Joseph O. Kuti and Eliseo S. Torres
- METHODOLOGY
- Nutritional Composition
- Possible Antidiabetic Effect
- RESULTS
- Nutritional Composition
- Possible Antidiabetic Effect
- CONCLUSION
- REFERENCES
- Table 1
- Table 2
- Fig. 1
- Fig. 2
- Fig. 3
The young shoots and tender leaves of chaya are cooked and eaten like spinach.They comprise part of the staple diet and are the main dietary source of leafyvegetable for the indigenous people of Yucatan peninsula of Mexico and Kekchipeople of Alta Verapaz in Guatemala (Harris and Munsell 1950; Booth et al.1992). There are many underexploited native leafy plants with potential as atraditional food source (NAS 1975). With current renewal of interest inhousehold gardens, attention is being focused on promoting some of these plantsas leafy green vegetables among populations in the developing countries (FAO1987). The edible parts of chaya plant, which taste like spinach when cooked,provide important nutritional sources for protein, vitamins (A and C), minerals(calcium, iron, phosphorus), niacin, riboflavin, and thiamine among populationsthat cannot afford expensive foods rich in these nutrients (Yang 1979). Theplant may also constitute a potentially valuable leafy green vegetable here inthe United States and elsewhere.
Chaya traditionally has been recommended for a number of ailments includingdiabetes, obesity, kidney stones, hemorrhoids, acne, and eye problems(Diaz-Bolio 1975). Chaya shoots and leaves have been taken as a laxative,diuretic, circulation stimulant, to improve digestion, to stimulate lactation,and to harden the fingernails (Rowe 1994). Like most food plants such as limabeans, cassava, and many leafy vegetables, the leaves contain hydrocyanicglycosides, a toxic compound easily destroyed by cooking. Even though somepeople tend to eat raw chaya leaves, it is unwise to do so.
While the nutritional value of chaya has been demonstrated (Martin and Ruberte1978; Booth et al. 1992), none of the purported therapeutic values of chayaleaves has been substantiated with scientific experimentation. Therefore, thepresent study reports on nutritional composition of raw and cooked chaya leavesand the results compared with the nutritional composition of spinach leaves.Also a possible antidiabetic effect of the aqueous leaf extracts or chaya tea,administered through drinking water to streptozotocin-induced diabetic rabbits,was evaluated.
METHODOLOGY
Nutritional Composition
Young leaves and shoots of C. chayamansa were collected fromgreenhouse-grown plants. Raw and cooked (in microwave oven for 5 min) samplesof the leaves and shoot were analyzed for their moisture content, crude fiber,fat, and ß-carotene using the AOAC standard methods (1984), for theprotein content (N2 content multiplied by 6.25) using modified semimicro-kjeldahl method of Searle (1974), for mineral contents using an atomicabsorption spectrohotometer and for total carbohydrate using gaschromatography. All samples were analyzed in triplicate. Nutritionalcomponents and average nutritive value (ANV) of chaya leaves were compared tospinach leaves. The ANV was calculated using the empirical formula proposed byGrubben (1978): ANV/100g = g protein/5 + g fiber + mg Ca++/100 + mgFe++/2 + mg carotene + mg vit C/40Possible Antidiabetic Effect
The experimental animals (rabbits) for this study were supplied by Dr. StevenLukefahr of the Department of Animal and Wildlife Sciences, Texas A&MUniversity-Kingsville. All animals were housed and maintained in compliancewith Texas A&M University-Kingsville IACUC policy on animal care and use.The rabbits were fed with standard rabbit chow and given water adlibitum. Diabetes was induced by a single subcuteanous injection of 60mg/kg streptozotocin (STZ), after fasting for 18 h, according to the methoddescribed by Bonner-Weir et al. (1981). The rabbits exhibited post-STZ bloodglucose levels that were at least double that of the pre-STZ levels one weekafter diabetes had been induced.The leaves of C. chayamansa were collected from plants grown inthe greenhouse. About 10 g of the leaves was extracted with boiling water(1000 mL) for 30 min until the volume of the water had been reduced to 90% ofthe original. The tea (900 mL) was filtered and used in the subsequentexperiments. Two groups of 8 rabbits each were used. The first group of 8rabbits were normoglycemic (non-diabetic). Four of the normoglycemic rabbitsrecieved water (control) only and the remaining 4 received chaya tea treatmentonly. The second group of 8 rabbits were hyperglycemic (diabetic). Four ofthe diabetic rabbits received water only and the remaining 4 received chaya teaonly.
Before administering the tea or water (control), blood samples were obtainedfrom the ears of 18 h fasted nondiabetic and diabetic rabbits using a capillarytube. Then the tea or water was administered orally through drinking waterbottles ad libitum. Blood sampling was repeated at hourly intervals for6 h after the oral administration. Blood glucose was determined using a bloodglucometer (Miles Inc., Diagnostic Division, Elkhart, IN, U.S.). The meanblood glucose values ±SE were determined and the significance of thedifference between the means of treated and control groups was established byStudent's t-test.
