Structure--activity studies on tetrahydro- and hexahydrocannabinol derivatives

In vitro activation of the CB1 receptor by the semi-synthetic cannabinoids hexahydrocannabinol (HHC), hexahydrocannabinol acetate (HHC-O) and hexahydrocannabiphorol (HHC-P)

Semi-synthetic cannabinoids (SSCs) including hexahydrocannabinol (HHC) are emerging on the drug market and sold openly as purportedly legal replacements for cannabis and Δ9-THC. By the beginning of 2024, 24 European countries had identified HHC, often sold openly in edibles (foods/candy), vapes and low-THC cannabis flowers and resins. The SSC market is developing rapidly, with HHC acetate (HHC-O), hexahydrocannabiphorol (HHC-P) and others recently identified. These developments may mark the first major change in the market for 'legal' replacements to cannabis since 'Spice' containing synthetic cannabinoids, such as JWH-018, emerged in 2008. Currently, there are some data available on the pharmacology of SSCs, which is crucial for understanding their effects, evaluating health risks and informing public health responses. This study focused on characterizing the in vitro activation of the human CB1 receptor by the (R)- and (S)-epimers of HHC, HHC-P and HHC-O. Using recombinant CHO-K1 cells expressing the human CB1 receptor, the potency (EC50) and efficacy were determined. It was established that (9R)-HHC and (9R)-HHC-P activated the CB1 receptor as partial agonists and with five and two times lower potency compared to JWH-018, respectively, while the (S)-epimers exhibited even lower potency. The (R)-epimer of HHC-O activate the CB1 receptor to even lesser extent and the (S)-epimer showed no activation. For HHC and HHC-P, all epimers exhibited similar level of efficacy. This available evidence suggests cannabimimetic effects of the tested SSC with the exception for the acetates that likely function as pro-drugs in vivo.

Hexahydrocannabinol and closely related semi-synthetic cannabinoids: A comprehensive review

Since the early 2000s, there has been a turmoil on the global illicit cannabinoid market. Parallel to legislative changes in some jurisdictions regarding herbal cannabis, unregulated and cheap synthetic cannabinoids with astonishing structural diversity have emerged. Recently, semi-synthetic cannabinoids manufactured from hemp extracts by simple chemical transformations have also appeared as recreational drugs. The burst of these semi-synthetic cannabinoids into the market was sparked by legislative changes in the United States, where cultivation of industrial hemp restarted. By now, hemp-derived cannabidiol (CBD), initially a blockbuster product on its own, became a "precursor" to semi-synthetic cannabinoids such as hexahydrocannabinol (HHC), which appeared on the drug market in 2021. The synthesis and cannabimimetic activity of HHC were first reported eight decades ago in quest for the psychoactive principles of marijuana and hashish. Current large-scale manufacture of HHC is based on hemp-derived CBD extract, which is converted first by cyclization into a Δ8 /Δ9 -THC mixture, followed by catalytic hydrogenation to afford a mixture of (9R)-HHC and (9S)-HHC epimers. Preclinical studies indicate that (9R)-HHC has THC-like pharmacological properties. The animal metabolism of HHC is partially clarified. The human pharmacology including metabolism of HHC is yet to be investigated, and (immuno)analytical methods for the rapid detection of HHC or its metabolites in urine are lacking. Herein, the legal background for the revitalization of hemp cultivation, and available information on the chemistry, analysis, and pharmacology of HHC and related analogs, including HHC acetate (HHC-O) is reviewed.

Hexahydrocannabinol poisoning reported to French poison centres

INTRODUCTION

Hexahydrocannabinol is a hexahydro derivative of cannabinol. Poisoning with hexahydrocannabinol was first observed in Europe in May 2022.

METHOD

This is a retrospective observational study of cases of self-reported hexahydrocannabinol exposure reported to French poison centres between 1 January 2022 and 31 May 2023.

RESULTS

There were 37 cases, including 19 in May 2023. The median age of the patients was 36 (interquartile range 28-43) years, and most were men. Eight patients had a history of substance use disorder. The route of exposure was ingestion in 24, inhalation (smoking or vaping) in 10, inhalation and ingestion in two and sublingual in one. Clinical features were neurological (85 per cent), cardiovascular (61 per cent), gastrointestinal (33 per cent), psychiatric (27 per cent) and ocular (21 per cent). Fifty-nine per cent of the patients were hospitalized. In four patients, the Poisoning Severity Score was 0 (asymptomatic); in 15 patients, the Score was 1 (minor); in 16, the Score was 2 (moderate); and in two cases, the Score was 3 (severe). In 70 per cent of patients, the outcome was known, and all recovered. Testing of biological samples was only undertaken in six cases. Five patients had positive blood or urine tests for hexahydrocannabinol; in two patients, tetrahydrocannabinol and metabolites were also detected. In addition, there was an additional patient in whom Δ8- and Δ9-tetrahydrocannabinol was detected in the substances used.

