The Antimicrobial Potential of Hexane Oils and Polyphenols-Rich Extracts from Pistacia vera L.
by
, and
Teresa Gervasi
1,*
,
Manuela D’Arrigo
2, 
Rossana Rando
1,
Maria Teresa Sciortino
2, 
Arianna Carughi
3,
Davide Barreca
2
and
Giuseppina Mandalari
2
1
Department of Biomedical and Dental Sciences and Morphofunctional Imaging, University of Messina, 98166 Messina, Italy
2
Department of Chemical, Biological, Pharmaceutical and Environmental Science, University of Messina, 98166 Messina, Italy
3
American Pistachio Growers, Fresno, CA 93720, USA
*
Author to whom correspondence should be addressed.
Appl. Sci. 2022, 12(9), 4389; https://doi.org/10.3390/app12094389
Submission received: 23 March 2022
/
Revised: 24 April 2022
/
Accepted: 24 April 2022
/
Published: 27 April 2022
(This article belongs to the Special Issue Frontier Research in Food Microbiology)
Abstract
:Pistachio (Pistacia vera L.) nuts contain nutrients and phytochemicals which have been linked to several positive outcomes. The aim of this research was to examine the antimicrobial effect of natural raw and roasted unsalted polyphenols-rich pistachio extracts (NRRE and RURE) and hexane oil fractions. American Type Culture Collection (ATCC), food and clinical isolates of Gram-positive bacteria (Listeria monocytogenes and Staphylococcus aureus), Gram-negative bacteria (Pseudomonas aeruginosa, Escherichia coli and Enterococcus faecium) and yeasts (Candida albicans) were used. In addition, the influence of the extraction method was evaluated. Generally, NRRE extracts were richer in polyphenolic compounds compared with RURE extracts. NRRE extracted with n-hexane was the most effective on Listeria monocytogenes food isolates strains (MIC values between 0.25 and 2.0 mg mL−1). All extracts, except for RURE extracted with n-hexane, were active against Listeria monocytogenes ATCC 13932. Both hexane oil fractions were active against Listeria monocytogenes ATCC 13932 and Enterococcus faecium DSZM 17050. The oil obtained from natural pistachio was active against three food isolates of Listeria monocytogenes. In conclusion, the present study indicates an inhibitory effect of pistachio polyphenols against Listeria monocytogenes, one of the most serious pathogens causing foodborne disease.
1. Introduction
The increased resistance to antimicrobials has brought a more global effort focused on natural drugs, used in combination with existing antibiotics or alone. Plant extracts are a complex mixture with a range of beneficial effects on human health, including antimicrobial potential. With reference to their chemical structure and properties, plant antimicrobial compounds can be classified into the following groups: essential oils, phenolics, alkaloids, saponins, and peptides [1]. Pistachio (Pistacia vera L.) nuts are known to contain nutrients and phytochemicals with beneficial health effects: they are a good protein, fiber, monounsaturated fatty acid, minerals and vitamin source, in addition to carotenoids, flavonoids phenolic acids and anthocyanins [2].
Previous studies have reported the antiviral [3] and antibacterial [4,5] effects of pistachio extract, showing that these activies are due to the interactions between bioactive components.
We have previously shown that pistachio polyphenols have bactericidal effect against Listeria monocytogenes, Staphylococcus aureus and MRSA (methicillin-resistant Staphylococcus aureus) strains [4,5]. L. monocytogenes is a pathogen found in moist environments which can even grow at 4 °C, temperature that would inhibit the growth or kill most pathogenic species. Listeriosis, particularly dangerous during pregnancy, can cause sepsis, meningitis, encephalitis, intrauterine infections and spontaneous abortions. S. aureus and MRSA are cause of a range of infections (respiratory, skin and bone joint), bacteremia, endocarditis, and toxic shock syndrome [6]. Furthermore, the increased rate of resistance amongst these strains makes current treatment particularly challenging, especially in immunocompromised patients.
Several authors investigated the influence of the processes, such as roasting, on the phenolic compound [2,7,8] content. Extracts obtained from pistachio using different methods, may have a different phenolic profile and, given that polyphenol activity is closely related to its chemical structure, a different biological activity.
