Polyphenol content and bioactivity of Achillea moschata from the Italian and Swiss Alps.

Achillea moschata Wulfen, which grows in the Alps, is extensively used by local people for its medicinal properties. Two studied samples were collected, at the flowering stage, in Val Mustair (Switzerland) and Valchiavenna (Italy), respectively. The aerial parts were defatted with petroleum ether (PET) and successively extracted with dichloromethane (DCM) and methanol (MeOH). High-performance liquid chromatography and electrospray ionization-tandem mass spectrometry analyses of the methanolic extracts evidenced that flavonoids were the predominant compounds compared to phenolic acids in both samples (89.5 vs. 33.0 µg/mg DW in A. moschata Valchiavenna and 82.5 vs. 40.0 µg/mg DW in A. moschata Val Mustair). Among flavonoid derivatives, luteolin and apigenin were the predominant aglycones, free and glycosilated. The A. moschata Valchiavenna extract was characterized by apigenin as the main compound (60.4 µg/mg DW), while A. moschata Val Mustair was characterized by its derivative apigenin 7-O-glucoside (44.7 µg/mg DW). The antioxidant activity of all the obtained extracts was tested by the DPPH (2,2-diphenyl-picryl hydrazyl) and ABTS (2,21-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)) methods, which showed their increasing scavenger capacity in relation to extract polarity (PET extract < DCM extract < MeOH extract). The extracts were also investigated against three Gram-positive (Bacillus cereus, Enterococcus faecalis and Staphylococcus aureus) and three Gram-negative (Escherichia coli, Proteus mirabilis and Pseudomonas aeruginosa) bacterial species using the disc diffusion assay. DMC and PET were the most active extracts (inhibition diameter: ≥12 mm).

Chemical Profile, Antioxidant and Antibacterial Activities of Achillea moschata Wulfen, an Endemic Species from the Alps.

Aerial parts of Achillea moschata Wulfen (Asteraceae) growing wild in the Italian Rhaetian Alps were investigated to describe, for the first time, their phenolic content, as well as to characterize the essential oil. Inspection of the metabolic profile combining HPLC-DAD and ESI-MS/MS data showed that the methanol extract contained glycosylated flavonoids with luteolin and apigenin as the main aglycones. Among them, the major compound was 7-O-glucosyl apigenin. Caffeoyl derivates were other phenolics identified. The essential oil obtained by steam distillation and investigated by GC/FID and GC/MS showed camphor, 1,8-cineole, and bornylacetate as the main constituents. The antioxidant capacity of three different extracts with increasing polarity and of the essential oil was evaluated by employing ABTS·+ and DPPH· radical scavenging assays. The methanolic extract was the only significantly effective sample against both synthetic radicals. All samples were also tested against Gram-positive (Bacillus cereus, Enterococcus faecalis, Staphylococcus aureus) and Gram-negative (Escherichia coli, Proteus mirabilis, Pseudomonas aeruginosa) bacterial species using the disk diffusion assay. The non-polar extracts (dichloromethane and petroleum ether) and the essential oil possessed a broad spectrum of antimicrobial activity expressed according to inhibition zone diameter (8-24 mm).

Antimicrobial susceptibility of Listeria monocytogenes isolates from human cases in northern Italy, 2008-2010: MIC determination according to EUCAST broth microdilution method.

Susceptibility of 96 Listeria monocytogenes human isolates collected in northern Italy between 2008 and 2010, to 15 antimicrobials, was investigated. Minimum inhibitory concentration (MIC) was evaluated by means of the standardized broth microdilution method, according to the European Committee on Antimicrobial Susceptibility Testing (EUCAST) international guidelines. All L. monocytogenes human isolates were susceptible to penicillin G (MIC(90)≤0·06 µg/ml), meropenem (MIC(90)≤0·06 µg/ml), and erythromycin (MIC(90) = 0·12 µg/ml). Susceptibility to the other tested antimicrobials could not be interpreted due to the lack of breakpoint values although two (2%) isolates were shown to have tetracycline MICs above EUCAST epidemiological cut-off values (ECOFF). Bactericidal activity for amoxicillin, gentamicin, and levofloxacin was generally observed at concentrations 2-4 times higher than MIC values. Though L. monocytogenes human strains, isolated in the north of Italy, appear to be susceptible to most antimicrobial agents used in human therapy, this study provides new data for epidemiological surveillance and clinical breakpoints definition.

