- Research article
- Open Access
- Open Peer Review
Influence of Cyperus esculentus tubers (Tiger Nut) on male rat copulatory behavior
© Allouh et al. 2015
- Received: 17 May 2015
- Accepted: 7 September 2015
- Published: 23 September 2015
Cyperus esculentus tubers (tiger nut) are one of the ancient food sources known to humanity. It is traditionally used in the Middle East to stimulate sexual arousal in men. However, there has been no scientific evidence about its assumed aphrodisiac properties. This study aimed to investigate the influence of tiger nut on the copulatory behavior of sexually active male rats.
Two sets of sexually active male rats -highly active and moderately active- were identified depending on baseline sexual activity. Rats in each set were randomly divided into a control and treated groups. Highly active rats were treated with doses of 1 and 2 g/kg/d of raw tiger nut powder, while moderately active rats were treated with a dose of 2 g/kg/d. After 30 days’ treatment, copulatory behavior and serum hormonal levels were measured and compared between the groups within each experimental set. Phytochemical analyses including liquid chromatography/mass spectrometry and atomic absorption were performed to elucidate the main constituents of tiger nut that may be responsible for altering serum hormones.
Tiger nut stimulated sexual motivation in both highly and moderately active rats, indicated by reduced mount and intromission latencies in these rats compared to controls. Furthermore, tiger nut improved sexual performance, indicated by increased intromission frequency and ratio, in treated moderately active rats compared to controls. Serum testosterone levels increased significantly after tiger nut administration. Lastly, phytochemical analyses revealed the presence of quercetin, vitamin C, vitamin E, and mineral zinc in tiger nut.
Tiger nut has positive effects on the copulatory behavior of adult male rats.
- Cyperus esculentus
- Earth almond
- Sexual behavior
Cyperus esculentus L. varsativus (C. esculentus) is a perennial plant species that belongs to the Cyperaceae family and grows abundantly in the Mediterranean region [1, 2]. Tubers of this plant are considered one of the earliest food sources known to humanity, where they have been documented to be cultivated by ancient Egyptians since 5000 BC [1, 3]. These tubers are commonly known by several names such as chufa, earth almond, and tiger nut [1, 2]. C. esculentus is a potentially valuable food source for humans and animals due to its rich nutritional contents of fat, carbohydrates, and minerals . However, it is very important to differentiate between this species and its variant wild type weed plant known as yellow nutsedge, which is native to North America [1, 2].
In addition to being a food source, C. esculentus tubers have several other purposes. For example, in Spain, they are used in the preparation of a milk-like beverage named “horchata” . The milk concentrate of the tubers is also used in the manufacturing of some cosmetic products . Furthermore, pork burgers containing liquid co-products from C. esculentus tubers have demonstrated improved cooking properties compared to those without .
According to Ayurvedic medicine, C. esculentus tubers can be used for their aphrodisiac properties . In the Middle East, they are known to the public as “Hab Al-zulom” (Arabic), which translates to “the seeds of men”, owing to their apparent ability to improve male sexual activity; thus, they are frequently given to grooms during their honeymoons as a sexual invigorator. However, there has been no scientific evidence to date on the influence of C. esculentus tubers on male sexual behavior.
In a previous study, Al-Shaikh et al.  reported protective effects of C. esculentus on testicular weight and spermatogenesis process in mice treated with lead acetate. They speculated that these effects could be due to either the antioxidant ability of C. esculentus or its positive influence on sex hormones. In addition, it has been claimed that treatment with C. esculentus methanolic extract improves sperm count and motility in male rats, which is associated with increased gonadotropins and testosterone serum levels .
Based on the previous facts, this study aimed to investigate the effects of C. esculentus tubers (tiger nut) on the copulatory behavior of adult male rats. In addition, serum hormonal assays and phytochemical analyses were conducted to elucidate the mechanism by which tiger nut may influence sexual behavior.
Adult male Sprague-Dawley rats (weight: approx. 250 g) raised in the Animal House Unit at Jordan University of Science and Technology (JUST) were used in this study. Animal care and experimental procedures were approved by the Animal Care and Use Committee at JUST and were in accordance with the NIH Guidelines. The animals were maintained under controlled temperature (21 ± 1 °C) with a 12 h light and 12 h darkness schedule (lights on, 06:00–18:00 h). Food and water were provided ad libitum. The rats were acclimatized for two weeks before beginning the experiments.