The objective of this work was to elucidate the influence of an innovative extraction method on the qualitative and quantitative polyphenolic profile and consequently on the bioactivity of the obtained extracts. In particular, the antimicrobial activity of these polyphenols’ rich extracts against a number of Gram-positive and Gram-negative bacteria and the yeast Candida albicans was assessed.
2. Materials and Methods
2.1. Pistachios
Californian natural shelled (NPs, Pistacchi Sgusciati California Pissgsu01/BSV1, L673-16221262) and roasted (RPs, Pistacchi Sgusciati Tostati California Pissgstu01/BSV1) pistachio kernels were kindly supplied by the American Pistachio Growers (Fresno, CA, USA).
2.2. Extraction Methods
Pistachio polyphenolic extracts were prepared following two different extraction methods. In the first method, NPs or RPs (10 g) were extracted as previously reported [7] with minor modifications. Firstly, they were homogenized with a mortar until they became powder and then extracted with 100 mL of n-hexane five times under regular agitation for 2 h to separate the lipid fraction. After filtration, the residues were combined with 100 mL of methanol/HCl 0.1% (v/v), and then extracted and centrifuged. The pellets were extracted other four times. All methanol fractions were mixed, dried for 20 min with Na2SO4, and evaporated under vacuum (Extraction method 1). The organic fractions obtained with n-hexane were also evaporated under vacuum and dried with Na2SO4 in order to obtain the oil fraction.
In the second method (Extraction method 2), NPs or RPs (10 g) were first homogenized with a mortar until they became powder and then exhaustively extracted with 100 mL of methanol/HCl 0.1% (v/v). This latter operation has been repeated until the solvent became colorless. The obtained factions were combined and evaporated under vacuum until they reached the final volume of 10 mL. The methanol extracts were passed through a Solid phase extraction column (SPE, Supelclean™ LC-18 SPE cartridge) to obtain a flavonoid enriched fraction.
2.3. RP-HPLC-DAD Identification and Quantification of Phenolic Compounds
The compounds in the extracts and in the hexane oil fractions from NPs and RPs were analyzed by Reverse Phase-High Performance Liquid Chromatography coupled with Diode Array Detection (RP-DAD-HPLC). The separation, identification and quantification were performed according to the method reported by Mandalari et al. [7], with few modifications. Briefly, the analyses have been performed by means of a Shimazu system, having a LC-10AD pump system, a vacuum degasser, a quaternary solvent mixing, a SPD-M10A diode array detector, a Rheodyne 7725i injector. An Ascentis Express C18 column (15.0 mm × 4.6 mm, 2.7 mm; Ascentis Express, Supelco, Bellefonte, PA, USA) equipped with a 20 mm × 4.0 mm guard column was used to separate each compound. The column was positioned in an oven set at 30 °C. The injection loop was 20 µL, and the flowrate was 1.0 mL/min. The mobile phase consists of water/formic acid (99.9:0.1, v/v; solvent A) and acetonitrile/formic acid (99.9:0.1, v/v; solvent B). The linear gradient profile was as follows: 0 min 0% B, 60 min 100% B, 70 min 100% B and 80 min 0% B. The UV spectra were recorded the wavelength region of 200–600 nm, and simultaneous detection by diode array was performed at 278 and 320 and 520 nm. Peak identity was verified by comparing their absorption spectra and retention times with those of pure (≥99%) commercial standards.
2.4. Chemical Composition of Pistachio Oils
Fatty acid methyl esters (FAMEs) were analyzed by gas chromatography (GC) following extraction and hydrolysis of triacylglycerols with potassium hydroxide in methanol. Briefly, about 0.1 g of oil samples were mixed with 2 mL of n-heptane. Then, 0.2 mL of KOH in MEOH solution were added and mixed for 30 s at room temperature for 30 s. After a decantation, the phase containing the diluted FAMEs in n-heptane was immediately analyzed by GC. The GC instrument (Dani Master GC1000) was equipped with a split/splitless injector, a flame ionization detector (FID) (Dani Instrument, Milan, Italy) and a ZB-WAX capillary column Phenomenex, 30 m × 0.25 mm ID, 0.25 μm film thickness, (Phenomenex, Torrance, CA, USA). The following chromatographic conditions were employed: injector and detector temperatures 220 °C and 240 °C, respectively; column oven temperature from 130 °C to 200 °C (20 min hold) at 3 °C/min; helium at a linear velocity of 30 cm/s (constant). The injection volume was 1 μL, and the split ratio was 1:75. Clarity Chromatography Software v4.0.2 was employed in the data acquisition and handling. All oil samples were analyzed in triplicate. The direct comparison with the retention times of reference compounds present in the standard mixture (Sigma-Aldrich, St. Louis, MO, USA) was used to identify FAMEs of nutritional interest. The individual FAME percentage was calculated in relation to total area of the chromatogram.
