tuned modulation of the activities of pro-survival Akt, ERK and p38 kinases and islet-enriched Pdx-1 and MafA regulatory factors. CONCLUSIONS: The results of this study provide evidence that CEE improves the structural and functional properties of pancreatic beta-cells by correcting the endogenous antioxidant regulatory mechanisms and by promoting proliferative and pro-survival pathways in beta-cells.

Centaurium erythraea methanol extract protects red blood cells from oxidative damage in streptozotocin-induced diabetic rats.

ETHNOPHARMACOLOGICAL RELEVANCE: Centaurium erythraea Rafn (CE) is a traditional medicinal herb in Serbia with antidiabetic, digestive, antipyretic and antiflatulent effects AIM OF THE STUDY: To investigate the potential protective effects of the methanol extract of the aerial parts of CE against glyco-oxidative stress in red blood cells (RBCs) in rats with experimentally induced diabetes. MATERIAL AND METHODS: Diabetes was induced in Wistar rats by intraperitoneal (i.p.) injection of multiple low-dose streptozotocin (STZ) (40mg/kg, for five consecutive days), with the 1st day after the last STZ injection taken as the day of diabetes onset. The methanol extract of CE (100mg/kg) was administered orally and daily, two weeks before the first STZ injection, during the 5-day treatment with STZ, and for four weeks after the STZ injections (pre-treated group) or for four weeks after diabetes onset (post-treated group). The effect of CE extract administration on the redox status of RBCs was evaluated by assessing lipid peroxidation, the ratio of reduced/oxidized glutathione (GSH/GSSG), the level of S-glutathionylated proteins (GSSP) and the enzymatic activities of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) and glutathione reductase (GR) in RBCs four weeks after diabetes onset. The major biochemical parameters of diabetes, protein glycation/glycosylation of erythrocytes and parameters which correlate with their aggregation and deformability were also evaluated. RESULTS: Daily application of CE extract to STZ-induced diabetic rats provided important antidiabetic effects, observed in both pre-treated and post-treated groups of diabetic rats as elevated serum insulin concentration, reduction of blood glucose and glycated hemoglobin concentrations and an improved lipid profile. Antioxidant effects of CE extract were detected in RBCs of diabetic rats and observed as decreased lipid peroxidation and ameliorated oxidative damage as a result of increased SOD, CAT and GR activities, an improved GSH/GSSG ratio and reduced GSSP levels. Moreover, the CE extract protected RBC proteins from hyperglycemia-induced damage by reducing non-enzymatic glycation and enzymatic glycosylation processes. CE extract was more effective when applied before diabetes induction (pre-treated group). CONCLUSIONS: The results of this study show that the Centaurium erythraea methanol extract protects RBCs in diabetic animals from oxidative damage. They provide additional support for the application of this traditionally used plant in diabetes management.

Simultaneous UHPLC/DAD/(+/-)HESI-MS/MS analysis of phenolic acids and nepetalactones in methanol extracts of Nepeta species: a possible application in chemotaxonomic studies.

INTRODUCTION: Nepeta species contain a variety of secondary metabolites, including iridoid monoterpenes - nepetalactones and phenolic acids - that are considered the main bioactive constituents. This work represents the first attempt to comparatively explore variations in these two major groups of secondary metabolites within the genus. OBJECTIVE: To develop an efficient analytical methodology for simultaneous analysis of nepetalactones and phenolic acids in methanol extracts of selected Nepeta species, and to evaluate its potential application in chemotaxonomic studies. MATERIAL AND METHODS: A UHPLC combined with linear-trap quadrupole (LTQ) orbitrap MS method was used to characterise chemical diversity and complexity of phenolics among 12 selected Nepeta species. A targeted metabolomic approach using UHPLC coupled to a diode array detector (DAD) and combined with (+/-) heated electrospray ionisation (HESI) MS/MS was developed and validated for quantitative analysis of six hydroxycinnamic acid derivatives and four nepetalactones. RESULTS: Phenolic profiling provided a valuable database of bioactive compounds in the plant group studied, including phenolic acids (hydroxybenzoic and hydroxycinnamic acids) and flavonoids (flavones, flavonols and flavanones). Principal component analysis and cluster analysis suggested the applicability of 10 targeted compounds as chemomarkers for chemotaxonomic studies. Pearson's correlation analysis revealed significant positive correlations between metabolites involved in different biosynthetic pathways (phenylpropanoid or monoterpenoid). CONCLUSION: The described targeted metabolomic approach proved to be highly beneficial in designing a phytochemical overview of the genus Nepeta, and might have applications in further clarification of phylogenetic relations. Furthermore, it has the potential to be implemented in a routine quality control of plant material and herbal preparations.

Centauries as underestimated food additives: antioxidant and antimicrobial potential.

Methanol extracts of aerial parts and roots of five centaury species (Centaurium erythraea, C. tenuiflorum, C. littorale ssp. uliginosum, C. pulchellum, and Schenkia spicata) were analysed for their main secondary metabolites: secoiridoid glycosides, a group of monoterpenoid compounds, and phenolics (xanthones and flavonoids), and further investigated for antioxidant capacity and antimicrobial activity. The results of ABTS, DPPH, and FRAP assays showed that above ground parts generally displayed up to 13 times higher antioxidant activity compared to roots, which should be related to higher phenolics content, especially flavonoids, in green plant organs. Secoiridoid glycosides showed no antioxidant activity. All the tested extracts demonstrated appreciative antibacterial (0.05-0.5 mg ml(-1)) and strong antifungal activity (0.1-0.6 mg ml(-1)). Our results imply that above ground parts of all centaury species studied, could be recommended for human usage as a rich source of natural antioxidants and also in food industry as strong antimicrobial agents for food preservation.

Antibacterial and antifungal screening of Centaurium pulchellum crude extracts and main secoiridoid compounds.

The main principles of C. pulchellum (Sw.) Druce, secoiridoid glycosides, have been studied as potent bioactive compounds. Here we scored their content in extracts of ten populations of this species. Antibacterial and antifungal assays of the extracts and pure secoiridoid glycosides were performed against eight bacterial strains and five fungal species. Methanol extracts from both aerial parts and roots exhibited excellent antibacterial (0.05-0.2 mg mL(-1)) and very good antifungal (0.1-2 mg mL(-1)) activity. Pure secoiridoid glycosides isolated from these extracts demonstrated very strong antibacterial (0.01-0.04 mg mL(-1)) and especially antifungal (0.001-0.1 mg mL(-1)) activity.

Nepetalactone content in shoot cultures of three endemic Nepeta species and the evaluation of their antimicrobial activity.

Rapid micropropagation of Nepeta rtanjensis, N. sibirica and N. nervosa was performed. Qualitative and quantitative nepetalactone content in methanol extracts of in vitro grown plants was analysed by reverse-phase HPLC coupled with UV and MS detection. Only trans,cis-nepetalactone was detected in shoots of N. rtanjensis, while cis,trans-nepetalactone stereoisomer was present in N. sibirica. No nepetalactone was observed in shoots of N. nervosa. The antimicrobial activity of methanol extracts, against eight bacterial and eight fungal species, was evaluated. All the tested extracts showed significant antibacterial and strong antifungal activity. However, N. rtanjensis extract exhibited the best antimicrobial potential.