Male rats were subjected to four pre-experimental mating tests to acquire sexual experience. After that, additional three mating tests were conducted with sexually receptive females to determine the baseline sexual activity of the rats. Male rats that achieved ejaculation in each of the three tests in less than 30 min were considered highly active, those that achieved ejaculation in one or two of the three tests in less than 30 min were considered moderately active, and those that failed to achieve ejaculation in any of the three tests in less than 30 min were considered sexually inactive and excluded from the study . Ejaculation was monitored by rhythmic contractions of the posterior abdomen that ended with slow raising of the forelimbs .
Highly active rats were randomly divided into three groups (n = 16 rats/group): a control (C) group that received distilled water; Tiger Nut 1 (T1), treated with 1 g/kg/d tiger nut; and Tiger Nut 2(T2), treated with 2 g/kg/d of tiger nut. Moderately active rats were randomly divided into two groups (n = 16 rats/group): a control (C) group that received distilled water, and a treated (T) group treated with 2 g/kg/d tiger nut. These doses are considered comparable with the human dose, since an average human male usually consumes between 100 and 200 g daily of dried tiger nut.
Female rats of the same strain were also used in this study. Each female was brought into estrus by sequential subcutaneous injections of 50 μg estradiol benzoate (Intervet International B.V., Holland) and 1 mg progesterone (Schering AG, Germany) 48 and 4 h before the mating tests, respectively. The females were screened with non-experimental males, and the ones that showed good sexual receptivity (solicitation and lordosis) were selected for the behavioral test.
Copulatory behavior test
The copulatory behavior of male rats was monitored by two trained observers blinded to the experimental design, in a sound-attenuated room. Ten male rats from each group were subjected to the sexual behavior test. The test was performed 24 h after the last treatment and during the dark phase of the light/dark cycle. A single male rat was placed in a rectangular Plexiglas observation chamber (45 × 40 × 30 cm) and allowed to acclimate for 5 min. A sexually receptive female rat was then introduced into the chamber. The following parameters of sexual behavior were measured as described previously [10, 13]: (1) Mount latency: time from introduction of the female until the first mount; (2) intromission latency: time from introduction of the female until the first intromission (vaginal penetration); (3) mount frequency: number of mounts preceding ejaculation; (4) intromission frequency: number of intromissions preceding ejaculation; (5) ejaculation latency: time from the first intromission until ejaculation; (6) post-ejaculatory interval: time from ejaculation until the next intromission; (7) intromission ratio: a measure of intromissive success calculated as intromission frequency/(mount frequency+intromission frequency); and (8) inter-intromission interval: the average interval between successive intromissions calculated as ejaculation latency/intromission frequency. Tests were ended immediately after the first post-ejaculatory intromission. The percentage of ejaculating rats was calculated based on the ratio of the number of rats that achieved ejaculation from the first test within a period of 30 min to the total number of rats assessed in that group.
Body and reproductive organ weights
Total body and internal reproductive organ weights were assessed in male rats that were not submitted to mating tests (n = 6/group). The rats were weighed and then euthanized with ethyl ether. Subsequently, blood was obtained by cardiac puncture and collected into centrifuge tubes for later analyses. The reproductive organs (testes, epididymides, seminal vesicles, prostate, and vasa deferentia) were removed, cleaned free of fat, and weighed.
Serum biochemistry and hormonal assays
Serum was prepared by centrifugation of the collected blood at 3000 rpm for 30 min and stored at −40 °C for later assays. Total serum protein, cholesterol, triglycerides, urea, creatinine, aspartate aminotransferase, alanine aminotransferase, creatinine kinase, and lactate dehydrogenase concentrations were determined by electrochemiluminescence immunoassay technology using appropriate assay kits (Roche Diagnostics, Mannheim, Germany). Similarly, the serum concentrations of lutropin (LH), follitropin (FSH), and testosterone were also measured.
