Chemical and Physical Properties of A9-THC

A9-THC (2.1 in Fig. 2) is the only major psychoactive constituent of C. sativa. It is a pale yellow resinous oil and is sticky at room temperature. A9-THC is hpophihc and poorly soluble in water (3 p,g mL ), with a bitter taste but without smell. Furthermore it is sensitive to light and air [4]. Some more physical and chemical data on A9-THC are fisted in Table 1. Because of its two chiral centers at C-6a and C-lOa, four stereoisomers are known, but only (-)-trans-A9-THC is foimd in the Cannabis plant [5]. The absolute configuration of the 

It must be noted that A9-THC is not present in C. sativa, but that the te-trahydrocannbinolic acid (THCA) is almost exclusively found. Two kinds of THCA are known. The first has its carboxylic function at position C-2 and is named 2-carboxy-A9-THC or THCA-A (2.2) the second has a carboxylic function at position C-4 and is named 4-carboxy-A9-THC or THCA-B (2.3). 

THCA shows no psychotropic effects, but heating (e.g., by smoking of Cannabis) leads to decarboxylation, which provides the active substance A9-THC. A9-THC is naturally accompanied by its homologous compounds containing a propyl side chain (e.g., tetrahydrocannabivarin, THCV, THC-C3,2.4) or a butyl side chain (THC-C4,2.5). 

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