Thiamine plays a critical role in the acid tolerance of Listeria monocytogenes.

Understanding the molecular basis of acid tolerance in the food-borne pathogen Listeria monocytogenes is important as this property contributes to survival in the food-chain and enhances survival within infected hosts. The aim of this study was to identify genes contributing to acid tolerance in L. monocytogenes using transposon mutagenesis and subsequently to elucidate the physiological role of these genes in acid tolerance. One mutant harboring a Tn917 insertion in the thiT gene (formerly lmo1429), which encodes a thiamine (vitamin B1) uptake system, was found to be highly sensitive to acid. The acid-sensitive phenotype associated with loss of this gene was confirmed with an independently isolated mutant, from which the thiT gene was deleted (∆thiT). Cells of both wild-type and ∆thiT mutant that were thiamine depleted were found to be significantly more acid sensitive than control cultures. Thiamine-depleted cultures failed to produce significant concentrations of acetoin, consistent with the known thiamine dependence of acetolactate synthase, an enzyme required for acetoin synthesis from pyruvate. As acetoin synthesis is a proton-consuming process, we suggest that the acid sensitivity observed in thiamine-depleted cultures may be owing to an inability to produce acetoin.

The relationships between phenolic content, pollen diversity, physicochemical information and radical scavenging activity in honey.

Honey is rich in different secondary plant metabolites acting as natural antioxidants and contributing to human health. Radical scavenging activity (RSA) is related to antioxidant activity, while the correlation between the phenolic content and RSA is often weak. Consequently, exclusive information on phenolics is often insufficient to qualify the RSA and the health promoting effects of honey. The paper deals with a case study of honey samples originating from the alpine areas of Italy's Lombardia and Veneto regions and realized by standard physicochemical and statistical analytical methods. In pure honey, the total phenolic content and the RSA were measured in spectrophotometric tests with the 2,2-diphenyl-1-picrylhydrazyl (DPPH·) free radical and Folin-Ciocalteu assays, respectively. Melissopalynological data was used to qualify pollen diversity through rank-frequency curves separating the samples into two groups. On the basis of physicochemical data, the samples were analyzed through multivariate classification and ranking procedures resulting in the identification of an outlier. Elimination of the outlier produced a high correlation between the total phenolic content and RSA in the two pollen diversity groups. The case study suggests that, after disregarding outliers, the RSA activity can be satisfactorily qualified on the basis of phenolics with pollen diversity as a covariate.

Influence of environmental factors on composition of phenolic antioxidants of Achillea collina Becker ex Rchb.

Effects of environmental growth conditions on the antioxidant capacity, total phenolic content and composition of Achillea collina Becker ex Rchb. were investigated. Methanol extracts and infusions obtained from leaves and inflorescences of plants cultivated in the Italian Alps at two different altitudes (600 and 1050 m a.s.l.) were evaluated. Infusions exhibited the highest antioxidant capacity (1/IC(50) values from 4.35 ± 0.72 to 8.90 ± 0.74), total phenolic content (from 31.39 ± 4.92 to 49.36 ± 5.70 mg gallic acid equivalents (GAE) g(-1) DW), chlorogenic acid (from 9.21 ± 1.52 to 31.27 ± 6.88 mg g(-1) DW), 3,5-di-O-caffeoylquinic acid (from 12.28 ± 3.25 to 25.13 ± 1.99 mg g(-1) DW) and 4,5-di-O-caffeoylquinic acid (from 7.38 ± 1.01 to 12.78 ± 2.61 mg g(-1) DW) content. Climate (as influenced by altitude) was shown to be the main environmental factor influencing yarrow composition and properties. Leaf extracts from the higher experimental site showed a 2-4-fold increase of chlorogenic acid level. Achillea collina can be considered as a very good source of bioactive phenolic compounds, and growing it at high altitude may constitute an effective way to significantly enhance its quality for both medicinal and nutritional uses.