evaluation of different doses of mashua (tropaeolum tuberosum) on the reduction of sperm production,...

ORIGINAL ARTICLE

Evaluation of different doses of mashua (Tropaeolumtuberosum) on the reduction of sperm production,motility and morphology in adult male ratsJ. Leiva-Revilla1,2, I. Cardenas-Valencia1,2, J. Rubio1,2, F. Guerra-Castanon1,3, P. Olcese-Mori1,2,M. Gasco1,2 & G. F. Gonzales1,2

1 Laboratory of Endocrinology and Reproduction, Faculty of Sciences and Philosophy, Universidad Peruana Cayetano Heredia, Lima, Peru;

2 Department of Biological and Physiological Sciences, Faculty of Sciences and Philosophy, Universidad Peruana Cayetano Heredia, Lima, Peru;

3 Faculty of Medicine, Universidad Peruana Cayetano Heredia, Lima, Peru

Introduction

Tropaeolum tuberosum Ruiz & Pavon, commonly known as

mashua, is an edible-tuber crop that grows in the Andean

region that belongs to the Tropeolaceae family (Grau et al.,

2003). Mashua is traditionally used for its nutritional and

medicine properties including beneficial effects on liver

and kidney (Hodge, 1946) and used to relief prostate and

urinary disorders (Salcedo, 1986). In addition, folk medi-

cine describes the use of mashua to reduce reproductive

function in men (Hodge, 1951; Leon, 1967).

Regarding its property to reduce male reproductive

function, Johns et al. (1982) reported that mashua has

anti-reproductive effects on male rats by reducing serum

levels of testosterone and dihydrotestosterone without any

effect in the capability to impregnate female rats. In addi-

tion, it was found that after 12 days of treatment (i.e. one

spermatogenic cycle), mashua (1 g kg)1) reduced testicu-

lar function [i.e. testicular spermatids and daily sperm

production (DSP)], increased epididymal sperm transit

rate and consequently reduced epididymal sperm number

without no effect on testosterone levels (Cardenas-

Valencia et al., 2008).

To our knowledge, no study was carried out to deter-

mine whether mashua shows a dose–response effect on

sperm quality (number, motility and morphology). For

this reason, the present study was undertaken to deter-

mine the effect of different doses of an aqueous extract of

mashua on sperm quality. For this purpose, rats were

treated with vehicle and mashua (0.01, 0.1, 1, or

2 g kg)1) for 12 days (one spermatogenic cycle), and the

following reproductive parameters were assessed: body

Keywords

Daily sperm production—epididymal sperm

transit—mashua—sperm motility and

morphology—sperm number

Correspondence

Johanna Leiva-Revilla, Laboratory of

Endocrinology and Reproduction, Faculty of

Sciences and Philosophy, Universidad Peruana

Cayetano Heredia, Lima, Peru.

Tel.: +511 3190000 (extension 2515);

Fax: +511 4821195;

E-mail: [email protected]

Accepted: November 29, 2010

doi: 10.1111/j.1439-0272.2011.01165.x

Summary

Mashua is an edible-tuber crop that grows in the Andean region. Folk medi-

cine describes the use of mashua to reduce reproductive function in men. The

present study aimed: (i) to determine whether different doses of mashua (0.01,

0.1, 1 and 2 g kg)1) produced a dose–response reduction on sperm production

and quality; and, (ii) to determine whether these anti-reproductive effects of

mashua can be reversible after cessation of treatment (12 and 24 days of recov-

ery time). Mashua-treated rats showed lower values of daily sperm production,

epididymal and vas deferens sperm count and sperm motility; meanwhile,

mashua increased the percentage of abnormal sperm morphology and epididymal

sperm transit rate. The following variables follow a dose–response effect: sperm

number in vas deferens, sperm motility and sperm transit rate. In addition, it was

demonstrated that the reduction in reproduction function in male rats treated

with mashua was reversible after 24 days of recovery time. Finally, lower doses

mashua reduces sperm number and quality (motility and morphology), and these

adverse effects on male reproductive system may be reversible after 24 days after

cessation of the treatment.

