Antimicrobial activity of gaseous Citrus limon var pompia leaf essential oil against Listeria monocytogenes on ricotta salata cheese.

Contamination by Listeria monocytogenes is a particularly challenging problem in the food industry due to the ability of the bacterium to develop under conditions normally used for food preservation. Here, we show that the gaseous phase of Citrus limon var pompia leaf essential oil (hereafter PLEO) exerts specific anti-Listeria activity on ricotta salata cheese stored at 5 °C. The synergic effect of gaseous PLEO treatment and refrigeration was first confirmed in vitro on L. monocytogenes strains treated for 3 h with gaseous PLEO and then stored at 5 °C. Ricotta cheese was then inoculated with L. monocytogenes strains and subjected to hurdle technology with different concentrations of gaseous PLEO. Cell counts revealed gaseous PLEO to exert a bactericidal effect on L. monocytogenes 20600 DSMZ and a bacteriostatic effect on a mix of L. monocytogenes strains. Scanning and transmission electron microscopy analyses of L. monocytogenes cells suggested that gaseous PLEO targets the bacterial cell wall and plasma membrane. Chemical analyses of the liquid and vapor phases of PLEO indicated linalyl acetate to be the predominant compound, followed by limonene and the two isomers of citral, whereas EO composition analysis, although generally in line with previous findings, showed the presence of linalyl acetate for the first time. Solid-phase microextraction coupled with gas chromatography confirmed the presence of all crude oil components in the headspace of the box.

Effectiveness of essential oil extracted from pompia leaves against Penicillium digitatum.

BACKGROUND: In recent years, interest in the use of natural compounds as possible substitutes for chemicals, to prevent microbial food spoilage has grown. The antimicrobial activity of the essential oils (EOs) is well known and nowadays there is renewed interest in their application as natural preservatives in postharvest management. The aims of this study were to characterize the EO extracted from pompia leaves and to evaluate its effectiveness for the control of the postharvest decay agent Penicillium digitatum, when applied as vapor contact in new airtight boxes, supplied with a heating system. RESULTS: Fumigation was performed in vitro and on food using two concentrations of the EO, heated at controlled temperature. The headspace analysis revealed that the heating of the EO favored the evaporation of the volatile compounds, without altering their functionality. The treatments reduced the pathogen growth in vitro and rot on inoculated food by about 50%. CONCLUSION: The chemical analysis of the vapor composition demonstrated that heating the oil did not alter the components and thus the antimicrobial effect of the oil. The treatment by vapor contact with the EO was effective in controlling the pathogen growth in vitro but, above all, it was successful in halving rot in vivo. Due to their bioactivity in the vapor phase, EOs could be delivered as fumigants during postharvest protection; however, the techniques commonly employed are not ideal for simulating real pre-treatment conditions. The new device allows real large-scale conditions to be reproduced. © 2020 Society of Chemical Industry.

Effect of NaHCO3 treatments on the activity of cell-wall-degrading enzymes produced by Penicillium digitatum during the pathogenesis process on grapefruit.

BACKGROUND: This study was performed to clarify the strategies of Penicillium digitatum during pathogenesis on citrus, assessing, on albedo plugs, the effects of treatment with sodium bicarbonate (NaHCO3 ), at two different pH values (5 and 8.3), on cell-wall-degrading enzyme activity over a period of 72 h. RESULTS: Treatment with NaHCO3 , under alkaline pH, delayed the polygalacturonase activity for 72 h, or 48 h in the case of the pectin lyase, compared with the control or the same treatment at pH 5. In contrast, pectin methyl esterase activity rapidly increased after 24 h, in plugs dipped in the same solution. In this case, the activity remained higher than untreated or pH 5-treated plugs up to 72 h. CONCLUSION: The rapid increase in pectin methyl esterase activity under alkaline conditions is presumably the strategy of the pathogen to lower the pH, soon after the initiation of infection, in order to restore an optimal environment for the subsequent polygalacturonase and pectin lyase action. In fact, at the same time, a low pH delayed the enzymatic activity of polygalacturonase and pectin lyase, the two enzymes that actually cleave the α-1,4-linkages between the galacturonic acid residues. © 2018 Society of Chemical Industry.

Profiling and Simultaneous Quantitative Determination of Anthocyanins in Wild Myrtus communis L. Berries from Different Geographical Areas in Sardinia and their Comparative Evaluation.

