Synthesis, Antimicrobial Evaluation, and Structure–Activity

Article pubs.acs.org/JAFC

Synthesis, Antimicrobial Evaluation, and Structure−Activity Relationship of α‑Pinene Derivatives Preeti Dhar,*,† PuiYee Chan,†,△ Daniel T. Cohen,†,○ Fadi Khawam,† Sarah Gibbons,† Teresa Snyder-Leiby,‡,▽ Ellen Dickstein,§ Prashant Kumar Rai,#,□ and Geeta Watal# †

Department of Chemistry and ‡Department of Biology, State University of New York, 1 Hawk Drive, New Paltz 12561, United States § Department of Plant Pathology, University of Florida, Gainesville, Florida 32611, United States # Drug Discovery and Development Division, Medicinal Research Laboratory, Department of Chemistry, University of Allahabad, Allahabad 211002, India S Supporting Information *

ABSTRACT: Several (+)- and (−)-α-pinene derivatives were synthesized and evaluated for their antimicrobial activity toward Gram-positive bacteria Micrococcus luteus and Staphylococcus aureus, Gram-negative bacterium Escherichia coli, and the unicellular fungus Candida albicans using bioautographic assays. (+)-α-Pinene 1a showed modest activity against the test organisms, whereas (−)-α-pinene 1b showed no activity at the tested concentration. Of all the α-pinene derivatives evaluated, the β-lactam derivatives (10a and 10b) were the most antimicrobial. The increase in the antimicrobial activity of 10a compared to 1a ranged from nearly 3.5-fold (C. albicans) to 43-fold (S. aureus). The mean ± standard deviation for the zone of inhibition (mm) for 10a (C. albicans) was 31.9 ± 4.3 and that for S. aureus was 51.1 ± 2.9. Although (−)-α-pinene 1b was not active toward the test microorganisms, the corresponding β-lactam 10b, amino ester 13b, and amino alcohol 14b showed antimicrobial activity toward the test microorganisms. The increase in the antimicrobial activity of 10b compared to 1b ranged from 32-fold (S. aureus) to 73fold (M. luteus). The mean ± standard deviation for the zone of inhibition (mm) for 10b (S. aureus) was 32.0 ± 0.60 and that for M. luteus was 73.2 ± 0.30. KEYWORDS: monoterpenes, α-pinene, antimicrobial, bioautographic assay

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INTRODUCTION Essential oils (EOs) are used in the cosmetics industry,1 food industry,2−6 and aromatherapy,7 and as antimicrobials.3−6,8−11 Because the composition of EOs largely depends on factors such as season of harvest, plant part used for extraction, location, and growth conditions of the plant,12 the physical properties and hence the biological efficacy of EOs vary. Accordingly, research about the properties of EOs has focused on the active constituents of EOs instead of focusing on the EOs themselves. The antimicrobial property of EOs is attributed to the monoterpenes and monoterpenoids present in these oils.3−6,8−11 The site of action of terpenes and their derivatives is the cell membrane.13−16 Due to their lipophilicity, terpenes and their derivatives insert in the membrane, causing membrane expansion and increased membrane fluidity/ permeability that subsequently affects the transport processes.14 These actions contribute to the antimicrobial activity of terpenes. Studies on the effects of selected EO components on outer membrane permeability in Gram-negative bacteria have shown that the monoterpene uptake is partly determined by the permeability of the outer envelope of the microorganism under investigation.17 Recent investigation into the mechanism of action of three monoterpenoids (linalyl acetate (2), (+)-menthol (3), and thymol (4)) (Chart 1) has suggested that antimicrobial activity may be significantly influenced by the © 2014 American Chemical Society

Chart 1. Various Monoterpene Natural Products

characteristics of the monoterpenoid as well as the microbial membrane composition.18 Another study that used molecular dynamics simulations and isothermal titration calorimetry to study the interaction of four terpenes (limonene (5), perillyl alcohol (6), perilladehyde (7), and deprotonated perillic acid (8)) with model lipid bilayers concluded that terpenes perturb Received: Revised: Accepted: Published: 3548

