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Cokelaere, M.M., G. Flo, P. Daenens, E. Decuypere, M. Van Boven, and S. Vermaut. 1996. Food intake inhibitory activity of simmondsin and defatted jojoba meal: Dose-response curves in rats. p. 377-382. In: J. Janick (ed.), Progress in new crops. ASHS Press, Arlington, VA.

Food Intake Inhibitory Activity of Simmondsin and Defatted Jojoba Meal: Dose-Response Curves in Rats

Marnix M. Cokelaere, Gerda Flo, Paul Daenens, Eddy Decuypere, Maurits Van Boven, and Sabien Vermaut

  1. METHODOLOGY
    1. Experiment 1
    2. Experiment 2
  2. RESULTS AND DISCUSSION
    1. Experiment 1
    2. Experiment 2
  3. SUMMARY
  4. REFERENCES
  5. Table 1
  6. Table 2
  7. Fig. 1
  8. Fig. 2
Jojoba (Simmondsia chinensis) is a shrub indigenous to the Sonoran desert of Arizona, California, and Mexico. The seeds contain liquid wax esters used as a high-temperature lubricant and in cosmetics. The meal by-product remaining after wax extraction cannot be used as animal feed because of the presence of several cyanide-containing glycosides, such as simmondsin, simmondsin 2'-ferulate, and several minor simmondsin derivatives (Booth et al. 1974; Elliger et al. 1973, 1974a, b; Van Boven et al. 1994a, b, c, 1995). Simmondsin and simmondsin-containing jojoba meal induce food intake inhibition, emaciation and, occasionally mortality, and because of this, simmondsins have been considered toxic (Booth et al. 1974; Ngoupayou et al. 1982; Verbiscar et al. 1980, 1981). However, long-term administration of lower doses of simmondsin or defatted jojoba meal to growing rats, which induced a sustained food intake inhibition of about 20%, showed no toxic effects (Cokelaere et al. 1993a, b), although, real toxicity, especially at higher doses cannot yet be ruled out. Furthermore, it has been demonstrated that food intake inhibition in rats can be reversed by the cholecystokinin receptor antagonist, devazepide (Cokelaere et al. 1995a, b), suggesting that the anorexia seen following simmondsin administration is due to stimulation of the cholecystokinin satiation system. Other studies have shown that the food intake reduction induced with lower doses of defatted jojoba meal is due to satiation (Cokelaere et al. 1995c). Some authors claim that the anorexia induced by defatted jojoba meal is caused by its bitter taste due to the presence of simmondsin 2'-ferulate and tannins, the latter being found in the skin of the jojoba seed (Medina et al. 1988, 1990; Ngoupayou et al. 1985; Verbiscar et al. 1981). Simmondsin itself is tasteless (Verbiscar et al. 1981).

In the present study, the anorexic effects of simmondsin and simmondsin 2'-ferulate are compared and dose-response curves constructed for food containing pure simmondsin or defatted jojoba meal (from commercially available presscake or deskinned jojoba seeds) in order to discriminate between the satiating effects of the simmondsins and other factors present in jojoba seeds.

The effects of jojoba meal from Israel and the United States will be compared.

METHODOLOGY

Adult male Wistar rats, weighing 350 to 425 g, were housed in iron wire cages under normal laboratory circumstances (22°C, 40% to 60% relative humidity, light from 08:00 h to 20:00 h, free access to water and food). Food was provided as meal in specially designed mangers to avoid spilling (Scholz, Overijse, Belgium).

Experiment 1

In the first experiment, 10 rats (5 groups of 2) were used to compare the food intake inhibitory effects of food supplemented with pure simmondsin (S) and simmondsin 2'-ferulate (SF), the two major simmondsins of jojoba meal. The control daily food intake was measured for 3 days (group C), then the rats were given food supplemented with 0.5% (w/w) of pure simmondsin for another 3 days (group SM) and the food intake measured daily. After a recovery period of 2 weeks, they were given normal food supplemented with 0.5% (w/w) of simmondsin 2'-ferulate for 3 days (group SMF) and the food intake again measured daily.