DISCUSSION

Clinical effects reported in this series included neuropsychiatric and somatic effects. Whilst these cases related to self-reported hexahydrocannabinol use, it is likely that tetrahydrocannabinol use also contributed to the effects in a substantial proportion of cases. This study has some limitations, such as the lack of available information due to the retrospective nature of the study. As a result, it probably overestimates the number of moderate and severe cases due to under-reporting of cases of little or no severity. Analysis of the patient's blood and urine was performed only in six patients, so we cannot be certain that the products consumed by the other patients were hexahydrocannabinol.

CONCLUSION

The clinical effects attributed to hexahydrocannabinol were neurological, cardiovascular, gastrointestinal, psychiatric and ocular predominantly and were sometimes serious.

Identification of hexahydrocannabinol (HHC), dihydro-iso-tetrahydrocannabinol (dihydro-iso-THC) and hexahydrocannabiphorol (HHCP) in electronic cigarette cartridge products

PURPOSE

Since 2021, products claiming to contain hexahydrocannabinol (HHC) and hexahydrocannabiphorol (HHCP), which are tetrahydrocannabinol (THC) analogs, have been distributed via the Internet. Owing to the presence of three asymmetric carbons in their structure, HHC and HHCP have multiple stereoisomers. This study aimed to identify the actual stereoisomers of HHC and HHCP isolated from electronic cigarette cartridge products using nuclear magnetic resonance (NMR) spectroscopy.

METHODS

Gas chromatography-mass spectrometry (GC-MS) and liquid chromatography-photodiode array-mass spectrometry (LC-PDA-MS) were used for the analyses of two major peaks and one minor peak in product A and two major peaks in product B. These five compounds were isolated by silica gel column chromatography, and their structures were analyzed by 1H, 13C-NMR and various two-dimensional NMR techniques, i.e., H-H correlation spectroscopy, heteronuclear multiple quantum coherence, heteronuclear multiple-bond correlation, and nuclear Overhauser effect spectroscopy.

RESULTS

Three compounds isolated from product A were identified as rel-(6aR,9R,10aR)-hexahydrocannabinol (11β-hexahydrocannabinol; 11β-HHC), rel-(6aR,9S,10aR)-hexahydrocannabinol (11α-hexahydrocannabinol, 11α-HHC), and a minor compound (2R,5S,6R)-dihydro-iso-tetrahydrocannabinol (dihydro-iso-THC). Meanwhile, the structural isomers of the major compound isolated from product B were identified as rel-(6aR, 9R, 10aR)-hexahydrocannabiphorol (11β-hexahydrocannabiphorol; 11β-HHCP) and rel-(6aR, 9S, 10aR)-hexahydrocannabiphorol (11α-hexahydrocannabiphorol; 11α-HHCP).

CONCLUSIONS

The presence of both 11β-HHC and 11α-HHC in the HHC products analyzed in this study suggests that they were most likely synthesized via the reduction reaction of Δ8-THC or Δ9-THC. Dihydro-iso-THC was probably obtained as a byproduct of the synthesis of Δ8-THC or Δ9-THC from cannabidiol. Similarly, 11β-HHCP and 11α-HHCP in the HHCP product could stem from Δ9-tetrahydrocannabiphorol.

Saturated Cannabinoids: Update on Synthesis Strategies and Biological Studies of These Emerging Cannabinoid Analogs

Natural and non-natural hexahydrocannabinols (HHC) were first described in 1940 by Adam and in late 2021 arose on the drug market in the United States and in some European countries. A background on the discovery, synthesis, and pharmacology studies of hydrogenated and saturated cannabinoids is described. This is harmonized with a summary and comparison of the cannabinoid receptor affinities of various classical, hybrid, and non-classical saturated cannabinoids. A discussion of structure-activity relationships with the four different pharmacophores found in the cannabinoid scaffold is added to this review. According to laboratory studies in vitro, and in several animal species in vivo, HHC is reported to have broadly similar effects to Δ9-tetrahydrocannabinol (Δ9-THC), the main psychoactive substance in cannabis, as demonstrated both in vitro and in several animal species in vivo. However, the effects of HHC treatment have not been studied in humans, and thus a biological profile has not been established.