August 12, 2013 March 23, 2014 April 1, 2014 April 9, 2014 dx.doi.org/10.1021/jf403586t | J. Agric. Food Chem. 2014, 62, 3548−3552

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negative control used was dichloromethane. The log phase microbes were sprayed on the TLC plates (∼7−10 mL) ensuring that the plates were evenly wet, followed by a spray of (∼7−10 mL) half-strength LB agar (maintained in a water bath at ∼55 °C). Each plate was placed on cork supports in a humid chamber (made by placing wet paper towels in plastic containers) in an incubator at 37 °C (25 °C for M. luteus) for 12−18 h to allow the bacteria to grow.23 A freshly prepared aqueous solution (5 mg/mL) of (3-(4,5-dimethylthiazol-2yl)-2,5-diphenyltetrazolium bromide) (MTT) was sprayed (1−2 mL) on the plate covered with bacteria, and the plate was put back in a humid chamber at the appropriate temperature for 4−5 h or until the purple color appeared. Actively growing microbes convert MTT (yellow) to formazan (purple). Zones of inhibition appear white against a purple background. Microbial Growth Inhibition Measurements. The inhibition diameter was taken as an average of four measurements per TLC plate. The diameter of each inhibition zone was further determined in four different directions (0°, 45°, 90°, and 135°) as described in the literature.27,28 The bioassay for each compound was done in triplicate. Statistical Analysis. Data were statistically evaluated using oneway ANOVA, followed by a post hoc Newman−Keuls multiplecomparison test. The values were expressed as the mean ± SD and considered significant at p ≤ 0.05. FAME Analysis. Bacterial and yeast cultures were grown, and fatty acids were extracted using the methods described by Sasser.29 Extracts were analyzed using an Agilent 6890N gas chromatograph with an Agilent Ultra 2 column. Sherlock Microbial ID system version 4.5 was used to analyze the data.

the lipid bilayer significantly and that insertion of each terpene in the bilayer is driven by a different balance of entropy and enthalpy, determined by the functional groups present on the terpene.19 One of the common antimicrobial monoterpenes found in several EOs is α-pinene. The strained four-membered ring of αpinene is very reactive and makes it prone to opening and skeletal rearrangements.20,21 In addition to research about the antimicrobial activity of monoterpenes/monoterpenoids, there has been some recent work by Wilderman and colleagues that has shown that (+)-α-pinene (1a) is a potent P450 2B inhibitor.22 With microbes becoming increasingly resistant to known antibiotics, it is imperative to develop drugs that are active against the next generation of microbes. Both enantiomers of α-pinene are readily available, and hence it is an excellent starting material for synthesizing a variety of functionally and skeletally altered α-pinene derivatives. In this study, we investigate the structure−antimicrobial activity relationship for both (+)- and (−)-α-pinene and the corresponding derivatives. Antimicrobial activity was assessed on four test microorganisms (Staphylococcus aureus, Micrococcus luteus, Escherichia coli, and Candida albicans) using a bioautographic assay.23,24 This bioassay gave good reproducibility. Lastly, membrane fatty acid composition of the test microorganisms was determined by fatty acid methyl ester (FAME) analysis.

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RESULTS AND DISCUSSION Investigation of this approach began with the synthesis of αpinene derivatives using modified literature procedures.20,25 Treatment of (+)-α-pinene (1a) with chlorosulfonylisocyanate furnished the β-lactam N-sulfonyl chloride 9a in 64% yield as a single stereoisomer (Scheme 1). The N−S bond was

