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Cannabinoid Conversion Rates
Many urban legends and a good deal of misinformation exists regarding the long-term effects of a variety of environmental factors (including time) on the integrity and potency of marijuana. This issue involves the conversion of cannabinoids and terpenes from one molecular state to another—something that has a significant impact upon the medicinal efficacy and lifestyle benefits derived by consumers.
Much research over several decades has been conducted about the conversion rate between different states within the biosynthetic pathway of certain phytocannabinoids, chiefly the two most commercially popular examples, CBD (cannabidiol) and THC (tetrahydrocannabinol).
Much research has been conducted about the conversion rate between different states within the biosynthetic pathway of certain phytocannabinoids, chiefly the two most popular examples, CBD and THC.
Factors that influence or cause a shift from one molecular state to another include temperature, humidity, wind/air flow, oxygen level, natural and artificial light level, and others. Typically, increased levels of any of these environmental factors will result in a corresponding increase in the rate at which a cannabinoid such as THC converts to another molecular state.
Cannabinoid Conversion Rates: Research
Cannabinoid Conversion Rates. A variety of studies published since the 1960s have revealed a wealth of data regarding the degradation rates and other dynamics of popular cannabinoids such as delta-9 THC and CBD. The relatively delicate biochemistry of the cannabinoids derived from hemp and cannabis and their volatility when exposed to different environmental conditions is a serious issue in terms of product integrity and packaging accuracy.
It should be noted that the research data below pertain to delta-8 and delta-9 THC, which both degrade into CBN under the same environmental conditions. CBN is known for its sedative properties, but is typically present in such small quantities that it does not usually cause overt sedation (other cannabinoids and terpenes also heavily influence this efficacy outcome).
A 1969 study revealed a 3-5 percent monthly degradation of THC at room temperature. The temperature is important because higher temperatures result in greater degradation rates.
A 1971 study entitled "The Identification, Isolation, and Preservation of Delta-9 THC" that was published in the Journal of Pharmacy and Pharmacology investigated the optimal environmental conditions under which cannabis should be "preserved" (stored). It revealed that a dark nitrogen bath (depriving the product of exposure to oxygen) was best for preserving THC.
"The effects of storage conditions on Δ9-THC stability...indicated the best method for preserving Δ9-THC was at 0° [Celsius], protected from light, stored under nitrogen."
Reported the study's authors, "The effects of storage conditions on Δ9-THC stability...indicated the best method for preserving Δ9-THC was at 0° [Celsius], protected from light, stored under nitrogen."
A 1999 study conducted at the University of Mississippi revealed the degradation rate of THC to CBN to be roughly 17 percent per year when stored at a temperature of 68-72° F (20-22° C). Summarized the study report:
"On the average, the concentration of THC in the plant material decreased by
17 percent of its original value after one year
27 percent after two years
35 percent after three years
41 percent after four years
A 2006 study entitled "Temperature Stability and Bioadhesive Properties of Δ9-Tetrahydrocannabinol" that was published in the journal Drug Development and Industrial Pharmacy investigated "the effect of processing temperature on the stability of THC and its extent of degradation to cannabinol (CBN)."
The researchers observed that "THC is susceptible to heat and oxidation, and the primary decomposition product observed is cannabinol (CBN), which is an oxidized degradant of THC."
"THC is susceptible to heat and oxidation, and the primary decomposition product observed is cannabinol (CBN)."
They reported that "UV light and heat accelerate THC degradation." Regarding the effect of temperature on the stability of THC, the study revealed that "little decomposition occurred at 65° C (149° F), but considerable losses occurred from 85–100° C (185-212° F)."
The study also reported that THC degradation was 2.8 percent, 5.1 percent, and 5.7 percent at 120° C (248° F), 160° C (320° F), and 200° C (392° F), respectively (when heated for approximately 75–90 minutes). "Although the degradation of THC is relatively low at 200° C, the extent of conversion of THC to CBN is high."
Note that the degradation rate reported by this study was not linear with respect to temperature. At the jump between 120° C and 160° C, the THC degradation rate nearly doubled from 2.8 to 5.1 percent (an 82 percent increase). But at the jump from 160° C to 200° C (the same 40 degree increment used throughout this study), the degradation rate increased from 5.1 percent to only 5.7 percent (a 12 percent increase in rate; only one seventh the degradation rate observed for the 120° C to 160° C test segment).
