Terpinolene (TPO), also known as alpha-terpinolene or isoterpinene, belongs to the class of organic compounds known as menthane monoterpenoids. These are monoterpenoids with a structure based on the o-, m-, or p-menthane backbone. P-menthane consists of the cyclohexane ring with a methyl group and a (2-methyl)-propyl group at the 1 and 4 ring position, respectively. The o- and m- menthanes are much rarer, and presumably arise by alkyl migration of p-menthanes. Thus, terpinolene is considered to be an isoprenoid lipid molecule. Terpinolene is a very hydrophobic monoterpenoid, practically insoluble in water, and relatively neutral. Monoterpenoids are terpenes that contain 10 carbon atoms and are comprised of two isoprene units. The biosynthesis of monoterpenes in plants is known to occur mainly through the methyl-erythritol-phosphate (MEP) pathway in the plastids (PMID:7640522 ). Geranyl diphosphate (GPP) is a key intermediate in the biosynthesis of cyclic monoterpenes. GPP undergoes several cyclization reactions to yield a diverse number of cyclic arrangements. Terpinolene is one of the constituents of turpentine and an isomer of terpinene. It appears colourless to pale yellow liquid. Alpha-terpinolene has been identified as an abundant monoterpene in the essential oil of Cannabis sativa plants (PMID:6991645 ). There are more than 140 known terpenes in cannabis and the combination of these terepenoids produces the skunky, fruity odor characteristic of C. savita. Although common in cannabis cultivars, terpinolene is typically found in relatively low amounts. On the other hand, the concentration of terpinolene can be has high as 30% of the essential oil. It is thought that terpinolene offers a mildly sedative effect and can reduce anxiety (PMID:28826544 ). In particular, terpinolene is a central nervous system depressant that has been shown to induce drowsiness (PMID:23339024 ). Terpinolene has been demonstrated to prevent LDL oxidation and is of potential interest in the treatment of atherogenesis and coronary artery disease (PMID:28826544 ). Terpinolene exhibits antifungal and larvicidal properties (PMID:28826544 ). Terpinolene is also an effective anti-microbial agent, particularly against E coli and Staphylococcus bacteria (PMID:16402540 ). Terpinolene is also employed as a fragrence ingredient in lotions, insect repellents (similar to other terpenes), perfumes, and soaps. Terpinolene is also a constituent of many other essential oils e. g. Citrus, Mentha, Juniperus, Myristica species. Parsnip oil (Pastinaca sativa) in particular, is a major source (40-70%). Terpinolene is a sweet, citrus, and fresh tasting compound. It produces a floral, woody or herbal aroma reminiscent of pine needles. In addition to being found in various plant essential oils, terpinolene is found in a few different foods and spices, such as allspice, apples, sage, rosemary, parsnips, nutmegs, and wild carrots and in a lower concentration in sweet bay, star anises, turmerics, apricots, cumins, evergreen blackberries, red bell peppers, and caraway.