Dose–response effects of Lepidium meyenii (Maca) aqueous extract on testicular function and weight of different organs in adult rats

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Abstract

Lepidium meyenii (Brassicaceae) known as Maca grows exclusively between 4000 and 4500 m over the sea level in the Peruvian central Andes. The dried hypocotyls of Maca are traditionally used as food and for its supposed fertility-enhancing properties.

A dose–response study was performed to determine the effect of 7 days oral administration of an aqueous lyophilized extract of Maca at 0.01–5 g/kg (corresponding to 0.022–11 g dry hypocotyls of Maca/kg) on body and different organ weights, stages of the seminiferous tubules, epididymal sperm count and motility, and serum testosterone and estradiol levels in rats. In doses up to 5 g extract/kg, no toxicity was observed. Almost all organ weights were similar in controls and in the Maca extract-treated groups. Seminal vesicles weight was significantly reduced at 0.01 and 0.10 g extract/kg. Maca increased in length of stages VII–VIII of the seminiferous tubules in a dose–response fashion, with highest response at 1.0 g/kg, while caput/corpus epididymal sperm count increased at the 1.0 g dose.

Cauda epididymal sperm count, sperm motility, and serum estradiol level were not affected at any of the doses studied. Serum testosterone was lower at 0.10 g extract/kg. Low-seminal vesicle weights correlated with low-serum testosterone levels (R2 = 0.33; P < 0.0001) and low-testosterone/estradiol ratio (R2 = 0.35; P < 0.0001). Increase in epididymal sperm count was related to lengths of stages VII–VIII. Highest effect on stages VII–VIII of the seminiferous tubules was observed at 1.0 g Maca aqueous extract/kg.

The present study demonstrated that Maca extract in doses up to 5 g/kg (equivalent to the intake of 770 g hypocotyls in a man of 70 kg) was safe and that higher effect on reproductive parameters was elicited with a dose of 1 g extract/kg corresponding to 2.2 g dry Maca hypocotyls/kg.

Introduction

Maca (Lepidium meyenii Walp) from the Brassicaceae family grows exclusively between 4000 and 4500 m above sea level at the Peruvian central Andes (Gonzales et al., 2001b). According to traditional beliefs reported by Spaniard chronicles in the XVII century (Cobo, 1956), Maca is a plant that enhances fertility in humans and domestic animals, which tends to be reduced after acute exposure to high altitudes.

The first evidence that Maca improved spermatogenesis was reported in male rats (Gonzales et al., 2001b). Thereafter, Gonzales et al. (2001a) demonstrated that Maca (1.5 or 3.0 g) also improved sperm count and sperm motility in normal men without affecting serum testosterone and estradiol levels.

We have studied the effect of aqueous extract of dried Maca hypocotyls in doses up to 2 g/kg body weight (Gonzales et al., 2001b, Gonzales et al., 2004). It is important to know what for effect are elicited with higher doses and how safe is consuming high amounts of Maca. A dose–response study was undertaken to determine the effect of an aqueous Maca extract at doses up to 5 g/kg body weight in male rats, corresponding to 11 g dry Maca hypocotyls/kg body weight.

Section snippets

Animals

Three-month-old male rats from the Holtzman strain obtained at the animal house of the Universidad Peruana Cayetano Heredia were used. Rats were allotted randomly into five groups according to the extract dose administered.

Rats were housed 4–6 per cage and maintained at 22 °C with a 12-h light:12-h dark cycle. Rats were provided with Purina Laboratory chow and tap water ad libitum.

Animals were managed and experiments were performed in accordance with the internationally accepted principles for

Effect of Maca on body and organ weights in male rats

After 7 days of treatments, all groups, except that treated with 5 g extract/kg increased body weight. Final body weight was similar in control rats and rats-treated with 0.01–1.0 g extract/kg. There was no evidence of toxicity after oral administration of Maca extract in doses up to 5 g extract/kg. Regarding organ weight, only seminal vesicle weight was significantly reduced at doses of 0.01 g extract/kg (from 1.01 ± 0.04 to 0.45 ± 0.15; P < 0.01) and 0.10 g extract/kg (from 1.01 ± 0.04 to 0.57 ± 0.11; P < 

Discussion

Herbal medicine is used by up to 80% of the population in the developing countries (Hilaly et al., 2004). In the United States, approximately one-quarter of adults reported use of herbs to treat a medical illness within the past year (Bent and Ko, 2004). Despite the widespread use, few scientific studies have been undertaken to ascertain the safety and efficacy of traditional remedies (Hilaly et al., 2004).

In the present study, Maca, a cultivated plant from highlands of Peru, administered to

Acknowledgement

The study was supported by a grant from the Vicerrectorado de Investigación at the Universidad Peruana Cayetano Heredia.

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