Naphthoylindoles are a class of synthetic cannabinoids. [1]
Behaving similarly in vivo to endocannabinoids such as anandamide or 2-arachidonoylglycerol (2-AG), Naphthoylindoles can bind to endocannabinoid receptors in animals, presenting as CB1 and/or CB2 partial/full agonists.
They have gained notoriety over the years for illicit usage and distribution in Europe and North America, typically marketed as "herbal incense blends." [2]
Cannabinoid receptors, located throughout the body, are part of the endocannabinoid system of vertebrates– a class of cell membrane receptors in the G protein-coupled receptor superfamily. As is typical of G protein-coupled receptors, the cannabinoid receptors contain seven transmembrane spanning domains. Cannabinoid receptors are activated by three major groups of ligands: endocannabinoids; phytocannabinoids ; and synthetic cannabinoids. All endocannabinoids and phytocannabinoids are lipophilic.
JWH-018 (1-pentyl-3-(1-naphthoyl)indole, NA-PIMO or AM-678) is an analgesic chemical from the naphthoylindole family that acts as a full agonist at both the CB1 and CB2 cannabinoid receptors, with some selectivity for CB2. It produces effects in animals similar to those of tetrahydrocannabinol (THC), a cannabinoid naturally present in cannabis, leading to its use in synthetic cannabis products that in some countries are sold legally as "incense blends".
JWH-073, a synthetic cannabinoid, is an analgesic chemical from the naphthoylindole family that acts as a full agonist at both the CB1 and CB2 cannabinoid receptors. It is somewhat selective for the CB1 subtype, with affinity at this subtype approximately 5× the affinity at CB2. The abbreviation JWH stands for John W. Huffman, one of the inventors of the compound.
JWH-250 or (1-pentyl-3-(2-methoxyphenylacetyl)indole) is an analgesic chemical from the phenylacetylindole family that acts as a cannabinoid agonist at both the CB1 and CB2 receptors, with a Ki of 11 nM at CB1 and 33 nM at CB2. Unlike many of the older JWH series compounds, this compound does not have a naphthalene ring, instead occupying this position with a 2'-methoxy-phenylacetyl group, making JWH-250 a representative member of a new class of cannabinoid ligands. Other 2'-substituted analogues such as the methyl, chloro and bromo compounds are also active and somewhat more potent.
JWH-398 is an analgesic chemical from the naphthoylindole family, which acts as a cannabinoid agonist at both the CB1 and CB2 receptors. It has mild selectivity for CB1 with a Ki of 2.3 nM and 2.8 nM at CB2. This synthetic chemical compound was identified by the EMCDDA as an ingredient in three separate "herbal incense" products purchased from online shops between February and June 2009. It was discovered by, and named after, John W. Huffman.
JWH-210 is an analgesic chemical from the naphthoylindole family, which acts as a potent cannabinoid agonist at both the CB1 and CB2 receptors, with Ki values of 0.46 nM at CB1 and 0.69 nM at CB2. It is one of the most potent 4-substituted naphthoyl derivatives in the naphthoylindole series, having a higher binding affinity (i.e. lower Ki) at CB1 than both its 4-methyl and 4-n-propyl homologues JWH-122 (CB1 Ki 0.69 nM) and JWH-182 (CB1 Ki 0.65 nM) respectively, and than the 4-methoxy compound JWH-081 (CB1 Ki 1.2 nM). It was discovered by and named after John W. Huffman.
Cannabicyclohexanol is a cannabinoid receptor agonist drug, developed by Pfizer in 1979. On 19 January 2009, the University of Freiburg in Germany announced that an analog of CP 47,497 was the main active ingredient in the herbal incense product Spice, specifically the 1,1-dimethyloctyl homologue of CP 47,497, which is now known as cannabicyclohexanol. The 1,1-dimethyloctyl homologue of CP 47,497 is in fact several times more potent than the parent compound, which is somewhat unexpected as the 1,1-dimethylheptyl is the most potent substituent in classical cannabinoid compounds such as HU-210.
JWH-019 is an analgesic chemical from the naphthoylindole family that acts as a cannabinoid agonist at both the CB1 and CB2 receptors. It is the N-hexyl homolog of the more common synthetic cannabinoid compound JWH-018. Unlike the butyl homolog JWH-073, which is several times weaker than JWH-018, the hexyl homolog is only slightly less potent, although extending the chain one carbon longer to the heptyl homolog JWH-020 results in dramatic loss of activity. These results show that the optimum side chain length for CB1 binding in the naphthoylindole series is the five-carbon pentyl chain, shorter than in the classical cannabinoids where a seven-carbon heptyl chain produces the most potent compounds. This difference is thought to reflect a slightly different binding conformation adopted by the naphthoylindole compounds as compared to the classical cannabinoids, and may be useful in characterizing the active site of the CB1 and CB2 receptors.
