Pro-erectile pharmacological effects
of Tribulus terrestris extract on
the rabbit corpus cavernosum
P.G. Adaikan, K. Gauthaman, and
R.N. Prasad
National University of Singapore and National University Hospital,
Department of Obstetrics and Gynecology, Singapore
Ann Acad Med Singapore 2000 Jan; 29(1): 22-26
SUMMARY
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 TT, exerts its
pharmacological effects. MATERIAL 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
A. Gauthaman, P.G. Adaikan,
R.N. Prasad
National University of Singapore, National University Hospital, Department
of Obstetrics and Gynecology, Singapore
Life Sci 2002 Aug 9; 71(12): 1385-96
SUMMARY
Tribulus
terrestris (TT) has long been used in traditional Chinese and Indian systems
of medicine for the treatment of various ailments and is popularly claimed
to improve sexual functions in man. Sexual behavior 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 behavior 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 behavior parameters as evidenced by increase in MF
and IFl; decrease in ML, IL and PEI. These results were statistically
significant. It is concluded that TT extracts appear to possess aphrodisiac
activity probably due to an androgen increasing property of TT (observed in
our earlier study on primates).
|