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Decarboxylation Study of Acidic Cannabinoids: A Novel Approach Using Ultra-High-Performance Supercritical Fluid Chromatography/Photodiode Array-Mass Spectrometry

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Introduction: Decarboxylation is an important step for efficient production of the major active components in cannabis, for example, Δ⁹-tetrahydrocannabinol (Δ⁹-THC), cannabidiol (CBD), and cannabigerol (CBG). These cannabinoids do not occur in significant concentrations in cannabis but can be formed by decarboxylation of their corresponding acids, the predominant cannabinoids in the plant. Study of the kinetics of decarboxylation is of importance for phytocannabinoid isolation and dosage formulation for medical use. Efficient analytical methods are essential for simultaneous detection of both neutral and acidic cannabinoids. Methods:C. sativa extracts were used for the studies. Decarboxylation conditions were examined at 80°C, 95°C, 110°C, 130°C, and 145°C for different times up to 60 min in a vacuum oven. An ultra-high performance supercritical fluid chromatography/photodiode array-mass spectrometry (UHPSFC/PDA-MS) method was used for the analysis of acidic and neutral cannabinoids before and after decarboxylation. Results: Decarboxylation at different temperatures displayed an exponential relationship between concentration and time indicating a first-order or pseudo-first-order reaction. The rate constants for Δ⁹-tetrahydrocannabinolic acid-A (THCA-A) were twice those of the cannabidiolic acid (CBDA) and cannabigerolic acid (CBGA). Decarboxylation of THCA-A was forthright with no side reactions or by-products. Decarboxylation of CBDA and CBGA was not as straightforward due to the unexplained loss of reactants or products. Conclusion: The reported UHPSFC/PDA-MS method provided consistent and sensitive analysis of phytocannabinoids and their decarboxylation products and degradants. The rate of change of acidic cannabinoid concentrations over time allowed for determination of rate constants. Variations of rate constants with temperature yielded values for reaction energy.
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ORIGINAL RESEARCH Open Access
Decarboxylation Study of Acidic Cannabinoids:
A Novel Approach Using Ultra-High-Performance
Supercritical Fluid Chromatography/Photodiode
Array-Mass Spectrometry
Mei Wang,
1
Yan-Hong Wang,
1
Bharathi Avula,
1
Mohamed M. Radwan,
1
Amira S. Wanas,
1
John van Antwerp,
2
Jon F. Parcher,
1
Mahmoud A. ElSohly,
1,3
and Ikhlas A. Khan
1,4,
*
Abstract
Introduction: Decarboxylation is an important step for efficient production of the major active components in
cannabis, for example, D
9
-tetrahydrocannabinol (D
9
-THC), cannabidiol (CBD), and cannabigerol (CBG). These can-
nabinoids do not occur in significant concentrations in cannabis but can be formed by decarboxylation of their
corresponding acids, the predominant cannabinoids in the plant. Study of the kinetics of decarboxylation is of
importance for phytocannabinoid isolation and dosage formulation for medical use. Efficient analytical methods
are essential for simultaneous detection of both neutral and acidic cannabinoids.
Methods: C. sativa extracts were used for the studies. Decarboxylation conditions were examined at 80C, 95C,
110C, 130C, and 145C for different times up to 60 min in a vacuum oven. An ultra-high performance super-
critical fluid chromatography/photodiode array-mass spectrometry (UHPSFC/PDA-MS) method was used for the
analysis of acidic and neutral cannabinoids before and after decarboxylation.
Results: Decarboxylation at different temperatures displayed an exponential relationship between concentration
and time indicating a first-order or pseudo-first-order reaction. The rate constants for D
9
-tetrahydrocannabinolic
acid-A (THCA-A) were twice those of the cannabidiolic acid (CBDA) and cannabigerolic acid (CBGA). Decarbox-
ylation of THCA-A was forthright with no side reactions or by-products. Decarboxylation of CBDA and CBGA was
not as straightforward due to the unexplained loss of reactants or products.
Conclusion: The reported UHPSFC/PDA-MS method provided consistent and sensitive analysis of phytocanna-
binoids and their decarboxylation products and degradants. The rate of change of acidic cannabinoid concen-
trations over time allowed for determination of rate constants. Variations of rate constants with temperature
yielded values for reaction energy.
Keywords: cannabinoids; Cannabis sativa; decarboxylation; kinetic analysis; UHPSFC/PDA-MS
Introduction
The plant Cannabis sativa, in the form of crude drugs,
marijuana, hashish, or hash oil, is the most widely con-
sumed and popular recreational/medicinal botanical
drug product in the world.