The study's authors concluded that THC degraded "fairly rapidly at room temperature," but that its degradation "slowed significantly at 4° C (39° F) and was arrested at −18° C (0° F)."
The study's authors concluded that THC degraded "fairly rapidly at room temperature," but that its degradation "slowed significantly at 4° C (39° F) and was arrested at −18° C (0° F)."
A 2012 study entitled "Long-term Storage and Cannabis Oil Stability" explored the decay of several cannabinoids (beyond merely THC) not in loose-leaf flower, but instead cannabis oil and included CBD and THC. The study gathered cannabinoid degradation data over a period of four years.
When the cannabis oil was stored in the darkness at 4° C (39° F), CBD degradation rates observed were as follow:
11 percent of the CBD was lost in the first year (average loss of three percent (every three months)
12 percent in the second year (average loss of three percent every three months)
Seven percent in the third year (average loss of two percent every three months)
10 percent in the fourth year (average loss of two percent every three months)
Cannabis oil stored under conditions that exacerbate cannabinoid degradation (the presence of light and higher temperatures) under laboratory artificial light and at 22° C (72° F) revealed the following degradation rates:
13 percent of CBD was lost in the first year (average loss of three percent every three months)
12 percent in the second year (average loss of three percent)
Seven percent in the third year (average loss of two percent)
Nine percent in the fourth year (average loss of two percent)
"After four years of storage, the samples stored in the darkness at 4° C (39° F) lost 40 percent of CBD." The cannabis oil samples stored in the laboratory light at 22° C (72° F) lost 45 percent of CBD. Added the researchers, "The same trend was recorded for all cannabis oil samples."
"After four years, the samples stored in the darkness at 4° C (39° F) lost 40% of CBD." The cannabis oil samples stored in the laboratory light at 22° C (72° F) lost 45% of CBD."
The study's authors concluded that delta-9 THC suffered "a steadily decay over the entire storage period" and that environmental conditions such as light and temperature affect cannabinoid degradation, with dark and colder environments resulting in the least amount of degradation.
A 2021 study entitled "Thermal Stability of Cannabinoids in Dried Cannabis: A Kinetic Study" that was published in the journal Analytical and Bioanalytical Chemistry investigated "the effect of temperature on the degradation of cannabinoids in dried cannabis flower."
The researchers investigated 14 cannabinoids using modern analysis methods, including liquid chromatography and tandem mass spectrometry. They found the average monthly THCA and THC degradation rate to be about two percent (at 68° F [20°C]).
Cannabinoid Conversion Rates: Conclusions
Cannabinoid Conversion Rates. Collectively, this body of research that spans back more than half a century reveals that a number of environmental factors increase the degradation rates of popular cannabinoids, including CBD and delta-9 THC.
Unfortunately, the distribution channels of legal cannabis markets can involve long periods of time between harvest or manufacturing and consumer purchase. With periods of more than a year sometimes experienced by consumers, this research proves that arguably significant degradation and conversion is occurring within the cannabinoids contained in their loose-leaf flower or manufactured extracts, concentrates, or infused edibles.
Patients attempting to accurately dose for particular ailments necessarily suffer complications and frustration when there is a misalignment between package label specifications and the actual contents of the medicine.
Patients and medical practitioners attempting to accurately dose for particular ailments necessarily suffer complications and frustration when there is a misalignment between package label specifications and the actual contents of the medicine or lifestyle product they are consuming.
According to this body of research, the ultimate cannabis storage for legal markets—for either loose-leaf flower or oils—seems to be an oxygen- and light-free environment involving a temperature below freezing. Unfortunately, the temperature element of the equation is costly and sometimes impossible to control. However, affordable packaging options already exist that deprive cannabis flowers and oils of light and oxygen.
One approach to this goal is specialized packaging involving the replacement of oxygen with nitrogen. Some companies and experts claim that nitrogen packaging, done right, can extend the shelf life of cannabis products by up to seven years.
"Whether companies are willing to tolerate the expenses of modern packaging tech (such as nitrogen) to prevent the degradation of cannabinoids remains to be seen."
Patients and consumers who purchase cannabis products via legal channels involving distribution that features distinct (and time-consuming) regulatory requirements that include testing, warehousing, transportation, and retail cycles are necessarily suffering a certain amount of degradation of target or featured cannabinoids.
Whether consumers—and the companies that serve them—are willing to tolerate the expenses involved in utilizing modern packaging tech (such as nitrogen) to prevent the degradation of cannabinoids remains to be seen.
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