COLEUS

Until recently, the more traditional use of the coleus herb was for the treatment of asthma and congestive heart failure. It has been shown that the same biological mechanism by which it helps these conditions is of value in helping the body shed excess fat, if patients are already following a proper weight-reduction program and performing at least a set amount of endurance exercise.

General Features

Coleus forskohlii is a small, perennial member of the mint family, used extensively for many applications in aryuredic medicine. Its unique active ingredient, diterpene forskolin, activates the enzyme adenylate cyclase in various tissues, which in turn, increases cellular levels of cyclic AMP (cyclic adenosine monophosphate). Cyclic AMP is nicknamed "the second messenger," as its synthesis triggers the action of various hormones, enzymes and other biological activities that have profound effects on local cells, and systemic effects (in some instances). It is primarily via the increased synthesis of cyclic AMP that coleus forskohlii may exert its medicinal influences on a significant number of common health conditions.1,11

Principle Active Constituents

The primary active constituent in coleus forkohlii is a diterpene compound (saponin) that is unique to the herb forskolin.1,11 Other diterpene compounds also have been isolated from it that may provide synergistic physiological effects.12

Clinical Application and Mechanism of Action

1. Cardiovascular Conditions

Congestive Heart Failure. As a therapeutic intervention in congestive heart failure, forskolin has been shown to activate the enzyme adenylate cyclase, which increases production of cyclic adenosine monophosphate (cAMP) in heart muscle cells (cardiac muscle). Epinephrine has a similar effect on increasing cAMP. Increased levels of cAMP, in turn, increase the ability of the heart muscle to produce ATP, the energy required for heart-muscle contraction and its optimal force with each beat (increased stroke volume). Forskolin also relaxes the artery wall, decreasing blood pressure and preload stress on the heart muscle. All of these effects appear to be mediated via increased cAMP synthesis, which acts as a secondary messenger on various cellular processes that manifest the stated outcomes.

Hypertension. As mentioned, forskolin relaxes blood vessel smooth muscles via increased cAMP synthesis, helping to reduce high blood pressure by reducing resistance to blood flow.

Platelet Function. Forskolin antagonizes the action of platelet-activating factor (PAF) by interfering with the binding of PAF to receptor sites on cells. In turn, this reduces platelet stickiness and smooth muscle contraction of blood vessels and bronchiole air passageways. Again, these effects are mediated through increased synthesis of cAMP.1-5

2. Asthma and Skin Conditions

Asthma and Eczema. These conditions are associated with a relative decrease in cAMP in bronchial smooth muscle and skin cells, respectively. In turn, this results in degranulation of mast cells and increased contraction of smooth muscle in the bronchiole passageways. Increased PAF also contributes to this problem. Pharmaceutical drugs for allergic conditions, asthma and eczema are often aimed at increasing cAMP levels (corticosteroids, methylxanthines).6

Corticosteroid drugs stimulate adenylate cyclase enzyme, increasing the synthesis of cAMP, whereas methylxanthine-containing drugs inhibit phosphodiesterase enzyme, which breaks down cAMP. Forskolin may be utilized alone, or in conjunction with these drugs, in the complementary management of these conditions.1,7,11

Psoriasis. Low levels of cAMP appear to disrupt its balance with cGMP (cyclic guanine monophosphate). This inbalance has been shown to cause rapid cellular proliferation (a rate that is 1,000 times faster than normal cells), which is a main feature of the psoriatic condition. In experimental studies, coleus forskohlii has been shown to slow the proliferation rate of skin cells by improving the relative balance of cAMP to cGMP.7

(Author's Note: In general, the abovementioned physiological effects associated with coleus forskohlii explain its historical use for the treatment of cardiovascular conditions, asthma, skin conditions, and as an antispasmodic in the management of irritable-bowel syndrome and uterine cramps. Unfortunately, no well-designed, large, clinical studies have been performed to establish its true therapeutic efficacy for any of these conditions and as such, recommending this herb for them is based primarily on historical use and animal experimental evidence supporting its role as an adenylate cyclase enzyme activator.11,13)