Liquid chromatography/mass spectrometry
Liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) was applied to identify the tiger nut constituents that may be responsible for elevating serum testosterone level. A 100 mg sample of tiger nut powder was dissolved in 4 ml methanol. The sample was vortexed for 1 min and centrifuged at 4500 rpm for 5 min, after which the supernatant was separated and evaporated at 40 °C under N2to dryness. The dry extract was reconstituted with 200 μl of deionized water and methanol (1:1) and then centrifuged again at 15000 rpm for 3 min. Twenty microliters of the reconstituted extract was injected into the LC-MS/MS analyzer (3200 Qtrap, AB, Canada) in the electrospray ionization positive-ion mode. Reverse-phase chromatography of the water/acetonitrile gradient program was performed for 15 min on a C18 column (Agilent Eclipse XDB; Agilent Technologies, CA, USA) to elute the extract. Proper standards were obtained and used as controls for quercetin (Sigma-Aldrich ChemieGmbh, Munich, Germany), and vitamins A (Toronto Research Chemicals, ON, Canada), C (Toronto Research Chemicals),E (Sigma-Aldrich) and B6 (Sigma-Aldrich).
Zinc and Selenium contents in tiger nut were determined using an atomic absorption spectrometer (AAS, Model SOLAAR M5, Unicam, UK) that was fully equipped for flame and graphite furnace atomization. Autosamplers (model FS 95) were used with the furnace to provide consistent sample introduction.
Rats were classified into highly active and moderately active categories based on their baseline sexual activity as described earlier. Highly active rats were randomly divided into three groups (one control and two treated groups). Moderately active rats were randomly divided into two groups (control and treated). The data were evaluated by either a one-way analysis of variance (ANOVA) for the highly active category or independent sample t-test for the moderately active category. If a significant difference (P <0.05) was detected among the highly active groups, then Fisher’s least significant difference (LSD) test was performed for post hoc analysis.
Effects of 30 days of treatment with C. esculentus tubers (tiger nut) on copulatory behavior parameters of highly active male rats
74.36 ± 11.25
4.36 ± 0.54
124.55 ± 14.14
11.00 ± 1.50
545.20 ± 97.41
395.70 ± 20.75
0.71 ± 0.02
42.38 ± 4.94
40.75 ± 3.32**
4.00 ± 0.47
90.22 ± 16.10*
10.67 ± 0.85
374.00 ± 89.79
365.56 ± 41.79
0.73 ± 0.01
34.32 ± 6.42
35.57 ± 2.97**
3.40 ± 0.43
54.00 ± 6.58**
11.60 ± 1.51
307.40 ± 23.15
330.90 ± 12.76
0.76 ± 0.02
29.71 ± 3.70
Effects of 30 days of treatment with C. esculentus tubers (tiger nut) on copulatory behavior parameters of moderately active male rats
111.45 ± 11.97
4.92 ± 0.43
192.50 ± 21.43
8.42 ± 0.87
878.67 ± 85.38
432.89 ± 20.80
0.63 ± 0.01
114.94 ± 16.53
52.30 ± 3.89**
4.10 ± 0.31
92.80 ± 8.69**
13.10 ± 0.72**
470.90 ± 81.69**
365.50 ± 16.13*
0.76 ± 0.01**
37.35 ± 7.34**
Body and internal reproductive organ weights
There were no significant (P >0.05) differences in body weight between control and treated rats in both highly active and moderately active categories. Similarly, the relative weights of reproductive organs to body weight were comparable (P >0.05) between control and treated rats in both categories.
Serum biochemical and hormonal levels
Serum hormonal levels in highly active male rats after 30 days of treatment with Cyperus esculentus tubers (tiger nut)
2.4 ± 0.3
2.1 ± 0.3
1.8 ± 0.2
2.0 ± 0.3
1.6 ± 0.3
3.0 ± 0.3*
1.7 ± 0.2
1.4 ± 0.3
3.4 ± 0.4**
Serum hormonal levels in moderately active male rats after 30 days of treatment with Cyperus esculentus tubers (tiger nut)
2.2 ± 0.3
2.1 ± 0.3
1.2 ± 0.2
2.0 ± 0.2
1.7 ± 0.2
2.7 ± 0.3**
Constituents identified in C. esculentus tubers (tiger nut) by liquid chromatography/mass spectrometry that are expected to contribute to higher levels of serum testosterone and to the improvement of copulatory behavior
To our knowledge, this is the first study to investigate the influence of C. esculentus tubers, known as tiger nut, on the copulatory behavior of adult male rats. Tiger nut was found to enhance sexual motivation (desire) in highly active and moderately active male rats, and to improve the sexual performance (potency) in moderately active rats. This was accompanied by an upsurge in total serum testosterone concentration in treated rats in both categories.