1
The legal status of cannabis
varies significantly from state to state within the United
States and also from country to country. As a result of
the rampant use and confounding legal issues, there
1
National Center for Natural Products Research, School of Pharmacy, University of Mississippi, University, Mississippi.
2
Waters Corporation, Milford, Massachusetts.
3
Department of Pharmaceutics and Drug Delivery, School of Pharmacy, University of Mississippi, University, Mississippi.
4
Division of Pharmacognosy, Department of BioMolecular Science, School of Pharmacy, University of Mississippi, University, Mississippi.
*Address correspondence to: Ikhlas A. Khan, PhD, National Center for Natural Products Research, University of Mississippi, University, MS 38677, E-mail: ikhan@olemiss.edu
ªMei Wang et al. 2016; Published by Mary Ann Liebert, Inc. This Open Access article is distributed under the terms of the Creative Commons
License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the
original work is properly credited.
Cannabis and Cannabinoid Research
Volume 1.1, 2016
DOI: 10.1089/can.2016.0020
Cannabis and
Cannabinoid Research
262
has been a significant case load increase seen in forensic
laboratories. Therefore, cannabis is now one of the
most thoroughly studied and analyzed plant materials.
More than 100 cannabinoids have been isolated and
identified in cannabis
2
along with the primary psychoac-
tive component, D
9
-tetrahydrocannabinol (D
9
-THC). In
addition to D
9
-THC, there are other components of
cannabis that have been shown to be medically benefi-
cial. For example, cannabidiol (CBD) and cannabigerol
(CBG) can moderate or influence the psychoactive ef-
fects of D
9
-THC.
3,4
Studies of cannabis have also inves-
tigated the potential benefits of phytocannabinoids as
anticancer, antiemetic, sedative, and palliative agents
for several other disease states and symptoms.
3,5
Efficient production of D
9
-THC, CBD, and CBG from
cannabisisimportantforthedevelopmentofdosagefor-
mulations to facilitate the successful medical use of canna-
bis. These neutral cannabinoids do not occur at significant
concentrations in the plants. Cannabis synthesize primar-
ily the carboxylic acid forms of D
9
-THC,CBD,andCBG,
namely, D
9
-tetrahydrocannabinolic acid A (THCA-A),
cannabidiolic acid (CBDA), and cannabigerolic acid
(CBGA). These acidic cannabinoids are thermally unsta-
ble and can be decarboxylated when exposed to light or
heat via smoking, baking, or refluxing. As a result, the
requisite forensic analyses are usually expressed as the
sum of the acidic and neutral forms of the cannabinoids.
Reports also show that D
9
-THC itself readily oxidizes to
cannabinol (CBN) with oxygen and light during the de-
carboxylation process.
6
To understand the decarboxylation reactions that
can occur with phytocannabinoids, efficient analytical
methods are necessary to determine the concentration
variations of decarboxylation reactants (acidic cannabi-
noids) and products (neutral cannabinoids) over time.
Many analytical instruments have been applied to ana-
lyze cannabinoids in cannabis.
3,6,7
Among them, gas
chromatography (GC) and liquid chromatography (LC)
are the most commonly used techniques.
GC is ideal in some ways for these low molecular
weight (280–360) neutral cannabinoids. However, the
labile acids cannot be analyzed by GCwithout decarbox-
ylation or derivatization.
8
Hewavitharana et al.
9
reported
the decarboxylation reaction conducted in a heated GC
injection port and suggested that this process can pro-
vide a means of complete conversion of the acids to neu-
tral cannabinoids. Likewise, Dussy et al.
6
also studied the
decarboxylation of pure D
9
-tetrahydrocannabinolic acid
A (THCA-A), however, the generation of D
9
-THC was
maximal at an intermediate temperature (225C) but
with only 65% conversion. At 300C, a significant
loss of D
9
-THC was observed, although no CBN, a pos-
sible oxidation product, was observed. Thus, the use of
a GC injection port to convert THCA-A to D
9
-THC
was not satisfactory under the experimental conditions
of that particular study. In summary, GC analyses are
complicated by the need for decarboxylation or deriv-
atization of the acid cannabinoids before analysis.
Moreover, both decarboxylation and derivatization
techniques are subject to efficiency issues.
