Antibacterial Cannabinoids from Cannabis sativa: A Structure−Activity Study
Giovanni Appendino *†‡, Simon Gibbons *
, Anna Giana †‡, Alberto Pagani †‡, Gianpaolo Grassi §, Michael Stavri , Eileen Smith and M. Mukhlesur Rahman
, Anna Giana †‡, Alberto Pagani †‡, Gianpaolo Grassi §, Michael Stavri , Eileen Smith and M. Mukhlesur Rahman
Dipartimento di Scienze Chimiche, Alimentari, Farmaceutiche e Farmacologiche, Università del Piemonte Orientale, Via Bovio 6, 28100 Novara, Italy, Consorzio per lo Studio dei Metaboliti Secondari (CSMS), Viale S. Ignazio 13, 09123 Cagliari, Italy, Centre for Pharmacognosy and Phytotherapy, The School of Pharmacy, University of London, 29-39 Brunswick Square, London WC1N 1AX, U.K., and CRA-CIN Centro di Ricerca per le Colture Industriali, Sede distaccata di Rovigo, Via Amendola 82, 45100 Rovigo, Italy
J. Nat. Prod., 2008, 71 (8), pp 1427–1430
DOI: 10.1021/np8002673
Publication Date (Web): August 6, 2008
Copyright © 2008 The American Chemical Society and American Society of Pharmacognosy
* To whom correspondence should be addressed. Tel: +39 0321 373744 begin_of_the_skype_highlighting 
+39 0321 373744 FREE end_of_the_skype_highlighting (G.A.); +44 207 753 5913 begin_of_the_skype_highlighting +44 207 753 5913 FREE end_of_the_skype_highlighting (S.G.). Fax: +39 0321 375621 (G.A.); +44 207 753 5909 begin_of_the_skype_highlighting +44 207 753 5909 FREE end_of_the_skype_highlighting (S.G.). E-mail: appendino@pharm.unipmn.it (G.A.); simon.gibbons@pharmacy.ac.uk (S.G.)., †
+39 0321 373744 FREE end_of_the_skype_highlighting (G.A.); +44 207 753 5913 begin_of_the_skype_highlighting +44 207 753 5913 FREE end_of_the_skype_highlighting (S.G.). Fax: +39 0321 375621 (G.A.); +44 207 753 5909 begin_of_the_skype_highlighting +44 207 753 5909 FREE end_of_the_skype_highlighting (S.G.). E-mail: appendino@pharm.unipmn.it (G.A.); simon.gibbons@pharmacy.ac.uk (S.G.)., †
Università del Piemonte Orientale.
, ‡
Consorzio per lo Studio dei Metaboliti Secondari.
,
University of London.
, §
Centro Ricerca Colture Industriali.
Section:Abstract
Marijuana (Cannabis sativa) has long been known to contain antibacterial cannabinoids, whose potential to address antibiotic resistance has not yet been investigated. All five major cannabinoids (cannabidiol (1b), cannabichromene (2), cannabigerol (3b), Δ9-tetrahydrocannabinol (4b), and cannabinol (5)) showed potent activity against a variety of methicillin-resistant Staphylococcus aureus (MRSA) strains of current clinical relevance. Activity was remarkably tolerant to the nature of the prenyl moiety, to its relative position compared to the n-pentyl moiety (abnormal cannabinoids), and to carboxylation of the resorcinyl moiety (pre-cannabinoids). Conversely, methylation and acetylation of the phenolic hydroxyls, esterification of the carboxylic group of pre-cannabinoids, and introduction of a second prenyl moiety were all detrimental for antibacterial activity. Taken together, these observations suggest that the prenyl moiety of cannabinoids serves mainly as a modulator of lipid affinity for the olivetol core, a per se poorly active antibacterial pharmacophore, while their high potency definitely suggests a specific, but yet elusive, mechanism of activity.
Several studies have associated the abuse of marijuana (Cannabis sativa L. Cannabinaceae) with an increase in opportunistic infections,(1) and inhalation of marijuana has indeed been shown to interfere with the production of nitric oxide from pulmonary macrophages, impairing the respiratory defense mechanisms against pathogens and causing immunosuppression.(2) The association of C. sativa with a decreased protection against bacterial infections is paradoxical, since this plant has long been known to contain powerful antibacterial agents.(3) Thus, preparations from C. sativa were investigated extensively in the 1950s as highly active topical antiseptic agents for the oral cavity and the skin and as antitubercular agents.(3) Unfortunately, most of these investigations were done at a time when the phytochemistry of Cannabis was still in its infancy, and the remarkable antibacterial profile of the plant could not be related to any single, structurally defined and specific constituent. Evidence that pre-cannabidiol (1a) is a powerful plant antibiotic was, nevertheless, obtained,(4) and more recent investigations have demonstrated, to various degrees, antibacterial activity for the nonpsychotropic cannabinoids cannabichromene (CBC, 2),(5) cannabigerol (CBG, 3b),(6) and cannabidiol (1b),(7) as well as for the psychotropic agent Δ9-tetrahydrocannabinol (THC, 4b).(7) These observations, and the inactivity of several noncannabinoid constituents of C. sativa as antibacterial agents, suggest that cannabinoids and their precursors are the most likely antibacterial agents present in C. sativa preparations.(8) However, differences in bacterial strains and end-points make it difficult to compare the data reported in these scattered studies, and the overall value of C. sativa as an antibacterial agent is therefore not easy to assess.