The enhancement in sexual arousal in highly active male rats was evidenced by reduced mount and intromission latencies in the tiger nut-treated groups (T1 and T2) compared to the control group. Mount and intromission latencies are measurements of, and inversely proportional to, sexual motivation . However, the lack of difference in other copulatory parameters suggests that there was no improvement in sexual performance in these animals.
Reduced mount and intromission latencies indicate that tiger nut treatment also stimulated sexual desire in moderately active rats. In addition, an improvement in sexual performance was evidenced in these rats through increased intromission frequency and ratio parameters after tiger nut administration. Intromission frequency reflects the efficient activation of ejaculatory reflexes, while intromission ratio, also known as copulatory efficacy or hit rate, represents the facilitation of erection and penile orientation [10, 13]. Both parameters are considered pure measurements of sexual performance in male rats. This improvement in sexual performance was further corroborated by the increased percentage of ejaculating rats in the treated moderately active group compared to the control group.
The enhanced sexual behavior in male rats after treatment with tiger nut could be attributed, in part, to the significant increase in serum testosterone levels observed in the treated animals compared to the controls. However, the role of testosterone in improving sexual behavior is still under debate. Some researchers suggest that testosterone has little, if any, impact on sexual activity [16–18]. For example, Damassa et al.  reported no correlation between circulating testosterone levels and male sexual behavior in normal active rats. Antonio-Cabrera and Paredes  reported that chronic treatment with testosterone did not improve the copulatory behavior of sexually sluggish male rats. Furthermore, a meta-analysis reported that testosterone has only small to moderate effects on sexual function in men . However, the lack of statistical clarity and the way in which different study designs were combined in this meta-analysis raises the possibility of bias.
Other researchers support the idea that sexual desire and potency are dependent on testosterone levels in the blood [20, 21]. It has been claimed that a slight elevation in testosterone level can lead to a significant increase in sexual desire in men [22, 23]. Anderson et al.  reported that administering supra-physiological doses of testosterone enanthate can stimulate sexual arousal, but not activity, in normal eugonadal men. This supports our results on sexually highly active rats, where the increase in testosterone after tiger nut treatment coincided with enhanced sexual motivation but not performance in these animals. In a recent meta-analysis, testosterone supplementation was found to significantly improve erectile function and libido in hypogonadal men with low testosterone levels . Our findings correspond with those of this meta-analysis, where an increase in testosterone level after tiger nut consumption coincided with improved sexual motivation and performance in moderately active male rats.
The exact mechanism by which tiger nut boosts testosterone levels is not entirely clear. However, we speculate that tiger nut may act directly on testicular cells, and not through the hypothalamus-pituitary axis, since no variations in FSH and LH levels were observed due to tiger nut treatment. The phytochemical analyses revealed the presence of several components (quercetin, vitamins E and C, and the mineral zinc) in tiger nut that could positively contribute to testosterone production and improve the erectile function.
Quercetin is a dietary flavonoid that exhibits strong antioxidant activity. A previous study revealed that oral administration of quercetin was associated with a significant increase in serum testosterone level in male rats . Taepongsorat et al.  reported that subcutaneous injections of quercetin over a period of 1 week significantly increased testis weight and improved sperm quality in rats. Zhang et al.  suggested that quercetin could ameliorate erectile dysfunction in diabetic rats by inhibiting oxidative stress. Moreover, a recent study revealed that quercetin treatment can improve the arterial erectile dysfunction by up-regulating intracavernous pressure in Wistar rats .
Vitamin E is an essential nutrient speculated to enhance testosterone synthesis and was found to increase serum testosterone in an experimental aged mice model . Salama et al.  reported that daily oral administration of 40 mg/kg vitamin E for 3 weeks restored serum testosterone concentration to normal value in an atherosclerotic rat model. The daily supplements of vitamin E in a dose of 75 mg/kg for 50 days ameliorated serum testosterone levels in rats exposed to noise stress . Furthermore, Helmy and Senbel  reported that antioxidant therapy with vitamin E ameliorates the age-associated erectile dysfunction in male rats. In a recent study, Kawakami et al.  reported that vitamin E therapy can improve the poor semen quality and increase plasma testosterone levels in dogs.