MATERIALS AND METHODS

Chemicals. Silica gel 60 Å 70−230 or 230−400 mesh ASTM from Sigma-Aldrich was used for gravity column chromatography. TLC plates containing silica on aluminum/glass with a fluorescent indicator (254 nm), starting materials (+)-α-pinene 98% and (−)-α-pinene 98%, lithium aluminum hydride (LAH) powder, and all ACS grade solvents were purchased from Sigma-Aldrich and used as such. Chlorosulfonylisocyanate (CSI) 98+% was purchased from Acros Organics. IR spectra were recorded on a Perkin-Elmer FTIR 1600 series in CH2Cl2 solution, and 1H and 13C NMR spectra were recorded on a JEOL Eclipse 300 MHz NMR spectrometer in CDCl3. Synthesized compounds were >95% pure as verified by 1H NMR and were purified by chromatography, recrystallization, or trituration. Modified experimental procedures25 for 9a, 10a, 11a, 12a, 13a, and 14a are provided in the Supporting Information along with the 1H NMR and 13C NMR spectra of the synthesized compounds. Microorganisms and Culture Media. Three of the microorganisms used in this study (M. luteus, E. coli, and S. aureus) were clinical isolates and were received as a gift from Katherine Greiner, Associate Professor of the Medical Technology Program at Marist College; C. albicans (ATCC 90294) was purchased from Sigma. The bacterial cultures were subcultured in Luria−Bertani (LB) medium, and the yeast was subcultured in Sabaraud (SAB) at 37 °C for 12−14 h (M. luteus was grown at 25 °C for 60−72 h) at 135 rpm. The optical density of the culture was measured with a UV−vis Beckman 650 spectrophotometer at 600 nm (OD 600 = 1 corresponds to approximately 109 cells/mL).26 Culture media were autoclaved at 120 °C for 20 min. Bioautographic Assay. The antimicrobial activity of the nine compounds synthesized was evaluated against four test microorganisms (Gram-positive bacteria S. aureus and M. luteus, Gramnegative bacterium E. coli, and unicellular fungus C. albicans) by bioautographic assay using a modified published procedure.23,27 Each TLC glass plate was divided into 20 equal squares. Stock solution of each of the compound was made (1 mg/10 μL of dichloromethane), and 25 μL of this solution was spotted (2.5 mg of the compound), making sure that all of the spots were close to 3 mm in diameter. The positive control used was Sigma A5955 (antibiotic−antimycotic solution comprising penicillin G (100,000 units/mL), streptomycin sulfate (10 mg/mL), and amphotericin B (25 μg/mL)), and the

Scheme 1. Synthetic Modifications of α-Pinene

subsequently cleaved using sodium sulfite to give H-β-lactam 10a in an 83% yield. Alternatively, rearrangement of the αpinene skeleton by refluxing lactam 9a in hexanes provided the γ-lactam N-sulfonyl chloride 11a in modest yield (40%). The sulfonyl group of γ-lactam 11a was cleaved as above to yield Hγ-lactam 12a in 72% yield. Finally, opening of the β-lactam with ethanol under acidic conditions provided ethyl ester 13a in 60% yield. Ester 13a was reduced with lithium aluminum hydride to provide amino alcohol 14a in 85% yield. 3549

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Additionally, the corresponding enantiomers of the β-lactam 10a, amino ester 13a, and amino alcohol 14a were synthesized using the same route except beginning with (−)-α-pinene (1b). Most common antimicrobial agents in use are those containing the β-lactam ring.30 Such antibiotics are known to work on bacteria via two mechanisms that target the cell wall synthesis.31 A Cambridge database-based study correlates biological activity in β-lactams with Woodward and Cohen structural parameters.32 It should be noted that well-known antibiotic β-lactams have a tertiary nitrogen in the β-lactam ring, whereas the α-pinene-based β-lactams 10a and 10b have a secondary nitrogen. Because lactams 10a and 10b are derived from α-pinene, we assume that they will also interact in the membrane like other pinene derivatives, although the antimicrobial activity of these compounds via inhibition of cell wall synthesis cannot be ruled out. The antimicrobial results are shown in Figures 1 and 2. β-Lactam 10b is more