2.5. Antimicrobial Assays
The antimicrobial potential of the pistachio polyphenols-rich extracts and the hexane oil fractions was assessed against bacterial and fungal pathogens.
2.5.1. Microbial Strains and Culture Conditions
The Gram-positive bacteria used were: S. aureus ATCC 6538, L. monocytogenes ATCC 13932 and 8 food-isolated strains of L. monocytogenes belonging to serotypes 1/2a (6 strains) and 1/2b (2 strains).
The Gram-negative bacteria used were: Escherichia coli ATCC 10536, Pseudomonas aeruginosa ATCC 9027, Enterococcus faecium DSZM 17050.
The yeasts used were: C. albicans ATCC 10231, a clinical isolate of C. albicans (C. albicans strain 6).
All bacteria were grown in Mueller-Hinton Broth (MHB, Oxoid, CM0405, Sigma, Milan, Italy) at 37 °C (18–20 h) in preparation for the susceptibility studies. The yeasts were grown in Roswell Park Memorial Institute (RPMI 1640, Sigma, Milan, Italy) at 30 °C for 24 h.
2.5.2. Susceptibility Studies
The broth microdilution method according to Clinical and Laboratory Standards Institute (CLSI) for bacteria [9] and yeasts [10] was employed to determine the minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC). Briefly, serial dilutions were carried out in the growth media at concentrations between 2.000 and 0.0019 mg/mL both for pistachio polyphenols-rich extracts and hexane pistachio oil fractions. A positive control was included in every assay. The MIC value was indicated as the lowest concentration able to inhibit bacterial or fungal growth after 20 h. The MBC value was determined by transferring 20 μL of each clear sample to an agar plate, which was incubated at 30 °C for 24 h. The MBC was indicated as the lowest extract concentration able to kill 99.9% of the inoculum after 24 h.
3. Results
3.1. Polyphenolic Composition of the Pistachio Extracts and Pistachio Oil
Thirteen compounds, belonging to flavonoids (flavanols, flavanones and anthocyanins) and phenolic acids, were identified in the pistachio extracts (Table 1).
The major compounds in all the pistachio extracts were gallic acid, catechin, cyanidin-3-O-galactoside and isoquercetin. Protocatechuic acid, caffeic acid, epicatechin and quercetin-3-O-rutinoside were found in significant amounts, while the other compounds were only present in very limited amounts or in trace. Amongst the two methods of extraction, method 2 resulted in an increase in the total amount of compounds compared with method one (~1.3-fold). Moreover, the natural raw polyphenols-rich extract (NRRE) extracts were generally richer in polyphenolic compounds compared with roasted unsalted polyphenols-rich extract (RURE) extracts. However, gallic acid and protocatechuic acid were higher in all the extracts obtained with roasted pistachios. Catechin, epicatechin and isoquercetin were present at more than double concentrations in NP compared with RP.
Only two compounds (protocatechuic acid and gallic acid) were present in significant amounts in the oil fractions, whereas traces of catechin and isoquercetin were detected.
3.2. Chemical Composition of Pistachio Oils
Table 2 reports the fatty acid composition of the pistachio oils. In line with previous results [11] palmitic acid (C16:0), with reference to saturated fatty acid, and oleic acid (C18:1) and linoleic acid (C18:2), with reference to unsaturated fatty acids, were the major compounds. Oleic acid was the main fatty acid, being 56.88 and 57.75% in raw and roasted pistachio oils, respectively, followed by linoleic acid (29.54% and 27.95%, respectively) and palmitic acid (10.23% and 10.93%, respectively).