ª 2011 Blackwell Verlag GmbHAndrologia 2012, 44, 205–212 205

and reproductive organ weights, DSP, sperm count in

epididymis and vas deferens, sperm transit rate, and

sperm motility and morphology. In addition, a second

experiment was performed to determine whether the

effects of mashua aqueous extract (1 g kg)1) on male

reproductive function (i.e. sperm production, quantity

and quality) were reversible after 12 and 24 days of treat-

ment cessation.

Materials and methods

Animals

Fifty-four male rats from the Holtzman strain (3 months

old) were obtained from the animal house of the Univers-

idad Peruana Cayetano Heredia (Lima, Peru). Rats were

housed at six per cage and were maintained under con-

trolled conditions at 22 �C with a 12 : 12 h light/dark

cycle in the animal house at the Universidad Peruana

Cayetano Heredia. Rats were provided with food and

water ad libitum.

Animals were treated according to the standards of the

National Institute of Health for the care and use of labo-

ratory animals (National Research Council, 1996). All

experiments were approved by the Institutional Review

Board at the Universidad Peruana Cayetano Heredia.

Experiment 1: Evaluation of different doses of mashua

Thirty rats were randomly divided into five groups

according to the dose administered. Male rats per group

received vehicle (distilled water), 0.01, 0.1, 1 or 2 g kg)1

of freeze-dried extract of mashua daily for 12 days

(Cardenas-Valencia et al., 2008). The freeze dried extract

or vehicle was administered by gavage with an intubation

needle no. 18 (Fisher Scientific, Pittsburgh, PA, USA).

Experiment 2: Reversibility of mashua effect

In this experiment, male rats were divided into five

groups (six rats per group) according to the treatment

and recovery time. In the first group, rats were treated

with vehicle (control group) for 12 days. Rats in the sec-

ond group received a freeze-dried aqueous extract of

1 g kg)1 mashua for 12 days without recovery time (No-

R group). Groups 3 and 4 were the recovery groups in

which rats were treated with an aqueous extract of mas-

hua for 12 days, but allowed to recover for 12 and

24 days after the withdrawal of mashua (R-12 and R-24

groups). The dose of mashua used in this experiment was

chosen based on the fact that previously it was found that

1 g kg)1 of mashua reduced sperm production after

12 days of treatment (Cardenas-Valencia et al., 2008). We

decided to use this higher dose to demonstrate that the

anti-reproductive effects of mashua are reversible after a

cessation of treatment even when higher doses are admin-

istered.

For this experiment, vehicle or mashua were adminis-

tered by gavage with an intubation needle no. 18 (Fisher

Scientific). The dose of mashua used in this experiment

was obtained from the first experiment.

Preparation of the aqueous extract of Tropaeolum

tuberosum (mashua)

For the present study, yellow variety of mashua tubers

was obtained from Cerro de Pasco, Peru at 4340 m alti-

tude. The freeze-dried extract was prepared as previously

described (Cardenas-Valencia et al., 2008): First, 500 g of

mashua tubers was cut in pieces, placed in a container

with 1500 ml of water and boiled for 60 min. Next, the

boiled water extract of mashua was left standing to cool,

filtered and freeze-dried. One gram of mashua tubers

produced 0.10 g of freeze-dried aqueous extract. The

freeze-dried mashua extracts were further diluted with

distilled water (vehicle) to obtain different concentrations

in 1 ml. These solutions were placed in small vials and

kept in a refrigerator at 4 �C until use.

Body and organ weights

Rats were weighed at the beginning and 24 h after last

treatment (initial and final body weights respectively).

After animals were sacrificed (24 h after last treatment),

selected organs (testes, epididymis, seminal vesicles and

ventral prostate) were carefully dissected out, cleaned of

adhering connective tissue and accurately weighed.

Daily sperm production (DSP) and sperm transit

Testes were homogenised in 10 ml of 0.9% saline-0.05%

(v/v) Triton X-100 solution for 1 min by a homogenizer

(Takahashi & Oishi, 2003) (Polytron homogenizer, Brink-

mann PT 3000; Brinkmann Instruments, Inc., Westbury,

NY, USA). After a dilution 1/10, the number of homoge-

nisation-resistant elongated spermatids nuclei per testis

was counted with a hemocytometer. Counts for four

hemocytometer chambers were averaged. DSP was deter-

mined by division of the elongated spermatid count per

testis and spermatids per g testis by 6.3 days of spermato-

genesis time during steps 17–19 spermatids for Holtzman

rats (Kubota et al., 2003; Takahashi & Oishi, 2003). The

epididymal sperm transit rate was calculated by dividing

the cauda epididymal sperm number by DSP (Dalsenter

et al., 2003).