There are currently considerable challenges with the treatment of infections caused by strains of clinically relevant bacteria that show multidrug-resistance (MDR), such as methicillin-resistant Staphylococcus aureus (MRSA) and the recently emerged and extremely drug-resistant Mycobacterium tuberculosis XDR-TB. New antibacterials are therefore urgently needed, but only one new class of antibacterial has been introduced in the last 30 years.(9) Despite the excellent antibacterial activity of many plant secondary metabolites(10) and the ability of some of them to modify the resistance associated with MDR strains(11) and efflux pumps,(12) plants are still a substantially untapped source of antimicrobial agents.
These considerations, as well as the observation that cross-resistance to microbial and plant antibacterial agents is rare,(10) make C. sativa a potential source of compounds to address antibiotic resistance, one of the most urgent issues in antimicrobial therapy. To obtain structure−activity data and define a possible microbiocidal cannabinoid pharmacophore, we investigated the antibacterial profile of the five major cannabinoids, of their alkylation and acylation products, and of a selection of their carboxylic precursors (pre-cannabinoids) and synthetic positional isomers (abnormal cannabinoids).
Results and Discussion
The antibacterial cannabinoid chemotype is poorly defined, as is the molecular mechanism of its activity. Since many simple phenols show antimicrobial properties, it does not seem unreasonable to assume that the resorcinol moiety of cannabinoids serves as the antibacterial pharmacophore, with the alkyl, terpenoid, and carboxylic appendices modulating its activity. To gain insight into the microbiocidal cannabinoid pharmacophore, we have investigated how the nature of the terpenoid moiety, its relative position compared to the n-pentyl group, and the effect of carboxylation of the resorcinyl moiety are translated biologically, assaying the major cannabinoids and a selection of their precursors and regioisomeric analogues against drug-resistant bacteria of clinical relevance. Within these, we have selected a panel of clinically relevant Staphylococcus aureus strains that includes the (in)famous EMRSA-15, one of the main epidemic methicillin-resistant strains,(13) and SA-1199B, a multidrug-resistant strain that overexpresses the NorA efflux mechanism, the best characterized antibiotic efflux pump in this species.(14) SA-1199B also possesses a gyrase mutation that, in addition to NorA, confers a high level of resistance to certain fluoroquinolones. A macrolide-resistant strain (RN4220),(15) a tetracycline-resistant line overexpressing the TetK efflux pump (XU212),(16) and a standard laboratory strain (ATCC25923) completed the bacterial panel.
Δ9-Tetrahydrocannabinol (THC, 4b), cannabidiol (CBD, 1b), cannabigerol (CBG, 3b), cannabichromene (CBC, 2), and cannabinol (CBN, 5) are the five most common cannabinoids.(17) They could be obtained in high purity (>98%) by isolation from strains of C. sativa producing a single major cannabinoid (THC, CBD, CBG), by total synthesis (CBC),(6) or by semisynthesis (CBN).(18) Their antimicrobial properties are listed in Table 1. All compounds showed potent antibacterial activity, with MIC values in the 0.5−2 μg/mL range. Activity was exceptional against some of these strains, in particular the multidrug-resistant (MDR) SA-1199B, which has a high level of resistance to certain fluoroquinolones. Also noteworthy is the potent activity demonstrated against EMRSA-15 and EMRSA-16, the major epidemic methicillin-resistant S. aureus strains occurring in U.K. hospitals.(13, 19) These activities compare highly favorably with the standard antibiotics for these strains. The potent activity against strains possessing the NorA and TetK efflux transporters suggests that cannabinoids are not substrates for the most common resistance mechanisms to current antibacterial agents, making them attractive antibacterial leads.
| compound | SA-1199B | RN-4220 | XU212 | ATCC25923 | EMRSA-15 | EMRSA-16 |
|---|---|---|---|---|---|---|
| 1a | 2 | 2 | 2 | 2 | 2 | 2 |
| 1b | 1 | 1 | 1 | 0.5 | 1 | 1 |
| 2 | 2 | 2 | 1 | 2 | 2 | 2 |
| 3a | 4 | 2 | 4 | 4 | 2 | 4 |
| 3b | 1 | 1 | 1 | 1 | 2 | 1 |
| 3f | 64 | c | 64 | c | c | c |
| 4a | 8 | 4 | 8 | 4 | 8 | 4 |
| 4b | 2 | 1 | 1 | 1 | 2 | 0.5 |
| 5 | 1 | 1 | 1 | 1 | 1 | c |
| 6 | 1 | 1 | 1 | 1 | 1 | 1 |
| 7 | 2 | 1 | 0.5 | 1 | 2 | c |
| 8 | 32 | 32 | 16 | 16 | 16 | 32 |
| 10 | 64 | 64 | 64 | 128 | 64 | 64 |
| norfloxacin | 32 | 1 | 4 | 1 | 0.5 | 128 |
| erythromycin | 0.25 | 64 | >128 | 0.25 | >128 | >128 |
| tetracycline | 0.25 | 0.25 | 128 | 0.25 | 0.125 | 0.125 |
| oxacillin | 0.25 | 0.25 | 128 | 0.125 | 32 | >128 |
a
Compounds 1c−g, 3c−e, 3g, and 9 exhibited MIC values of >128 μg/mL for all organisms in which they were evaluated.
b
Compound 11 exhibited MIC values of >256 μg/mL for all organisms in which they were evaluated.
c
Not tested.
