The present study was designed to determine if different ecotypes of Lepidium meyenii (Maca), a cruciferous plant that grows exclusively over 4000 m in Peruvian Andes, affect ventral prostate size. It was of great interest to demonstrate that Red Maca reduced significantly ventral prostate weight. This effect was not observed after treatment with Yellow or Black Maca. The effect of Red Maca was specific for prostate, since other organs as testes, epididymis, seminal vesicles, kidneys, spleen, liver, lungs and heart were not affected.
It was also demonstrated an effect of Red Maca on rats in which ventral prostate size was enlarged by two injections of testosterone enanthate. In fact, Red Maca administered for 14 or 42 days reduced the effect of TE. At 42 days, the ventral prostate size of rats treated with TE plus Red Maca was similar to that of control rats treated only with vehicle. Epithelial height and luminal areas were proved to be sensitive parameters for the evaluation of androgen effects on prostates [26
]. The present study shows that prostatic epithelial height increased after treatment with TE. The same effect has been observed when castrated rats were treated with testosterone [26
] suggesting that prostatic epithelial height is androgen dependent. Red Maca was able to reduce the prostatic epithelial height of TE treated rats. This would means that Red Maca interferes the androgen action.
Growth of the prostate is a hormone-mediated phenomenon regulated by both androgens and estrogens [27
]. However, data showed that Red Maca affect ventral prostate size without affecting serum testosterone or estradiol levels. This is not surprising because previously, it has been published that dietary phytoestrogens may affect prostate size without modify circulating testosterone or estrogen level [28
], but affecting the androgen action in the rat prostate [27
]. Our data on effect of Red Maca on ventral prostate size in rats previously treated with testosterone enanthate suggest that this cruciferous is acting by interfering the androgen action. Maca is characterized by its higher content on aromatic glucosinolates [19
]. Recently, it has been described a metabolite of the aromatic glucosinolates that specifically antagonizes androgen receptor [18
]; therefore, it is possible that effect of Red Maca on ventral prostate size may be due in part to an action of glucosinolate metabolites on androgen receptor. However, further studies will be required to clarify mechanism of action of this cruciferous plant.
Recently, increasing evidence has been presented suggesting that cruciferous (Brassicas) vegetables may reduce the risk of prostate cancer development [3
]. The genus Lepidium
could be an important alternative for treatment of prostate diseases. Other Brassica from the genus Lepidium
, as Lepidium latifolium
reduced prostate weight [6
] suggesting that cruciferous from the genus Lepidium
may have important anti-proliferative and proapoptotic effects. In Red Maca treated rats, cell size has decreased and membrane blebbing and nuclear distortion are apparent suggesting a pro-apoptotic effect.
It is still unknown the active principle for the effect of Red Maca on ventral prostate and why the action is specific since any other organ was affected. Moreover, the different effects among ecotypes seem to be due to different amount of active metabolites.
This study used aqueous extract of dried hypocotyls of Lepidium meyenii
. In the aqueous extract is possible to find glucosinolates [7
] and anthocyanines [29
]. Both compounds have antiproliferative and proapoptotic properties in prostate cancer cells [14
]. As effect was specific for Red Maca and not for Yellow or Black Maca, it is probably that Red Maca has more glucosinolate content than other ecotypes. Results from the infrared (IR) spectroscopy showed that peaks of absorbance were higher for Red Maca, intermediate for Yellow Maca and lower for Black Maca. Each peak reflects specific chemical functional groups. Several functional groups found in the different Maca ecotypes correspond among others to benzyl glucosinolate. In such sense, it is suggested that benzyl glucosinolate content is higher in Red Maca, intermediate in Yellow Maca and lower in Black Maca. In addition to the potential glucosinolates effects on prostate, it is possible that other active metabolites may be acting on prostate. Maca aqueous extracts were further extracted with ethanol or methanol and assessed for different compounds. The compounds found are potential candidates to affect prostate; however, it is difficult at this time to ascertain which specific compound has the prostate effect. In fact, the phyto-chemical screening data showed that aqueous extract of Red Maca has alkaloids, steroids, tannins, saponins and cardiotonic glycosides, all of them may have effects on prostate. Phytochemical study showed that Red Maca was more positive for alkaloids than from other compounds. The alkaloid, (1R,3S)-1-methyltetrahydro-β-carboline-3-carboxylic acid has been reported as a constituent of Maca [20
]. This alkaloid acts as antioxidants and free radical scavengers [31
]. Beta carbolines are also proapoptotic compounds [32
] and they have antitumor activities [33
]. Further studies will be required to determine the impact of tetrahydro-beta-carbolines from Maca on prostate.