Dose–response effect of mashua J. Leiva-Revilla et al.

ª 2011 Blackwell Verlag GmbH206 Andrologia 2012, 44, 205–212

Epididymal sperm count

Homogenisation-resistant epididymal spermatozoa from

nonperfused rats were counted as described previously

(Gonzales C et al., 2006). Caput and corpus epididymis

were cut and homogenised (Polytron homogenizer,

Brinkmann PT 3000) separately to the cauda epididymis.

Homogenisation was performed in 5 ml saline (NaCl

0.9%). Homogenates were kept refrigerated at 4 �C for

24 h to allow spermatozoa be released from the walls.

Then, 5 ml of eosine (2%) was added and vortexed. One

millilitre of this mixture is diluted with 2 ml of eosine

(2%), and a sample is placed in a Neubauer chamber,

and head spermatozoa were counted in 25 squares. Sperm

counts in the 25 squares were multiplied by 0.06 (sperma-

tozoa · 106 ml)1) and then by 5 ml (spermatozoa · 106

per caput/corpus or cauda). Data are referred as sperma-

tozoa per caput/corpus or cauda epididymis. Data in the

present study were expressed as total amount of epididy-

mal spermatozoa (sperm count in caput/corpus + sperm

count in cauda).

Vas deferens sperm count

Sperm number in vas deferens was determined as

previously described (Gonzales et al., 2006a,b). Briefly,

vas deferens was dissected in two parts: one corresponding

to the proximal end and the second to the distal end.

Each part was homogenised with 1 ml saline (Polytron

homogenizer, Brinkmann PT 3000). An aliquot was

diluted with two parts of eosine (2%). Homogenisation-

resistant sperm heads were counted in the 25 squares of

the Neubauer chamber. Four chambers were measured in

each sample, and they were averaged. Results from each

part (proximal or distal end) were multiplied by 0.03 and

defined as spermatozoa · 106 per part of vas deferens.

Data were expressed as total amount of spermatozoon in

vas deferens (sperm count in proximal end + sperm

count in distal end).

Epididymal sperm motility and morphology

For sperm motility and morphology, the contralateral epi-

didymis was cut in the cauda, and drops of fluid were

obtained and diluted with phosphate-buffered saline (pH

7.2 and 0.1 m). To determine sperm motility, one fresh

sample was observed in a compound microscope at 40·.

One-hundred spermatozoa were counted. Data were

referred as percent of motile spermatozoa (Gonzales et al.,

2006a,b). Sperm morphology was assessed using a stained

sperm suspension (eosine 2%) to prepare a slide smear

that was observed under light microscope (40·). One-

hundred spermatozoa were counted and classified into

normal and abnormal (i.e. spermatozoa with defective

heads and/or tails). Data were expressed as a percentage

of abnormal spermatozoa (Shetty, 2007).

Statistical analyses

Data were analysed using the statistical package stata (v.

8.0) for PC (Stata Corporation, College Station, TX,

USA). Data are presented as mean ± standard error of

the mean (SEM). Barlett test was performed to determine

the homogeneity of variances. When variances were

homogeneous, differences between groups were assessed

by analysis of variance (anova). If F value in the anova

test was significant, the differences between pair of means

were assessed by the Scheffe test. Mann–Whitney U non-

parametric test was used when variances where not

homogeneous. A value of P < 0.05 was considered to be

statistically significant.

Results

Effect of different doses of aqueous extract of mashua

No differences were observed regarding to initial body

weights between all groups of treatment (data not

shown). After 12 days, anova one-way analysis revealed

that rats treated with 0.01, 0.1, 1.0 and 2.0 g kg)1 of mas-

hua (367.36 ± 10.35, 335.43 ± 10.95, 353.83 ± 17.61, and

344.63 ± 6.61 g respectively) showed significantly higher

final body weights than those in control group

(319.71 ± 8.41 g; F4,34 = 2.97; P < 0.05). No differences

were found when relative reproductive organ weights

were compared (P > 0.05). All doses of mashua reduced

DSP values when compared to control group (P < 0.05).