Given their nonpsychotropic profiles, CBD (1b) and CBG (3b) seemed especially promising, and were selected for further structure−activity studies. Thus, acetylation and methylation of their phenolic hydroxyls (compounds 1c−e and 3c−e, respectively) were both detrimental for activity (MIC >100 μg/mL), in accordance with the essential role of the phenolic hydroxyls in the antibacterial properties. However, in light of the potent activity of the monophenols CBC (2), THC (4b), and CBN (5), it was surprising that monomethylation of the diphenols CBD (1b) and CBG (3b) was so poorly tolerated in terms of antibacterial activity.
Cannabinoids are the products of thermal degradation of their corresponding carboxylic acids (pre-cannabinoids).(17) Investigation of the antibacterial profile of the carboxylated versions of CBD, CBG, and THC (compounds 1a, 3a, and 4a, respectively) showed a substantial maintenance of activity. On the other hand, methylation of the carboxylic group (compounds 1f and 3f, respectively) caused a marked decrease of potency, as did esterification with phenethyl alcohol (compounds 1g and 3g, respectively). This operation is associated with a potentiation of the antibacterial properties of phenolic acids, as exemplified by phenethyl caffeate (CAPE), the major antibacterial from propolis, compared to caffeic acid.(20) Remarkably, the synthetic abnormal cannabinoids abn-CBD (6)(21) and abn-CBG (7)(22) showed antibacterial activity comparable to, although slightly less potent than, their corresponding natural products, while olivetol (10) showed modest activity against all six strains, with MICs of 64−128 μg/mL, and resorcinol (11) did not exhibit any activity even at 256 μg/mL. Thus, the pentyl chain and the monoterpene moiety greatly enhance the activity of resorcinol.
Taken together, these observations show that the cannabinoid antibacterial chemotype is remarkably tolerant to structural modification of the terpenoid moiety and its positional relationship with the n-pentyl chain, suggesting that these residues serve mainly as modulators of lipid affinity, and therefore cellular bioavailability. This view was substantiated by the marked decrease of activity observed when the antibacterial activity of CBG (3b) was compared to that of its polar analogue carmagerol (8).(23) The results against the resistant strains confirm this suggestion, and it is likely that the increased hydrophilicity caused by the addition of two hydroxyls greatly reduces the cellular bioavailability by substantially reducing membrane permeability. Conversely, the addition of a further prenyl moiety, as in the bis-prenylated cannabinoid 9,(21) while increasing membrane solubility, may result in poorer aqueous solubility and therefore a lower intracellular concentration, similarly leading to a substantial loss of activity. A single unfunctionalized terpenyl moiety seems therefore ideal in terms of lipophilicity balance for the antibacterial activity of olivetol derivatives. The great potency of cannabinoids suggests a specific interaction with a bacterial target, whose identity is, however, still elusive.
Given the availability of C. sativa strains producing high concentrations of nonpsychotropic cannabinoids, this plant represents an interesting source of antibacterial agents to address the problem of multidrug resistance in MRSA and other pathogenic bacteria. This issue has enormous clinical implications, since MRSA is spreading throughout the world and, in the United States, currently accounts for more deaths each year than AIDS.(24) Although the use of cannabinoids as systemic antibacterial agents awaits rigorous clinical trials and an assessment of the extent of their inactivation by serum,(25) their topical application to reduce skin colonization by MRSA seems promising, since MRSA resistant to mupirocin, the standard antibiotic for this indication, are being detected at a threatening rate.(26) Furthermore, since the cannabinoid anti-infective chemotype seems remarkably tolerant to modifications in the prenyl moiety, semipurified mixtures of cannabinoids could also be used as cheap and biodegradable antibacterial agents for cosmetics and toiletries, providing an alternative to the substantially much less potent synthetic preservatives, many of which are currently questioned for their suboptimal safety and environmental profile.(27)
Experimental Section
General Experimental Procedures
IR spectra were obtained on a Shimadzu DR 8001 spectrophotometer. 1H NMR (300 MHz) and 13C NMR (75 MHz) spectra were obtained at room temperature with a JEOL Eclipse spectrometer. The spectra were recorded in CDCl3, and the solvent signals (7.26 and 77.0 ppm, respectively) were used as reference. The chemical shifts (δ) are given in ppm, and the coupling constants (J) in Hz. Silica gel 60 (70−230 mesh) and Lichroprep RP-18 (25−40 mesh) were used for gravity column chromatography. Reactions were monitored by TLC on Merck 60 F254 (0.25 mm) plates and were visualized by UV inspection and/or staining with 5% H2SO4 in ethanol and heating. Organic phases were dried with Na2SO4 before evaporation. All known cannabinoids were identified according to their physical and spectroscopic data.(28) Semisynthetic cannabinoids 1c−f, and 3c−f were prepared and identified according to their corresponding literature references.(22, 29, 30) Synthetic [abnormal (6,(21) 7(6)) and polyprenyl (9)(21)] cannabinoids were synthesized and characterized according to the literature.
