Forskolin

Forskolin, also called coleonol, is a labdane diterpene, a type of oil-soluble plant compound built from the same isoprenoid building blocks as many natural terpenes ^[1][3]. It is obtained from the roots of Plectranthus barbatus, an aromatic plant of the mint family native to India and long known as Coleus forskohlii, which has a place in traditional Ayurvedic medicine ^[1][3]. Its molecular formula is C22H34O7, and it dissolves readily in organic solvents such as ethanol and DMSO rather than in water ^[1]. The compound was isolated and characterised in the 1970s and 1980s, when its striking effect on cellular signalling was discovered ^[3][4].

What made forskolin famous was its action on adenylyl cyclase, the enzyme that manufactures the second messenger cyclic AMP inside cells ^[2][3]. Unlike hormones, which switch on this enzyme indirectly through cell-surface receptors and G proteins, forskolin activates it directly, rapidly, and reversibly, and it does so across a wide range of tissues ^[2][4]. This unusual property turned forskolin into a standard laboratory reagent; researchers use it to raise cAMP at will in order to probe the countless processes that this messenger controls, and it has been applied in studies of the nervous, endocrine, cardiovascular, respiratory, and other systems ^[3]. Chemical derivatives such as colforsin daropate have been developed as more potent, water-soluble relatives and explored for uses such as widening the airways and supporting the failing heart ^[1].

Outside the laboratory, forskolin is sold as a dietary supplement, typically as an extract of Coleus forskohlii root, and is marketed above all for weight loss and body composition ^[1][4]. The rationale offered is that raising cAMP could encourage the breakdown of stored fat, but the human evidence is thin ^[4]. Reviews of weight-loss supplements have concluded that studies of forskolin are few, small, and of low quality, so its usefulness for shedding weight remains unproven ^[1][4]. It has also been promoted for other conditions on the strength of its cAMP-raising activity, again without robust clinical support ^[1].

As a supplement ingredient rather than an approved medicine, forskolin is not tightly regulated, and the strength and purity of commercial products can vary ^[4]. Because raising cAMP can relax blood vessels and affect the heart, it may lower blood pressure and could interact with blood-pressure and blood-thinning medicines, so caution is advised for people taking such drugs ^[1][4]. It is available as oral capsules of the root extract and, for research purposes, as a purified reagent ^[1].

Generally tolerated in short studies, but the vasodilation can lower blood pressure and it may increase heart rate, so people on blood pressure or blood thinning medication should be cautious. It can increase stomach acid and cause GI upset. Avoid before surgery due to bleeding risk, and avoid combining with other blood-pressure-lowering agents without guidance.