Tribulus Terrestris
Tribulus terrestris is a flowering plant in the family Zygophyllaceae, native to warm temperate and tropical regions of the Old World in southern Europe, southern Asia, throughout Africa, and in northern Australia. It can thrive even in desert climates and poor soil.
Etymology
The Latin name tribulus originally meant the caltrop (a spiky weapon), but in Classical times already meant this plant as well.
Alternate names
*Similar: Pedalium murex Linn.
*English: Like many weedy species, this plant has many common names. Puncturevine, Caltrop, Yellow *Vine, and Goathead, Burra Gokharu are the most widely used.
*Indian:Bhar-Gokharu, Selusaran, Gokshura, Hatticharatte, Bhaankadi.
*Sanskrit:Gokśūra, Surya, Gokanṭaka, Svādanstra, Svādukanṭaka, Trikanṭaka, Bhadrakanṭaka
Cultivation and uses
The plant is widely naturalised in the Americas and also in Australia south of its native range. In some states in the United States, it is considered a noxious weed and an invasive species.
It has been reported that puncture vine seeds have been used in homicidal weapons in southern Africa; murderers smear them with the poisonous juice of Acokanthera venenata and put them where victims are likely to step.
Dietary supplement
T. terrestris is now being promoted as a booster for the purpose of increasing sex drive. Its use for this purpose originated in Eastern Europe in the 1970s. It was popularized in America by 1970s strongman Jeffrey Petermann. Independent studies have suggested that Tribulus terrestris extract slightly increases hormone levels, though leaving them in the normal range.
The extract is claimed to increase the body's natural testosterone levels and thereby improve male sexual performance and help build muscle.
But T. terrestris has consistently failed to increase testosterone levels in controlled studies. It has also failed to demonstrate strength-enhancing properties. However, many supplement brands have sold products that combine various herbs with T. terrestris, with debatable effects.
T. terrestris has been shown to enhance sexual behaviour in an animal model by stimulating androgen receptors in the brain.
Some body builders use T. terrestris as post cycle therapy or "PCT". After they have completed an anabolic-steroid cycle, they use it under the assumption that it will restore the body's natural testosterone levels.
Medicinal uses
In Traditional Chinese Medicine Tribulus terrestris is known under the name Bai Ji Li (白蒺藜).
Tribulus terrestris has long been a constituent in tonics in Indian ayurveda practice, where it is known by its Sanskrit name, "gokshura." It is also used as an aphrodisiac, diuretic and nervine in Ayurveda, and in Unani, another medical system of India.
Animal studies in rats, rabbits and primates have demonstrated that administration of Tribulus terrestris extract can produce statistically significant increases in levels of testosterone, dihydrotestosterone and dehydroepiandrosterone (DHEA), and produces effects suggestive of aphrodisiac activity. On the other hand, one recent study found that T. terrestris caused no increase in testosterone or LH in young men, and another found that a commercial supplement containing androstenedione and herbal extracts, including T. terrestris, was no more effective at raising testosterone levels than androstenedione alone.
The active chemical in T. terrestris is likely to be protodioscin (PTN), a cousin to DHEA. In a study with mice, Tribulus was shown to enhance mounting activity and erection better than testosterone cypionate. This however, is not as convincing as one might think. Although an OTC supplement outpacing a pharmaceutical is big news, testosterone cypionate is a synthetic ester of testosterone engineered for its longer activity. To be effective, its level must build up in the system of the animal using it. This process usually takes 2–3 weeks. Since 2007-11-15 National Institutes of Health retrieved that the proerectile aphrodisiac properties were concluded to likely be due to the release of nitric oxide from the nerve endings innervating the corpus cavernosum penis.
Adverse effects from supplementation with Tribulus terrestris are rare and tend to be insignificant. However, some users report an upset stomach, which can usually be counteracted by taking it with food. Another rare side effect which has been reported is gynaecomastia, which while potentially problematic does tend to support the purported androgenic-anabolic effects of this plant.
Active Ingredient
Protodioscin is a steroidal saponin compound found in a number of plant species, most notably in the Tribulus, Trigonella and Dioscorea families. In plants, saponins may serve as anti-feedants and to protect the plant against microbes and fungi. Some plant saponins (e.g. from oat and spinach) may enhance nutrient absorption and aid in animal digestion. However, saponins are often bitter to taste, and so can reduce plant palatability (e.g., in livestock feeds), or even imbue them with life-threatening animal toxicity. Data make clear that some saponins are toxic to cold-blooded organisms and insects at particular concentrations. There is a need for further research to define the roles of these natural products in their host organisms—which have been described as "poorly understood" to date (Role in plant ecology and impact on animal foraging).
Protodioscin is best known as the putative active component of the herbal aphrodisiac plant Tribulus terrestris.
Extacts from T. terrestris standardised for protodioscin content have been demonstrated to produce proerectile effects in isolated tissues and aphrodisiac action in several animal species.
The mechanism for these effects has not been clearly established, and while protodioscin has been demonstrated to trigger release of nitric oxide in corpus cavernosum tissue, and also to produce statistically significant increases in the levels of the hormones testosterone, dihydrotestosterone and dehydroepiandrosterone in animal studies, evidence for efficacy in humans is limited and remains controversial (The effect of five weeks of Tribulus terrestris supplementation on muscle strength and body composition during preseason training in elite rugby league players, 2007).
Biological effects.