Experiment 2

In a second series of experiments, the food intake inhibitory effect of food supplemented with increasing doses of simmondsin (0.1%, 0.25%, 0.50%, 0.75%, and 1.00%) (group SIM) was compared with the effect of food supplemented with increasing doses of 4 different preparations of defatted jojoba meal (Table 2). These jojoba meals were obtained from commercially available presscake (1) from Israel (Jojoba Israel, Kibbutz Hatzarim) (group PCI) or (2) from the United States (International Flora Technologies, Apache Junction) (group PCU), from deskinned jojoba seeds from (3) Israel (group DI), and (4) from the United States (group DU). The Israeli seeds were deskinned by peeling after cooking for 30 min, while American seeds were deskinned using razor blades. The seeds were then pressed in a hand screw press to extrude most of the jojoba oil. The presscakes and pressed deskinned Israeli seeds were Soxhlet-extracted using n-hexane for 8 h, while the pressed deskinned American seeds were defatted by stirring in a container with n-hexane at room temperature. Pure simmondsin was prepared and the content of S and SF determined as described previously (Van Boven et al. 1993, 1994b).

Fifty rats, caged in pairs, were used for each experiment, 10 for each simmondsin (S) or jojoba meal concentration. Rats were provided normal food for 7 days and the food intake was measured daily to obtain the control food intake; they were then given the S- or jojoba meal-supplemented foods for a further 7 days, and the daily food intake was recorded. The amount of food eaten during treatment was then expressed as a percentage of their own control intake.

RESULTS AND DISCUSSION

Experiment 1

The daily food intake of control group C was 20.7±0.4 g. 0.5% pure S or SF mixed in the food reduced food intake to 7.6±1.4 g or 12.5±1 g, respectively; in terms of food intake reduction, on a weight basis, SF was therefore only 62.5% as effective as S. However, the molecular weight of S is only 68% that of SF (375 and 551, respectively) and this therefore suggests that a similar food intake reduction is obtained with equimolar amounts of SF and S. These results contradict the suggestion of Weber (1978, quoted by Verbiscar et al. 1981) that SF has no significant involvement in anti nutritional aspects of jojoba meal.

The sum of the contents of S and SF x 0.68 (in %), of defatted jojoba meal was used as indicator of simmondsin activity (SA). The concentrations of defatted jojoba meals to be mixed in the food for the second experiment were calculated taking their SA into account.

Experiment 2

The S and SF contents of the different meals are shown in Table 1 and the concentrations to be mixed with the food in Table 2. The control daily food intake was 21.05±0.45 g (pooled for the 5 subgroups).

Fig. 1 shows the food intake inhibitory effect of food supplemented with increasing doses of pure simmondsin (SIM) or defatted jojoba meal obtained after deskinning jojoba seeds from Israel (DI) and the United States (DU). There was a clear, and similar, dose-response effect for SIM, DI, and DU up to a SA of 0.75% and it was only at a SA of 1%, that a greater degree of anorexia was seen in DI and DU animals compared with the SIM group. Food intake reduction was identical in the DI and the DU groups, although the jojoba meal concentration was significantly higher for the DI group (Table 2). It can thus be concluded that, up to a SA of 0.75%, the anorexic effect of food containing defatted jojoba meal, prepared from deskinned jojoba seeds, can be predicted from its SA rather than from the concentration of the jojoba meal mixed in the diet, and that it is only at higher concentrations that other factors, such as other minor simmondsins or taste effects, may play an additional role. The SF content of food supplemented with high concentrations of jojoba meal may produce a bitter taste, as SF is the major bitter principle of jojoba meal (Medina et al. 1990). An anorexic effect of other simmondsin analogues, present at lower concentrations in defatted jojoba meal, has also been suggested (Verbiscar et al. 1981) but remains to be proven. On the basis of the present results, they may have only a small additional effect. This confirms the results of Abbott et al. (1990) who fed mice with jojoba meal, detoxified enzymatically or with microorganisms that degraded simmondsin and simmondsin 2'-ferulate but did not attack the other simmondsin derivatives. Mice did well on this treated jojoba meals.

Fig. 2 shows the food intake reducing effect of food containing defatted jojoba meal produced from commercially available presscake. Up to a SA of 0.25%, PCI and PCU had a similar anorexic effect as SIM. At higher concentrations, food intake reduction became more pronounced, especially for PCU, although the difference in concentration of defatted jojoba meal used to obtain similar SAs in the PCI and PCU groups, were very small. This difference in anorexic effect probably results from a more pronounced influence of other factors than SA in jojoba meal. Taste could be one such factor since the skin of jojoba seeds (about 20% of the presscake, data not shown) contains high concentrations of tannins and taste very bitter (Verbiscar and Banigan 1978; Medina et al. 1990). The American jojoba seeds used were much smaller than those from Israel, so the presscake made from complete American jojoba seeds contained a higher percentage of skin than that from Israel and probably caused a more pronounced aversion to the supplemented food. This effect, additional to the anorexic effect of the simmondsins, was already evident at a lower SA content than in the experiments using deskinned seeds, which again points to a supplementary taste effect of skin components.

