Comparative topical anti-inflammatory activity of cannabinoids and cannabivarins

Article abstract of DOI:10.1016/j.fitote.2010.04.009

A selection of seven phytocannabinoids representative of the major structural types of classic cannabinoids and their corresponding cannabivarins was investigated for in vivo topical anti-inflammatory activity in the Croton oil mouse ear dermatitis assay. Differences in the terpenoid moiety were far more important for anti-inflammatory activity than those at the C-3 alkyl residue, suggesting the involvement not only of cannabinoid receptors, but also of other inflammatory end-points targeted by phytocannabinoids.

Full text of DOI:10.1016/j.fitote.2010.04.009

Fitoterapia 81 (2010) 816–819
Contents lists available at ScienceDirect
Fitoterapia
journal homepage: www.elsevier.com/locate/fitote
Comparative topical anti-inflammatory activity of cannabinoids
and cannabivarins
a
a
b
c
Aurelia Tubaro a, , Anna Giangaspero , Silvio Sosa , Roberto Negri , Gianpaolo Grassi ,
⁎
Salvatore Casano c, Roberto Della Loggia a, Giovanni Appendino b
Dipartimento dei Materiali e delle Risorse Naturali, Università di Trieste, Via A. Valerio 6, 34127 Trieste, Italy
Dipartimento di Scienze Chimiche, Alimentari, Farmaceutiche e Farmacologiche, Università del Piemonte Orientale, Via Bovio 6, 28100 Novara, Italy
CRA-CIN, Sede distaccata di Rovigo, Viale G. Amendola 82, 45100 Rovigo, Italy
a
b
c
a r t i c l e i n f o
a b s t r a c t
Article history:
A selection of seven phytocannabinoids representative of the major structural types of classic
cannabinoids and their corresponding cannabivarins was investigated for in vivo topical anti-
inflammatory activity in the Croton oil mouse ear dermatitis assay. Differences in the terpenoid
moiety were far more important for anti-inflammatory activity than those at the C-3 alkyl
residue, suggesting the involvement not only of cannabinoid receptors, but also of other
inflammatory end-points targeted by phytocannabinoids.
Received 24 March 2010
Received in revised form 23 April 2010
Accepted 27 April 2010
Available online 5 May 2010
Keywords:
© 2010 Elsevier B.V. All rights reserved.
Cannabis sativa L.
Phytocannabinoids
Anti-inflammatory activity
Croton oil assay
Cannabinoids
Cannabivarins
1. Introduction
as cannabivarins, at the expense of classic C5-phytocannabi-
noids [1]. The alkyl residue is a critical element of the
Phytocannabinoids are meroterpenoids biogenetically
derived from the prenylation of a 3-alkylresorcinyl derivative
[1]. They are typical constituents of hemp (Cannabis sativa L.,
Cannabinaceae), and no other natural source is known,
although cannabinoid-like moieties have been found in
some prenylated aromatics [2]. In classic phytocannabinoids,
the resorcinyl alkyl residue is a n-pentyl group, but these
compounds are commonly accompanied by trace amounts of
lower homologues with a shorter, n-propyl side chain,
derived from the prenylation of a pentaketide (divarinic
acid) rather than a hexaketide precursor (olivetolic acid) [1].
Because of a mutation in polyketide synthesis, some strains of
hemp accumulate this type of C3-phytocannabinoids, known
phytocannabinoid pharmacophore [3], and important differ-
ences between the biological profiles of cannabinoids and
cannabivarins have, in fact, been reported. Thus, while Δ9-
tetraidrocannabinol (Δ9-THC; 1a) is the archetypal agonist of
cannabinoid receptors CB1 and CB2, its lower homologue Δ9-
tetrahydrocannabivarin (Δ9-THCV; 1b) behaves as a “neutral”
antagonist toward CB1 and as an agonist for CB2 [4,5]. These
observations, and the growing interest for the medicinal
properties of minor phytocannabinoids [3], provided a
rationale for undertaking a comparative study on the
biological profile of cannabinoids and cannabivarins.
Within the many facets of the phytocannabinoid pre-
clinical potential, the topical anti-inflammatory activity is one
of the best documented [6], but differences in end-points and
experimental protocols make it difficult to assess the relative
potency of the compounds investigated. The Croton oil mice
ear assay [7] is an in vivo anti-inflammatory test, capable to
discriminate between the profiles of various agents. It can
⁎
Corresponding author. Dipartimento dei Materiali e delle Risorse
Naturali, Università di Trieste, Via A. Valerio 6, 34127 Trieste, Italy.
Tel.: +39 40 558 7910; fax: +39 40 5583215.
E-mail address: tubaro@units.it (A. Tubaro).
0367-326X/$ – see front matter © 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.fitote.2010.04.009