INTRODUCTION: Myrtus communis L. (Myrtaceae) is a self-seeded shrub, widespread in Sardinia, with anti-inflammatory, antiseptic, antimicrobial, hypoglycemic and balsamic properties. Its berries, employed for the production of sweet myrtle liqueur, are characterised by a high content of bioactive polyphenols, mainly anthocyanins. Anthocyanin composition is quite specific for vegetables/fruits and can be used as a fingerprint to determine the authenticity, geographical origin and quality of raw materials, products and extracts. OBJECTIVE: To rapidly analyse and determine anthocyanins in 17 samples of Myrtus communis berries by developing a platform based on the integration of UHPLC-MS/MS quantitative data and multivariate analysis with the aim of extracting the most information possible from the data. METHODOLOGY: UHPLC-ESI-MS/MS methods, working in positive ion mode, were performed for the detection and determination of target compounds in multiple reaction monitoring (MRM) mode. Optimal chromatographic conditions were achieved using an XSelect HSS T3 column and a gradient elution with 0.1% formic acid in water and 0.1% formic acid in acetonitrile. Principal component analysis (PCA) was applied to the quantitative data to correlate and discriminate 17 geographical collections of Myrtus communis. RESULTS: The developed quantitative method was reliable, sensitive and specific and was successfully applied to the quantification of 17 anthocyanins. Peonidin-3-O-glucoside was the most abundant compound in all the extracts investigated. CONCLUSION: The developed methodology allows the identification of quali-quantitative differences among M. communis samples and thus defines the quality and value of this raw material for marketed products. Moreover, the reported data have an immediate commercial value due to the current interest in developing antioxidant nutraceuticals from Mediterranean plants, including Sardinian Myrtus communis. Copyright © 2016 John Wiley & Sons, Ltd.

Rollover-assisted C(sp2)-C(sp3) bond formation.

Rollover cyclometalation involves bidentate heterocyclic donors, unusually acting as cyclometalated ligands. The resulting products, possessing a free donor atom, react differently from the classical cyclometalated complexes. Taking advantage of a "rollover"/"retro-rollover" reaction sequence, a succession of oxidative addition and reductive elimination in a series of platinum(II) complexes [Pt(N,C)(Me)(PR3)] resulted in a rare C(sp(2))-C(sp(3)) bond formation to give the bidentate nitrogen ligands 3-methyl-2,2'-bipyridine, 3,6-dimethyl-2,2'-bipyridine, and 3-methyl-2-(2'-pyridyl)-quinoline, which were isolated and characterized. The nature of the phosphane PR3 is essential to the outcome of the reaction. This route constitutes a new method for the activation and functionalization of C-H bond in the C(3) position of bidentate heterocyclic compounds, a position usually difficult to functionalize.

Grape and Wine Composition in Vitis vinifera L. cv. Cannonau Explored by GC-MS and Sensory Analysis.

GC-FID/MS is a powerful technique used to analyze food and beverage aromas. Volatile organic compounds (VOCs) in grape berries play an important role in determining wine quality and are affected by many factors, such as climate and soil that mainly influence their relative concentrations. Wine aroma is generated by a complex mixture of compounds, and the sensory relevance of individual VOCs is far from elucidated. Herein, the VOC content (free and glycosylated) of Cannonau grape skin and juice and of Cannonau wine collected in different areas of Sardinia is explored. Wine sensory analysis was also carried out and the relationship between sensory attributes and VOCs was investigated. Although Cannonau grapes showed the same VOC fingerprint, great variability was identified between samples, although only the differences in 2-phenylethanol and benzyl alcohol concentration in the grape skins and benzyl alcohol and a terpenoid in grape juice were significantly different according to ANOVA. The correlation between VOC content and the sensory profile highlights the role played by 2-methyl-1-butanol and 2-phenylethanol in increasing wine sensory complexity.

Antimicrobial Activity and Chemical Characterization of a Non-Polar Extract of Saffron Stamens in Food Matrix.

The production of saffron spice generates large quantities of plant by-products: over 90% of the plant material collected is discarded, and a consideration fraction of this waste is plant stamens. This work investigated the chemical composition and the antimicrobial activities of the non-polar fraction extracted from four different saffron flower stamens. The chemical composition of ethereal extracts of the saffron stamens was qualitatively assessed by means of gas-chromatography-mass spectrometry (GC-MS) and nuclear magnetic resonance (NMR) analyses. These analyses revealed ethereal extracts to possess a high polyunsaturated fatty acid content. In vitro antibacterial activity of stamen extracts showed no large differences between Gram-positive and Gram-negative bacteria in terms of minimal inhibitory concentration (MIC). In food matrix microbial analysis of the bacterial strains belonging to the main foodborne pathogen species, including Staphylococcus aureus DSM 20231, Escherichia coli DSM 30083, and Listeria monocytogenes DSM 20600, using low-fat UHT milk, revealed a statistically significant reduction in the number of cells (particularly for E. coli and S. aureus with a complete elimination of the population of the two target bacteria following incubation in diethyl ether extracts of saffron stamen (DES) at high concentrations tested, both at 37 °C and 6 °C (for 48 h and 7 days, respectively). A synergic effect was observed when the pathogens were incubated at 6 °C with DES. This work shows these by-products to be excellent sources of bioactive compounds, which could be exploited in high-added-value products, such as food, cosmetics, and drugs.

