RESUMO
Synthetic cannabinoids, including some from the John W. Huffman (JWH) family, emerged on the drug scene around 2004 as "alternative marijuana," despite being considerably more potent than marijuana. Like Δ9-tetrahydrocannabinol (THC), the principal psychoactive ingredient in marijuana, synthetic cannabinoids have also been found to interact with cannabinoid receptors CB1 and CB2, found in the brain, immune system, and peripheral organs. The JWH compounds and other synthetic cannabinoids have become important subjects of research in the forensic science community due to their drug-abuse potential, undetectability under routine drug screening, and unpredictable toxicity. In this study, an active-state CB1 receptor model was used to assess the receptor-ligand interactions between the CB1 receptor and ligands from the JWH synthetic cannabinoid family, as well as some newly designed JWH-like virtual compounds, labeled as MGCS compounds, using docking, binding free-energy calculations (ΔG), and molecular dynamics simulations (MDs). The calculated ΔG revealed that the carbonyl group between the naphthalene and the indole, characteristic of the JWH family, and the length of the N-linked alkyl chain were two important structural characteristics that influenced the predicted CB1 binding affinity, especially as increasing the length of the alkyl chain led to better predicted binding affinity. MDs and per-residue-breakdown results showed that the designed MGCS compounds with a pentyl chain attached to the naphthalene moiety and selected JWH compounds formed stable and strong hydrophobic interactions with the key residues Phe170, Phe174, Phe177, Phe200, Phe268, and Trp279 of the CB1 receptor. Comprehension of these critical interactions can help forensic chemists predict the structure of undiscovered families of synthetic cannabinoids.