Various physiological processes such as male sexual differentiation, testicular descent, and spermatogenesis are mediated by androgens through AR, which in turn binds to the androgen responsive element on DNA and regulates gene transcription (Structural analysis of complementary DNA and amino acid sequences of human and rat androgen receptors, 1988; Cloning of human androgen receptor complementary DNA and localization to the X chromosome, 1988; Cloning, structure and expression of a cDNA encoding the human androgen receptor, 1988; Characterization and expression of a cDNA encoding the human androgen receptor, 1989).
http://www.ncbi.nlm.nih.gov.proxy-medicina.unito.it/pubmed/12804079?itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_RVDocSum&ordinalpos=2
Any mutations in AR will ultimately result in impaired development and function of the reproductive organs (Directed pharmacological therapy of ambiguous genitalia due to an androgen receptor gene mutation, 1999).
Protodioscin (PTN) that forms 45% (dry weight) of the Tribulus terrestris extract (TT) is the active ingredient (Purification, molecular weight and subunit structure of NAD-dependent glyceraldehyde 3-phosphate dehydrogenase from Chlorella, 1981). PTN is found to increase the levels of testosterone, lutinizing hormone, dehydroepiandrosterone (A dose-response study of alprostadil sterile powder (S.Po.) (Caverject) for the treatment of erectile dysfunction in Korean and Indonesian men, 1997; Is seminal prostatic acid phosphatase a reliable marker for male infertility?, 1996), dihydrotestosterone and dehydroepiandrosterone sulphate (Proerectile pharmacological effects of Tribulus terrestris extract on the rabbit corpus cavernosum, 2000). Administration of TT to humans and animals improved libido and spermatogenesis (NAD-dependent glyceraldehyde 3-phosphate dehydrogenase from Chlorella. Kinetics of inhibition by the reaction products NAD and NADP], 1981); it increased the sexual behaviour and intracavernous pressure in male rats (Aphrodisiac properties of Tribulus Terrestris extract (Protodioscin) in normal and castrated rats, 2002; Sexual effects of puncturevine (Tribulus terrestris) extract (protodioscin): an evaluation using a rat model, 2003), and also had a proerectile effect on isolated rabbit corpus cavernosal tissues in vitro (Proerectile pharmacological effects of Tribulus terrestris extract on the rabbit corpus cavernosum, 2000); most of these responses of TT are attributed to the presence of protodioscin and its phytoandrogenic properties.
In a study on rats, brain sections showed NADPH-d positive neurons in the paraventricular region of the hypothalamus. The staining intensity and the number of positive neurons were significantly higher in TT treated group than control. There was a statistically significant increase by 67% in the TT treated group compared to the control (p < 0.05); there was smaller number of AR in the control group compared to the TT treated one (p < 0.05); this increase was 58% in the TT treated group compared to control and was statistically significant (Effect of Tribulus terrestris on nicotinamide adenine dinucleotide phosphate-diaphorase activity and androgen receptors in rat brain, 2005).
Medial preoptic area (Social aspects of venereal disease. II. Relationship of personality to other sociological determinants of venereal disease, 1973), the paraventricular nucleus (Participation of paraventricular nucleus of hypothalamus in central regulation of penile erection in the rat,1997) and the hippocampus (Effects of anterior roof deafferentation on lordosis behavior and estrogen receptors in various brain regions of female rats, 1992) are some of the important sexual dimorphic areas of the brain. In addition, nucleus paragigantocellularis in the medulla is also found to influence sexual function. TT has been found to increase sexual behaviour in rats (Aphrodisiac properties of Tribulus Terrestris extract (Protodioscin) in normal and castrated rats, 2002; Sexual effects of puncturevine (Tribulus terrestris) extract (protodioscin): an evaluation using a rat model, 2003). TT also increases the levels of androgens and the synthesis of cyclic nucleotides in CCSM cells. Androgens are known to influence NO production in the brain (Testosterone, preoptic dopamine, and copulation in male rats, 1997) as well as in the periphery (Nitric oxide mediated erectile activity is a testosterone dependent event: a rat erection model, 1995). NO is synthesized by the enzyme nitric oxide synthase (NOS) which plays an important role in many brain functions. NO function as a neurotransmitter and NOS is present in the regions of the brain that regulate sexual functions. NADPH-d positive neurons are the same as those containing NOS (Nitric oxide synthetase (NOS)-containing sympathoadrenal cholinergic neurons of the rat IML-cell column: evidence from histochemistry, immunohistochemistry, and retrograde labeling, 1992) and hence NADPH-d immunohistochemistry helps to localize NOS neurons.
In the present investigation the NADPH-d positive neurons were significantly increased compared to control. This indicates that TT has the ability to increase the NOS in the sexual dimorphic areas of hypothalamus. The distribution pattern of NADPH-d positive neurons in the rat hypothalamus was in
general similar to those described in earlier reports (Reduction in the number of NADPH-diaphorase-positive cells in the cerebral cortex and striatum in aged rats, 1996).
The significant increase in AR immunoreactivity following TT indicates that prolonged treatment with TT has up regulated AR expression. The results are comparable with other reports where increase in androgens causes an increase in brain AR immunoreactivity (Dihydrotestosterone and estrogen regulation of rat brain androgen-receptor immunoreactivity, 2000). It has also been reported earlier that hypogonadal mice has less AR immunoreactivity (Androgen receptor immunoreactivity in specific neural regions in normal and hypogonadal male mice: effect of androgens, 1999). The probable mechanism for the TT induced increase in both NADPH-d positive neurons and AR immunoreactivity in the hypothalamus of rat brain is likely to be the androgen increasing property of the plant or through direct affinity of protodioscin molecule for AR receptors.