Vitamin C is a strong antioxidant that facilitates the formation of testosterone, and was found in a considerable concentration in tiger nut in this study. It has been reported that vitamin C increases testosterone content in rat testis in vitro , and oral administration of vitamin C for 10 weeks significantly increased serum testosterone levels in male rats . Moreover, vitamin C supplementation attenuated testosterone deficiency and some male reproductive deficits induced in hyperglycemic rats [37, 38]. Vitamin C, also, stimulates vascular nitric oxide production, which consequently improves the erectile function .
The trace element zinc is speculated to play a critical role in sexual development. Zinc deficiency was found to disrupt testicular tissue , impair spermatogenesis , and reduce testosterone levels , while zinc supplementation improved the sexual behavior of adult male rats in a dose-dependent manner by enhancing testosterone secretion . Moreover, Prasad et al.  reported a positive correlation between cellular zinc concentration and serum testosterone level in healthy men.
The present study supports the hypothesis that C. esculentus tubers have aphrodisiac activity, enhancing male sexual libido and performance. The observed improvements in copulatory behavior after the administration of tiger nut could be partially attributed to increased serum testosterone levels in male rats. This increase in testosterone level is most likely related to the presence of quercetin, vitamins, and zinc in tiger nut, all of which have been shown to boost testosterone production. Nevertheless, future investigations are warranted to confirm these effects of tiger nut in humans, and to examine the safety of these tubers on developing boys, since they are involved in the food and beverage industry.
Funds for this project were provided by a grant awarded to MZA from the Deanship of Research at JUST (174/2012).
Open AccessThis article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.
- Ezeh O, Gordon MH, Niranjan K. Tiger nut oil (Cyperus esculentus L.): a review of its composition and physic-chemical properties. Eur J Lipid Sci Technol. 2014;116:783–94.Google Scholar
- Pascual B, Maroto JV, Lopez-Galarza S, Sanbautista A, Alagarda J. Chufa (Cyperus esculentus L. varsativusBoeck.): an unconventional crop. Studies related to applications and cultivation. Econ Bot. 2000;54:439–48.View ArticleGoogle Scholar
- Defelice MS. Yellow nutsedge Cyperus esculentus L.─Snack food of the gods. Weed Technol. 2002;16:901–7.View ArticleGoogle Scholar
- Tunde-Akintunde TY, Oke MO. Thin-layer drying characteristics of tiger nut (Cyperus esculentus) seeds. J Food Process Preserv. 2012;36:457–64.View ArticleGoogle Scholar
- Forner DT, Conde JAN. Tiger nut milk base concentrate and method for obtaining a cosmetic product from said base concentrate. U.S. Patent 20100183526 A1. Published July 22, 2010.Google Scholar
- Sánchez-Zapata E, Pérez-Alvarez JA, Fernández-López J. Effects of tiger nut (Cyperus esculentus) milk liquid co-products on the quality of pork burgers. Int J Food Sci Technol. 2012;47:2198–204.View ArticleGoogle Scholar
- Caius JF. The medicinal and poisonous plants of India. Jodhpur: Scientific Publishers; 1998. p. 167–8.Google Scholar
- Al-Shaikh MN, Abdul Wahab TA, Abdul Kareem SH, Hamoudi SR. Protective effect of chufa tubers (Cyperus esculentus) on induction of sperm abnormalities in mice treated with lead acetate. Int J Drug Dev Res. 2013;5:387–92.Google Scholar