3.3. Antimicrobial Potential of the Pistachio Extracts
Table 3 reports the MIC values of the pistachio polyphenols-rich extracts against the tested strains. As previously reported [4], the pistachio extracts were not active against the Gram-negative bacteria and the yeast C. albicans.
Amongst the food isolates strains of L. monocytogenes, NRRE extracted with n-hexane (extraction method 1) was the most effective (MIC values between 0.25 and 2.0 mg mL−1) whereas all extracts, with the exception of RURE extracted with n-hexane (extraction method 1), were active against L monocytogenes ATCC 13932. The effect was always bacteriostatic rather than bactericidal. No activity was observed, using the extracts at a concentration between 2.000 and 0.0019 mg mL, against the other strains and yeasts tested.
3.4. Antimicrobial Potential of the Hexane Pistachio Oil Fractions
The MIC values of the hexane pistachio oil fractions obtained from both NPs and RPs against the tested strains are reported in Table 4. Both oils were active against L. monocytogenes ATCC 13932 and E. faecium DSZM 17050. Three food isolates of L. monocytogenes were sensitive to the hexane oil obtained from NP. No activity was observed, using the extracts in a concentration range between 2.000 and 0.0019 mg/mL, against the other bacterial and yeast strains tested. As for the polyphenols-rich extracts, the activity was always bacteriostatic rather than bactericidal. These data confirmed that the oil obtained from natural pistachios was more effective, following the same trend detected with the extracts.
4. Discussion
This research highlighted the inhibitory effect of polyphenol-rich fractions of pistachio and pistachio oil against E. faecium DSZM 17050, L. monocytogenes ATCC 13932 and food isolates strains of L. monocytogenes.
In particular, the polyphenol-rich fractions of NRRE extracted with n-hexane (extraction method 1) were active against all the food isolate strains of L. monocytogenes. All NRRE extracts and the RURE extracts obtained with the extraction method 2 were active against L. monocytogenes ATCC 13932. These results are in line with previous studies, which reported on the antimicrobial activity of polyphenol pistachio extracts against Gram-positive bacteria. These strains are more susceptible than Gram-negative ones [4,12]. Compared with our previous report [4], the polyphenol-rich extracts were not active against E. faecium and S. aureus. This could be due to different strains being used in the present study, as well as a different phytochemical composition (both qualitatively and quantitatively) compared with the previous report.
The hexane oil fractions from both NPs and RPs were reported to be active against L. monocytogenes ATCC 13932 and E. faecium DSZM 17050. The NP oil fractions were active against three food isolate strains.
Although both NP and RP polyphenolic extracts and oil fractions were effective against L. monocytogenes ATCC 13932, NP was more active than RP. This effect could be justified not only by the higher polyphenol amount of NP extracts compared with RP extracts, but also by their qualitative composition. These results are in line with previous studies which report this trend [4,5].
It is known that the drying process highly influence the phenolic and polyphenolic content, causing the loss of high amount of some compounds. As previously reported, the stability of the various phenolic and polyphenolic compounds is different and the roasting process can be responsible of their lower content in RPs [2,7,13]. We have previously reported higher amounts of phenolic acids and flavonoids in NPs compared with RPs, except for hydroxybenzoic acids and luteolin, whereas daidzein and chlorogenic acid were detected in RPs only [7]. Ballistreri and coauthors reported that the drying process negatively affected the content of the following compounds: anthocyanins, with a loss of about 60%, naringenin with a loss of 50%, eriodyctiol daidzein, luteolin and genistein, with a loss of about 36%, and quercetin recorded a loss of about 22%, whereas no loss was detected after the drying process for genistin, which was the most stable flavonoid [13].
Pistachios contain several antioxidant compounds, including vitamin C (5.6 mg/100 g as total ascorbic acid), alpha and beta carotene (10 and 305 µg/100 g, respectively), lutein + zeaxanthin (2900 µg/100 g), alpha and gamma tocopherol (2.9 and 20.4 mg/100 g, respectively) (https://fdc.nal.usda.gov/fdc-app.html#/food-details/170184/nutrients, accessed on 5 March 2022). The synergistic combination of these antioxidant compounds, as well as the identified polyphenols (Table 1) in the pistachio oils may be responsible for the observed antimicrobial action against the tested Gram-positive bacteria.