A. Tubaro et al. / Fitoterapia 81 (2010) 816–819
817
rank them in comparison with various non-steroidal anti-
inflammatory drugs (NSAIDs) as well as corticosteroids, and
was therefore selected for this study, comparing the anti-
inflammatory activity of the three archetypal anti-inflamma-
tory cannabinoids [Δ9-THC (1a), CBD (2a) and CBC (3a)] with
that of their corresponding cannabivarins.
was fractionated by gravity column chromatography on silica
gel (200 g), using a petroleum ether-acetone gradient, from
98:2 to 90:10. Fractions 8–22 afforded 3.6 g (0.89%) CDB (2a)
as a white powder, while fractions 24–37 gave a mixture of 2b
and 3b (2.1 g). These compounds were further separated on
neutral alumina (50 g), using a petroleum ether-EtOAc
gradient (from 95:5 to 70:30). Fractions 6–14 yielded 1.74 g
(0.43%) CBDV (2b), and fractions 35–54 160 mg (0.04%) CBCV
(3b), identified by comparison of their spectroscopic data
with those reported in the literature [8,9].
2.4. Synthesis of Δ8-THCV (4b) from CBDV (2b)
A solution of CBDV (2b, 200 mg, 0.70 mmol) and p-
toluensulfonic acid (13 mg, 0.075 mmol) was refluxed for 2 h.
After cooling, the reaction was worked up by dilution with
EtOAc and washing with sat. NaHCO3. The organic phase was
washed with brine, dried (Na2SO4), and evaporated, affording
a brownish oil. This was purified by gravity column
chromatography on silica gel (7 g), using petroleum ether-
EtOAc 9:1 as eluant, affording 192 mg (96%) Δ8-THCV (4b) as
an orange powder, identified by comparison with the
spectroscopic data reported in the literature [4].
2. Experimental
2.1. General
Silica gel 60 (70–230 mesh) was 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. Croton oil and indomethacin were purchased
from Sigma–Aldrich (Milan, Italy). Ketamine hydrochloride
(Inoketam 100) was purchased from Virbac s.r.l. (Milan,
Italy). The other chemicals of analytical grade were purchased
from Carlo Erba (Milan, Italy). Male CD-1 mice weighing 28–
32 g were supplied by Harlan Laboratories (San Pietro al
Natisone, Italy).
2.5. Anti-inflammatory activity
Topical inflammation was induced on the right ear
(surface: about 1 cm2) of anaesthetised mice (145 mg/kg
ketamine hydrochloride, intraperitoneally) applying 80 µg of
Croton oil dissolved in 15 µl acetone. The left ear remain
untreated. Control animals received only the irritant solution,
whereas other animals received both the irritant and the
tested substances [7]. After 6 h, at the maximum oedema
formation in control mice, animals were sacrificed and a
punch (6 mm Ø) was taken from both the treated and the
untreated ears to evaluate the oedematous response. Oedema
was quantified by the difference in weight between the
punches taken from the treated and the controlateral ears.
The anti-inflammatory activity was expressed as percent
inhibition of the oedematous response in animals treated
with the test substances in comparison to that of control mice
[7]. Ten animals were used for each group of treatment. All
animal experiments complied with the Italian D.L. n. 116 of 27
January 1992 and associated guidelines in the European
Communities Council Directive of 24 November 1986 (86/609
ECC).
2.2. Plant material
A single non-psychotropic cannabivarin plant was identi-
fied in a landrace from Sicily (Italy) during a large screening
of germplasm. Selection and self pollination of this plant
made it possible to develop inbred lines S1 with different
contents of cannabivarins, estimated from approximately 5%
to 53% of the content of the respective pentyl cannabinoids by
GC analysis. Plants were cultivated in a greenhouse at CRA-
CIN, Rovigo (Italy). The seedlings were kept under artificial
light for 18 h photoperiod for the first 5 weeks, and flowering
was next induced by reducing the photoperiod to 12 h of light
until plants were harvested (9 weeks old). Plants were
judged mature when the inflorescences showed the brown
mature stigma, and were then harvested at the end of the
flowering and seed formation stage. A voucher specimen is
available from SC (ecobise@gmail.com).
2.6. Statistical analysis
Pharmacological data were analyzed by one-way analysis
of variance, followed by the Dunnett's test for multiple
comparisons of unpaired data, and a probability level lower
than 0.05 was considered as significant. The dose giving 50%
inhibition of the oedematous response (ID50) was calculated
by linear regression analysis of the dose–response curves,
using the Pharmacologic Calculation System software [10].
2.3. Isolation of CBDV (2b) and CBCV (3b)
Dried plant material (inflorescences, 404 g) was pow-
dered and then heated in a ventilated oven at 120 °C for 4 h to
decarboxylate pre-cannabinoids to cannabinoids. After cool-
ing to room temperature, the plant material was extracted
with acetone (2×2 L) at room temperature, yielding 15 g of a
dark-black oil, that was dissolved in methanol and filtered
through a short column of RP-silica gel (ca. 50 g) to remove
waxes and pigments. The resulting purified extract (70 g)
3. Results and discussion
Capitalizing on the availability of a variety of Cannabis rich
in cannabivarins, CBDV (2b) [8] and CBCV (3b) [9] were