3. Lipolysis and Body Fat Reduction

Several clinical trials have shown coleus forskohlii may help reduce body fat in overweight adults. As with other substances (such as caffeine, adrenaline, ephedrine, epinephrine) that increase cAMP, forskolin enhances the breakdown and release of fat from fat cells. The synthesis of cAMP in fat cells initiates a chain of events that results in hydrolysis of stored triglycerides by hormone-sensitive lipase enzyme, with the subsequent release of free fatty acids and glycerol from fat cells.8,9,10 Unlike ephedrine and other central-nervous-system stimulants, forskolin does not produce the serious undesirable side-effects associated with stimulant drugs and supplements, such as rapid heart rate; elevated blood pressure; seizures; fatal heart attack; stroke; nervousness; anxiety; insomnia; and atrial fibrillation of the heart.

Forskolin appears to facilitate an increase in cAMP within fat cells in a manner that bypasses stimulation of beta-adrenergic receptors on the fat cell membrane. By comparison, stimulant drugs, hormones and supplements stimulate beta-adrenergic receptors on fat cells, heart muscle and the sympathetic nervous system, which results in increased cAMP levels and induces a direct stimulatory effect on the heart, cardiovascular and nervous system. In one study, subjects showed an average of 10 pounds of weight loss within an eight-week period, and an increase in their lean mass. Experimental evidence indicates that forskolin also mildly stimulates thyroid cells, which may explain its reported thermogenic properties. This may further account for its ability to facilitate reductions in body fat in overweight subjects.14-18

Dosage and Standardized Grade

For all of the above conditions, the usual dose of coleus forskohliiis is 250 mg, twice per day (standardized grade of 1 percent forskolin content) or 50 mg, twice per day (standardized grade of 18 percent forskolin, or 9 mg of forskolin per 50-mg tablet).11,19

Adverse Side-Effects, Toxicity and Contraindications

Coleus forskohlii has been shown to be extremely nontoxic and is not associated with any significant side-effects. It should be avoided in patients with peptic ulcers, as it may increase stomach acidity, although no adverse events of this nature have been published.11,20

Drug-Nutrient Interactions

Use with caution with patients on antiasthmatic and antihypertensive drugs, as forskolin may potentiate the effects of these drugs. As such, appropriate patient monitoring under these conditions is recommended.11-19

References

1. Laurenza A, Sutkowski AM, Seamon KB. Forskolin: a specific stimulator of adenylyl cyclase or a diterpene with multiple sites of action? Trends Pharmacol Sci 1989; 10:442-7.

2. Wong S, et.al. Forskolin inhibits platelet-activating factor binding to platelet receptors independently of adenylyl cyclase activation. Eur J Pharmacol 1993;245:55-61.

Synonym:Coleus barbatus

Synonym:Plectranthus forskohlii

Synonym:Coleus forskohlii

Category:
Perennials

Height:
18-24 in. (45-60 cm)

Spacing:
15-18 in. (38-45 cm)

Hardiness:
USDA Zone 9a: to -6.6° C (20° F)
USDA Zone 9b: to -3.8° C (25° F)
USDA Zone 10a: to -1.1°C (30° F)
USDA Zone 10b: to 1.7° C (35° F)

Sun Exposure:
Sun to Partial Shade

Danger:
Unknown - Tell us

Bloom Color:
Light Blue

Bloom Time:
Late Spring/Early Summer
Mid Summer
Late Summer/Early Fall
Mid Fall
Late Fall/Early Winter

Foliage:
Grown for foliage
Evergreen

Other details:
May be a noxious weed or invasive

Soil pH requirements:
Unknown - Tell us

Propagation Methods:
Unknown - Tell us

Seed Collecting:
Unknown - Tell us