The present results confirm the results of Medina et al. (1990) in rats using jojoba meal made from complete or deskinned seeds, showing that debittering and tannin-extraction reduces the anorexic effect of jojoba meal. The dose-response curves obtained in the present experiment are in good agreement with previous separate results in rodents (Cokelaere et al. 1993a, b; Verbiscar et al. 1981), rabbits (Ngoupayou et al. 1985), cattle (Swingle et al. 1985), or chicken (Arnouts et al. 1993; Ngoupayou et al. 1982). We therefore conclude that, in rats, the anorexic effect of food containing S is dose-related, sustained, and predictable. On a molar base, SF and S are equipotent. Using the combined % S + % (SF x 0.68) content, designated as SA, the anorexic effect of food containing defatted jojoba meal prepared from deskinned jojoba seeds can be predicted from its SA up to a SA of 0.75%. At higher concentration of jojoba meal, a more pronounced anorexic effect is observed. Food mixed with defatted jojoba meal containing the skin of jojoba seeds, at a SA higher than 0.25%, has a more pronounced anorexic effect than can be predicted from its SA. This additional anorexic effect is probably due to taste or to other factors present in the skin.

SUMMARY

Over a 3-day period, the anorexic effects of pure simmondsin (MW=375) and simmondsin-2'-ferulate (MW = 551) were compared in adult male rats. On a weight base, the anorexic effect of simmondsin-2'-ferulate was only ±68% of that of simmondsin, but, on molar base, they were equipotent. The sum of the concentrations, expressed as percent, of simmondsin plus (simmondsin 2'- ferulate x 0.68) in jojoba meal was taken as an indicator of simmondsin activity (SA).

Dose-response curves of food intake inhibition, produced by increasing concentrations of pure simmondsin mixed in normal food (0.1% to 1.0%), were obtained in adult rats over a 7-day period and compared with those for increasing concentrations of defatted jojoba meal. The anorexic effect of pure simmondsin was dose-related up to a concentration of 1% in the diet (15% to 70% food intake reduction). Up to concentrations giving a SA of 0.75% in the diet, hexane-defatted jojoba meal, obtained from deskinned seeds, gave a similar dose-response curve to pure simmondsin and the anorexic effect of these jojoba meal containing mixtures could be predicted from their SA.

Hexane-defatted jojoba meal, obtained from commercially available jojoba presscake, had a similar food intake reducing effect to simmondsin up to concentrations giving a SA of 0.25%, but, at higher concentrations food intake was reduced to a greater extent than expected from the SA. This supplementary effect is probably due to the presence of the skins in the press cake, causing a bitter taste.

REFERENCES

Table 1. Simmondsin (S) and simmondsin 2'-ferulate (SF) concentrations of different jojoba meals. (SA = calculated simmondsin activity; DI = defatted jojoba meal from deskinned seeds from Israel; DU = defatted jojoba meal from deskinned seeds from the United States; PCI = defatted complete jojoba meal from Israel, PCU = defatted complete jojoba meal from the United States.

Concentration (%)
Defatted
jojoba meal		 S SF SA
DI 4.0 1.4 4.9
DU 7.2 1.8 8.5
PCI 4.8 1.4 5.6
PCU 4.6 1.2 5.4

Table 2. Concentrations of defatted jojoba meal mixed in the food of rats to obtain supplemented food with an SA equivalent to that of pure simmondsin. (DI = defatted jojoba meal from deskinned seeds from Israel; DU = defatted jojoba meal from deskinned seeds from the United States; PCI = defatted complete jojoba meal from Israel, PCU = defatted complete jojoba meal from the United States.

Amount of defatted jojoba meal (%) equivalent to stated simmondsin amount
Simmondsin
Defatted jojoba meal 0.10% 0.25% 0.50% 0.75% 1.00%
DI 2.0 5.0 10.0 15.0 20.0
DU 1.2 3.0 5.9 8.6 11.9
PCI 1.7 4.4 8.7 13.0 17.4
PCU 1.9 4.7 9.3 14.0 18.6

Fig. 1. Food intake as percent of control food intake (±SEM), at increasing concentrations of pure simmondsin and defatted jojoba meal from deskinned jojoba seeds (Israel and United States), n = 10; comparison of means within concentrations by Duncan multiple range test, 5% level.

Fig. 2. Food intake as percent of control food intake (±SEM) at increasing concentrations of pure simmondsin and defatted jojoba meal from commercial presscake (Israel and United States), n = 10; comparison of means within concentrations by Duncan multiple range test, 5% level.

Last update August 21, 1997 aw