Herbs and Natural Supplements: An Evidence-Based Guide
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Proerectile pharmacological effects of Tribulus terrestris extract on the rabbit corpus cavernosum.
INTRODUCTION: The objective of the present study was to investigate the effect of oral treatment of Tribulus terrestris (TT) extract on the isolated corpus cavernosal tissue of New Zealand white (NZW) rabbits and to determine the mechanism by which protodioscin (PTN), a constituent of the TT, exerts its pharmacological effects.
MATERIALS AND METHODS: Twenty-four NZW rabbits were randomly assigned to 4 experimental groups of 6 each. Group I served as control. Groups II to IV were treated with the extract at different dose levels, i.e. 2.5 mg/kg, 5 mg/kg and 10 mg/kg body weight, respectively. The TT extract was administered orally, once daily, for a period of 8 weeks. The rabbits were then sacrificed and their penile tissue isolated to evaluate the responses to both contracting and relaxing pharmacological agents and electrical field stimulation (EFS).
RESULTS: PTN on its own had no effect on the isolated corpus cavernosal strips. The relaxant responses to EFS, acetylcholine and nitroglycerin in noradrenaline precontracted tissues from treated groups showed an increase in relaxation of a concentration dependent nature compared to that of the tissues from control group. However, the contractile, anti-erectile response of corpus cavernosal tissue to noradrenaline and histamine showed no significant change between the treatment and the control groups.
CONCLUSIONS: The relaxant responses to acetylcholine, nitroglycerin and EFS by more than 10%, 24% and 10% respectively compared to their control values and the lack of such effect on the contractile response to noradrenaline and histamine indicate that PTN has a proerectile activity. The enhanced relaxant effect observed is probably due to increase in the release of nitric oxide from the endothelium and nitrergic nerve endings, which may account for its claims as an aphrodisiac. However, further study is needed to clarify the precise mechanism of its action.
Aphrodisiac properties of Tribulus Terrestris extract (Protodioscin) in normal and castrated rats
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Tribulus terrestris (TT) has long been used in the traditional Chinese and Indian systems of medicine for the treatment of various ailments and is popularly claimed to improve sexual functions in man.
Sexual behaviour and intracavernous pressure (ICP) were studied in both normal and castrated rats to further understand the role of TT containing protodioscin (PTN) as an aphrodisiac.
Adult Sprague-Dawley rats were divided into five groups of 8 each that included distilled water treated (normal and castrated), testosterone treated (normal and castrated, 10 mg/kg body weight, subcutaneously, bi-weekly) and TT treated (castrated, 5 mg/kg body weight, orally once daily).
Decreases in body weight, prostate weight and ICP were observed among the castrated groups of rats compared to the intact group.
There was an overall reduction in the sexual behaviour parameters in the castrated groups of rats as reflected by decrease in mount and intromission frequencies (MF and IF) and increase in mount, intromission, ejaculation latencies (ML, IL, EL) as well as post-ejaculatory interval (PEI).
Compared to the castrated control, treatment of castrated rats (with either testosterone or TT extract) showed increase in prostate weight and ICP that were statistically significant.
There was also a mild to moderate improvement of the sexual behaviour parameters as evidenced by increase in MF and IF; decrease in ML, IL and PEI. These results were statistically significant.
It is concluded that TT extract appears to possess aphrodisiac activity probably due to androgen increasing property of TT (observed in our earlier study on primates).
The hormonal effects of Tribulus terrestris and its role in the management of male erectile dysfunction – an evaluation using primates, rabbit and rat
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Hormonal effects of Tribulus terrestris (TT) were evaluated in primates, rabbit and rat to identify its usefulness in the management of erectile dysfunction (ED). TT extract was administered intravenously, as a bolus dose of 7.5, 15 and 30 mg/kg, in primates for acute study.
Rabbits and normal rats were treated with 2.5, 5 and 10 mg/kg of TT extract orally for 8 weeks, for chronic study. In addition, castrated rats were treated either with testosterone cypionate (10 mg/kg, subcutaneously; biweekly for 8 weeks) or TT orally (5 mg/kg daily for 8 weeks).
Blood samples were analyzed for testosterone (T), dihydrotestosterone (DHT) and dehydroepiandrosterone sulphate (DHEAS) levels using radioimmunoassay. In primates, the increases in T (52%), DHT (31%) and DHEAS (29%) at 7.5 mg/kg were statistically significant.
In rabbits, both T and DHT were increased compared to control, however, only the increases in DHT (by 30% and 32% at 5 and 10 mg/kg) were statistically significant. In castrated rats, increases in T levels by 51% and 25% were observed with T and TT extract respectively that were statistically significant.