LC is another chromatographic technique commonly
used for decarboxylation studies because it is capable of
detecting both neutral and acidic cannabinoids. No de-
carboxylation or derivatization is necessary using this
technique. Veress et al.
10
studied the generation of D
9
-
THC by heating dried extracts of cannabis over a
range of temperature and time, and the products were
analyzed by high-performance liquid chromatography/
diode-array (HPLC/DAD). Maximum formation of
D
9
-THC was observed in *5–10 min at 145C followed
by a significant loss at longer times possibly due to
evaporation of D
9
-THC. Dussy et al.
6
also heated
pure THCA-A in an oven for a fixed time (15 min) at
120C, 140C, 160C, and 180C. The reaction prod-
ucts were also analyzed by HPLC/DAD. Conversion
of THCA-A was complete at 160C; however, forma-
tion of an oxidation product, CBN, was observed at
160C and 180C. Thus, the conversion of the acid to
D
9
-THC was never perfectly complete without loss or
degradation of starting material. In this study, the
molar sum of D
9
-THC and THCA-A measured by
HPLC/DAD was always higher than the total D
9
-
THC measured by GC, indicating an incomplete decar-
boxylation reaction. More recently, Perrotin-Brunel
et al.
11
studied the kinetics and molecular modeling of
the decarboxylation of THCA-A using HPLC. The pro-
posed pseudo-first-order, acid catalyzed keto–enol mech-
anism for the decarboxylation process was found to
be >95% efficient. The major problem with the HPLC/
DADanalysisofacidicorneutral cannabinoids is the
low molar absorptivity of these components, which re-
sults in relatively high limits of detection and restricts
DAD detection to low wavelengths where there is often
strong background absorbance from the eluant compo-
nents, especially during gradient elution experiments.
This problem can be overcome by using mass spectro-
metric detection.
Supercritical fluid chromatography (SFC) is a mild
separation technique by which decarboxylation of the
acid cannabinoids can be avoided.
12
It is fast, cost-
Wang, et al.; Cannabis and Cannabinoid Research 2016, 1.1
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263
effective, and able to provide the resolution necessary
to separate neutral and acidic cannabinoids simulta-
neously.
13
Thus, ultra-high performance supercritical
fluid chromatography (UHPSFC) with photodiode
array (PDA) and mass spectrometry (MS) detections
was used the first time to our knowledge to conduct a
decarboxylation study of phytocannabinoids in a sol-
vent extract of cannabis.
Most of the previously reported decarboxylation re-
sults emphasized only the conversion of THCA-A to
D
9
-THC. In the current studies, decarboxylation stud-
ies of three acidic cannabinoids, namely, THCA-A,
CBDA, and CBGA, were carried out over a range of
temperature and time to determine the most appropri-
ate conditions for complete decarboxylation. Beside the
neutral and acidic cannabinoids from decarboxylation
reaction, the possible oxidation product (CBN), the
isomerization product D
8
-tetrahydrocannabinol (D
8
-
THC), and tetrahydrocannabivarin (THCV) were also
quantified simultaneously. In addition, the kinetic
analysis, including the determination of decarboxyl-
ation reaction rate constants and reaction energies,
was conducted based on the decrease in acidic cannabi-
noid concentrations over a range of time.
Materials and Methods
Materials and reagents
Optima-grade isopropanol and acetonitrile were pur-
chased from Fisher Scientific. Deionized water was gener-
ated by the Millipore Milli-Q water purification system.
Regular-grade carbon dioxide was obtained from New Air.
Nine cannabinoid reference standards, namely,
CBD, D
8
-THC, THCV, D
9
-THC, CBN, CBG, THCA-
A, CBDA, and CBGA, were isolated in-house at The
National Center for Natural Products Research, Uni-
versity of Mississippi, from cannabis plant materials
(structures are shown in Fig. 1). The identity and purity
of the isolated standards were established by infrared
spectroscopy, nuclear magnetic resonance, and liquid
chromatography/quadrupole time-of-flight.
Sample information
The extracts of C. sativa flowering buds, sample C-9, were
used to conduct the decarboxylation studies. The sample
was obtained from the supply of materials provided to
‘‘The University of Mississippi NIDA Marijuana Project’
as part of the ‘‘Cannabis Potency Monitoring Program.’’
Plants were grown from C. sativa cuttings, and then
the whole buds of mature female plants were harvested,
FIG. 1. Structures of major cannabinoids in Cannabis sativa.