JWH-164 is a synthetic cannabinoid receptor agonist from the naphthoylindole family. It has approximately equal affinity for the CB1 and CB2 receptors, with a Ki of 6.6 nM at CB1 and 6.9 nM at CB2. JWH-164 is a positional isomer of the related compound JWH-081, but with a methoxy group at the 7-position of the naphthyl ring, rather than the 4-position as in JWH-081. Its potency is intermediate between that of JWH-081 and its ring unsubstituted derivative JWH-018, demonstrating that substitution of the naphthyl 7-position can also result in increased cannabinoid receptor binding affinity.
JWH-098 is a synthetic cannabinoid receptor agonist from the naphthoylindole family. It is the indole 2-methyl derivative of a closely related compound JWH-081, but has markedly different affinity for the CB1 and CB2 receptors. While JWH-081 is around tenfold selective for CB1 over CB2, in JWH-098 this is reversed, and it is around four times weaker than JWH-081 at CB1 while being six times more potent at CB2, giving it a slight selectivity for CB2 overall. This makes JWH-098 a good example of how methylation of the indole 2-position in the naphthoylindole series tends to increase CB2 affinity, but often at the expense of CB1 binding.
JWH-424 is a drug from the naphthoylindole family, which acts as a cannabinoid agonist at both the CB1 and CB2 receptors, but with moderate selectivity for CB2, having a Ki of 5.44nM at CB2 vs 20.9 nM at CB1. The heavier 8-iodo analogue is even more CB2 selective, with its 2-methyl derivative having 40 times selectivity for CB2. However the 1-propyl homologues in this series showed much lower affinity at both receptors, reflecting a generally reduced affinity for the 8-substituted naphthoylindoles overall.
JWH-116 is a synthetic cannabinoid receptor ligand from the naphthoylindole family. It is the indole 2-ethyl derivative of related compound JWH-018. The binding affinity of JWH-116 for the CB1 receptor is reported as Ki = 52 ± 5 nM.
JWH-185 is a synthetic cannabinoid receptor ligand from the naphthoylindole family. It is the carbonyl-reduced derivative of related compound JWH-081. The binding affinity of JWH-185 for the CB1 receptor is reported as Ki = 17 ± 3 nM.
SDB-005 is an indazole-based synthetic cannabinoid that has been sold online as a designer drug. It is presumed to be an agonist of the CB1 and CB2 cannabinoid receptors. SDB-005 is the indazole core analog of PB-22 where the 8-hydroxyquinoline has also been replaced with a naphthalene group.
MDMB-CHMICA is an indole-based synthetic cannabinoid that is a potent agonist of the CB1 receptor and has been sold online as a designer drug. While MDMB-CHMICA was initially sold under the name "MMB-CHMINACA", the compound corresponding to this code name (i.e. the isopropyl instead of t-butyl analogue of MDMB-CHMINACA) has been identified on the designer drug market in 2015 as AMB-CHMINACA.
FUB-JWH-018 is a naphthoylindole-based synthetic cannabinoid, representing a molecular hybrid of JWH-018 and AB-FUBICA or ADB-FUBICA.
NM-2201 (also known as CBL-2201 and NA-5F-PIC) is an indole-based synthetic cannabinoid that presumably has similar properties to the closely related 5F-PB-22 and NNE1, which are both full agonists and unselectively bind to CB1 and CB2 receptors with low nanomolar affinity.
MMB-2201 is a potent indole-3-carboxamide based synthetic cannabinoid, which has been sold as a designer drug and as an active ingredient in synthetic cannabis blends. It was first reported in Russia and Belarus in January 2014, but has since been sold in a number of other countries. In the United States, MMB-2201 was identified in Drug Enforcement Administration drug seizures for the first time in 2018.
XLR-12 is an indole-based synthetic cannabinoid drug that was invented by Abbott Laboratories in 2006. It is an analogue of XLR-11 where the 5-fluoropentyl chain has been replaced with a 4,4,4-trifluorobutyl chain. XLR-12 is relatively highly selective for the CB2 receptor, with a Ki of 0.09 nM and 167x selectivity over the related CB1 receptor, however it still retains appreciable affinity for CB1 with a Ki of 15 nM.
To combat the illicit synthetic cannabinoid industry many jurisdictions have created a system to control these cannabinoids through their general structure as opposed to their specific identity. In this way new analogs are already controlled before they are even created. A large number of cannabinoids have been grouped into classes based on similarities in their chemical structure, and these classes have been widely adopted across a variety of jurisdictions.