- Agbai EO, Nwanegwo CO. Effect of methanolic extract of Cyperus esculentus L. (Tigernut) on luteinizing hormone, follicle stimulating hormone, testosterone, sperm count and motility in male albino wistar rats. J Med App Biosci. 2013;5:52–61.Google Scholar
- Allouh MZ. Effects of swimming activity on the copulatory behavior of sexually active male rats. Int J Impot Res. 2015;27:113–7.View ArticlePubMedGoogle Scholar
- Ågmo A. Male rat sexual behavior. Brain Res Protoc. 1997;1:203–9.View ArticleGoogle Scholar
- Mainwaring WIP. The mechanism of action of androgens. New York: Springer; 1977. p. 37.View ArticleGoogle Scholar
- Allouh MZ, Daradka HM, AlBarbarawi MM, Mustafa AG. Fresh onion juice enhanced copulatory behavior in male rats with and without paroxetine-induced sexual dysfunction. Exp Biol Med (Maywood). 2014;239:177–82.View ArticleGoogle Scholar
- Alemán CL, Más RM, Rodeiro I, Noa M, Hernández C, Menéndez R, et al. Reference database of the main physiological parameters in Sprague–Dawley rats from 6 to 32 months. Lab Anim. 1998;32(4):457–66.View ArticlePubMedGoogle Scholar
- Allouh MZ, Khouri NA, Daradka HM, Kaddumi EG. Orchis anatolica root ingestion improves sexual motivation and performance in male rats. J Complement Integr Med. 2010;7:39.View ArticleGoogle Scholar
- Bolona ER, Uraga MV, Haddad RM, Tracz MJ, Sideras K, Kennedy CC, et al. Testosterone use in men with sexual dysfunction: a systematic review and meta-analysis of randomized placebo-controlled trials. Mayo Clin Proc. 2007;82:20–8.View ArticlePubMedGoogle Scholar
- Antonio-Cabrera E, Paredes RG. Effects of chronic estradiol or testosterone treatment upon sexual behavior in sexually sluggish male rats. Pharmacol Biochem Behav. 2012;101:336–41.View ArticlePubMedGoogle Scholar
- Kim JY, Wood RI. Anabolic-androgenic steroids and appetitive sexual behavior in male rats. Horm Behav. 2014;66:585–90.View ArticlePubMedPubMed CentralGoogle Scholar
- Damassa DA, Smith ER, Tennent B, Davidson JM. The relationship between circulating testosterone levels and male sexual behavior in rats. Horm Behav. 1977;8:275–86.View ArticlePubMedGoogle Scholar
- Mills TM, Reilly CM, Lewis RW. Androgens and penile erection: a review. J Androl. 1996;17:633–8.PubMedGoogle Scholar
- Lewis RW, Mills TM. Effect of androgens on penile tissue. Endocrine. 2004;23:101–5.View ArticlePubMedGoogle Scholar
- Yakubu MT, Akanji MA. Effect of aqueous extract of Massulariaacuminata stem on sexual behavior of male wistar rats. Evid Based Complement Alternat Med. 2011;738103.Google Scholar
- Thakur M, Dixit VK. Aphrodisiac activity of Dactylorhizahatagirea (D.Don) Soo in male albino rats. Evid Based Complement Alternat Med. 2007;4:29–31.View ArticlePubMedPubMed CentralGoogle Scholar
- Anderson RA, Bancroft J, Wu FC. The effects of exogenous testosterone on sexuality and mood of normal men. J Clin Endocrinol Metab. 1992;75:1503–7.PubMedGoogle Scholar
- Corona G1, Isidori AM, Buvat J, Aversa A, Rastrelli G, Hackett G, et al. Testosterone supplementation and sexual function: a meta-analysis study. J Sex Med. 2014;11:1577–92.View ArticlePubMedGoogle Scholar
- Ma Z1, Hung Nguyen T, Hoa Huynh T, Tien Do P, Huynh H. Reduction of rat prostate weight by combined quercetin-finasteride treatment is associated with cell cycle deregulation. J Endocrinol. 2004;181:493–507.Google Scholar
- Taepongsorat L, Tangpraprutgul P, Kitana N, Malaivijitnond S. Stimulating effects of quercetin on sperm quality and reproductive organs in adult male rats. Asian J Androl. 2008;10:249–58.View ArticlePubMedGoogle Scholar
- Zhang W1, Wang Y, Yang Z, Qiu J, Ma J, Zhao Z, et al. Antioxidant treatment with quercetin ameliorates erectile dysfunction in streptozotocin-induced diabetic rats. J Biosci Bioeng. 2011;112(3):215–8.View ArticlePubMedGoogle Scholar