increase in antimicrobial activity toward S. aureus, a 73-fold increase toward M. luteus, a 35-fold increase toward E. coli, and a 60-fold increase toward C. albicans. We next examined the differences in antimicrobial potential between β-lactam (10a) and γ-lactam (12a) derived from (+)-α-pinene (1a) (Figure 1). Overall, β-lactam 10a showed a stronger antimicrobial activity than γ-lactam 12a. Although M. luteus and S. aureus are both Gram-positive bacteria, there is a statistically significant difference in antimicrobial activity of 10a and 12a toward S. aureus. Compound 10a shows more than twice the area of inhibition with S. aureus compared to 12a but similar antimicrobial activity toward M. luteus. Lactam 12a showed the largest zones of inhibition for E. coli (Gramnegative) and M. luteus (Gram-positive). Compound 12a is half as effective toward C. albicans and S. aureus as compared to M. luteus and E. coli. β-Lactam-containing antibiotics, such as penicillin G, are effective against Gram-positive bacteria, but not as effective against Gram-negative bacteria, whereas ampicillin and amoxicillin are effective against both Grampositive and Gram-negative bacteria.33 γ-Lactam 12a is effective against both Gram-positive and Gram-negative bacteria, but its activity is found to be less than that of β-lactam 10a. Lower antimicrobial activity of γ-lactam in comparison to β-lactam can partly be attributed to the ring strain found in the latter. γLactam contains a five-membered ring, which is more stable than the four-membered ring found in a β-lactam. Due to the ring strain present in β-lactam, it is prone to opening by nucleophilic addition.21 Stronger intramolecular hydrogen bonding is known to exist in γ-lactams, which may also contribute to its lower antimicrobial activity.34 The bioassay shows that the two N-sulfonyl chlorides of β-lactam and γlactam (9a and 11a, respectively) have similar antimicrobial activity. Earlier studies have shown that introducing a single alcoholic (or amino functional group) in the α-pinene nucleus increases the antimicrobial activity, compared to the antimicrobial activity of (+)-α-pinene derivatives having other functional groups.27 It is speculated that the presence of the alcoholic or amino functional group makes the compound more water-soluble and thereby helps it transverse the polar cell wall.35−37 This allows the compound to reach the site of action, the microbial membrane, in greater concentration and hence permeate it more efficiently.35−37 Therefore, we chose to synthesize amino ester 13a and amino alcohol 14a to determine if adding both the alcoholic and amino functions to the α-pinene nucleus will make the compound more antimicrobial than when only one of the two functional groups is present. Consequently, we synthesized two pairs of enantiomeric compounds (13a and 13b; 14a and 14b). Overall, amino alcohol 14a was found to be less antimicrobial than the starting material (1a) (Figure 1). Amino alcohol 14b shows antimicrobial activity toward all four microorganisms used in the study (Figure 2) and by comparison is more antimicrobial than the starting material (1b), which under the test conditions did not exhibit any antimicrobial activity. However, the differences in antimicrobial activity of the two amino alcohols 14a and 14b were found to be statistically not significant. Both 14a and 14b were less antimicrobial than the previously evaluated (1R,2R,3R,5S)(−)-iso-pinocampheol or (1R,2R,3R,5S)-(−)-iso-pinocampheylamine.27 Lastly, ester 13b was found to be more antimicrobial than the starting material (1b) (Figure 2). Conversely, ester 13a displayed less antimicrobial activity

Figure 1. Antimicrobial activity of (R)-(+)-α-pinene (1a) and its derivatives: β-lactam 10a, β-lactam N-sulfonyl chloride 9a, γ-lactam 12a, γ-lactam N-sulfonyl chloride 11a, amino ester 13a, and amino alcohol 14a. (∗) P < 0.05 and (∗∗) P < 0.01, compared to 1a at the corresponding time. The antimicrobial potential of 13a and 14a was found to be not significant compared to 1a at the corresponding time.

