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Antibacterial Cannabinoids from Cannabis sativa: A Structure-Activity Study

Authors:
  • University of Eastern Piedmont, Novara (IT)

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), Delta (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.
Antibacterial Cannabinoids from Cannabis satiWa: A Structure-Activity Study
Giovanni Appendino,*
,†,‡
Simon Gibbons,*
,
Anna Giana,
†,‡
Alberto Pagani,
†,‡
Gianpaolo Grassi,
§
Michael Stavri,
Eileen Smith,
and M. Mukhlesur Rahman
Dipartimento di Scienze Chimiche, Alimentari, Farmaceutiche e Farmacologiche, UniVersita` 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
ReceiVed May 1, 2008
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
satiVaL. Cannabinaceae) with an increase in opportunistic infec-
tions,
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.
satiVawith 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 antituber-
cular 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 investiga-
tions 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 con-
stituents of C. satiVaas antibacterial agents, suggest that cannab-
inoids and their precursors are the most likely antibacterial agents
present in C. satiVapreparations.
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. satiVaas 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. satiVaa 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 microbio-
cidal 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 unreason-
able 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
* To whom correspondence should be addressed. Tel: +39 0321
373744 (G.A.); +44 207 753 5913 (S.G.). Fax: +39 0321 375621 (G.A.);
+44 207 753 5909 (S.G.). E-mail: appendino@pharm.unipmn.it (G.A.);
simon.gibbons@pharmacy.ac.uk (S.G.).
Universita` del Piemonte Orientale.
Consorzio per lo Studio dei Metaboliti Secondari.
University of London.
§
Centro Ricerca Colture Industriali.
J. Nat. Prod. 2008, 71, 1427–1430 1427
10.1021/np8002673 CCC: $40.75 2008 American Chemical Society and American Society of Pharmacognosy
Published on Web 08/06/2008
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 tet-
racycline-resistant line overexpressing the TetK efflux pump
(XU212),
16
and a standard laboratory strain (ATCC25923) com-
pleted the bacterial panel.
9-Tetrahydrocannabinol (THC, 4b), cannabidiol (CBD, 1b),
cannabigerol (CBG, 3b), cannabichromene (CBC, 2), and cannab-
inol (CBN, 5) are the five most common cannabinoids.
17
They could
be obtained in high purity (>98%) by isolation from strains of C.
satiVaproducing 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 sub-
strates for the most common resistance mechanisms to current
antibacterial agents, making them attractive antibacterial leads.
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-eand 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 monophe-
nols 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 modi-
fication 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. satiVastrains producing high
concentrations of nonpsychotropic cannabinoids, this plant repre-
sents 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
1428 Journal of Natural Products,2008, Vol. 71, No. 8 Appendino et al.
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% H2SO4in ethanol
and heating. Organic phases were dried with Na2SO4before evaporation.
All known cannabinoids were identified according to their physical and
spectroscopic data.
28
Semisynthetic cannabinoids 1c-f, and 3c-fwere
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 satiVaused 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 °Cfor2hinaventilated 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 chroma-
tography 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). CBG (2) was synthesized from
olivetol,
6
and CBN was prepared from THC (6) by aromatization with
sulfur.
18
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)δ12.08 (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)δ172.1 (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].
Table 1. MIC (µg/mL) Values of Cannabinoids and Their Analogues toward Various Drug-Resistant Strains of Staphylococcus
aureus
a,b
compound SA-1199B RN-4220 XU212 ATCC25923 EMRSA-15 EMRSA-16
1a 222 2 2 2
1b 1 1 1 0.5 1 1
2221 2 2 2
3a 424 4 2 4
3b 111 1 2 1
3f 64
c
64
cc c
4a 848 4 8 4
4b 2 1 1 1 2 0.5
5111 1 1 c
6111 1 1 1
72 1 0.5 1 2 c
832 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 9exhibited 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.
Antibacterial Cannabinoids from Cannabis satiVa Journal of Natural Products,2008, Vol. 71, No. 8 1429
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)δ12.13 (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)δ172.2 (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 ×105cfu 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 µLofMHB
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.