Hexahydrocannabinol Pharmacology, Toxicology, and Analysis: The First Evidence for a Recent New Psychoactive Substance

BACKGROUND

During the last two years, hexahydrocannabinol (HHC), the hydrogenated derivative of tetrahydrocannabinol has been freely sold by internet websites as a "legal" replacement to THC and cannabis in a range of highly attractive branded and unbranded products, some of which are sold as "legal highs". Potentially, there could be a large demand for HHC products by individuals in Europe and internationally.

METHODS

Studies reporting HHC pharmacology, toxicology and analysis were identified from Pubmed and Scopus databases, and official international organizations' websites were considered.

RESULTS

HHC showed the effects of the typical cannabinoid on the central nervous system, with lower potency than Δ9-THC. A few studies highlighted that 9(R)-HHC is more potent than 9(S)-HHC. This molecule showed an affinity for cannabinoid receptor CB1 both in vitro and in vivo, suggesting a possible therapeutic effect in several pathologies. However, the affinity for the CB1 receptor suggests a possible addiction potential, inducing the users to misuse it. Since actual intoxication cases have not yet been reported, the HHC harmful potential was not described, probably due to the lack of effective analytical methods to detect HHC in biological matrices. Conversely, different analytical assays were developed and validated to separate HHC epimers in natural and non-natural sources.

CONCLUSION

Similarly to other NPS, the HHC represents a cheaper alternative to the controlled Δ9-THC. Its monitoring is a crucial challenge for toxicological and forensic purposes. To this concern, it is essential to further investigate HHC to support health providers in the identification of related intoxications.

Enantioselective Total Synthesis of Potent 9β-11-Hydroxyhexahydrocannabinol

The first total synthesis of potent cannabinoid, 9β-11-hydroxyhexahydrocannabinol, is achieved through a proline-catalyzed inverse-electron-demand Diels-Alder reaction. Using this asymmetric catalysis, the cyclohexane ring is constructed with two chiral centers as a single diastereomer with 97% ee. The creation of the third chiral center and benzopyran ring is demonstrated with the elegant synthetic strategies. This mild and efficient synthetic methodology provides a new route for the asymmetric synthesis of the other potent hexahydrocannabinols.

Dark Classics in Chemical Neuroscience: Δ9-Tetrahydrocannabinol

Cannabis ( Cannabis sativa) is the most widely used illicit drug in the world, with an estimated 192 million users globally. The main psychoactive component of cannabis is (-)- trans-Δ⁹-tetrahydrocannabinol (Δ⁹-THC), a compound with a diverse range of pharmacological actions. The unique and distinctive intoxication caused by Δ⁹-THC primarily reflects partial agonist action at central cannabinoid type 1 (CB₁) receptors. Δ⁹-THC is an approved therapeutic treatment for a range of conditions, including chronic pain, chemotherapy-induced nausea and vomiting, and multiple sclerosis, and is being investigated in indications such as anorexia nervosa, agitation in dementia, and Tourette's syndrome. It is available as a regulated pharmaceutical in products such as Marinol, Sativex, and Namisol as well as in an ever-increasing range of unregistered medicinal and recreational cannabis products. While cannabis is an ancient medicament, contemporary use is embroiled in legal, scientific, and social controversy, much of which relates to the potential hazards and benefits of Δ⁹-THC itself. Robust contemporary debate surrounds the therapeutic value of Δ⁹-THC in different diseases, its capacity to produce psychosis and cognitive impairment, and the addictive and "gateway" potential of the drug. This review will provide a profile of the chemistry, pharmacology, and therapeutic uses of Δ⁹-THC as well as the historical and societal import of this unique, distinctive, and ubiquitous psychoactive substance.

Changes in body temperature after administration of antipyretics, LSD, delta 9-THC, CNS depressants and stimulants, hormones, inorganic ions, gases, 2,4-DNP and miscellaneous agents

This survey concludes a series of complications of data from the literature, primarily published since 1965, on thermoregulatory effects of antipyretics in afebrile as well as in febrile subjects, LSD and other hallucinogens, cannabinoids, general CNS depressants, CNS stimulants including xanthines, hormones, inorganic ions, gases and fumes, 2,4-dinitrophenol and miscellaneous agents including capsaicin, cardiac glycosides, chemotherapeutic agents, cinchona alkaloids, cyclic nucleotides, cycloheximide, 2-deoxy-D-glucose, dimethylsulfoxide, insecticides, local anesthetics, poly I:poly C, spermidine and spermine, sugars, toxins and transport inhibitors. The information listed includes the species used, route of administration and dose of drug, the environmental temperature at which the experiments were performed, the number of tests, the direction and magnitude of body temperature change and remarks on the presence of special conditions such as age or lesions, or on the influence of other drugs, such as antagonists, on the response to the primary agents.