No differences between mashua-treated groups were

noted (>0.05) (Table 1).

Sperm transit rate was increased in rats treated with

0.01 g kg)1 (5.44 ± 0.70 days), 0.1 g kg)1 (5.45 ±

0.39 days) and 1 g kg)1 (4.25 ± 0.07 days) of mashua

extract compared to control group (3.03 ± 0.32 days,

P < 0.05) (Fig. 1). Again, no differences between mashua-

treated groups were noted (P > 0.05) (Fig. 1). Sperm

transit rate in mashua-treated rats showed a dose–

response behavior (r = )0.55; P < 0.05).

Regarding to epididymal sperm number, rats treated

with 0.01 g kg)1 (72.96 ± 0.57 spermatozoa · 106 per

epididymis) and 1 g kg)1 (72.78 ± 3.06 spermato-

zoa · 106 per epididymis) of mashua extract showed

lower values when compared to control group

(89.11 ± 3.12 spermatozoa · 106 per epididymis;

P < 0.05). In mashua-treated groups, rats treated with

0.1 g kg)1 presented higher values than rats from 0.01, 1

and 2 g kg)1 groups (P < 0.05) (Table 1). Vas deferens

J. Leiva-Revilla et al. Dose–response effect of mashua


sperm count were reduced in rats treated with all doses

of mashua when compared to control group (P < 0.05)

(Table 1). Reduction in vas deferens sperm number

showed a dose-dependent behavior (r = 0.40; P < 0.05).

When the percentage of sperm motility and abnormal

sperm morphology was assessed, rats treated with mashua

showed a dose-dependent reduction in sperm motility

(r = )0.62; P < 0.05) when compared to control group

(P < 0.05) (Fig. 2a); meanwhile, an increase in abnormal

sperm morphology was observed in rats treated with

mashua compared to control group (P < 0.05) (Fig. 2b)

with no dose–response behavior.

Determination of the reversibility of mashua effects on

reproductive function

At the beginning of the experiment, all groups showed

similar body weights (data not shown). Final body weight

was lower in control group (289.14 ± 18.19 g; P < 0.05)

than No-R (353.83 ± 17.61 g; P < 0.05), R-12

(340.60 ± 7.12 g; P < 0.05) and R-24 groups

(353.17 ± 15.64 g; P < 0.05). No differences in relative

reproductive organ weights were found between groups

(P > 0.05).

As mentioned earlier, mashua reduced DSP (from

12.54 ± 0.51 to 9.20 ± 0.59 spermatozoa · 106 per testis;

P < 0.05) and epididymal sperm number (from

83.80 ± 4.18 to 67.19 ± 4.34 spermatozoa · 106 per epi-

didymis; P < 0.05) when compared to control group.

DSP and epididymal spermatozoa were recovered in the

Table 1 Effect of different doses of aqueous extract of Tropaeolum tuberosum (mashua) on daily sperm production (DSP) and sperm number in

epididymis and vas deferens

Control

Mashua (g kg)1)

0.01 0.1 1.0 2.0

DSP (·106 spermatozoa per testis) 12.29 ± 1.05 8.04 ± 0.86* 9.56 ± 0.48* 9.70 ± 0.63* 9.31 ± 0.58*

Epididymal sperm count

(·106 spermatozoa per epididymis)

89.11 ± 3.12 72.95 ± 0.57* 104.52 ± 9.25*,a 72.78 ± 3.06*,b 81.58 ± 4.71*,b

Vas deferens sperm number

(·106 spermatozoa per vas deferens)

5.98 ± 0.59 2.92 ± 0.27* 2.91 ± 0.28* 2.86 ± 0.63* 3.33 ± 0.71*

Data are expressed as mean ± SEM.

*P < 0.05 versus control group.aP < 0.05 versus rats treated with 0.01 g kg)1 of mashua.bP < 0.05 versus rats treated with 0.1 g kg)1 of mashua.

