Cannabidiol, also known as CBD, is a cannabinoid found in Cannabis. It is a major constituent of the plant, representing up to 40% in its extracts.
CBD alone is not intoxicating, but it appears to moderate the euphoric effect of tetrahydrocannabinol (THC), which is an isomer of cannabidiol and add a sedative quality. Some research, however, indicates that CBD can increase alertness. It may decrease the rate of THC clearance from the body, perhaps by interfering with the metabolism of THC in the liver. CBD does not appear to affect either the CB1 or CB2 receptors.
Medically, it appears to relieve convulsion, inflammation, anxiety, and nausea, and to inhibit cancer cell growth. Recent studies have shown cannabidiol to be as effective as atypical antipsychotics in treating schizophrenia. In November 2007 it was reported that CBD reduces growth of aggressive human breast cancer cells in vitro and reduces their invasiveness. It thus represents the first non-toxic exogenous agent that can lead to down-regulation of tumor aggressiveness. It is also a neuroprotective antioxidant.
In April 2005, Canadian authorities approved the marketing of Sativex, a mouth spray for multiple sclerosis to alleviate pain. Sativex contains tetrahydrocannabinol together with cannabidiol. It is marketed in Canada by GW Pharmaceuticals.
Initial research is showing that CBD has an effect in reducing schizophrenic symptoms in patients.
Cannabidiol does not bind to CB1 or CB2 receptors but it does block the effects of cannabinoid agonists by an unknown indirect way. Recently it was found to be an antagonist at the putative new cannabinoid receptor, GPR55, a GPCR expressed in the caudate nucleus and putamen.
Cannabidiol has also been shown to inhibit cancer cell growth, with low potency in non-cancer cells. Although the inhibitory mechanism is not yet fully understood, Ligresti et al suggest that “cannabidiol exerts its effects on these cells through a combination of mechanisms that include either direct or indirect activation of CB2 and TRPV1 receptors, and induction of oxidative stress, all contributing to induce apoptosis.” In November 2007, researchers at the California Pacific Medical Center reported that CBD shows promise for controlling the spread of metastatic breast cancer. In vitro CBD down regulates the activity of the gene Id-1 which is responsible for tumor metastasis.
Cannabidiol is insoluble in water but soluble in organic solvents. At room temperature it is a colorless crystalline solid. In strongly basic medium and the presence of air it is oxidized to a quinone. Under acidic conditions it cyclizes to THC. The synthesis of cannabidiol has been accomplished by several research groups.
Cannabidiol is a Schedule I drug in the USA, despite having no psychoactive effects and no known abuse potential. The strict legal status may be due to the fact that CBD has been shown to inhibit the anxiety that THC can induce at high doses ~0.5mg/kg and also how easily CBD could be converted to THC, as outlined above.