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NP8002673
1430 Journal of Natural Products,2008, Vol. 71, No. 8 Appendino et al.
... Recent studies have observed CBD's antibacterial activity against several clinically relevant pathogens including Staphylococcus aureus, Streptococcus pneumoniae, Clostridium difficile, Neisseria spp., Moraxella catarrhalis, Legionella pneumophila, and Salmonella spp. [13][14][15][16][17]. With the increased prevalence and occurrence of antimicrobial resistance posing a significant threat to public health, the development of novel antibacterial agents is a necessity [18][19][20][21]. ...
... While CBD has been utilized in several applications over the last several years, the antibacterial potential of CBD has been of growing interest [13][14][15][16]24,25]. Several studies have outlined the efficacy of CBD against several clinically relevant bacterial strains [13-15,24], however, there remains questions of the mechanisms of antibacterial activity and the potential application methods of CBD. ...
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New generation antibiotics are needed to combat the development of resistance to anti-microbials. One of the most promising new classes of antibiotics is cannabidiol (CBD). It is a non-toxic and low-resistance chemical that can be used to treat bacterial infections. The antibacterial activity of Cannabis sativa L. byproducts, specifically CBD, has been of growing interest in the field of novel therapeutics. As research continues to define and characterize the antibacterial activity that CBD possesses against a wide variety of bacterial species it is important to examine potential interaction between CBD and common therapeutics such as broad-spectrum antibiotics. Here, we show that CBD-antibiotic co-therapy can effectively fight S. typhimurium via membrane integrity disruption. This research serves to examine the potential synergy between CBD and three broad-spectrum antibiotics for potential antibiotic-CBD co-therapy. In this study, we reveal that Salmonella typhimurium (S. typhimurium) growth is inhibited at very low dosages of CBD-antibiotic. This interesting finding demonstrates that CBD and CBD-antibiotic co-therapies are viable novel alternatives to combating Salmonella typhimurium.
... The molecular mechanisms behind the antibacterial activity of cannabinoids have yet to be fully elucidated. Studies by Appendino et al. (2008) examined the effects of structural modification on the bactericidal activity of five major cannabinoids (CBD, CBC, CGB, THC, and CBN). All five cannabinoids demonstrated potent activity against a variety of MRSA strains, with MIC values between 0.5 and 2 µg/mL. ...
... Whereas antibacterial activity was tolerant to the nature of the prenyl moiety, its relative position compared to the n-pentyl moiety (abnormal cannabinoids), and the carboxylation of the resorcinol moiety (pre-cannabinoids). The authors rationalised that these results demonstrated tolerance to the structural modification of the terpenoid moiety, suggesting that these residues serve mainly as modulators of lipid affinity, while the addition of further prenyl moiety may result in poorer aqueous solubility, leading to a loss of antibacterial activity [45]. ...
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Antibiotics are used as the first line of treatment for bacterial infections. However, antibiotic resistance poses a significant threat to the future of antibiotics, resulting in increased medical costs, hospital stays, and mortality. New resistance mechanisms are emerging and spreading globally, impeding the success of antibiotics in treating common infectious diseases. Recently, phytocannabinoids have been shown to possess antimicrobial activity on both Gram-negative and Gram-positive bacteria. The therapeutic use of phytocannabinoids presents a unique mechanism of action to overcome existing antibiotic resistance. Future research must be carried out on phytocannabinoids as potential therapeutic agents used as novel treatments against resistant strains of microbes.
... Among these compounds, CBD seems to be the most effective from a pharmaceutical point of view, although CBG and CBC, which are present in female hemp flowers, have remarkable antibacterial activity [53]. Appendino et al. [54] investigated the efficacy of five major cannabinoids (CBD, CBC, CBG, THC, and CBN) against six methicillin-resistant S. aureus (MRSA) strains of current clinical relevance and all showed MIC values in the range of 0.5-2 µg mL −1 . The lowest MIC value against S. aureus was exhibited by extract run 6, which corresponds to a CBD content of 0.7 µg mL −1 . ...