0

1

2

3

4

5

6

7

Control 0.01 0.1 1 2

Doses (g kg–1)

Sper

m tr

ansi

t (da

ys)

*

**

a,b

Fig. 1 Effect of different doses of aqueous extract of mashua (Trop-

aeolum tuberosum) on sperm transit rate in adult rats. Data are

expressed as mean ± SEM. *P < 0.05 versus control group; aP < 0.05

versus rats treated with 0.01 g kg)1 of mashua; bP < 0.05 versus rats

treated with 0.1 g kg)1 of mashua.

0

10

20

30

40

50

60

70

Control 0.01 0.1 1 2

Doses (g kg–1)

Sper

m m

otili

ty (%

)***

*

5

10

15

20

25

30

Control 0.01 0.1 1 2

Doses (g kg–1)

Sper

m a

bnor

mal

mor

phol

ogy

(%)

****

(a)

(b)

Fig. 2 Percentage of sperm motility (a) and abnormal sperm mor-

phology (b) in adult rats treated with different doses of aqueous

extract of Tropaeolum tuberosum (mashua). Data are expressed as

mean ± SEM. *P < 0.05 versus control group.



R-12 and R-24 groups showing similar values to the con-

trol group (P > 0.05) (Table 2).

Rats treated with mashua showed a reduction in sperm

number in vas deferens compared to control group (from

5.75 ± 0.52 to 2.85 ± 0.63 spermatozoa · 106 per vas def-

erens). Furthermore, an increase in sperm number in vas

deferens was observed in R-12 (5.28 ± 0.95 spermato-

zoa · 106 per vas deferens) and R-24 (5.29 ± 0.92 sper-

matozoa · 106 per vas deferens) groups when compared

to No-R group reaching similar values to control group

(Table 2).

Sperm transit rate was increased in the group treated

with mashua when compared to control group

(4.33 ± 0.44 days versus 2.77 ± 0.15 days; P < 0.05).

Moreover, reversibility of mashua effect was noted after

12 and 24 days (R-12 and R-24) cessation of treatment

(Fig. 3).

Percentage of motile spermatozoa was reduced in rats

treated with mashua (22.08 ± 2.93%) with respect to con-

trol group (57.14 ± 3.28%; P < 0.05). In rats with

12 days of recovery time (R-12), the effect of mashua was

partially reversed. Similar values than control group was

reached when rats were allowed to recover for 24 days

(R-24) after cessation of mashua treatment (Fig. 4a).

Abnormal sperm morphology was higher in rats treated

with mashua (24.94 ± 0.2.05%) than in control group

(16.57 ± 0.99%; P < 0.05). Again, the effect of mashua

on the percentage of abnormal sperm morphology was

completely reversed after 12 and 24 days (R-12 and R-24)

cessation of treatment (Fig. 4b).

Table 2 Daily sperm production (DSP) and sperm number in epididymis and vas deferens in adult rats after 0, 12 and 24 days (No-R, R-12 and R-

24 respectively) after cessation of treatment with mashua (1 g kg)1)

Control

Reversibility time (R)

No-R R-12 R-24

DSP (·106 spermatozoa per testis) 12.54 ± 0.51 9.20 ± 0.59* 10.41 ± 0.84 10.53 ± 0.25

Epididymal sperm count (·106 spermatozoa per epididymis) 83.80 ± 4.18 67.19 ± 4.34* 71.87 ± 5.16 77.88 ± 1.80

Vas deferens sperm number (·106 spermatozoa per vas deferens) 5.75 ± 0.52 2.85 ± 0.61* 5.27 ± 0.95a 5.28 ± 0.92a

Data are expressed as mean ± SEM.

*P < 0.05 versus control group.aP < 0.05 versus rats in No-R group.

0

1

2

3

4

5

6

Control No-R R-12 R-24

Sper

m tr

ansi

t (da

ys)

*

aa

Fig. 3 Reversibility of mashua (1 g kg)1) effect on sperm transit rate

after 0, 12 and 24 days (No-P, R12 and R24 respectively) after termi-

nation of treatment. Data are expressed as mean ± SEM. *P < 0.05

versus control group; aP < 0.05 versus rats in No-R group.