Wang, et al.; Cannabis and Cannabinoid Research 2016, 1.1
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264
air-dried, manicured, packed in barrels, and stored at low
temperature (24C). The plant was authenticated by Dr.
Suamn Chandra from the University of Mississippi. The
extraction procedure involved maceration of 20 g pow-
dered plant material in methylene chloride for 24 h
(250 mL ·2 times). The extraction solution was then evap-
orated under vacuum to dryness yielding 1.9 g of extract.
UHPSFC/PDA-MS analysis
The UHPSFC/PDA-MS method was described previous-
ly.
14
Briefly, the analysis was conducted on a Waters ACQ-
UITY UPC
2
system equipped with a photodiode array
detector. The column was a Waters ACQUITY UPC
2
BEH 2-EP column (150 ·3.0 mm I.D., 1.7 lm). Data ac-
quisition was performed with MassLynx (4.1) software.
Mobile phases consisted of CO
2
(A) and isopropanol:
acetonitrile (80:20) with 1% water (B). The gradient condi-
tions were as follows: 4.0% B to 9.0% B in 4.5 min, and
then to 30.0% B in the next 2.5 min (hold 3 min). The sys-
tem was re-equilibrated for 6.5 min before the next injec-
tion. The flow rate was 1.4 mL/min. The injection
volume was 1.0 lL. The column and autosampler temper-
atures were maintained at 30C and 10C, respectively.
The UV wavelength was set to scan from 190 to 400 nm,
and 220 nm was used for the quantification.
The MS data were acquired on a Waters ACQUITY sin-
gle quadrupole mass spectrometer equipped with an elec-
trospray ionization source operating at 150Cinscan
mode from 100 to 800 amu for both positive and negative.
The capillary voltage was 4.5 kV and cone voltage was
40V.Nitrogenwasusedasdesolvationandconegasat
flow rates of 500 and 50 L/h, respectively. The desolvation
temperature was 400C. The make-up flow composed
of methanol with 8 mM ammonium formate and 0.5%
formic acid was delivered at a flow rate of 0.6 mL/min.
The active back pressure regulator pressure was 1500 psi.
Sample preparation and decarboxylation reactions
of C. sativa extract
For the decarboxylation reactions, separate vials were
used for each experiment. The vial containing 3.0 mg/
mL extracts dissolved in acetonitrile:methanol (80:20)
was dried using a SpeedVac concentrator. An individual
vialwasplacedinanovenforafixedtimeatafixedtem-
perature for the decarboxylation reactions. A vacuum
oven was used to eliminate oxygen and light that could
possibly produce decomposition of D
9
-THC to CBN.
Conditions for decarboxylation were examined at 80C,
95C, 110C, 130C, and 145C for different times up
to 60 min to determine the most appropriate experimen-
tal condition. After decarboxylation, the extracts were
redissolved in acetonitrile:methanol (80:20) to give
1.0 mg/mL solutions for the UHPSFC/PDA-MS analysis.
Duplicate samples were tested for each reaction.
FIG. 2. UHPSFC/PDA (220 nm) chromatogram of a mixture of cannabinoid standards. Peak assignment:
(1) CBD, (2) D
8
-THC, (3) THCV, (4) D
9
-THC, (5) CBN, (6) CBG, (7) THCA-A, (8) CBDA, (9) CBGA. CBD, cannabidiol;
CBDA, cannabidiolic acid; CBG, cannabigerol; CBGA, cannabigerolic acid; CBN, cannabinol; THC,
tetrahydrocannabinol; THCA-A, tetrahydrocannabinolic acid-A; THCV, tetrahydrocannabivarin; UHPSFC,
ultra-high-performance supercritical fluid chromatography.
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265
FIG. 3. Concentration (mM) of (A) THCA-A and (B) D
9
-THC as a function of time and temperature.
FIG. 4. Experimental results for THCA-A, D
9
-THC and CBN at 110C.
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266
Results and Discussion
Decarboxylation studies
A previously developed and validated UHPSFC/PDA-
MS method
14
was used for the analysis of cannabinoids
from decarboxylation. The PDA (220 nm) data were
used for the quantification. The calibration plots for
all the analyzed cannabinoid standards were linear
over the concentration range of 5.0–1000.0 lg/mL
with the correlation coefficients (R
2
)>0.994. The MS
data were used for the compound identification and
chromatographic peak purity check purpose. In this
study, the nine cannabinoids (CBD, D
8
-THC, THCV,
D
9
-THC, CBN, CBG, THCA-A, CBDA, and CBGA)
were quantitatively determined before and after canna-
bis extracts were heated in a vacuum oven at 80C,
95C, 110C, 130C, and 145C for up to 60 min.