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Natural products are increasingly in demand in dermatology and cosmetology. In the present study, highly valuable supercritical CO2 (sCO2) extracts rich in bioactive compounds with antiradical and antibacterial activity were obtained from the inflorescences of industrial hemp. Volatile compounds were analyzed by gas chromatography in tandem with mass spectrometry (GC-MS), while cannabinoids were determined by high performance liquid chromatography (HPLC-DAD). Extraction yields varied from 0.75 to 8.83%, depending on the pressure and temperature applied. The extract obtained at 320 bar and 40 °C with the highest content (305.8 µg mg−1) of cannabidiolic acid (CBDA) showed the best antiradical properties. All tested extract concentrations from 10.42 µg mL−1 to 66.03 µg mL−1 possessed inhibitory activities against E. coli, P. aeruginosa, B. subtilis, and S. aureus. The sCO2 extract with the highest content of cannabidiol (CBD) and rich in α-pinene, β-pinene, β-myrcene, and limonene was the most effective. The optimal conditions for sCO2 extraction of cannabinoids and volatile terpenes from industrial hemp were determined. The temperature of 60 °C proved to be optimal for all responses studied, while the pressure showed a different effect depending on the compounds targeted. A low pressure of 131.2 bar was optimal for the extraction of monoterpenes, while extracts rich in sesquiterpenes were obtained at 319.7 bar. A high pressure of 284.78 bar was optimal for the extraction of CBD.
... The minimum inhibitory concentration (MIC) was evaluated on the basis of Clinical Laboratory Standards Institute (CLSI) guidelines by the conventional two-fold microbroth gradient dilution assay [33,34]. S. aureus ATCC 25904 was inoculated to the Brain Heart Infusion (BHI) agar plates and cultured for 18~24 h at 35 • C for activation. ...
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Despite the rapid advances in drug R&D, there is still a huge need for antibacterial medications, specifically for the methicillin-resistant Staphylococcus aureus (MRSA). Inspired by the research where a viable class of MRSA inhibitors was found in the species Platanus occidentalis, a S. aureus inhibition screening-guided phytochemical reinvestigation on Platanus × acerifolia (London plane tree) leaves were performed with four flavonoid glycosides garnered, including two new compounds, quercetin-3-O-α-l-(2″-E-p-coumaroyl-3″-Z-p-coumaroyl)-rhamnopyranoside (E,Z-3′-hydroxyplatanoside, 1) and quercetin-3-O-α-l-(2″-Z-p-coumaroyl-3″-E-p-coumaroyl)-rhamnopyranoside (Z,E-3′-hydroxyplatanoside, 2). All of the isolates showed significant S. aureus ATCC 25904 inhibitory activity with MICs ranging from 4 to 64 μg/mL, suggesting the potential of discovering drug leads for the control of S. aureus from such a rich, urban landscaping plant in the Platanus genus.
Chapter
With global warming and the economic crisis threatening agricultural production in the Mediterranean basin, there are new challenges and opportunities for renewing plant material. Industrial hemp (Cannabis sativa L.) has great potential as a multifunctional crop for many different environments. Although hemp is a controlled and multifaceted crop, today, its production is amply undergoing resurgence. The European Union directives restricted its expansion; however, with the renewal in hemp interest and an increase in its cultivation, the hemp industry in Europe has increased in recent decades. This review addresses hemp as a sustainable high-yielding crop that is well adapted to most European conditions, with suitable environmental and agronomic benefits. Specifically, this multiuse crop is able to supply raw material to a large number of traditional and innovative industrial applications, which will be enhanced if the market shows a continuous increasing demand for it. That is, hemp cultivation is perceived as a promising option in terms of crop diversification; particularly in the Mediterranean semiarid region, its implementation remains limited, which reduces the progress of hemp value chains at a larger scale. We concluded that although more knowledge is needed regarding the agronomic practices for cultivating hemp, there is a large amount of evidence that in the coming years, the global market of products made from hemp could be significantly augmented. Thus, hemp can rebuild its reputation with huge opportunities as a promising raw material and a leading crop for sustainable agriculture.
Chapter
Hemp is a crop that has been used since ancient times for its medicinal and textile applications, which is experiencing a resurgence today. This growing interest is due to the fact that hemp is a crop with multipurpose applications: a source of cellulosic and woody fibers, produces oil-rich seeds, is a raw material for phytochemicals and is driven by consumer demand for more natural and sustainable products. Residues recovered during the harvesting and processing of hemp fibers and/or seeds can be utilized to obtain an essential oil rich in phytochemicals with multiple applications. We review the recent progress and developments in hemp essential oil as a complex mixture of bioactive compounds with antiinflammatory, antibacterial, insecticidal and therapeutic properties, and whose exploitation can add value to hemp cultivation. Essential oils are widely used globally, and their use is constantly increasing. This could boost the utilization and market value of hemp essential oil.