Figure 2. Antimicrobial activity of (S)-(−)-α-pinene (1b) and its derivatives, β-lactam10b, amino ester13b, and amino alcohol14b. (∗)P < 0.05 and (∗∗) P < 0.01, compared to 1b at the corresponding time.

antimicrobial than 10a toward M. luteus and C. albicans, whereas lactam 10a shows greater antimicrobial activity toward S. aureus. Lastly, N−H lactams 10a and 10b show similar zones of inhibition toward E. coli. It should be noted that both βlactams have greatly enhanced antimicrobial activity toward all four test microorganisms in comparison to the starting materials, (+)- and (−)-α-pinene, respectively. β-Lactam 10a (as compared to its starting material (+)-α-pinene 1a) showed an approximately 43-fold increase in antimicrobial activity toward S. aureus, a 22-fold increase toward M. luteus, a 4.5-fold increase toward E. coli, and a nearly 3.5-fold increase toward C. albicans. Similarly, β-lactam 10b (as compared to its starting material (−)-α-pinene 1b) showed an approximately 32-fold 3550

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Table 1. Major Membrane Fatty Acids of the Four Microorganisms Used in the Studya S. aureus

a

M. luteus

E. coli

C. albicans

FA

%

FA

%

FA

%

FA

%

15:0 ANTEISO 17:0 ANTEISO 15:0 ISO 18:00

43.67 11.81 11.19 10.06

15:0 ANTEISO 17:0 ANTEISO

84.04 4.92

16:00 17:0 cyclo 18:1 w7c 12:0 ALDE 14:0 3OH/16:1 ISO 1

30.34 20.82 16.30 9.18 9.08

18:1 cis 9 (w9) 18:2 cis 9,12/18:0a 16:00 16:1 cis 9 (w7)

39.18 29.57 13.80 12.59

Percentage composition reported as an average of two runs.

derivatives would have to be synthesized and evaluated to make a conclusive inference, our results suggest that derivatives of the most antimicrobial compound may not necessarily be more antimicrobial. FAME results of the membrane composition of the test microbes (Table 1) show that the membrane composition of the four test microorganisms is very different and no linear relationship can be seen between a particular lipid and antimicrobial activity of the compounds evaluated in this study. Despite that, there is one interesting result from the FAME analysis. For all of the pinene derivatives (10b, 13b, and 14b) obtained from (−) α-pinene, M. luteus seemed to be the most susceptible microorganism. For the pinene derivatives obtained from the (+)-α-pinene, M. luteus seems to be the most susceptible microorganism for the two N-sulfonyl chlorides of β-lactam and γ-lactam. The membrane composition of M. luteus (Table 1) is unique and is mainly composed of 15:0 ANTEISO fatty acid (∼84%). The other three microorganisms have a spread of different membrane fatty acids.

toward the four microorganisms in comparison to (1a); however, statistically the difference is not significant. The antimicrobial potential of the enantiomeric starting materials (1a and 1b) and β-lactams (10a and 10b) is significantly different from each other not only toward various microorganisms used in this study but also in their extent of antimicrobial activity, whereas the antimicrobial potential of the amino esters (13a and 13b) and amino alcohols (14a and 14b) derived from the corresponding α-pinenes is found to be not significant as compared to their respective starting materials. Because the amino alcohols (14a and 14b) have both hydroxyl as well as the amino functional groups, it is expected that these enantiomers will have much greater antimicrobial activity than α-pinene derivatives containing either of the two functional groups. This, however, was not the case. A possible explanation for this could be that amino alcohols and amino esters are known to form strong intramolecular hydrogen bonds due to the formation of a six-membered ring.38,39 It is known that intramolecular hydrogen bonding affects the physical properties such as solubility of molecules.40 Therefore, H-bonding capacity (inter versus intra) directly would affect the water solubility of a compound. The strong intramolecular hydrogen bonding in the amino alcohols (14a and 14b) as well as the amino esters (13a and 13b) would lower the water solubility of these compounds and hence might prevent these compounds from crossing the polar cell wall to reach the site of action, the cell membrane.35−37 Structural features (carbon skeleton and functional groups) being the same, additional factors such as chirality and the capacity to hydrogen bond (intramolecular Hbonding seems to lower it, and intermolecular H-bonding seems to increase it) play an important role in determining the antimicrobial activity of this class of compounds. Skeletally modified α-pinene derivatives studied were 9a, 10a, 10b, 11a, 11b, and 12a. All of these skeletally modified derivatives were much more antimicrobial than their corresponding starting material (+)-α-pinene 1a and (−)-α-pinene 1b, indicating that the carbon skeleton affects the antimicrobial activity. Functional groups present also affect antimicrobial activity. The starting materials (+)-α-pinene 1a and (−)-αpinene 1b have alkene functionality that was converted to amino ester (13a, 13b) amino alcohol (14a, 14b), lactams (10a, 10b, 12a,) and lactam N-sulfonyl chloride (9a, 11a,11b). Of the various functional groups evaluated, lactams proved to be the most antimicrobial followed by lactam N-sulfonyl chlorides. It also matters which enantiomer was used to synthesize a particular derivative (derived from (+)-α-pinene versus (−)-α-pinene). Of the two starting materials, (+)- and (−)-α-pinene, only (+)-α-pinene was found to be antimicrobial against all four test microorganisms at the reported concentration. However, derivatives obtained from (−)-αpinene proved to be more antimicrobial than their mirror images obtained from the (+)-enantiomer. Although additional