The full results of the experiments are given in Supple-
mentary Table S1 in the Supplementary Data. Figure 2
shows the chromatogram of the nine major cannabi-
noids with PDA detection at 220 nm. The standards
were well resolved with an elution order of neutral can-
nabinoids eluting before their precursor acids. This
order is reversed from that observed for HPLC sys-
tems.
13
Therefore, SFC analysis can serve as orthogonal
methods to HPLC/GC and provide different relative re-
tentions of peaks that are needed to ensure full charac-
terization and confirmation analysis of cannabis.
Table 1. The Relative Loss for the Total Molar
Concentration (Sum of Acidic Reactants and Neutral
Products) Upon Completion of Decarboxylation
Decarboxylation
reaction Form
Temperature
(C)
Relative loss
in total molar
concentration
(%)
THCA-A/THC Extracts 110 7.94
CBDA/CBD Extracts 110 18.05
CBDA/CBD Extracts 130 25.2
CBGA/CBG Extracts 110 52.67
CBDA/CBD Pure standard 110 13.75
CBD, cannabidiol; CBDA, cannabidiolic acid; CBG, cannabigerol; CBGA,
cannabigerolic acid; THC, tetrahydrocannabinol; THCA-A, tetrahydrocan-
nabinolic acid-A.
FIG. 5. Concentration (mM) of (A) CBDA and (B) CBD as a function of time and temperature.
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267
D
9
-Tetrahydrocannabinolic acid A. Figure 3 shows the
results of the decarboxylation reactions for THCA-A/
D
9
-THC. At temperatures lower than 100C, the reaction
did not reach completion within 60 min. At higher tem-
peratures, the concentration of THCA-A approached
zero in 30, 9, and 6 min at 110C, 130C, and 145C, re-
spectively. The stoichiometry of the reaction is shown
in Figure 4, where the concentrations of D
9
-THC and
THCA-A and their sum are plotted as a function of
time. The results indicate complete conversion of
THCA-A/D
9
-THC. The sum of the molar concentra-
tion of THCA-A and D
9
-THC decreased slightly after
the decarboxylation, the relative loss is given in
Table 1. Figure 4 also shows the data for CBN, which
is a possible oxidation product of D
9
-THC. In this
case, heating in the dark and in the absence of oxygen
(vacuum oven) did not result in any significant oxida-
tion of D
9
-THC to CBN. Finally, decarboxylation stud-
ies with pure THCA-A showed clearly that D
9
-THC
was the only decomposition product observed after
heating at 110C for 40 min.
Cannabidiolic acid. The experimental results for the
decarboxylation of CBDA are shown in Figures 5
and 6. In this case, the mass balance is not as clear
as the THCA-A data. In both 110C and 130C, the
sum of the molar concentration of CBDA and CBD
diminishedasthetimeandtemperatureofthe
experiments increase. This indicates more complex
chemistry than the stoichiometric conversion of
FIG. 6. Experimental results for the decarboxylation of (A) CBDA in extracts at 110C; (B) pure CBDA
reference standard at 110C; (C) CBDA in extracts at 130C.
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268
CBDA/CBD. It might also be an indication of com-
pound evaporation under vacuum condition or uniden-
tified products produced at the higher temperature.
To elucidate the possible matrix effect, pure CBDA
reference standard isolated in-house was studied.
This is the first time any such matrix effects have
been investigated. Vials containing 1.0 mg of pure
CBDA were simultaneously decarboxylated in the vac-
uum oven with the extracts at 110C over a range of
time. Three milliliters of acetonitrile:methanol (80:20)
was added to each vial to form a concentration of
333.33 lg/mL solution before the UHPSFC/PDA-MS
analysis. The total molar concentrations of the acidic
and neutral products were measured as a function of
time and temperature, and the results are given in
Figure 6B. The sum of the molar concentration of
pure CBDA and its decarboxylation product CBD
showed a 14% decrease compared to 18% for the ex-
tract. The results are given in Table 1.
Cannabigerolic acid. Similar results were obtained for
the decarboxylation of CBGA, as shown in Figure 7 and
Table 1. In this case, the results are difficult to interpret
because of the low concentrations (<0.1 mM) com-
pared to THCA-A and CBD (<1 mM). Despite the
low concentrations, the results are very similar to
those of CBDA (Figs. 5 and 6).
