Biological Effects
A 2010 ethnopharmacological inventory study on Eurycoma longifolia stated: "The plant parts have been traditionally used for its antimalarial, aphrodisiac, anti-diabetic, antimicrobial and antipyretic activities…"
Even though there are many other legitimate medical areas of interest in Eurycoma longifolia (as evident from the quote included above), most Southeast Asians consume it for the plant's impact on sexual conduct. Already in 2001, Malaysian scientific researchers opened their peer-reviewed, Medline-archived report on Eurycoma longifolia's effect on lab rats with the statement "that Eurycoma longifolia Jack commonly known as Tongkat Ali has gained notoriety as a symbol of man's ego and strength by the Malaysian men because it increases male virility and sexual prowess during sexual activities."
An article on the website of the scientific journal Nature referred to Eurycoma longifolia as Malaysia's home-grown Viagra and cited "increased sexual desire, enhanced performance and general well-being". This journal article is also indexed on Medline, but without abstract.
Some scientific studies found that it enhances sexual characteristics and performance in rodents. Other laboratory animal tests have produced positive indications, with one extract having been observed to increase sexual activity in mature rats, including arousal, sniffing, and mounting behavior.
In an experiment conducted on male rats, it was found that eurycoma longifolia increases sperm count. The authors also reported that the plasma testosterone level of Eurycoma longifolia extract treated rats "was significantly increased when compared with that of the control and infertile animals."
Another group of scientists confirmed that Eurycoma longifolia has the capacity to "reverse the inhibitory effects of estrogen on testosterone production and spermatogenesis."
One Medline-indexed journal article cited as result that Eurycoma longifalia had an effect similar to testosterone replacement therapy in counteracting osteoporosis.
An Italian study on Eurycoma longifolia noted improved sexual performance in lab animals and concluded that the "effect could be mainly ascribed to increased testosterone levels."
After scientists investigating Eurycoma longifolia's effect on sexual parameters had established that sexualizing effects went hand-in-hand with increased testoterone tone, researchers in the field of sports medicine started to look into the anabolic potential of the plant.
In a placebo-controlled human study with healthy young men in a weight-training program, it was found that "the lean body mass of the treatment group showed a significant increment, from 52.26 (7.18) kg to 54.39 (7.43) kg (p = 0.012)." Furthermore, "the increase in strength in the treatment group was larger than in the placebo group (6.78% and 2.77% respectively)… The mean arm circumference of the treatment group increased significantly by 1.8 cm after the supplementation… but there was no significant increase in the placebo group." The results of the study were published in the peer-reviewed British Journal of Sports Medicine.
The anabolic impact of Eurycoma longifolia has been confirmed in the animal model, when the size and weight of just one muscle was measured in treated and untreated rats of equal size. "Results showed that 800 mg/kg of butanol, methanol, water and chloroform fractions of E. longifolia Jack significantly increased (p<0.05) the levator ani muscle…"
Because of Eurycoma longifolia's testosterone-enhancing capacity, it has been included, at least by name, in numerous supplements, marketed primarily to bodybuilding men. One such product lists Eurycoma longifolia as one of more than 30 unquantified ingredients.
In such formulas, the minimal Eurycoma longifolia part isn't a therapeutic dose by any standard, as the quassinoids of Eurycoma longifolia are characterized by poor oral bioavailability.
A study into this aspect concluded: "The results indicate that eurycomanone is poorly bioavailable when given orally… the absolute bioavailability of the compound was low with 10.5%… its poor oral bioavailability may be due to poor membrane permeability in view of its low P value and/or high first-pass metabolism."
In vivo studies with lab animals used root powder of 250, 500, or 1000 mg per kg of body weight, or 200 to 800 mg/kg twice daily, or 50, 100, and 200 mg of Eurycoma longifolia extract per kg of body weight. At the higher dosages (800 mg of the water, chloroform, methanol, or butanol extracted fraction of Eurycoma longifolia per kg of body weight), the effects were more pronounced for both sexual motivation and levator ani size increase.
Apart from the testosterone-related effects, the antimalarial, antibacterial, antipyretic, antiulcer, antitumor, and cytotoxic properties are well documented.
Taiwanese scientists isolated 65 biochemical compounds from the roots of Eurycoma longifolia, of which ten exhibited "strong cytotoxicity" towards human lung and breast cancer cell lines.
Apart from the better-known quassinoids, the same group of scientist also isolated beta-carboline alkaloids, several of which were active against lung and breast cancer cell lines.
Investigating the activity of 24 Eurycoma longifolia quassinoids against cancer cell lines, including lung cancer cells, medical researchers in Japan found that eurycomalactone was as effective against cancer cells as the established anti-cancer drug doxorubicin.
The same group of researchers also discovered several new biochemical compounds in Eurycoma longifolia and screened them for cytotoxic properties. They concluded that different fractions were effective against different cancers.
Another study confirmed that fractions of Eurycoma longifolia extract induced apoptosis in breast-cancer cells.
One extract has since been co-patented by the government of Malaysia and the Massachusetts Institute of Technology. However, the idea that products of nature on which there exists a large body of knowledge among indigenous peoples can be the subject of intellectual property rights, even of national governments, has long been challenged in peer-reviewed law journals.
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