Polyphenol compounds promote several benefits including the antimicrobial one [14,15]. The antimicrobial action of phenolic compounds can be due to different mechanisms, including the interaction with bacterial cell wall protein and fimbria which damages the cytoplasmic membrane, the inhibition of the energy metabolism and the inhibition of the synthesis of nucleic acids [14,16,17].
The main identified polyphenols in the pistachio extracts were hydroxybenzoic acids (as gallic), flavan-3-ols (as (+)-catechin), anthocyanins (as cyanidin 3-O-galactoside) and flavonols (as isoquercetin). The bactericidal action of gallic acid is due to the increase in fluidity of both the outer and the inner bacterial membrane, disturbing the membrane potential [17,18]. The catechin antimicrobial activity is promoted by its hydrogen peroxide generation [19], which damages the bacterial cell membrane [20]. Cyanidin-3-O-galactoside acts also on the cytoplasmic membrane by adding phenolic groups to the lipid bilayer of cell membranes, causing an alteration of their structure, function and permeability [21]. The antimicrobial mechanism of isoquercetin, which has been observed on E. coli, is due to lipid oxidation causing membrane damage [22]. However, it has been shown that mixes of polyphenols, such as these extracts, have a higher antimicrobial activity than single compounds [23].
In this study, the inhibitory effect of pistachio polyphenols against L. monocytogenes has been reported. This microorganism is responsible for causing the listeriosis. This infection is one of the most serious and important foodborne diseases, given the severity of its sequelae and the high fatality rate (20% and 30%) [24]. In humans, the 99% of Listeria infections are foodborne [25,26].
These results, in line with previous studies, show that pistachio phytochemicals could be used in several biotechnological application. Alone, or in association with known antimicrobial agents, they could be a starting point for the development of novel formulations or topical agents. In combination with other preservatives, its phytochemicals could be used in the food industry to promote microbial stability and safety in foods [27].
5. Conclusions
In conclusion, by evaluating the influence of an innovative extraction method on the polyphenolic profile of the obtained extracts and, therefore, on their antimicrobial activity, our study reports an inhibitory effect of pistachio polyphenols against one of the most common pathogens causing foodborne disease, Listeria monocytogenes. Additional studies are essential to determine potential synergetic effects with other known antimicrobials or preservative agents for its use in different biotechnological applications.
Author Contributions
Conceptualization, G.M., D.B. and M.T.S.; methodology, T.G., M.D. and R.R.; writing—original draft preparation, T.G.; writing—review and editing, G.M., D.B. and A.C.; funding acquisition, G.M. and D.B. All authors have read and agreed to the published version of the manuscript.
Funding
This research was funded by the University of Messina.
Institutional Review Board Statement
Not applicable.
Informed Consent Statement
Not applicable.
Data Availability Statement
The data presented in this study are available on request from the corresponding author.
Acknowledgments
We thank the American Pistachio Growers for providing the pistachios.
Conflicts of Interest
The authors declare no conflict of interest.
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Table 1.
Polyphenolic composition of the pistachio extracts. Results are expressed as mg/100 g and represent the mean of triplicate determinations ± SD.
Table 1.
Polyphenolic composition of the pistachio extracts. Results are expressed as mg/100 g and represent the mean of triplicate determinations ± SD.