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ASSOCIATED CONTENT

S Supporting Information *

Additional experimental details. This material is available free of charge via the Internet at http://pubs.acs.org.

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AUTHOR INFORMATION

Corresponding Author

*(P.D.) E-mail: [email protected]. Phone: 845-257-3797. Fax: 845 257-3791. Present Addresses △

(P.C.) Department of Pharmacology and Physiology, University of Rochester Medical Center, 601 Elmwood Ave., Box 711, Rochester, NY 14642, USA. ○ (D.T.C.) Department of Chemistry, Weinberg College of Arts and Sciences, 2145 Sheridan Rd., Northwestern University, Evanston, IL 60208, USA. ▽ (T.S.-L.) Soft Genetics, 100 Oakwood Place, State College, PA 16803, USA. □ (P.K.R.) Department of NMR, All India Institute of Medical Sciences, New Delhi 110029, India. Funding

SURE, AYURE, and Research and Creative grants, SUNY New Paltz. Notes

The authors declare no competing financial interest.

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REFERENCES

(1) Chowdhury, S.; Nishteswar, K. Role of volatile oil of natural source in the cosmetics and health care industries. Pharma Sci. Monit. 2013, 4, 3738−3750.

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(21) Kamath, A.; Ojima, I. Advances in the chemistry of β-lactam and its medicinal applications. Tetrahedron 2012, 68, 10640−10664. (22) Wilderman, P. R.; Shah, M. B.; Jang, H.-H.; Stout, C. D.; Halpert, J. R. Structural and thermodynamic basis of (+)-α-pinene binding to human cytochrome P450 2B6. J. Am. Chem. Soc. 2013, 135, 10433−10440. (23) Rios, J. L.; Recio, M. C.; Villar, A. Screening methods for natural products with antimicrobial activity: a review of the literature. J. Ethnopharmacol. 1988, 23, 127−149. (24) Brantner, A. H. Influence of various parameters on the evaluation of antibacterial compounds by the bioautographic tlc assay. Pharm. Pharmacol. Lett. 1997, 4, 152−154. (25) Szakonyi, Z.; Martinek, T.; Hetényi, A.; Fülöp, F. Synthesis and transformations of enantiomeric 1,2-disubstituted monoterpene derivatives. Tetrahedron: Asymmetry 2000, 11, 4571−4579. (26) Sambrook, J.; Russell, D. Molecular Cloning; CSHL Press: Cold Spring Harbor, NY, USA, 2001; Vol. 1, p 117. (27) Dhar, P.; Ayala, U.; Andarge, E.; Morisseau, S.; Snyder-Leiby, T. Study of the structural changes on the antimicrobial activity of [3.1.1.]bicyclics. J. Essent. Oil Res. 2004, 16, 612−616. (28) Nieva Moreno, M. I.; Isla, M. I.; Cudmani, N. G.; Vattuone, M. A.; Sampietro, A. R. Screening of antibacterial activity of Amalcha del Valle (Tucumán, Argentina) propolis. J. Ethnopharmacol. 