0

10

20

30

40

50

60

70


Sper

m m

otili

ty (%

)

*

*

a

a,b

0

5

10

15

20

25

30


Abn

orm

al s

perm

mor

phol

ogy

(%) *

aa

(a)

(b)

Fig. 4 Reversibility of mashua (1 g kg)1) effect on the percentage of

sperm motility (a) and abnormal sperm morphology (b) after 0, 12

and 24 days (No-R, R12 and R24 respectively) after termination of

treatment. Data are expressed as mean ± SEM. *P < 0.05 versus con-

trol group; aP < 0.05 versus rats in No-R group; bP < 0.05 versus rats

with 12 days of recovery time (R12).



Discussion

To our knowledge, studies reported in the peer-reviewed

journals about the anti-reproductive effect of mashua

are scarce. In fact, only two studies were found related

to this effect (Johns et al., 1982; Cardenas-Valencia et al.,

2008). In the first study, male rats that were allowed to

fed a diet containing mashua showed no differences in

the capability in impregnating females, although a drop

on blood levels of testosterone/dihydrotestosterone was

observed (Johns et al., 1982). A second study demon-

strated that mashua reduced sperm production after 12,

21 or 42 days of treatment without modification in

serum testosterone levels (Cardenas-Valencia et al.,

2008).

The aim of the present study was to determine

whether the anti-reproductive effect of mashua showed a

dose-dependent behavior. As mentioned above, the effect

of mashua was observed after 12 days of treatment

(Cardenas-Valencia et al., 2008), which represents the

duration of a seminiferous cycle in rats (Aslam et al.,

1999). Mashua reduced DSP suggesting a reduction in

late spermatids maturation and/or release from testis.

The latter is supported by the fact that mashua dimin-

ished epididymal sperm number. Also, mashua acceler-

ated sperm transit time, and this alteration may

contribute to lower epididymal sperm number. In fact,

previous studies demonstrated that an increase in rat

sperm transit rate appeared associated with reduced

epididymal sperm number and to harm normal sperm

maturation by decreasing sperm quality and fertility

capacity (Fernandez et al., 2008). According to this,

increased sperm transit values in mashua-treated rats may

explain the lower sperm motility and higher abnormal

sperm morphology that, in turn, may be related to a

reduction in sperm number in vas deferens. Although dif-

ferent doses of mashua showed a dose–response effect on

sperm motility, transit rate and number in vas deferens,

no differences between rats treated with different doses of

mashua were found. For this reason, it is possible to

suggest that the anti-reproductive effect of mashua can be

observed using lower doses of the aqueous extract of this

tuber.

Results from the present study showed that mashua did

not modify reproductive organ weights, so it is possible

to suggest that the effect of mashua on reproductive

organ weights and function should not be related to any

alteration in androgen levels as showed and suggested by

others (Cardenas-Valencia et al., 2008). A possible expla-

nation may be related to the action of adrenergic, cholin-

ergic and nonadrenergic noncholinergic systems on

vasoactivity within the testis and sperm transport in the

epididymis and vas deferens (Kempinas et al., 1998a,b;

Lafayette et al., 2008). Additional research is needed to

determine the mechanism related to the anti-reproductive

effect of mashua tubers.

The dose of mashua that used in the second experi-

ment (1 g kg)1) was chosen to demonstrate whether the

anti-reproductive effect of the administration of a higher

dose of mashua can be reversible after 12 and 24 days of

recovery time. In fact, it was previously demonstrated that

1 g kg)1 of mashua aqueous extract reduced sperm pro-

duction when it was administered for 12, 21 and 42 days

with no changes in testosterone levels (Cardenas-Valencia

et al., 2008). After 12 days of the last treatment with mas-

hua, from all variables assessed only sperm motility

showed intermediate values between control and No-R

groups. Outcomes from the second experiment reported

that mashua effect can be reversible after 24 days after

cessation of treatment where variables related to sperm

production (DSP, epididymal and vas deferens sperm

count and sperm transit rate) and sperm quality (percent-

age of sperm motility and with abnormal morphology)

return to similar values than those observed in control

group. Similar to the first experiment, the fact that no

differences in reproductive organ weights were observed

may suggest that mashua can be used as a natural male

contraceptive without hormonal and other side effects

(Lopez et al., 2005; Cardenas-Valencia et al., 2008). On

the other hand, mashua was able to increase body weight

in both experiments suggesting that this plant may have

nutritional properties as suggested by others (Shah et al.,

1993; Stegemann & Shah, 1993; Grau et al., 2003).