- Zhang Y, Huang C, Liu S, Bai J, Fan X, Guo J, et al. Effects of quercetin on intracavernous pressure and expression of nitrogen synthase isoforms in arterial erectile dysfunction rat model. Int J Clin Exp Med. 2015;8(5):7599–605.PubMedPubMed CentralGoogle Scholar
- Mohammadirad A, Aghamohammadali-Sarraf F, Badiei S, Faraji Z, Hajiaghaee R, Baeeri M, et al. Anti-aging effects of some selected Iranian folk medicinal herbs-biochemical evidence. Iran J Basic Med Sci. 2013;16:1170–80.PubMedPubMed CentralGoogle Scholar
- Salama AF, Kasem SM, Tousson E, Elsisy MK. Protective role of L-carnitine and vitamin E on the testis of atherosclerotic rats. Toxicol Ind Health. 2015;31:467–74.View ArticlePubMedGoogle Scholar
- Saki G, Jasemi M, Sarkaki AR, Fathollahi A. Effect of administration of vitamins C and E on fertilization capacity of rats exposed to noise stress. Noise Health. 2013;15:194–8.View ArticlePubMedGoogle Scholar
- Helmy MM, Senbel AM. Evaluation of vitamin E in the treatment of erectile dysfunction in aged rats. Life Sci. 2012;90(13–14):489–94.View ArticlePubMedGoogle Scholar
- Kawakami E, Kobayashi M, Hori T, Kaneda T. Therapeutic effects of vitamin E supplementation in 4 dogs with poor semen quality and low superoxide dismutase activity in seminal plasma. J Vet Med Sci. 2015. [Epub ahead of print].Google Scholar
- Biswas NM, Chaudhuri A, Sarkar M, Biswas R. Effect of ascorbic acid on in vitro synthesis of testosterone in rat testis. Indian J Exp Biol. 1996;34:612–3.PubMedGoogle Scholar
- Ashamu E, Salawu E, Oyewo O, Alhassan A, Alamu O, Adegoke A. Efficacy of vitamin C and ethanolic extract of Sesamum indicum in promoting fertility in male wistar rats. J Hum Reprod Sci. 2010;3:11–4.View ArticlePubMedPubMed CentralGoogle Scholar
- Fernandes GS, Gerardin DC, Assumpção TA, Campos KE, Damasceno DC, Pereira OC, et al. Can vitamins C and E restore the androgen level and hypersensitivity of the vas deferens in hyperglycemic rats? Pharmacol Rep. 2011;63:983–91.View ArticlePubMedGoogle Scholar
- Fernandes GSA, Fernandez CDB, Campos KE, Damasceno DC, Anselmo-Franci JA, Kempinas WDG. Vitamin C partially attenuates male reproductive deficits in hyperglycemic rats. Reprod Biol Endocrinol. 2011;9:100.View ArticlePubMedPubMed CentralGoogle Scholar
- Meldrum DR, Gambone JC, Morris MA, Ignarro LJ. A multifaceted approach to maximize erectile function and vascular health. Fertil Steril. 2010;94:2514–20.View ArticlePubMedGoogle Scholar
- Hafiez AA, el-Kirdassy ZH, el-Malkh NM, el-Zayat EM. Role of zinc in regulating the testicular function. Part 3. Histopathological changes induced by dietary zinc deficiency in testes of male albino rats. Nahrung. 1990;34:65–73.View ArticlePubMedGoogle Scholar
- Hamdi SA, Nassif OI, Ardawi MS. Effect of marginal or severe dietary zinc deficiency on testicular development and functions of the rat. Arch Androl. 1997;38:243–53.View ArticlePubMedGoogle Scholar
- Gilabert ER, Ruiz E, Osorio C, Ortega E. Effect of dietary zinc deficiency on reproductive function in male rats: biochemical and morphometric parameters. J Nutr Biochem. 1996;7:403–7.View ArticleGoogle Scholar
- Dissanayake D, Wijesinghe PS, Ratnasooriya WD, Wimalasena S. Effect of zinc supplementation on sexual behavior of male rats. J Hum Reprod Sci. 2009;2:57–61.View ArticlePubMedPubMed CentralGoogle Scholar
- Prasad AS, Mantzoros CS, Beck FW, Hess JW, Brewer GJ. Zinc status and serum testosterone levels of healthy adults. Nutrition. 1996;12:344–8.View ArticlePubMedGoogle Scholar