1999, 68, 97−102. (29) Sasser, M. Microbial Identification by Gas Chromatographic Analysis of Fatty Acid Methyl Esters (GC-FAME); MIDI Tehnical Note 101; MIDI Inc.: Newark, DE, USA, 2009; 6 pp. (30) Georg, G. I. The Organic Chemistry of β-Lactams; VCH: New York, 1992; and references cited therein.. (31) Joumana, N. S.-K.; George, F. A. Recent developments in β lactamases and extended spectrum β lactamases. BMJ 2003, 327, 1209. (32) Nangia, A.; Biradha, K.; Desiraju, G. R. Correlation of biological activity in β-lactam antibiotics with Woodward and Cohen structural parameters − a Cambridge database study. J. Chem. Soc., Perkin Trans. 2 1996, 5, 943−53. (33) Neu, H. C. Antimicrobial activity and human pharmacology of amoxicillin. J. Infect. Dis. 1974, 129, S123−S131. (34) Dobrowolski, J. C.; Sadlej, J.; Mazurek, A. P. Why are g- and dless active than b-lactams? An ab initio study. Pol. J. Chem. 2001, 75, 1277−1286. (35) Gallucci, M. N.; Oliva, M.; Casero, C.; Dambolena, J.; Luna, A.; Zygadlo, J.; Demo, M. Antimicrobial combined action of terpenes against the food-borne microorganisms Escherichia coli, Staphyloccus aureus, and Bacillus cereus. Flavour Fragrance J. 2009, 24, 348−354. (36) Griffin, S. G.; Wyllie, S. G.; Markham, J. L.; Leach, D. N. The role of structure and molecular properties of terpenoids in determining their antimicrobial activity. Flavour Fragrance J. 1999, 14, 322−332. (37) Knobloch, K.; Pauli, A.; Iberl, B.; Weigand, H.; Weis, N. Antibacterial and antifungal properties of essential oil components. J. Essent. Oil Res. 1989, 1, 119−128. (38) Freedman, H. H. Intramolecular H-bonds. I. A spectroscopic study of the hydrogen bond between hydroxyl and nitrogen. J. Am. Chem. Soc. 1961, 83, 2900−2905. (39) Mulla, S.; Jose, C. I. Intramolecular hydrogen bonding and intermolecular association of amino alcohols. J. Chem. Soc., Faraday Trans. 1 1986, 82, 691−706. (40) Kuhn, B.; Mohr, P.; Stahl, M. Intra molecular hydrogen bonding in medicinal chemistry. J. Med. Chem. 2010, 53, 2601−2611.