Glucosinolates are found in many plant families such

as Brassicaceae, Capparaceae and Tropaeolaceae, including

mashua. In fact, the major secondary metabolite of mas-

hua is the p-methoxybenzylglucosinolate (Johns et al.,

1982; Cardenas-Valencia et al., 2008). Previously, it has

been demonstrated that glucosinolates after ingestion by

humans or rats are metabolized, by gut mirosinase

enzyme, to isothiocyanates (Shapiro et al., 1998; Rouzaud

et al., 2003) showing anti-proliferative and pro-apoptotic

properties (Gonzales et al., 2005; Rubio et al., 2006). In

addition, other studies have shown that glucosinolates

and their breakdown products are beneficial to prevent

cancer (Mithen et al., 2000; Fahey et al., 2001). For

instance, the consumption of Brassica vegetables is related

to a reduced risk of colon, rectal and prostate cancers

(Wattenberg, 1977, 1981; Kristal & Lampe, 2002). The

latter is supported by the fact that Brassica vegetables

such as Lepidium latifolium and the red variety of Lepidi-

um meyenii reduced prostate size in rats where hyperpla-

sia was induced by exogenous testosterone administration

(Martinez Caballero et al., 2004; Gonzales et al., 2005;

Gasco et al., 2007). Other authors suggested that benefi-

cial effects of this tuber may be related to the presence of



phenolic compounds, mainly anthocyanins (Campos

et al., 2006; Chirinos et al., 2007). Furthermore, previous

works demonstrated that mashua phenolic compounds

correlate with its high antioxidant activity when

compared to other Andean corps such as colored pota-

toes, olluco and oca (Campos et al., 2006; Chirinos et al.,

2006, 2007, 2008a,b). Among mashua varieties, it was

found that the purple variety is the one that presents the

highest phenolic and glucosinolate content and antioxi-

dant activity when compared, for example, with yellow

variety (Ramallo et al., 2004; Campos et al., 2006; Chiri-

nos et al., 2006, 2007, 2008a,b); however, yellow tubers of

mashua are the most abundant and commercialised

among all varieties (Grau et al., 2003). Concerning to

mashua phenolic content and its antioxidant activity, the

fact that yellow mashua showed the lowest content of

phenolic compounds and antioxidant activity when com-

pared to dark varieties make possible to suggest that these

differences may be related to the anti-reproductive effect

of this variety. Nevertheless, additional studies have to be

undertaken to determine the differences in the biological

properties of different varieties of mashua, including its

anti-reproductive effect. In this point of view, it was sug-

gested that the higher glucosinolate content in mashua

tubers could be related to its anti-reproductive effects

(Johns et al., 1982; Ramallo et al., 2004; Cardenas-Valen-

cia et al., 2008). This suggestion is supported by the fact

that our laboratory found that mashua (yellow variety)

had a higher content of glucosinolates (3.7 g per 100 g)

than the Brassica plant Lepidium meyenii (maca)

(Cardenas-Valencia et al., 2008; Gonzales et al., 2007) that

has beneficial effect on male reproductive system, so it is

possible to suggest that the higher content of glucosino-

lates in mashua could be related to its anti-reproductive

effect. Also, other compounds with anti-reproductive

effects have not been elucidated yet in mashua tubers. For

these reasons, additional studies need to be undertaken to

find specific compound or compounds related to the

anti-reproductive activity described in this study and by

others.

Conclusion

In conclusion, the present study demonstrated that lower

doses of mashua reduced sperm number and quality

(motility and morphology) and the effect of the adminis-

tration of higher doses of this tuber can be reversible

24 days after the termination of the treatment.

Acknowledgements

The authors thank Nadia Hurtado and Sandra Barrueta

for their support during the study. The present study was

supported by a Grant from Universidad Peruana Cayet-

ano Heredia.

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