Kinetic analyses
To study the decarboxylation reaction, it is important
to consider not only the chemical properties of the
acidic cannabinoids but also the conditions under
which the reaction occurs. The relationship between
the rate of the decarboxylation reaction, dC½
dt , and the
concentrations of the acidic cannabinoids, C½,can
be expressed by Eq. (1) or the alternative Eq. (2):
dC½
dt =kC½ (1)
ln [C]0
[C]t
=kt (2)
where kpresents the rate constant, and [C]0and [C]tare the
concentrations of reactants at time 0and tmin, respectively.
The activation energy, E
A
, which indicates the minimum en-
ergy for the reaction to occur, can be determined from the
temperature dependence of the rate constants by the so-called
Arrhenius equation, Eq. (3):
ln k=ln k0EA
RT (3)
where k
0
is the frequency factor, and Ris the gas constant.
Perrotin-Brunel et al.
11
proposed that the decarbox-
ylation of THCA-A was a direct acid catalyzed keto–
enol reaction. The kinetics was first order and the
catalyst was a naturally occurring acid in the plant.
FIG. 7. Experimental results for CBG and CBGA at 110C.
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269
The results for THCA-A indicated an activation energy,
E
A
,of84.8kJ/molwithak
0
value of 3.7 ·10
8
sec
1
.
The results from the current study are shown in
Figure 8 for THCA-A. First-order kinetics is indicated
by a logarithmic relationship between the acid concentra-
tion and time at a fixed temperature. Figure 8 indicates
that first-order kinetics was observed at 80C, 95C
over the full-time scale, and 110Cand130Cupto
the time when decarboxylation was complete. However,
at higher temperature, such as 145C, the reaction rate
was high and the reaction order was difficult to deter-
mine. The slopes of the linear plots for 80C, 95Cand
110C gave a first-order rate constant for the reaction
[from Eq. (2)] and the temperature dependence of
theserateconstantsindicatedanE
A
value of 88 kJ/mol
with a k
0
of 8.7 ·10
8
sec
1
calculated from the Eq. (3).
Similar kinetic analyses were carried out for the three
acids used in this study. The first-order rate constants
were measured for 80C, 95C, and 110C. The tem-
perature dependence of the rate constants was used
to calculate an E
A
value for each acid. The results are
shown in Table 2. The rate constants for THCA-A
were always approximately twice those of CBDA or
CBGA, which were nearly identical.
Conclusions
The increasing medical applications of cannabinoids
other than D
9
-THC demand further investigation of
these components and their generation from the acidic
precursors that are enzymatically produced in the can-
nabis plants. This study represents a comprehensive
use of UHPSFC/PDA-MS for the analysis of neutral
and acidic cannabinoids in determination of the kinet-
ics of phytocannabinoids in cannabis extracts. It also
reports the first investigation of the decarboxylation ki-
netics of all three acid precursors of D
9
-THC, CBD, and
CBG. UHPSFC has proven to be an excellent separa-
tion and quantitation technique for the nine cannabi-
noids investigated in the current study. The acids and
neutrals could be detected in the same experiment
without prior decarboxylation or derivatization.
UHPSFC allowed the quantitative determination of
the concentrations of acids and their decarboxylation
products over a range of temperature and time. The
variation of acid concentration over times allowed the
determination of first-order rate constants. Variation
of the rate constants with temperature yielded values
for the energy of reaction.
The rate constants for the decarboxylation of THCA-
A were higher than those of the other two acids, CBDA
and CBGA. The decarboxylation reaction for THCA-A
was essentially stoichiometric with no side reactions. In
particular, no CBN (a common oxidation by-product)
was observed under the experimental conditions. The de-
carboxylation reactions for CBDA and CBGA were more
complex with undetermined side reactions accounting
for a loss of 18% (CBDA) to 53% (CBGA) for the extracts.
Further study is necessary and will be conducted to pro-
vide better understanding of these two acids.
Acknowledgments
This research was partially supported by ‘‘The University
of Mississippi NIDA Marijuana Project’’ as part of the
‘‘Cannabis Potency Monitoring Program’’ funded by the
National Institute on Drug Abuse (N01DA-15-7793).
Author Disclosure Statement
No competing financial interests exist.