Plant Material
The three strains of Cannabis sativa used for the isolation of THC, CBD, and CBG came from greenhouse cultivation at CRA-CIN, Rovigo (Italy), where voucher specimens are kept for each of them, and were collected in September 2006. The isolation and manipulation of all cannabinoids were done in accordance with their legal status (License SP/101 of the Ministero della Salute, Rome, Italy).
Isolation of Cannabinoids (1b, 3b, 4b)
The powdered plant material (100 g) was distributed in a thin layer on cardboard and heated at 120 °C for 2 h in a ventilated oven to affect decarboxylation, then extracted with acetone (ratio solvent to plant material 3:1, ×3). The residue (6.5 g for the CBD chemotype, 4.1 g for the CBG chemotype, 7.4 g for the THC chemotype) was purified by gravity column chromatography on silica gel (ratio stationary phase to extract 6:1) using a petroleum ether−ether gradient. Fractions eluted with petroleum ether−ether (9:1) afforded 1b (628 mg, 0.63%, from the CBD chemotype) and 3b (561 mg, 0.56%, from the CBG chemotype), precipitated from hot hexane to obtain white powders. Crude THC (3.2 g, 3.2%, from the THC chemotype) was obtained as a greenish oil, part of which (400 mg) was further purified by RP-18 flash chromatography with methanol−water (1:1) as eluant, affording 4b as a colorless oil (315 mg).
Isolation of Pre-cannabinoids (1a, 3a, 4a)
The powdered plant material (100 g) was extracted with acetone (ratio solvent to plant material 5:1, ×3). After removal of the solvent, the residue (7.7 g for the CBD chemotype, 4.9 g for the CBG chemotype, 7.9 g for the THC chemotype) was fractionated by vacuum chromatography on RP-18 silica gel (ratio stationary phase to extract 5:1) using methanol−water (75:25) as eluant. Fractions of 100 mL were taken, and those containing pre-cannabinoids were pooled, concentrated to ca. half-volume at 30 °C, saturated with NaCl, and extracted with EtOAc. After removal of the solvent, the residue was further purified by gravity column chromatography on silica gel (ratio stationary phase to crude compound 5:1) using a petroleum ether−EtOAc gradient (from 8:2 to 5:5) to afford 1.59 g (1.6%) of 1a from the CBD chemotype, 0.93 g (0.93%) of 3a from the CBG chemotype, and 2.1 g (2.1%) of 4a from the THC chemotype. All pre-cannabinoids were obtained as white foams that resisted crystallization.
Synthesis of CBC (2) and CBN (5)
Mitsunobu Esterification of Pre-cannabinoids (synthesis of 3g as an example)
To a cooled (ice bath) solution of 3a (360 mg, 1.1 mmol) in dry CH2Cl2 (4 mL) were added sequentially phenethyl alcohol (92 μL, 0.76 mmol, 0.75 molar equiv), triphenylphosphine (TPP) (220 mg, 0.84 mmol, 0.80 molar equiv), and diisopropyldiazodicarboxylate (DIAD) (228 μL, 1.1 mmol, 1 molar equiv). At the end of the addition, the cooling bath was removed, and the reaction was stirred at room temperature. After 16 h, the reaction was worked up by evaporation, and the residue was dissolved in toluene and cooled at 4 °C overnight to remove most of the TPPO-dihydroDIAD adduct. The filtrate was evaporated and purified by gravity column chromatography on silica gel (10 g, petroleum ether as eluant) to afford 126 mg (32%) of 3g. Under the same reaction conditions, the yield of 1g from 1a was 26%.
Pre-cannabigerol Phenethyl Ester (3g):
colorless foam; IR νKBrmax 3746, 3513, 3313, 1715, 1589, 1421, 1274, 1164, 980, 804, 690 cm−1; 1H NMR (300 MHz, CDCl3) δ 12.08 (1H, s), 7.25 (5H, m), 6.02 (1H, s), 5.98 (1H, s), 5,25 (1H, br t, J = 7.0 Hz), 5.01 (1H, br t, J = 6.5 Hz), 4.56 (2H, t, J = 6.6 Hz), 3.40 (2H, d, J = 7.3 Hz), 3.1 (2H, t, J = 6.6 Hz), 2.7 (2H, t, J = 6.6 Hz), 2.05 (4H, m), 1.79 (3H, s), 1.65 (3H, s), 1.57 (3H, s), 1.24 (6H, m), 0.88 (3H, t, J = 7.1 Hz); 13C NMR (75 MHz, CDCl3) δ 172.1 (s), 162.7 (s), 159.5 (s), 148.8 (s), 139.1 (s), 137.4 (d), 132.1 (s), 128.8 (d), 126.8 (d), 125.9 (d), 121.5 (d), 111.5 (s), 110.8 (s), 65.8 (t), 39.8 (t), 36.6 (t), 35.0 (t), 32.0 (t), 31.5 (t), 26.5 (t), 25.8 (q), 22.2 (t), 17.8 (q), 16.3 (q), 14.2 (q); CIMS m/z [M + H] 465 [C30H40O4 + H].
Pre-cannabidiol Phenethyl Ester (1g):
colorless oil; IR (KBr) νmax 3587, 3517, 3423, 3027, 1642, 1499, 1425, 1274, 1172, 1143, 980, 894 cm−1; 1HNMR (300 MHz, CDCl3) δ 12.13 (1H, s), 6.23 (5H, m), 6.48 (1H, s), 6.19 (1H, s), 5,55 (1H, s), 4.52 (3H, m), 4.4 (1H, s), 4.08 (1H, br s), 3.08 (2H, t, J = 7.0 Hz), 2.7 (2H, m), 2.11 (1H, m), 1.78 (3H, s), 1.71 (3H, s), 1.5 (4H, m), 1.28 (6H, m), 0.88 (3H, t, J = 6.9 Hz); 13C NMR (75 MHz, CDCl3) δ 172.2 (s), 171.5 (s), 163.5 (s), 160.0 (s), 148.8 (s), 147.0 (s), 145.9 (s), 140.2 (s), 137.4 (s), 128.7 (d), 126.7 (d), 124.0 (d), 114.4 (t), 112.3 (d), 105.8 (s), 65.6 (t), 46.6 (d), 39.1 (t), 37.0 (d), 31.9 (d), 31.5 (t), 27.8 (t), 25.3 (q), 22.6 (t), 21.9 (t), 18.5 (q), 14.1 (q); CIMS m/z [M + H] 463 [C30H38O4 + H].
Bacterial Strains and Chemicals
A standard S. aureus strain (ATCC 25923) and a clinical isolate (XU212), which possesses the TetK efflux pump and is also a MRSA strain, were obtained from E. Udo.(16) Strain RN4220, which has the MsrA macrolide efflux pump, was provided by J. Cove.(30) EMRSA-15(13) and EMRSA-16(19) were obtained from Paul Stapleton. Strain SA-1199B, which overexpresses the NorA MDR efflux pump, was the gift of Professor Glenn Kaatz.(14) Tetracycline, norfloxacin, erythromycin, and oxacillin were obtained from Sigma Chemical Co. Oxacillin was used in place of methicillin as recommended by the NCCLS. Mueller-Hinton broth (MHB; Oxoid) was adjusted to contain 20 mg/L Ca2+ and 10 mg/L Mg2+.
Antibacterial Assays
Overnight cultures of each strain were made up in 0.9% saline to an inoculum density of 5 × 105 cfu by comparison with a MacFarland standard. Tetracycline and oxacillin were dissolved directly in MHB, whereas norfloxacin and erythromycin were dissolved in DMSO and then diluted in MHB to give a starting concentration of 512 μg/mL. Using Nunc 96-well microtiter plates, 125 μL of MHB was dispensed into wells 1−11. Then, 125 μL of the test compound or the appropriate antibiotic was dispensed into well 1 and serially diluted across the plate, leaving well 11 empty for the growth control. The final volume was dispensed into well 12, which being free of MHB or inoculum served as the sterile control. Finally, the bacterial inoculum (125 μL) was added to wells 1−11, and the plate was incubated at 37 °C for 18 h. A DMSO control (3.125%) was also included. All MICs were determined in duplicate. The MIC was determined as the lowest concentration at which no growth was observed. A methanolic solution (5 mg/mL) of 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazoliium bromide (MTT; Lancaster) was used to detect bacterial growth by a color change from yellow to blue.
References
This article references 30 other publications.
- 1.Caiffa, W. T., Vlahov, D., Graham, N. M. H., Astemborski, J., Solomon, L., Nelson, K. E., and Munoz, A. Am. J. Resp. Crit. Care Med. 1994, 150, 1593– 1598There is no corresponding record for this reference.
- 3.(a) Krjci, Z. Lekarske Listy 1952, 7, 500– 503; Chem. Abstr. 1952, 48, 78326[PubMed]There is no corresponding record for this reference.(b) Ferenczy, L., Gracza, L., and Jakobey, I. Naturwissenschaften 1958, 45, 188(c) Krejci, Z. Pharmazie 1958, 13, 155– 156(d) Rabinovich, A. S., Aizenman, B. L., and Zelepukha, S. I. Mikrobiol. Zh 1959, 21, 40– 48(PubMed ID 14435632)[PubMed]There is no corresponding record for this reference.(e) Turner, C. E., Elsohly, M. A., and Boeren, E. G. J. Nat. Prod. 1980, 43, 169– 243
- 9.Barrett, C. T. and Barrett, J. F. Curr. Opin. Biotechnol. 2003, 14, 621– 626[CrossRef], [PubMed], [CAS]9.https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3sXps1OqtL0%253D&md5=9e5e74ecffd4dd037f41a5449c1d0dafBarrett, Christine T.; Barrett, John F.Current Opinion in Biotechnology (2003),A review. Fifty years of making analogs based on less than ten antibacterial scaffolds has resulted in the development and marketing of over 100 antibacterial agents but, with the exception of the oxazolidinone core, no new scaffolds have emerged in the past 30 yr to address emerging resistance problems. As the support for antibacterial research shifts away from large pharmaceutical companies, a wave of biotechnol. companies have pursued a diverse choice of targets resulting in several novel classes of agent in late-stage development. Although crit. for certain resistance niche needs, these agents are unlikely to provide the soln. to the requirement for a major novel scaffold class of antibacterials.
- 10.Gibbons, S. Nat. Prod. Rep. 2004, 21, 263– 277[CrossRef], [PubMed], [CAS]10.https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2cXksFalt7Y%253D&md5=e8de7c60b78ee4659fcb9bd18d2db460Gibbons, SimonNatural Product Reports (2004),A review. The occurrence of vancomycin-resistant Staphylococcus aureus and multidrug-resistant strains of this organism necessitate the discovery of new classes of antistaphylococcal drugs. This review describes plant natural products that either modify resistance in S. aureus or are antibacterial through bacteriostatic or bactericidal properties.
- 11.Stavri, M., Piddock, L. J. V., and Gibbons, S. J. Antimicrob. Chemother. 2007, 59, 1247– 1260[CrossRef], [PubMed], [CAS]11.https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2sXnvVahtbg%253D&md5=08b885dc3f4641c9ecf0037e4a513868Stavri, Michael; Piddock, Laura J. V.; Gibbons, SimonJournal of Antimicrobial Chemotherapy (2007),A review. The rapid spread of bacteria expressing multidrug resistance (MDR) has necessitated the discovery of new antibacterials and resistance-modifying agents. Since the initial discovery of bacterial efflux pumps in the 1980s, many have been characterized in community- and hospital-acquired Gram-pos. and Gram-neg. pathogens, such as Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli and, more recently, in mycobacteria. Efflux pumps are able to extrude structurally diverse compds., including antibiotics used in a clin. setting; the latter are rendered therapeutically ineffective. Antibiotic resistance can develop rapidly through changes in the expression of efflux pumps, including changes to some antibiotics considered to be drugs of last resort. It is therefore imperative that new antibiotics, resistance-modifying agents and, more specifically, efflux pump inhibitors (EPIs) are characterized. The use of bacterial resistance modifiers such as EPIs could facilitate the re-introduction of therapeutically ineffective antibiotics back into clin. use such as ciprofloxacin and might even suppress the emergence of MDR strains. Here we review the literature on bacterial EPIs derived from natural sources, primarily those from plants. The resistance-modifying activities of many new chem. classes of EPIs warrant further studies to assess their potential as leads for clin. development.
- 12.Smith, E. C. J., Kaatz, G. W., Seo, S. M., Wareham, N., Williamson, E. M., and Gibbons, S. Antimicrob. Agents Chemother. 2007, 51, 4480– 4483[CrossRef], [PubMed], [CAS]12.https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2sXhsVWisbjF&md5=48908bc2fbd5fc5cab2303ae7e88512cSmith, Eileen C. J.; Kaatz, Glenn W.; Seo, Susan M.; Wareham, Neale; Williamson, Elizabeth M.; Gibbons, SimonAntimicrobial Agents and Chemotherapy (2007),The phenolic diterpene totarol had good antimicrobial activity against effluxing strains of Staphylococcus aureus. Subinhibitory concns. reduced the MICs of selected antibiotics, suggesting that it may also be an efflux pump inhibitor (EPI). A totarol-resistant mutant that overexpressed norA was created to sep. antimicrobial from efflux inhibitory activity. Totarol reduced ethidium efflux from this strain by 50% at 15 μM (1/4 × MIC), and combination studies revealed marked redns. in ethidium MICs. These data suggest that totarol is a NorA EPI as well as an antistaphylococcal antimicrobial agent.
- 14.Kaatz, G. W., Seo, S. M., and Ruble, C. A. Antimicrob. Agents Chemother. 1993, 37, 1086– 1094[CrossRef], [PubMed], [CAS]14.https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK3sXltFehs7g%253D&md5=84a3d2bd6f2d6edc7f83f6fab9ecffe7Kaatz, Glenn W.; Seo, Susan M.; Ruble, Cheryl A.Antimicrobial Agents and Chemotherapy (1993),Transport processes are used by all organisms to obtain essential nutrients and to expel wastes and other potentially harmful substances from cells. Such processes are important means by which resistance to selected antimicrobial agents in bacteria is achieved. The recently described Staphylococcus aureus norA gene encodes a membrane-assocd. protein that mediates active efflux of fluoroquinolones from cells. SA-1199B is a fluoroquinolone-resistant strain of S. aureus from which an allele of norA (norA1199) was cloned. Similar to that of norA, the protein product of norA1199 preferentially mediates efflux of hydrophilic fluoroquinolones in both S. aureus and an Escherichia coli host, a process driven by the protonmotive force. Detn. of the nucleotide sequence of norA1199 revealed an encoded 388-amino-acid hydrophobic polypeptide 95% homologous with the norA-encoded protein. Significant homol. with other proteins involved in transport processes also exists, but esp. with tetracycline efflux proteins and with the Bacillus subtilis Bmr protein that mediates active efflux of structurally unrelated compds., including fluoroquinolones. In S. aureus, the norA1199-encoded protein also appears to function as a multidrug efflux transporter. Southern hybridization studies indicated that norA1199 (or an allele of it) is a naturally occurring S. aureus gene and that related sequences are present in the S. epidermidis genome. The nucleotide sequence of the wild-type allele of norA1199, cloned from the fluoroquinolone-susceptible parent strain of SA-1199B, did not differ from that of norA1199 throughout the coding region. Northern (RNA) and Southern hybridization studies showed that increased transcription, and not gene amplification, of norA1199 is the basis for fluoroquinolone resistance in SA-1199B.
- 15.Ross, J. I., Farrell, A. M., Eady, E. A., Cove, J. H., and Cunliffe, W. J. J. Antimicrob. Chemother. 1989, 24, 851– 862[CrossRef], [PubMed], [CAS]15.https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK3cXhtlGrtLc%253D&md5=1f1d8b72c99b4ff60a620df780f4f27fRoss, Jeremy I.; Farrell, Angela M.; Eady, E. Anne; Cove, Jonathan H.; Cunliffe, William J.Journal of Antimicrobial Chemotherapy (1989),Some 110 staphylococcal isolates from human skin were found to express a novel type of erythromycin resistance. The bacteria were resistant to 14-membered ring macrolides (MIC 32-128 mg/L) but were sensitive to 16-membered ring macrolides and lincosamides. Resistance to type B streptogramins was inducible by erythromycin. A similar phenotype, designated MS resistance, was previously described in clin. isolates of coagulase-neg. staphylococci from the USA. In the UK, MS resistance is widely distributed in coagulase-neg. staphylococci but was not detected in 100 erythromcyin-resistant clin. isolates of S. aureus. Tests for susceptibility to a further 16 antibiotics failed to reveal any other selectable marker assocd. with the MS phenotype. Plasmid pattern anal. of 48 MS isolates showed considerable variability between strains and no common locus for the resistance determinant. In one strain of S. epidermidis, co-resistance to tetracycline, penicillin, and erythromycin (MS) was assocd. with a 31.5 kb plasmid, pUL5050, which replicated and expressed all three resistances when transformed into S. aureus RN4220. The MS resistance determinant was localized to a 1.9 kb fragment which was cloned onto the high-copy-no. vector, pSK265. A constitutive mutant of S. aureus RN4220 contg. the 1.9 kb fragment remained sensitive to clindamycin. This observation, together with the concn.-dependent induction (optimum 5 mg/L of erythromycin) of virginiamycin S resistance, suggests that the MS phenotype is not due to altered expression of MLS resistance determinants (erm genes) but probably occurs via a different mechanism.
- 16.Gibbons, S. and Udo, E. E. Phytother. Res. 2000, 14, 139– 140[CrossRef], [PubMed], [CAS]16.https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3cXisVeis7o%253D&md5=a651ac16cc68268ec2b2f23e05958913Gibbons, Simon; Udo, E. E.Phytotherapy Research (2000),As part of a screening program to identify modulators of multidrug efflux in methicillin resistant Staphylococcus aureus (MRSA), we have validated our assays using the antihypertensive plant alkaloid reserpine. Clin. isolates of MRSA were resistant to tetracycline and shown to possess the tet(K) determinant which encodes for the Tet(K) efflux protein, which conferred high level resistance to tetracycline (MIC = 128 μg/mL). In the presence of reserpine, a known inhibitor of multidrug resistance (mdr) efflux pumps, this MIC was significantly reduced (MIC = 32 μg/mL).
- 17.(a) Mechoulam, R., McCallum, N. K., and Burstein, S. Chem. Rev. 1976, 76, 75– 112[ACS Full Text
], [CAS]17.https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaE28XotlygtA%253D%253D&md5=da7372722757bb7521126d7daa69150bMechoulam, Raphael; McCallum, Neil K.; Burstein, SumnerChemical Reviews (Washington, DC, United States) (1976),A review with 409 refs.(b) Elsohly, M. A. and Slade, D. Life Sci. 2005, 78, 539– 548[CrossRef], [PubMed], [CAS]17.https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2MXht1ejsrfJ&md5=8ce2f1f0a827b2e737cc4855f353448aElSohly, Mahmoud A.; Slade, DesmondLife Sciences (2005),A review. The cannabis plant (Cannabis sativa L.) and products thereof (such as marijuana, hashish and hash oil) have a long history of use both as a medicinal agent and intoxicant. Over the last few years there have been an active debate regarding the medicinal aspects of cannabis. Currently cannabis products are classified as Schedule I drugs under the Drug Enforcement Administration (DEA) Controlled Substances act, which means that the drug is only available for human use as an investigational drug. In addn. to the social aspects of the use of the drug and its abuse potential, the issue of approving it as a medicine is further complicated by the complexity of the chem. make up of the plant. This manuscript discusses the chem. constituents of the plant with particular emphasis on the cannabinoids as the class of compds. responsible for the drug's psychol. properties. - 18.(a) Ghosh, R., Todd, A. R., and Wilkinson, S. J. Chem. Soc. 1940, 1393– 1396(b) Bastola, K. P., Hazekamp, A., and Verpoorte, R. Planta Med. 2007, 73, 273– 275[CrossRef], [PubMed], [CAS]18.https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2sXkvVSktb4%253D&md5=751b39cd052aa6200a032c44a5556b49Bastola, Krishna Prasad; Hazekamp, Arno; Verpoorte, RobertPlanta Medica (2007),Cannabinoids, the main constituents of the cannabis plant, are being increasingly studied for their medicinal properties. Cannabinolic acid (I) was synthesized from tetrahydrocannabinolic acid, a major constituent of the cannabis plant, by aromatization using selenium dioxide mixed with trimethylsilyl polyphosphate as catalyst in chloroform. Purifn. was achieved by centrifugal partition chromatog., and the final product had a purity of over 96% by GC anal. Spectroscopic data on I such as 1H-NMR and IR, and molar extinction coeffs., as well as chromatog. data are presented as useful refs. for further research on I. The developed method allows prodn. of I on a preparative scale, making it available for further studies on its biol. activities as well as use as a ref. std. for anal. procedures.
- 19.Cox, R. A., Conquest, C., Mallaghan, C., and Maples, R. R. J. Hosp. Infect. 1995, 29, 87– 106[CrossRef], [PubMed], [CAS]19.https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A280%3ADyaK2M3nvFOmsw%253D%253D&md5=2137e3798d638c7180446531ddcaaa8eCox R A; Conquest C; Mallaghan C; Marples R RThe Journal of hospital infection (1995),An outbreak of methicillin-resistant Staphylococcus aureus (MRSA) infection caused by a novel phage-type (now designated EMRSA-16) occurred in three hospitals in East Northamptonshire over a 21-month period (April 1991--December 1992). Four hundred patients were colonized or infected. Seven patients died as a direct result of infection. Chest infections were significantly associated with the outbreak strain when compared with methicillin-sensitive S. aureus. Twenty-seven staff and two relatives who cared for patients were also colonized. A 'search and destroy' strategy, as advocated in the current UK guidelines for control of epidemic MRSA was implemented after detection of the first case. Despite extensive screening of staff and patients and isolation of colonized and infected patients, the outbreak strain spread to all wards of the three hospitals except paediatrics and maternity. A high incidence of throat colonization (51%) was observed. Failure to recognize the importance of this until late in the outbreak contributed to the delay in containing its spread. Key parts of the strategy which eventually contained the local outbreak were the establishment of isolation wards in two hospitals, treatment of all colonized patients and staff to eradicate carriage and screening of all patients upon discharge from wards where MRSA had ever been detected. EMRSA-16 spread to neighbouring hospitals by early 1992 and to London and the South of England by 1993. It is distinguished from other epidemic strains by its characteristic phage-type, antibiogram (susceptibility to tetracycline and resistance to ciprofloxacin), and in the pattern given on pulse field electrophoresis.
- 21.Razdan, R. K., Dalzell, H. C., and Handrick, G. R. J. Am. Chem. Soc. 1974, 96, 5860– 5865[ACS Full Text], [PubMed], [CAS]21.https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaE2cXlt1Sgur8%253D&md5=8a7a97cf169ecbdc0dfb72ed5c7e7bf3Razdan, Raj K.; Dalzell, Haldean C.; Handrick, G. RichardJournal of the American Chemical Society (1974),Optically pure (-)-Δ1-THC (I) was produced in 50% yield in a single step synthesis from cis/trans-(+)-p-mentha-2,8-dien-1-ol and olivetol in the presence of 1% boron trifluoride etherate and anhyd. MgSO4 in CH2Cl2 at 0°. The other major product formed was trans-Δ8-iso-THC [II, R = OH, R1 = (CH2)4Me]. By the same procedure (-)-cannabidiol [III, R = OH, R1 = (CH2)4Me] was obtained on a preparative scale when <0.5% boron trifluoride etherate or wet p-toluenesulfonic acid was used. Cannabidiols III [R = (CH2)4Me, R1 = OH; R = OH, R1 = (CH2)4Me] are the key intermediates in this reaction. Acid catalyzed reactions of p-mentha-2,8-dien-1-ol and olivetol gave the cannabinoids II [R = (CH2)4Me, R1 = OH], IV and V.
- 23.Appendino, G..Unpublished resultsThere is no corresponding record for this reference.
- 29.Vailancourt, V. and Albizati, K. F. J. Org. Chem. 1992, 57, 3627– 3631[ACS Full Text]There is no corresponding record for this reference.