TT increases some of the sex hormones, possibly due to the presence of protodioscin in the extract. TT may be useful in mild to moderate cases of ED.
The aphrodisiac herb Tribulus terrestris does not influence the androgen production in young men
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The aim of the current study is to investigate the influence of Tribulus terrestris extract on androgen metabolism in young males.
Design and methods:
Twenty-one healthy young 20–36 years old men with body weight ranging from 60 to 125 kg were randomly separated into three groups—two experimental (each n = 7) and a control (placebo) one (n = 7). The experimental groups were named TT1 and TT2 and the subjects were assigned to consume 20 and 10 mg/kg body weight per day of Tribulus terrestris extract, respectively, separated into three daily intakes for 4 weeks. Testosterone, androstenedione and luteinizing hormone levels in the serum were measured 24 h before supplementation (clear probe), and at 24, 72, 240, 408 and 576 h from the beginning of the supplementation.
There was no significant difference between Tribulus terrestris supplemented groups and controls in the serum testosterone (TT1 (mean ± S.D.: 15.75 ± 1.75 nmol/l); TT2 (mean ± S.D.: 16.32 ± 1.57 nmol/l); controls (mean ± S.D.: 17.74 ± 1.09 nmol/l) (p > 0.05)), androstenedione (TT1 (mean ± S.D.: 1.927 ± 0.126 ng/ml); TT2 (mean ± S.D.: 2.026 ± 0.256 ng/ml); controls (mean ± S.D.: 1.952 ± 0.236 ng/ml) (p > 0.05)) or luteinizing hormone (TT1 (mean ± S.D.: 4.662 ± 0.274 U/l); TT2 (mean ± S.D.: 4.103 ± 0.869 U/l); controls (mean ± S.D.: 4.170 ± 0.406 U/l) (p > 0.05)) levels.
All results were within the normal range. The findings in the current study anticipate that Tribulus terrestris steroid saponins possess neither direct nor indirect androgen-increasing properties. The study will be extended in the clarifying the probable mode of action of Tribulus terrestris steroid saponins.
Short term impact of Tribulus terrestris intake on doping control analysis of endogenous steroids .
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Tribulus terrestris is a nutritional supplement highly debated regarding its physiological and actual effects on the organism.
The main claimed effect is an increase of testosterone anabolic and androgenic action through the activation of endogenous testosterone production. Even if this biological pathway is not entirely proven, T. terrestris is regularly used by athletes.
Recently, the analysis of two female urine samples by GC/C/IRMS (gas chromatography/combustion/isotope-ratio-mass-spectrometry) conclusively revealed the administration of exogenous testosterone or its precursors, even if the testosterone glucuronide/epitestosterone glucuronide (T/E) ratio and steroid marker concentrations were below the cut-off values defined by World Anti-Doping Agency (WADA).
To argue against this adverse analytical finding, the athletes recognized having used T. terrestris in their diet. In order to test this hypothesis, two female volunteers ingested 500mg of T. terrestris, three times a day and for two consecutive days. All spot urines were collected during 48h after the first intake.
The 13C/12C ratio of ketosteroids was determined by GC/C/IRMS, the T/E ratio and DHEA concentrations were measured by GC/MS and LH concentrations by radioimmunoassay.
None of these parameters revealed a significant variation or increased above the WADA cut-off limits. Hence, the short-term treatment with T. terrestris showed no impact on the endogenous testosterone metabolism of the two subjects.
Ergogenic effects of Tribulus terrestris supplementation in men
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The main objective of this research project was to evaluate the effects of Tribulus terrestris supplementation on body composition, muscularstrength and serum hormone profile in men.
The research material in-cluded 24 competitive basketball players (age- 26.2±3.4 years, bodyheight 191.2±6.7 cm, body mass- 91.5±9.8 kg) divided into 3 groups of 8 subjects each.
One group received a supplement called “Tribusteron” which contained only saponins from Tribulus terrestris; another was sup-plemented with “Acetosteron”, a product containing the same amount of saponins but fortified with zinc, magnesium and vitamin B6.
The third group of players received a placebo containing gelatin and was treated as a control group.
The experiment lasted for 4 weeks during which all sub-jects performed six basketball training sessions weekly and three specific strength workouts. Body composition (electrical impedance), muscular strength (hack squat and bench press) and serum hormone profile (tes-tosterone, estradiol and luteinizing hormone) were evaluated before and after the cessation of the experiment.
The results indicate that in young, physically active men serum testosterone concentrations are high and supplementation with Tribulus terrestris do not influence these values significantly. Supplements containing saponins do not stimulate signifi-cant changes in body mass and composition as well as muscular strength in well trained athletes.