Table 2. Rate Constants, k·10
3
(sec
1
), and Activation
Energetics, E
A
, for the Decarboxylation of the Acidic
Cannabinoids
Rate constants k·10
3
(sec
1
) Activation
energy E
A
(kJ/mol)
Reactant 80C95C 110C
Extracts
THCA-A 0.18 0.66 1.83 88 (84
a
)
CBDA 0.05 0.27 0.83 112
CBGA 0.06 0.25 1.00 109
Pure Standard
CBDA 0.16
a
Literature value.
11
FIG. 8. Kinetic results for THCA-A over a range of
time and temperature.
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Cite this article as: Wang M, Wang Y-H, Avula B, Radwan MM, Wanas
AS, van Antwerp J, Parcher JF, ElSohly MA, Khan IA (2016)
Decarboxylation study of acidic cannabinoids: a novel approach using
ultra-high-performance supercritical fluid chromatography/
photodiode array-mass spectrometry, Cannabis and Cannabinoid
Research 1:1, 262–271, DOI: 10.1089/can.2016.0020.
Abbreviations Used
ABPR ¼active back pressure regulator
CBD ¼cannabidiol
CBDA ¼cannabidiolic acid
CBG ¼cannabigerol
CBGA ¼cannabigerolic acid
CBN ¼cannabinol
GC ¼gas chromatography
HPLC/DAD ¼liquid chromatography-diodide detection
LC ¼liquid chromatography
MS ¼mass spectrometry
PDA ¼photodiode array
SFC ¼supercritical fluid chromatography
THC ¼tetrahydrocannabinol
THCA-A ¼tetrahydrocannabinolic acid-A
THCV ¼tetrahydrocannabivarin
UHPSFC ¼ultra-high-performance supercritical fluid
chromatography
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Supplementary resource (1)

... Additionally, the conversion efficiencies of six acidic cannabinoids (CBDVA, CBGA, CBDA, THCVA, ∆9-THCA, and CBCA) to their neutral forms under specific decarboxylation conditions were assessed. A previous study using ∆9-THCA and CBDA showed that the conversion of ∆9-THCA and CBDA to ∆9-THC and CBD, respectively, reached completion with relatively less loss after decarboxylation at 105 • C or 110 • C for 1 h [28,31]. Decarboxylation was conducted at 110 • C for 1 h, and conversion efficiencies were measured using six acidic cannabinoid mixtures as references (Figure 2b). ...
... THCA, and CBCA) to their neutral forms under specific decarboxylation conditions were assessed. A previous study using Δ9-THCA and CBDA showed that the conversion of Δ9-THCA and CBDA to Δ9-THC and CBD, respectively, reached completion with relatively less loss after decarboxylation at 105 °C or 110 °C for 1 h [28,31]. Decarboxylation was conducted at 110 °C for 1 h, and conversion efficiencies were measured using six acidic cannabinoid mixtures as references (Figure 2b). ...
... In the present study, we applied an HPLC analytical system to evaluate the decarboxylation efficiencies of acidic cannabinoids and detect neutral cannabinoids. In previous studies on the decarboxylation of acidic cannabinoids, only three acidic cannabinoids, ∆9-THCA, CBDA, and CBGA, were focused on, and the conversion of their corresponding neutral forms under a range of temperatures and times were confirmed [28,31]. Our study provided additional information about the decarboxylation of acidic cannabinoids, CBDVA, ∆9-THCVA, and CBCA, by analyzing the products of their neutral forms. ...
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Cannabis (Cannabis sativa L.) is widely cultivated and studied for its psychoactive and medicinal properties. As the major cannabinoids are present in acidic forms in Cannabis plants, non-enzymatic processes, such as decarboxylation, are crucial for their conversion to neutral active cannabinoid forms. Herein, we detected the levels of cannabidivarin (CBDV), cannabidiol (CBD), cannabichromene (CBC), and Δ9-tetrahydrocannabinol (Δ9-THC) in the leaves and vegetative shoots of five commercial Cannabis cultivars using a combination of relatively simple extraction, decarboxylation, and high-performance liquid chromatography analyses. The CBDV, CBC, and Δ9-THC levels were 6.3–114.9, 34.4–187.2, and 57.6–407.4 μg/g, respectively, and the CBD levels were the highest, ranging between 1.2–8.9 μg/g in leaf and vegetative shoot tissues of Cannabis cultivars. Additionally, correlations were observed between cannabinoid accumulation and transcription levels of genes encoding key enzymes for cannabinoid biosynthesis, including CsCBGAS, CsCBDAS, CsCBCAS, and CsTHCAS. These data suggest that the high accumulation of cannabinoids, such as CBC, Δ9-THC, and CBD, might be derived from the transcriptional regulation of CsCBGAS and CsCBDAS in Cannabis plants.