(2) Maškovic, P.; Radojkovic, M.; Ristic, M.; Slavica, S. Studies on the antimicrobial and antioxidant activity and chemical composition of the essential oils of Kitaibelia vitifolia. Nat. Prod. Comm. 2013, 8, 667−670. (3) Bozin, B.; Mimica-Dukic, N.; Samojlik, I.; Jovin, E. J. Antimicrobial and antioxidant properties of rosemary and sage (Rosmarinus of f icinalis L. and Salvia of f icinalis L., Lamiaceae) essential oils. J. Agric. Food Chem. 2007, 55, 7879−7885. (4) Iscan, G.; Kirimer, N.; Kurkcuoglu, M.; Baser, K. H. C.; Demirci, F. Antimicrobial screening of Mentha piperita essential oils. J. Agric. Food Chem. 2002, 50, 3943−3946. (5) Dadalioglu, I.; Evrendilek, G. A. Chemical compositions and antibacterial effects of essential oils of Turkish oregano (Origanum minutif lorum), bay laurel (Laurus nobilis), Spanish lavender (Lavandula stoechas L.), and fennel (Foeniculum vulgare) on common foodborne pathogens. J. Agric. Food Chem. 2004, 52, 8255−8260. (6) Daferera, D.; Ziogas, B. N.; Polissiou, M. G. GC-MS analysis of essential oils from some Greek aromatic plants and their fungitoxicity on Penicillum digitatum. J. Agric. Food Chem. 2000, 48, 2576−2581. (7) Lis-Balchin, M. Aromatherapy with essential oils. In Handbook of Essential Oils; CRC Press: Boca Raton, FL, USA, 2009; pp 549−736 (8) Irshad, M.; Rehman, H.; Shahid, M.; Aziz, S.; Ghous, T. Antioxidant, antimicrobial and phytotoxic activities of essential oil of Angelica glauca. Asian J. Chem. 2011, 23, 1947−1951. (9) Cardile, V.; Russo, A.; Formisano, C.; Rigano, D.; Senatore, F.; Arnold, N. A.; Piozzi, F. Essential oils of Salvia bracteata and Salvia rubifolia from Lebanon: chemical composition, antimicrobial activity and inhibitory effect on human melanoma cells. J. Ethnopharmacol. 2009, 126, 265−272. (10) Sharma, A.; Mann, A. S.; Gajbhiye, V.; Kharya, M. D. Phytochemical profile of boswellia serrata: an overview. Pharmacogn. Rev. 2007, 1, 137−142. (11) Ö ztürk, M.; Duru, M. E.; Aydoğmuş-Ö ztürk, F.; Harmandar, M.; Mahlıçlı, M.; Kolak, U.; Ulubelen, A. GC-MS analysis and antimicrobial activity of essential oil of Stachys cretica subsp. smyrnae. Nat. Prod. Commun. 2009, 4, 109−114. (12) Kiran, C. R.; Chakka, A. K.; Amma, K. P. P.; Menon, A. N.; Kumar, M. M. S.; Venugopalan, V. V. Influence of cultivar and maturity at harvest on the essential oil composition, oleoresin and [6]gingerol contents in fresh ginger from northeast India. J. Agric. Food Chem. 2013, 61, 4145−4154. (13) Sikkema, J.; Poolman, B.; Konings, W. N.; de Bont, J. A. Effects of the membrane action of tetralin on the functional and structural properties of artificial and bacterial membranes. J. Bacteriol. 1992, 174, 2986−2992. (14) Sikkema, J.; de Bont, J. A.; Poolman, B. Interactions of cyclic hydrocarbons with biological membranes. J. Biol. Chem. 1994, 269, 8022−8028. (15) Griffin, S. G.; Wyllie, S. G.; Markham, J. L. Antimicrobially active terpenes cause K+ leakage in E. coli cells. J. Essent. Oil Res. 2005, 17, 686−690. (16) Pasqua, R. D.; Betts, G.; Hoskins, N.; Edwards, M.; Ercolini, D.; Mauriello, G. Membrane toxicity of antimicrobial compounds from essential oils. J. Agric. Food Chem. 2007, 55, 4863−4870. (17) Helander, I. M.; Alakomi, H.-L.; Latva-Kala, K.; MattilaSandholm, T.; Pol, I.; Smid, E. J.; Gorris, L. G. M.; von Wright, A. Characterization of the action of selected essential oil components on Gram-negative bacteria. J. Agric. Food Chem. 1998, 46, 3590−3595. (18) Trombetta, D.; Castelli, F.; Sarpietro, M. G.; Venuti, V.; Cristani, M.; Daniele, C.; Saija, A.; Mazzanti, G.; Bisignano, G. Mechanisms of antibacterial action of three monoterpenes. Antimicrob. Agents Chemother. 2005, 49, 2474−2478. (19) Witzke, S.; Duelund, L.; Kongsted, J.; Petersen, M.; Mouritsen, O. G.; Khandelia, H. Inclusion of terpenoid plant extracts in lipid bilayers investigated by molecular dynamics simulations. J. Phys. Chem. B 2010, 114, 15825−15831. (20) Sasaki, T.; Eguchi, S.; Yamada, H. Reactions of isoprenoids. XVIII. Reactions of chlorosulfonyl isocyanate with bicyclic monoterpene olefins. Novel isomerization of 1-chlorosulfonyl-2-azetidinone. J. Org. Chem. 1973, 38, 679−686. 3552

dx.doi.org/10.1021/jf403586t | J. Agric. Food Chem. 2014, 62, 3548−3552