Effect Of Root Extracts Of Eurycoma Longifolia Jack On Rabbit Penile Erection And Underlying Mechanism Of Action

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Date
2016-09
Authors
Wizneh, Faramarz Majidi
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Abstract
The objective of this study was to assess the effect of hydro-alcoholic root extracts of Eurycoma longifolia Jack on penile erection and its underlying mechanisms. Extraction of roots of E. longifolia Jack using methanol, ethanol, and water as solvent produced three extracts namely; METEL, ETHEL, and AQUEL, respectively. Acute oral toxicity in male rats found LD50 of ≥ 2000 mg/kg for both METEL and ETHEL and ≥ 5000 mg/kg for AQUEL. Oral administration of a PDE5 inhibitor, sildenafil at 1.5, 3, 15, and 30 mg/kg in rabbit caused penile erections of 1.6 ± 0.4, 3.1 ± 0.3, 8.6 ± 1.1, and 10.9 ± 3.0 mm, respectively. Out of the three extracts, only METEL 500 and 1000 mg/kg caused penile erections of 4.9 ± 1.4 and 2.9 ± 0.9 mm respectively, with the latter reached toxicity level already. Nitric oxide (NO) donor, sodium nitroprusside (0.2 mg/kg, i.v.) significantly potentiated (p < 0.001) sildenafil-induced erection higher than METEL (50 mg/kg, i.v.; p < 0.05). Six week daily administration of METEL (200 mg/kg, p.o.) and testosterone enanthate (30 mg/kg, s.c.) significantly increased the testosterone level in both normal rats and rabbits (p < 0.001 – 0.01). Similarly, NO level was significantly elevated in normal and diabetic rabbits with both treatments (p < 0.001 – 0.05). In addition, diminished responsiveness to sildenafil in diabetic rabbits was significantly reversed by both testosterone enanthate and METEL after six weeks treatments. Protein expression studies showed that both nNOS as well as PDE5 proteins were reduced in diabetic rabbits which was reversed by both METEL and testosterone administration. HPLC analysis found that METEL, ETHEL, and AQUEL contain 20.04 μg/mL, 19.79 μg/mL, and 21.71 μg/mL, of eurocomanone (EN), respectively. Therefore, the erection could not have been induced by EN – a potent quassinoid, although quassinoids have been implicated in the spermatogensis and testosterone production. In conclusion, acute administration of E. longifolia extract on its own has very little penile erection activity and only at near toxic doses. However, similar to testosterone, after chronic use it may improve partial erectile dysfunction such as in diabetic patient.
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The effect of hydro-alcoholic root extracts of Eurycoma longifolia Jack , on penile erection and its underlying mechanisms.
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