... This series is of importance because CBGA is a common precursor to CBCA, Δ 9 -THCA, and CBDA that occur via three different biochemical pathways by particular synthases, among which the most prominent are tetrahydrocannabinolic acid-, cannabidiolic acid-, and cannabichromenic acid-synthase, leading to the production of THCA, CBDA, and CBCA, respectively [28,29]. IN addition, then they can be decarboxylated through various processes such as light exposure, heating, or through chemical reactions [30]. ...
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... The plant contains over 100 cannabinoids, with the most abundant being cannabidiolic acid (CBDA) and tetrahydrocannabinolic acid (THCA). Better known and marketed compounds are cannabidiol (CBD) and tetrahydrocannabinol (THC) which are the decarboxylated form of the prior molecules produced during heat extraction when processing hemp products (13)(14)(15)(16)(17)(18). THC is responsible for the psychotropic activity in cannabis primarily through interactions at the CB1 receptor in the central nervous system, while CBD, CBDA and THCA have no psychotropic effects and are widely regarded as being highly tolerable with minimal reported adverse side effects (5,7,8,14,15,(19)(20)(21)(22). ...
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Objective To determine the impact of a cannabidiol (CBD) and cannabidiolic acid (CBDA) rich hemp product on acute post-operative pain in dogs following a tibial plateau leveling osteotomy (TPLO), and to evaluate for changes in early bone healing, serum chemistry profiles, and complete blood counts. Methods In this randomized, placebo controlled, blinded clinical trial, 44 client-owned dogs were assigned to receive either a CBD/CBDA product dosed at 2–2.5 mg/kg PO every 12 h or a placebo for 4 weeks following a TPLO. Variables evaluated before (week 0), and at 2 and 4 weeks post-operatively included standardized veterinary assessments for pain score, weight-bearing, and lameness, the Canine Brief Pain Inventory (pain interference score–PIS, pain severity score–PSS), and serum biochemistry. Complete blood counts were performed at weeks 0 and 4. Additionally, orthogonal radiographs evaluating the degree of healing were taken at week 4. A mixed model analysis, analyzing changes of variables of interest from enrollment baseline to all other time points was utilized, with a p -value ≤ 0.05 considered significant. Results Of the 44 enrolled patients, 3 were lost to follow up and excluded from analysis. No significant differences were noted between placebo ( n = 19) and CBD/CBDA ( n = 22) groups at any point in pain score, degree of lameness, degree of weight-bearing, PIS, PSS, or radiographic healing of the osteotomy. A significant finding of elevation of ALP above normal reference range in the treatment group was identified ( p = 0.02) and eosinophil count was affected by treatment ( p = 0.01), increasing from baseline in placebo and decreasing in treatment groups. Finally, a significant difference ( p = 0.03) was noted at 2 weeks post-operatively where 4 patients in the placebo group and no treatment patients received trazodone to facilitate activity restrictions. Clinical significance Use of a CBD/CBDA rich hemp product dosed at 2–2.5 mg/kg PO every 12 h did not have a significant impact on pain or delay early bone healing. A statistically significant increase in ALP, decrease in eosinophils, and reduced use of trazodone was identified in the treatment group.
... Most of the experimental works have focused on establishing the most efficient conditions for the extraction of the CBD and D9-THC from the biological matrix [6][7][8] and purifying them in an efficient way. Regarding the extraction, one of the most common techniques uses supercritical CO 2 (sCO 2 ) as solvent [9][10][11][12]. ...
... On the contrary, detectable residues of ∆9-THCA remained only at 115 • C (Table 1). This was due to the higher activation energy required by CBDA compared to ∆9-THCA to obtain the decarboxylation reaction and it is in line with literature data since decarboxylation close to 130 • C led to a greater conversion of CBDA [11]. Similarly, both temperatures doubled the CBN content with respect to those quantified in FM2 (Table 2). ...
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... 23 The larger amount of decarboxylated phytocannabinoids contained in these extracts was probably due to the evaporation of ethanol in a vacuum evaporator and the subsequent dissolving of the dry matter in DMSO. [35][36][37] However, from a statistical point of view, this contributed to the more significant heterogeneity of the cannabis extracts and the subsequent proof of their possible effect. ...
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