Comparison between Citral and Pompia Essential Oil Loaded in Phospholipid Vesicles for the Treatment of Skin and Mucosal Infections.

Citrus species extracts are well known sources of bio-functional compounds with health-promoting effects. In particular, essential oils are known for their antibacterial activity due to the high content of terpenes. In this work, the steam-distilled essential oil from the leaves of Citrus limon var. pompia was loaded in phospholipid vesicles. The physico-chemical characteristics of the essential oil loaded vesicles were compared with those of vesicles that were loaded with citral, which is one of the most abundant terpenes of Citrus essential oils. The biocompatibility of the vesicles was assessed in vitro in human keratinocytes. Furthermore, the antimicrobial activity of the vesicles was tested while using different bacterial strains and a yeast: Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, and Candida albicans, respectively. The vesicles were small in size (~140 nm), slightly polydispersed (PI ~ 0.31), highly negatively charged (~ -73 mV), and able to incorporate high amounts of essential oil or citral (E% ~ 86%). Pompia essential oil and citral exhibited antimicrobial activity against all of the assayed microorganisms, with P. aeruginosa being the least sensitive. Citral was slightly more effective than pompia essential oil against E. coli, S. aureus, and C. albicans. The incorporation of citral in vesicles improved its antifungal activity against C. albicans.

Entrapment of Citrus limon var. pompia Essential Oil or Pure Citral in Liposomes Tailored as Mouthwash for the Treatment of Oral Cavity Diseases.

This work aimed at developing a mouthwash based on liposomes loading Citrus limon var. pompia essential oil or citral to treat oropharyngeal diseases. Vesicles were prepared by dispersing phosphatidylcholine and pompia essential oil or citral at increasing amounts (12, 25 and 50 mg/mL) in water. Transparent vesicle dispersions were obtained by direct sonication avoiding the use of organic solvents. Cryogenic transmission electron microscopy (cryo-TEM) confirmed the formation of unilamellar, spherical and regularly shaped vesicles. Essential oil and citral loaded liposomes were small in size (~110 and ~100 nm, respectively) and negatively charged. Liposomes, especially those loading citral, were highly stable as their physico-chemical properties did not change during storage. The formulations were highly biocompatible against keratinocytes, were able to counteract the damages induced in cells by using hydrogen peroxide, and able to increase the rate of skin repair. In addition, liposomes loading citral at higher concentrations inhibited the proliferation of cariogenic bacterium.

Bioactive compounds and antioxidants from a Mediterranean garland harvested at two stages of maturity.

Chrysanthemum coronarium L. (garland) is an herbaceous plant rich in bioactive compounds. The chemical composition, bioactive compounds and antioxidant properties of a Mediterranean garland population were investigated in different organs at two phenological stages. Antioxidant capacity varied from 7.9 (vegetative) to 14.4 (flowering) mmol Trolox equivalent antioxidant capacity 100 g-1 dry weight (DW). A significant correlation between antioxidant capacity and total phenolics and total flavonoids was found at flowering stage. LC-MS/MS analysis revealed that chlorogenic acid reached a maximum of 4.7 µg g-1 DW in leaves; flowers were high in luteolin (2.37 µg g-1 DW), whereas leaves showed a remarkable content of rutin (1.78 µg g-1 DW). Results highlight differences in bioactive compound levels and antioxidant capacity related to plant stages and organs. This research provides new insights into antioxidant activities and chemistry of garland, in view of its exploitation in areas of fodder resources, functional foods and natural antioxidants.

Acclimatization study of Tagetes lucida L. in Egypt and the chemical characterization of its essential oils.

Seeds of Tagetes lucida were imported to Egypt from Canada and propagated under greenhouse conditions in peat moss media. Soil was sandy in texture and the irrigation system was dripping irrigation. The growth parameters were determined at five successive plant ages, fresh and dry weights of herb were determined at three successive plant ages. The yield of aerial parts after 175 days, was about 7.5 Mg/ha. The essential oil (EO) was extracted by hydro-distillation for three hours with a yield of about 0.5% (w/v). The EO of each sample was subjected to gas-chromatography/mass spectrometry analyses to study the chemical composition. The main component of the EO was identified as methyl chavicol which matched over 90% of the whole composition. Chlorophyll a and carotenes increased with increasing plant age in both sites and seasons. Flavonoids decreased with the development of plant age, while the opposite was true with coumarines content.

In vitro inhibitory effects of Limonium contortirameum and L. virgatum extracts from sardinia on alpha-amylase, alpha-glucosidase and pancreatic lipase.