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A. Tubaro et al. / Fitoterapia 81 (2010) 816–819
obtained by isolation. Starting from CBDV (2b), we next
attempted to synthesize Δ9-THCV (1b), but, despite consid-
erable experimentation, only its more stable Δ8-isomer (Δ8-
THCV, 4b) [11] could be obtained, even under conditions that
are reported to produce, in a regiospecific way, Δ9-THC (1a)
from CBD (2a) [12]. Δ8-THC was therefore enclosed in the
reference group of classic cannabinoids to act as a tetrahy-
drocannabinol reference. Δ8-THC (4a) and Δ9-THC (1a) show
similar agonistic affinity for cannabinoid receptors (CBs) [3],
as do, in antagonistic way, Δ8-THCV (4b) and Δ9-THCV (1b)
for CB1 [4], suggesting that the biological profile of the two
regio-isomers is very similar.
The anti-inflammatory activity of cannabinoids has long
been known, and has been shown to involve mechanism(s)
that go beyond the activation of CB [5–13]. Thus, Δ9-THC (1a),
the major psychotropic constituent of marijuana and the
archetypal CBs ligand, shows an impressive anti-inflammatory
activity, outperforming aspirin and hydrocortisone in the
carrageenan-induced paw oedema model in rats [14], and
being also active topically in the tetradecanoyl phorbol-acetate
(TPA)-induced mice ear erythema assay [15]. On the other
hand, also non-psychotropic cannabinoids like cannabidiol
(CBD, 2a) [16] and cannabichromene (CBC, 3a) [17,18] show
outstanding potency in in vivo assays of inhibition of inflam-
matory responses, despite their negligible activity as activators
of CBs [3]. The excellent activity of CBD against a series of
molecular targets of relevance for inflammation, like vanilloid
receptor TRPV1, cycloxigenase-2 and inducible nitric oxide
synthase, and its increasing activity on adenosine signalling
might underlie these observations [12,19,20], whose clinical
potential was supported by the activity of CBD in a rodent
model of osteo-arthrosis [21]. To assess the relative anti-
inflammatory potency of cannabinoids and cannabivarins, their
anti-oedematous activity was evaluated at the dose range of
0.1–1 µmol/cm2, and compared to that of the non-steroidal
anti-inflammatory drug (NSAID) indomethacin. The psychoac-
tive compounds Δ9-tetraidrocannabinol (Δ9-THC, 1a), Δ8-
tetraidrocannabinol (Δ8-THC, 4a) as well as the cannabinoid
antagonist Δ8-tetraidrocannabivarin (Δ8-THCV, 4b) exerted a
significant dose-dependent oedema inhibition, which ranged
