Coleus forskohlii (also called Plectranthus barbatus and Coleus barbatus) is an aromatic perennial plant belonging to the Lamiaceae (mint) family. It is found in tropical and subtropical regions of the world, including the Indian subcontinent, Thailand, Brazil, Ethiopia, and Egypt.^[2] Coleus forskohlii has traditionally been used in Ayurvedic medicine for the treatment of cardiovascular, gastrointestinal, respiratory, urinary, and central nervous system disorders.^[3][4] Forskolin, the main bioactive compound in Coleus forskohlii, has been investigated as a potential treatment for asthma, glaucoma, and high blood pressure, as well as a fat burner and testosterone booster.^{[5][6][7][8][9]}

The application of eye drops containing 0.3–1% of forskolin (the main bioactive compound in Coleus forskohlii) may cause small reductions in intraocular pressure, suggesting potential therapeutic effects of forskolin in eye disorders involving ocular hypertension, such as glaucoma.^[10][11] Although trials administering forskolin orally in participants with glaucoma have also noted reductions in intraocular pressure, the findings were confounded by simultaneous supplementation with rutin and vitamins vitamin B1 and vitamin B2.^[12][13]

Limited preliminary clinical research suggests that supplementation with Coleus forskohlii extract or forskolin may reduce the number of asthma attacks in children,^[5] protect against methacholine-induced airway restriction in healthy adults,^[14] increase testosterone levels and bone mineral density (BMD) in men with overweight/obesity,^[8] and reduce blood pressure and improve body composition and/or metabolic health in older adults and in adults with overweight/obesity.^[7][8][15] However, much more evidence is needed in these research areas before firm conclusions can be drawn.

Findings from some in vitro and animal studies suggest that Coleus forskohlii may have anticancer,^[16][17][18] antifibrotic,^[19] thyroid-stimulating,^[20] and anti-inflammatory^[21] properties. However, human trials exploring these potential effects are lacking.

Although supplementation with Coleus forskohlii extract or forskolin is generally considered to be safe and well tolerated at recommended doses, it has been associated with side effects relating mainly to gastrointestinal disturbances (primarily diarrhea).^[22][23]

Because supplementation with Coleus forskohlii extract or forskolin has been noted to reduce blood pressure, increase stomach acid levels, and inhibit platelet aggregation, its use may be contraindicated for some individuals.^[1]

The primary mechanism through which forskolin (the main bioactive compound in Coleus forskohlii) exerts its effects is by activating almost all (8 out of 9) isoforms of the enzyme adenylyl cyclase,^[24] which, in turn, increases the production of cyclic adenosine monophosphate (cAMP) within cells.^[25] This increase in cAMP levels results in the subsequent modulation of various cellular processes through the activation of protein kinase A (PKA) and other proteins or enzymes, which, in turn, affect a wide range of physiological processes, including metabolism, hormone secretion, muscle contraction, and neurotransmission.^[26][27]