Pancreatic triacylglycerol lipase (PL), alpha-amylase and alpha-glucosidase are interesting pharmacological targets for the management of dyslipidemia, atherosclerosis, and obesity-diabetes. Limonium spp (Plumbaginaceae) are endemic to Sardinia, Italy. Comparable with acarbose, aqueous extracts (AE) of L. contortirameum and L. virgatum, and their phytoconstituent gallic acid concentration gradients (mg/mL) were identified as in vitro potent (p<0.001, n=3) and efficacious dual inhibitors of alpha-amylase and alpha-glucosidase with respective IC50 (mg/mL) values of 0.6 +/- 0.1, 1.2 +/- 0.1 and 0.15 +/- 0.02. Equivalent to orlistat (PL IC50 of 0.114 +/- 0.004 microg/mL), L. contortirameum, L. virgatum AE and their phytoprinciple gallic acid inhibited PL substantially (p<0.001, n=3) in a dose-dependent manner in vitro with PL- IC50 (microg/mL) of 920.4 +/- 105.2, 593.1 +/- 56.8 and 8.4 +/- 0.9, respectively. LC-MS analysis of extracts revealed the presence of several phenolic compounds in their aglycon and glycoside forms. These are catechins, flavones, epigallocatechins and flavonols. Flavonoid- and polyphenol-rich L contortirameum and L. virgatum, modulating gastrointestinal carbohydrate and lipid digestion and absorption, may be advocated as candidates for obesity-diabetes prevention and phytotherapy.

Genetic and metabolite diversity of Sardinian populations of Helichrysum italicum.

BACKGROUND: Helichrysum italicum (Asteraceae) is a small shrub endemic to the Mediterranean Basin, growing in fragmented and diverse habitats. The species has attracted attention due to its secondary metabolite content, but little effort has as yet been dedicated to assessing the genetic and metabolite diversity present in these populations. Here, we describe the diversity of 50 H. italicum populations collected from a range of habitats in Sardinia. METHODS: H. italicum plants were AFLP fingerprinted and the composition of their leaf essential oil characterized by GC-MS. The relationships between the genetic structure of the populations, soil, habitat and climatic variables and the essential oil chemotypes present were evaluated using Bayesian clustering, contingency analyses and AMOVA. KEY RESULTS: The Sardinian germplasm could be partitioned into two AFLP-based clades. Populations collected from the southwestern region constituted a homogeneous group which remained virtually intact even at high levels of K. The second, much larger clade was more diverse. A positive correlation between genetic diversity and elevation suggested the action of natural purifying selection. Four main classes of compounds were identified among the essential oils, namely monoterpenes, oxygenated monoterpenes, sesquiterpenes and oxygenated sesquiterpenes. Oxygenated monoterpene levels were significantly correlated with the AFLP-based clade structure, suggesting a correspondence between gene pool and chemical diversity. CONCLUSIONS: The results suggest an association between chemotype, genetic diversity and collection location which is relevant for the planning of future collections aimed at identifying valuable sources of essential oil.

Chemical and biological study on the essential oil of Artemisia caerulescens L. ssp. densiflora (Viv.).

Artemisia caerulescens L. ssp. densiflora (Viv.) is a wild shrub that grows in the archipelago of La Maddalena, Sardinia, Italy. The antifungal activity of the volatile oil of this sub-species has not been evaluated earlier. This study aimed to identify the main components of the essential oil of A. caerulescens L. ssp. densiflora and to investigate its antifungal activity. Identification of the different components of the essential oil obtained by hydrodistillation from A. caerulescens L. ssp. densiflora was done by both techniques: GC-MS and NMR analyses ((1)H, (13)C, HSQC-NMR). Antifungal activity was evaluated by agar disc diffusion technique against environmental isolates of fungal strains: two yeasts (Rhodotorula spp., Candida spp.), three moulds (Aspergillus spp., Alternaria spp., Fusarium spp.) and a mixture of moulds. GC-MS analysis of the essential oil yielded 42 compounds, out of which, 26 compounds were identified. The main compound was identified as terpinen-4-ol (22%) followed by p-cymene (7.6%) and α-terpineol (3.02%). The significant inhibition spectrum of the essential oil of A. caerulescens L. ssp. densiflora can be considered as an alternative to common disinfectants.

Platinum(II) N-heterocyclic carbene complexes: coordination and cyclometallation.

Four different NHC ligands have been coordinated to Pt(II) centres; for the first time cyclometallation of the NHC ligand was observed, but only when the platinum centre had a DMSO and two methyl co-ligands. Cyclometallation resulted in the exclusive formation of five-membered rings, and the absence of any double cyclometallation reactions with appropriate ligands rules out the possibility of an oxidative addition type mechanism for the cyclometallation reaction.