| Compound | Extraction Method 1 | Extraction Method 2 | Oil Fraction | |||
|---|---|---|---|---|---|---|
| NRRE | RURE | NRRE | RURE | NRRE | RURE | |
| Gallic acid | 1.05 ± 0.12 | 1.83 ± 0.15 | 1.47 ± 0.13 | 2.28 ± 0.14 | 0.25 ± 0.02 | 0.22 ± 0.01 |
| Protocatechuic acid | 0.71 ± 0.08 | 0.80 ± 0.10 | 0.80 ± 0.05 | 1.27 ± 0.11 | 0.15 ± 0.01 | 0.20 ± 0.01 |
| Chlorogenic acid | Trace | 0.11 ± 0.01 | Trace | 0.24 ± 0.04 | - | - |
| Catechin | 2.01 ± 0.15 | 0.86 ± 0.07 | 2.74 ± 0.11 | 1.34 ± 0.10 | Trace | Trace |
| Caffeic acid | 0.91 ± 0.10 | Trace | 0.8 ± 0.07 | Trace | - | - |
| Epicatechin | 0.20 ± 0.03 | 0.10 ± 0.01 | 0.35 ± 0.02 | 0.09 ± 0.01 | ||
| Cyanidin-3-O-galactoside | 0.92 ± 0.11 | 0.85 ± 0.12 | 1.1 ± 0.14 | 1.0 ± 0.11 | - | - |
| Eriodictyol-7-O-glucoside | Trace | Trace | Trace | Trace | ||
| Quercetin-3-O-rutinoside | 0.50 ± 0.04 | 0.60 ± 0.07 | 0.86 ± 0.03 | 0.74 ± 0.08 | - | - |
| Isoquercetin | 1.36 ± 0.12 | 0.80 ± 0.07 | 1.85 ± 0.10 | 0.71 ± 0.06 | Trace | Trace |
| Daidzein | Trace | Trace | Trace | Trace | - | - |
| Eriodictyol | Trace | Trace | Trace | Trace | ||
| Luteolin | 0.14 ± 0.02 | 0.24 ± 0.03 | 0.29 ± 0.01 | 0.41 ± 0.08 | - | - |
NRRE, natural raw polyphenols-rich extract; RURE, roasted unsalted polyphenols-rich extract; -, not detected.
Table 2.
Fatty acid composition (expressed as %) of oils extracted from pistachio samples.
| Fatty Acids | Raw Pistachio Oil | Roasted Pistachio Oil |
|---|---|---|
| Myristic acid (C14:0) | 0.01 | 0.01 |
| Palmitic acid (C16:0) | 10.23 | 10.93 |
| Palmitoleic acid (C16:1) | 1.01 | 1.1 |
| Heptadecanoic acid (C17:0) | 0.04 | 0.05 |
| Heptadecenoic acid (C17:1) | 0.09 | 0.09 |
| Stearic acid (C18:0) | 1.27 | 1.26 |
| Oleic acid (C18:1) | 56.88 | 57.75 |
| Linoleic acid (C18:1) | 29.54 | 27.95 |
| γ-linolenic acid (C18:3) | 0.02 | 0.01 |
| α-linolenic acid (C18:3) | 0.43 | 0.4 |
| Arachidic acid (C20:0) | 0.12 | 0.12 |
| Eicosenoic acid (C20:1) | 0.32 | 0.3 |
| Eicosadienoic acid (C20:2) | 0.02 | 0.01 |
| Behenic acid (C22:0) | 0.01 | 0.01 |
| Lignoceric acid (C24:0) | 0.01 | 0.01 |
| SFA | 11.69 | 12.39 |
| MUFA | 58.3 | 59.24 |
| PUFA | 30.01 | 28.37 |
Table 3.
MICs of Pistachio Extracts (expressed as mg mL−1) against tested strains. NRRE: natural raw polyphenols-rich extract; RURE: roasted unsalted polyphenols-rich extract.
Table 3.
MICs of Pistachio Extracts (expressed as mg mL−1) against tested strains. NRRE: natural raw polyphenols-rich extract; RURE: roasted unsalted polyphenols-rich extract.
