Bioactive products found in Ephedra Sinica
Mechanism of Action
Pharmacology:
Constituents: Ephedra contains the alkaloids ephedrine, pseudoephedrine (isoephedrine), norpseudoephedrine (cathine), norephedrine, methylephedrine, methylpseudoephedrine, tannins, and other constituents, including quinoline and 6-hydroxykynurenic acid. The stem contains approximately 0.5-2.5% alkaloids, with ephedrine accounting for 30- 90% of the total alkaloid content. The variation in content depends upon the species harvested and the part of the plant used. For example, the woody stems are low in alkaloids and the fruits and roots have practically none, while the softer stems contain up to 2.5% active alkaloids. Ephedra sinica generally contains substantially greater concentrations of alkaloids than Ephedra Intermedia. The North American species, Ephedra Nevadensis (Mormon Tea, Mexican Tea, Squaw Tea, or Desert Tea), is apparently devoid of alkaloids altogether. Different extraction methods also yield different quantities of active compounds. In Ephedra sinica, pseudoephedrine is typically found as dextro-rotatory (D-pseudoephedrine) and ephedrine is typically levo-rotatory (L-ephedrine), while synthetically manufactured ephedrine is usually a racemic mixture.
Alkaloids: Ephedrine and pseudoephedrine are found in the leaves and stems of ephedra and are structurally related to amphetamines. They increase the availability and action of the endogenous neurotransmitters norepinephrine and epinephrine and stimulate catecholamine receptors in the brain, heart, and blood vessels both directly and indirectly. Both ephedrine and pseudoephedrine elicit central nervous system stimulation, bronchodilation, hypertension, and chronotropic/inotropic effects. The synthetic form of pseudoephedrine is widely used in non-prescription decongestants. Pseudoephedrine is a more potent diuretic than ephedrine. Ephedrine stimulates thermogenesis in adipocytes in vitro and in animal studies, an effect that appears to be enhanced by chronic administration. In mice, rats, and monkeys, ephedrine has been associated with significant weight loss, possibly by enhancing thermogenesis or anorexia. These effects have been enhanced by combining ephedrine with aspirin and/or methylxanthines (caffeine or theophylline). Jonderko et al. reported that ephedrine inhibits gastric emptying, which may result in a feeling of satiety and thereby aid in weight loss.
Pharmacodynamics/Kinetics:
The ephedra plant has been identified as an excellent source of ephedrine and pseudoephedrine, both of which can be chemically reduced to form the widely abused illicit drug methamphetamine. Ephedra contains several additional alkaloids that undergo analogous reductions to form amphetamine and N,N-dimethylamphetamine (also drugs of abuse).
