Tetrahydrocannabinol, or THC for short, is a chiral molecule with 2 stereocenters. It is the main psychoactive constituent of cannabis, or marijuana. Cannabinoids are compounds that have a similar structure to THC. Marijuana has been in the news a lot lately with certain states legalizing specific small amounts and it being medically prescribed by some physicians. Some medical benefits include: pain relief, appetite stimulation (in AIDS wasting syndrome and anorexia), for glaucoma, epilepsy, easing the spasticity seen in MS and spinal cord injuries, and control of nausea and vomiting in chemo patients - just to name a few. THC also produces psychoactive effects.
THC is a lipophilic molecule. It acts on G-protein coupled receptors, decreasing cAMP and in turn inhibiting adenylate cyclase. Some studies believe that THC has anticholinesterase action, meaning it could possibly be a form of treatment for Alzheimer's disease! Maybe Bob Marley knew what was up.