Phytochemicals and Potential Health Effects
The dried rhizomes contained essential oil with the main chemical classes: monoterpene hydrocarbons, monoterpene alcohols and straight-chain aliphatic alcohols were the most abundant volatiles detected in the essential oil, and a total of 86 compounds were identified (Rohloff, 2002). Geraniol was identified as the most important rose-like odor compound besides geranyl formate, geranyl acetate, benzyl alcohol and phenylethyl alcohol. Its oxygenated metabolite rosiridol is an aglycon of rosiridin (Kurkin et al., 1985a; Kurkin and Zapesochnaya, 1986b) - one of the most active constituents of Rhodiola in bioassay guided fractionation of Rhodiolathe extract. Rosiridin was found to inhibit monoamine oxidases A and B in vitro implying its potential beneficial effect in depression and senile dementia. More than 50 polar compounds were isolated from the water alcoholic extracts, they are: monoterpene alcohols and their glycosides, cyanogenic glycosides, phenylethanoids and phenylpropanoids, flavonoids, aryl glycosides, proanthocyanidins and other gallic acid derivatives. (Zapeschnaya, and Kurkin, 1983, 1983; Kurkin et al., 1985a; Kurkin, and Zapesochnaya, 1986a,b; Ganzera et al., 2001; Tolonen et al.,2003; Saratikov and Krasnov, 2004; Akgul et al., 2004; Ma et al.2006, Yousef et al., 2006, Ali et al.,2008; Avula et al., 2008).
Rhodiola rosea contains a variety of compounds that may contribute to its effects, including the class of rosavins which include rosavin, rosarin, and rosin. Several studies have suggested that the most active components are likely to be rhodioloside and tyrosol, with other components being inactive when administered alone, but showing synergistic effects when a fixed combination of rhodioloside, rosavin, rosarin and rosin was used.
Although rosavin, rosarin, rosin and salidroside (and sometimes p-tyrosol, rhodioniside, rhodiolin and rosiridin) are among suspected active ingredients of Rhodiola rosea, these compounds are mostly polyphenols for which no physiological effect in humans is proved to prevent or reduce risk of disease.
Although these phytochemicals are typically mentioned as specific to Rhodiola extracts, there are many other constituent phenolic antioxidants, including proanthocyanidins, quercetin, gallic acid, chlorogenic acid and kaempferol.
While animal tests have suggested a variety of beneficial effects for Rhodiola rosea extracts, there is scientific evidence only for depression as a benefit in humans. A clinical trial showed significant effect for a Rhodiola extract in doses of 340–680 mg per day in male and female patients from 18 to 70 years old with mild to moderate depression. Another study also found antidepressant properties, possibly via the plant's inhibition of MAO-A and MAO-B.
R. rosea promotes the release of NO from rat penile corpus cavernosum smooth muscle cell and artery endothelium cell, which was correlated with its effect to resist senility.
Rhodiola rosea extract exerts an antifatigue effect that increases mental performance, particularly the ability to concentrate in healthy subjects and burnout patients with fatigue syndrome. Rhodiola significantly reduced symptoms of fatigue and improved attention after four weeks of repeated administration.
Studies on whether Rhodiola improves physical performance have been inconclusive, with some studies showing some benefit, while others show no significant difference.
Inhibitory activities against HIV-1 protease have also been studied.
Read more about this topic: Rhodiola Rosea
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