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Cannabis preparations are gaining popularity among patients with various skin diseases. Due to the lack of scientific evidence, dermatologists remain cautious about their prescriptions. So far, only a few studies have been published about the effects of high-potency cannabis extracts on microorganisms (especially dermatophytes) causing skin problems that affect more than 25% of the worldwide population. Even though, the high-potency cannabis extracts prepared by cold extraction are mostly composed of non-psychoactive tetrahydrocannabinolic acid (THCA) and only low amount of THC, their use in topical treatment can be stigmatized. The in vitro antimicrobial and antifungal activity of two high potent cannabis strains extracted by three solvents traditionally or currently used by cannabis users (ethanol; EtOH, butane; BUT, dimethyl ether; DME) was investigated by broth dilution method. The chemical profile of cannabis was determined by high-performance liquid chromatography with ultraviolet detection and gas chromatography with mass spectrometer and flame ionization detector. The extraction methods significantly influenced chemical profile of extracts. The yield of EtOH extracts contained less cannabinoids and terpenes compared to BUT and DME ones. Most of the extracts was predominantly (>60%) composed of various cannabinoids, especially THCA. All of them demonstrated activity against 18 of the 19 microorganisms tested. The minimal inhibitory concentrations (MICs) of the extracts ranged from 4 to 256 μg/mL. In general, the bacteria were more susceptible to the extracts than dermatophytes. Due to the lower content of biologically active substances, the EtOH extracts were less effective against microorganisms. Cannabis extracts may be of value to treat dermatophytosis and other skin diseases caused by various microorganisms. Therefore, they could serve as an alternative or supportive treatment to commonly used antibiotics.
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This study was designed to check the potential of secondary metabolites of the selected plants; Citrullus colocynthis, Solanum nigrum, Solanum surattense, Calotropis procera, Agave americana, and Anagallis arvensis for antioxidant, antibacterial, antifungal, and antidiabetic agents. Plant material was soaked in ethanol/methanol to get the crude extract, which was further partitioned via solvent extraction technique. GCMS and FTIR analytical techniques were applied to check the compounds responsible for causing antioxidant, antimicrobial, and antidiabetic activities. It was concluded that about 80% of studied extracts/fractions were active against α-amylase, ranging from 43 to 96%. The highest activity (96.63%) was exhibited by butanol fractions of A. arvensis while the least response (43.65%) was shown by the aqueous fraction of C. colocynthis and the methanol fraction of fruit of S. surattense. The highest antioxidant activity was shown by the ethyl acetate fraction of Anagallis arvensis (78.1%), while aqueous as well as n-hexane fractions are the least active throughout the assay. Results showed that all tested plants can be an excellent source of natural products with potential antimicrobial, antioxidant, and antidiabetic potential. The biological response of these species is depicted as a good therapeutic agent, and, in the future, it can be encapsulated for drug discovery.
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Chromatographic and spectroscopic data was determined for 16 different major cannabinoids from Cannabis sativa plant material as well as 2 human metabolites of Δ‐tetrahydrocannabinol. Spectroscopic analysis included UV absorbance, infrared‐spectral analysis, (GC‐) mass spectrometry, and spectrophotometric analysis. Also, the fluorescent properties of the cannabinoids are presented. Most of this data is available from literature but scattered over a large amount of scientific papers. In this case, analyses were carried out under standardised conditions for each tested cannabinoid so spectroscopic data can be directly compared. Different methods for the analysis of cannabis preparations were used and are discussed for their usefulness in the identification and determination of separate cannabinoids. Data on the retention of the cannabinoids in HPLC, GC, and TLC are presented.
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The syntheses of (-)-cannabidiol and (-)-cannabidiol dimethyl ether were accomplished via fragmentation of an appropriately substituted 9-bromocamphor derivative. A new method of alpha-arylation of 3,9-dibromocamphor was shown to provide a variety of alpha-arylated camphor derivatives in good yields.
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