| Strain | Extraction Method 1 | Extraction Method 2 | ||
|---|---|---|---|---|
| NRRE | RURE | NRRE | RURE | |
| E. faecium DSZM 17050 | >2.000 | >2.000 | >2.000 | >2.000 |
| S. aureus ATCC 6538 | >2.000 | >2.000 | >2.000 | >2.000 |
| P. aeruginosa ATCC 9027 | >2.000 | >2.000 | >2.000 | >2.000 |
| E. coli ATCC 10536 | >2.000 | >2.000 | >2.000 | >2.000 |
| C. albicans ATCC 10231 | >2.000 | >2.000 | >2.000 | >2.000 |
| C. albicans strain 16 | >2.000 | >2.000 | >2.000 | >2.000 |
| L. monocytogenes ATCC 13932 | 1.000 | >2.000 | 1.000–2.000 | 2.000 |
| L. monocytogenes (food isolate) | 0.250–1.000 | >2.000 | >2.000 | >2.000 |
| L. monocytogenes (food isolate) | 0.500–1.000 | >2.000 | >2.000 | >2.000 |
| L. monocytogenes (food isolate) | 1.000–2.000 | >2.000 | >2.000 | >2.000 |
| L. monocytogenes (food isolate) | 1.000–2.000 | >2.000 | >2.000 | >2.000 |
| L. monocytogenes (food isolate) | 0.500–1.000 | >2.000 | >2.000 | >2.000 |
| L. monocytogenes (food isolate) | 0.500–1.000 | >2.000 | >2.000 | >2.000 |
| L. monocytogenes (food isolate) | 0.500–1.000 | >2.000 | >2.000 | >2.000 |
| L. monocytogenes (food isolate) | 0.500–1.000 | >2.000 | >2.000 | >2.000 |
Table 4.
MICs of Hexane Pistachio Oil Fractions (expressed as % v/v) against Gram-positive bacteria, Gram-negative bacteria and yeasts. NP: natural raw pistachios; RP: roasted unsalted pistachios.
Table 4.
MICs of Hexane Pistachio Oil Fractions (expressed as % v/v) against Gram-positive bacteria, Gram-negative bacteria and yeasts. NP: natural raw pistachios; RP: roasted unsalted pistachios.
| Strain | Hexane Oil Fraction from NPs | Hexane Oil Fraction from RPs |
|---|---|---|
| E. faecium DSZM 17050 | 0.250 | 0.500 |
| St. aureus ATCC 6538 | >2.000 | >2.000 |
| P. aeruginosa ATCC 9027 | >2.000 | >2.000 |
| E. coli ATCC 10536 | >2.000 | >2.000 |
| C. albicans ATCC 10231 | >2.000 | >2.000 |
| C.albicans strain 16 | >2.000 | >2.000 |
| L. monocytogenes ATCC 13932 | 0.031–0.125 | 0.125–0.250 |
| L. monocytogenes (food isolate) | 0.250–1.000 | >2.000 |
| L. monocytogenes (food isolate) | >2.000 | >2.000 |
| L. monocytogenes (food isolate) | >2.000 | >2.000 |
| L. monocytogenes (food isolate) | >2.000 | >2.000 |
| L. monocytogenes (food isolate) | 0.250 | >2.000 |
| L. monocytogenes (food isolate) | 0.500 | >2.000 |
| L. monocytogenes (food isolate) | >2.000 | >2.000 |
| L. monocytogenes (food isolate) | >2.000 | >2.000 |
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Gervasi, T.; D’Arrigo, M.; Rando, R.; Sciortino, M.T.; Carughi, A.; Barreca, D.; Mandalari, G. The Antimicrobial Potential of Hexane Oils and Polyphenols-Rich Extracts from Pistacia vera L. Appl. Sci. 2022, 12, 4389. https://doi.org/10.3390/app12094389
AMA Style
Gervasi T, D’Arrigo M, Rando R, Sciortino MT, Carughi A, Barreca D, Mandalari G. The Antimicrobial Potential of Hexane Oils and Polyphenols-Rich Extracts from Pistacia vera L. Applied Sciences. 2022; 12(9):4389. https://doi.org/10.3390/app12094389
Chicago/Turabian StyleGervasi, Teresa, Manuela D’Arrigo, Rossana Rando, Maria Teresa Sciortino, Arianna Carughi, Davide Barreca, and Giuseppina Mandalari. 2022. "The Antimicrobial Potential of Hexane Oils and Polyphenols-Rich Extracts from Pistacia vera L." Applied Sciences 12, no. 9: 4389. https://doi.org/10.3390/app12094389
APA StyleGervasi, T., D’Arrigo, M., Rando, R., Sciortino, M. T., Carughi, A., Barreca, D., & Mandalari, G. (2022). The Antimicrobial Potential of Hexane Oils and Polyphenols-Rich Extracts from Pistacia vera L. Applied Sciences, 12(9), 4389. https://doi.org/10.3390/app12094389
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