Forskolin

source plant is Coleus forskohlii.

used in Ayurveda for heart conditions, respiratory disorders, abdominal colic, and digestive stimulation. Coleus forskohlii is the sole natural source of the labdane terpenoid forskolin (C₂₂H₃₄O₇), and its tuberous roots contain the highest concentration of this metabolite.

forskolin is the only plant-derived compound known to stimulate the enzyme adenylate cyclase and subsequently affect cyclic AMP (cAMP) synthesis.

it is a lipid-soluble compound that can penetrate cell membranes and stimulates adenylate cyclase directly. in the eye, this stimulates ciliary epithelium, activates cAMP, and decreases intraocular pressure by reducing aqueous humor inflow.

oral forskolin may reduce asthma attacks. when administered intravenously or inhaled, forskolin had a bronchodilation effect.

the most cited body composition RCT by Godard et al. enrolled 30 overweight men randomized to 250 mg of 10% forskolin extract or placebo twice daily for 12 weeks. the forskolin group showed significant decrease in body fat percentage (35.5% to 33.8%) and significant increase in lean mass, along with elevated serum free testosterone levels.

intravenous forskolin (0.5–2 µg/kg/min) studied as a positive inotrope with vasodilatory properties in congestive heart failure showed increased cardiac output, reduced systemic vascular resistance, and reduced pulmonary capillary wedge pressure — comparable to milrinone. milrinone is a pharmaceutical inotrope used in ICU settings for acute heart failure.

Coleus forskohlii extract displayed a bone-conserving effect via osteogenic and anti-resorptive mechanisms, maintaining bone mass, microarchitecture, material, and strength in ovariectomized rats — a model of post-menopausal osteoporosis. cAMP increases in osteoblasts have a documented osteogenic effect.

in vitro, coleusin factor (a related diterpene from the same plant) induced G0/G1 cell cycle arrest and apoptosis in gastric cancer cells. forskolin has been shown to synergize with dexamethasone in inducing cell death in myeloma cells via BIM — a pro-apoptotic protein.

for asthma

cAMP is the cellular signal that relaxes bronchial smooth muscle. by flooding airways cells with cAMP, forskolin produces bronchodilation through the same pathway that beta-2 agonist drugs like albuterol use, but through a mechanistically distinct route — which means it could work where beta-agonists fail or cause tachyphylaxis.

oral use at commercial doses is generally well-tolerated. main risks: hypotension at higher doses, GI effects. not appropriate with antihypertensives without monitoring, and caution warranted in arrhythmia or with anticoagulants given antiplatelet activity. avoid in pregnancy — uterine stimulant effects documented in animal studies.