from about 20% (0.1 µmol/cm2) to about 70% (1 µmol/cm2)
(Fig. 1). The non-psychoactive cannabinoid cannabichromene
Fig. 2. Dose-dependent anti-inflammatory activity of CBC, CBCV, CBD, CBDV
and indomethacin (*pb0.05 at the analysis of variance, as compared to
controls).
(CBC, 3a), cannabidiol (CBD, 2a), and their lower homologues
CBCV (3b) and CBDV (2b) showed a lower potency (Fig. 2),
withoedemareduction atthe highesttested dose(1 µmol/cm2)
being only 40% for CBC (3a) and CBCV (3b), 36% for CBD (2a)
and 29% for CBDV (2b), respectively. The NSAID indomethacin
could affect a significant oedema reduction, ranging from 22%
to 86%, depending on the tested doses (0.1–1 µmol/cm2)
(Figs. 1, 2).
To better compare the anti-inflammatory potency of the
tested compounds, the dose capable to inhibit the oedematous
response by 50% (ID50) was evaluated for each compound. Δ9-
THC (1a) and its analogues Δ8-THC (4a) and Δ8-THCV (4b)
showed comparable ID50 values, in the range of 0.46–
0.55 µmol/cm2, and were only about two fold less potent than
the reference drug indomethacin (ID50 =0.25 µmol/cm2).
Conversely, the ID50 of the non-psychoactive cannabinoid
CBD (2a) and CBC (3a) and of their lower homologues CBDV
(2b) and CBCV (3b) was higher than 2 µmol/cm2, much less
active than indomethacin (Table 1).
These results suggest that the tricyclic tetrahydrocannabi-
nol motif necessary for binding to cannabinoid receptors, either
in an agonistic or an antagonistic way [4,5], is important also for
the topical anti-inflammatory activity of phytocannabinoids,
since the lack of this feature was detrimental for activity. The
contribution of cannabinoid receptors to the outcome of
the assay is, however, difficult to assess, owing not only to
the complex receptor profile of tetrahydrocannabivarins, but
also to the possible involvement of TRPA1, another target of
Table 1
Anti-inflammatory potency of cannabinoids (ID50 values).
Substance
ID50
(µmol/cm2)
Δ9-THC
Δ8-THCV
Δ8-THC
CBC
0.46
0.41
0.55
n.e.
CBCV
CBD
CBDV
2.38
2.42
n.e.
Fig. 1. Dose-dependent anti-inflammatory activity of Δ8-THCV, Δ8-THC, Δ9-
THC and indomethacin (*pb0.05 at the analysis of variance, as compared to
controls).
Indomethacin
0.25
n.e.: not evaluable by the Pharmacologic Calculation System software [9].

A. Tubaro et al. / Fitoterapia 81 (2010) 816–819
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highest potency being consistently associated to compounds
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