Coleus / Forskolin

Plectranthus barbatus (syn. Coleus forskohlii)

LamiaceaeIndia (Rajasthan, Uttar Pradesh, Karnataka, Tamil Nadu), Nepal, Sri Lanka, East Africa, Ethiopia; widely naturalized across tropical Asia

Description

overall appearance

A perennial herb or subshrub growing 30–90 cm tall with erect, branching stems and aromatic foliage. The plant has a distinctive camphor-like scent and produces attractive blue-violet flower spikes.

roots

Fleshy, tuberous, carrot-shaped roots up to 10 cm long and 2 cm in diameter; yellowish-white exterior; the roots contain the highest concentration of forskolin

stem

Erect, quadrangular (square), succulent stems covered with fine, soft hairs; often tinged purple; branching from base

leaves

Opposite, ovate to oblong, 4–9 cm long and 2–4 cm wide; margins crenate-serrate; fleshy texture; glandular hairs on both surfaces; light to mid-green with occasional purplish tints

flowers

Tubular, bilabiate, pale blue to violet-blue; borne in whorls on terminal spikes 10–20 cm long; each flower 1–1.5 cm long; blooms October–February

fruits/seeds

Four small nutlets (mericarps) enclosed in persistent calyx; seeds tiny, dark brown

Active Compounds

Forskolin (coleonol) — primary diterpene, cAMP activator, 0.1–0.3% fresh root weightColeonols A–F (related labdane diterpenes)Rosmarinic acid (phenylpropanoid, anti-inflammatory)Luteolin, apigenin (flavones with COX inhibitory activity)Ursolic acid and oleanolic acid (triterpenoids)Terpene phenols: thymol and carvacrol derivatives7-deacetyl-7-benzoyloxy-6-acetoxy-8,13-epoxy-labd-14-en-11-one (bioactive diterpene)Caffeic acid esters and chlorogenic acid

Traditional Uses

Ayurveda (makandi/garmar): heart tonic for congestive heart conditions, hypertension, and angina
Traditional Indian medicine: treatment of abdominal colic, urinary retention, and painful menstruation
Unani medicine: used for skin conditions including psoriasis and eczema
Traditional use in glaucoma treatment: eye drops prepared from root extract in India
Indian folk medicine: as a digestive and carminative for bloating and gas
Traditional treatment for thyroid conditions and hypothyroidism in Ayurveda
Topical application for skin infections, burns, and insect bites
Used as a condiment and pickle ingredient in Indian cuisine (leaves)

Modern Applications

Adenylyl cyclase activation: forskolin raises intracellular cAMP, affecting virtually all cell types; used as a research tool worldwide
Weight loss and body composition: clinical trials show modest fat mass reduction (125 mg 10% extract 2×/day); FDA-recognized as a supplement ingredient
Cardiovascular: positive inotropic effect, vasodilation, and mild antihypertensive action in clinical pilots
Glaucoma: topical 1% forskolin eye drops reduce intraocular pressure comparably to beta-blocker drops
Asthma: bronchodilatory via cAMP-mediated smooth muscle relaxation; inhaled preparations studied
Testosterone support: cAMP stimulation of Leydig cells increases testosterone in one RCT (men, 12 weeks)
Hypothyroidism: stimulates thyroid hormone synthesis and release via TSH-independent cAMP pathway
Cancer research: apoptosis induction in colon, prostate, and breast cancer cell lines via cAMP/PKA pathway

⚠️ Safety Information

Contraindications

Hypotension: vasodilatory effect can cause dangerous blood pressure drops
Hemorrhagic conditions or pre-surgery: antiplatelet activity
Pregnancy and lactation: insufficient safety data; uterine-relaxant effects possible
Polycystic kidney disease: cAMP elevation may promote cyst growth
Peptic ulcer disease: increases gastric acid secretion via cAMP pathway

Side Effects

Flushing, rapid heartbeat, and hypotension at high doses
Upper respiratory irritation with inhaled preparations
Tremor and restlessness at doses >500 mg/day
Increased bleeding time and easy bruising
Headache during initial use

Drug Interactions

Antihypertensive agents (calcium channel blockers, beta-blockers, ACE inhibitors): potentiates hypotensive effect
Anticoagulants and antiplatelets (warfarin, aspirin, clopidogrel): enhanced bleeding risk
Thyroid hormones (levothyroxine): additive thyroid-stimulating effects; hyperthyroidism risk
Phosphodiesterase inhibitors (sildenafil, tadalafil): additive cAMP elevation; cardiovascular risk
Beta-2 agonists (albuterol): synergistic bronchodilation; potential cardiac overstimulation