RESULTS
Nutritional Composition
The nutritional analysis of chaya (C. chayamansa) leaves andspinach (Spinacia oleracea L.) are presented in Table 1 for comparison.Chaya leaves were found to contain substantially greater amounts of nutrientsthan the spinach leaves. The chaya leaf is especially high in protein (5.7%),crude fiber (1.9%), calcium (199.4 mg/100 g), potassium (217.2 mg/100 g), iron(11.4 mg/100 g), vitamin C (164.7 mg/100 g), and carotene (0.085 mg/100 g).The levels of chaya leaf nutrients, in this study, agree with published reports(Martin and Ruberte 1978; Munsell et al. 1949; Booth et al. 1992) and are twoto threefold greater than most edible leafy green vegetables. In terms of theaverage nutritive value, chaya leaves [14.9] is by far superior to other leafygreen vegetables such as spinach [6.4], amaranth [11.3], Chinese cabbage [7.0],and lettuce [5.4] (Grubben 1978). While some edible leafy green vegetables areusually good sources of mineral macronutrients (Levander 1990), chaya leaffurnishes appreciable quantities of several of the essential mineralmacronutrients necessary for human health maintenance. For example, potassiumhas been shown to be an important mineral nutrient in the control ofhypertension and in the reduction of risks of stroke (NRC 1989), calcium isimportant for ossification and iron is necessary for normal hematopoiesis(Hodges et al. 1978). Brise and Hallberg (1962) reported that vegetables, suchas chaya, with high vitamin C content may enhance absorption of nonheme iron.Analysis of raw and cooked samples of chaya leaves revealed that cooking mayincrease the relative composition of carbohydrate and fat and decrease relativecomposition of crude fiber and protein (Fig. 2). On the other hand, cookedsamples of chaya leaves were considerably higher in calcium, phosphorus andiron while the potassium content was relatively lower than in the raw samples(Fig. 3). The increase in some of the mineral nutrients may be due to thecooking process, which allows extraction of the nutrients from the tissues,therefore increasing the percentage of mineral elements while decreasingmoisture content (Booth et al. 1992).
Possible Antidiabetic Effect
Following the oral administration of chaya tea, the blood glucose levels of thediabetic rabbits were gradually lowered from a high of 118 (baseline at 0.0 h)to 87 six hours after administration. The blood glucose level of 87 is similarto blood glucose levels of normoglycemic rabbits on drinking water (Table 2).The blood glucose levels of non-diabetic control rabbits that were given chayatea showed a slight increase (i.e. hyperglycemia) above the baseline 85 at 1 to2 h after administration, but rapidly stabilized thereafter (Table 2).The reason for this transient hyperglycemia is unknown and needs to beinvestigated. The results obtained in this study suggest that in STZ-induceddiabetic rabbits, aqueous leaf extracts of C. chayamansa may beeffective for treatment of non-insulin dependent diabete mellitus (NIDDM)symptomatology. This is a first report on hypoglycemic effect of chaya plants.The present report is preliminary in nature and additional studies will beneeded to properly characterize the antidiabetic potential of chaya in diabeticanimals. Also further studies will be necessary to determine the effectivedosage, mechanism of the hypoglycemic activity and the active hypoglycemicprinciple present in the leaves of C. chayamansa.CONCLUSION
The potential of C. chayamansa for human food and health has asignificant implication for the plant as a horticultural crop. Although demandfor chaya, as a medicinal plant, has recently increased among the Hispanicpopulation in the United States, the plant has the potential to make asignificant nuritional contribution to the vegetable diet as well, because ofits high nutrient content. The development of chaya as a new horticulturalcrop would transcend the ethnic popularity and create a worldwide market forthe plant and its products, whether as a leafy green vegetable and/or as atherapeutic herbal tea.It is noteworthy that the chaya plant is drought resistant, which is of aparticular value in areas with short seasonal rainfall and shortage of greenvegetables (Peregrine 1983). Growth of the plant is rapid and edible leavesand shoots could be produced within a short period (8 to 10 weeks).Propagation by cutting is easy and the woody stem sections readily root. Fewpests and diseases are known to be of any significance in the cultivation ofchaya plants. One disadvantage is the presence of toxic hydrocyanic glucosidesin the leaves. However, cooking, which is essential, inactivates the toxiccompound. Other Cnidoscolus (chaya) species are being examined in ourlaboratory at Texas A&M University-Kingsville to genetically select specieswith high leaf and shoot biomass yield and lower hydrocyanic glycoside content.Additionally, we are conducting research on genetic improvement, propagation,field production, potential for processing and marketing of chaya and itsproducts in south Texas.
REFERENCES
- AOAC. 1984. Official methods of analysis, 14th ed. Assoc. