Killing Bacteria With Cannabis

[EDDIEKIRK]

Killing bacteria with cannabis







Pharmacists and chemists have found another use for the multipurpose cannabis as a source of antibacterial chemicals for multidrug resistant bacteria. Ironically, inhaling cannabis is known to damage the lung's ability to fend off invading pathogens, but the ingredients in cannabis, particularly the cannabinoids, have antiseptic properties. Although scattered research has been conducted since the 1950s, no comprehensive study existed that relates the structure of cannabinoids with antibacterial activity. Giovanni Appendino, Simon Gibbons, and coworkers attempted to remedy that problem by examining the activity of five common cannabinoids and their synthetic derivatives.





Five of the most common cannabinoids. All five cannabinoids (THC, CBD, CBG, CBC, and CBN) were potent against bacteria. Notably, they performed well against bacteria that were known to be multidrug resistant, like the strains of MRSA that plagued U.K. hospitals. CBD and CBG have the most potential for consumer use because they are nonpsychotropic.



Besides identifying antibacterial capability, the researchers wanted to figure out why these cannabinoids are so good at killing bacteria. They obviously are very effective at specifically targeting some vital process in the bacteria. Unfortunately, even after extensive work at modifying the cannabinoids and comparing their activities, that targeting mechanism remains a mystery. The scientists were able to figure out that the position of the n-pentyl chain (orange) relative to the terpenoid moiety (blue) serves to control lipid affinity.



These cannabinoids are promising enough to warrant rigorous clinical trials. They are applicable as topical antiseptics, biodegradable antibacterial compounds for cosmetics, and systematic antibacterial agents.



J. Nat. Prod., 2008. DOI: 10.1021/np8002673





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), ⁹-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 ⁹-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 structureactivity 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. ⁹-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 0.52 g/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.



Table 1. MIC (g/mL) Values of Cannabinoids and Their Analogues toward Various Drug-Resistant Strains of Staphylococcus aureus^a^b compoundSA-1199BRN-4220XU212ATCC25923EMRSA-15EMRSA-161a2222221b1110.51122212223a4244243b1111213f64^c64^c^c^c4a8484844b211120.5511111c61111117210.512c8323216161632106464641286464norfloxacin321410.5128erythromycin0.2564>1280.25>128>128tetracycline0.250.251280.250.1250.125oxacillin0.250.251280.12532>128 a Compounds 1cg, 3ce, 3g, and 9 exhibited MIC values of >128 g/mL for all organisms in which they were evaluated.



b Compound 11 exhibited MIC values of >256 g/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 structureactivity studies. Thus, acetylation and methylation of their phenolic hydroxyls (compounds 1ce and 3ce, respectively) were both detrimental for activity (MIC >100 g/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 64128 g/mL, and resorcinol (11) did not exhibit any activity even at 256 g/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.

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Citing Articles

7 citations to this article are listed below, sorted in reverse-chronological order. Citation data is made available by participants in CrossRef's Cited-by Linking service. For a more comprehensive list of citations to this article, users are encouraged to perform a search in SciFinder.





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[offdababa]

Far out bro, Ive been using bacteria to make cannabis. :th_emoticons_adu:

[Guest]

Far out bro, Ive been using bacteria to make cannabis. :th_emoticons_adu:

I was thinking the same thing! ;P

[Kitten]

I hope there is not going to be a test.....I read this stuff but most of it floats just above my head....Love it though. [img]/emoticons/yahooimages_egyptian.gif[/img]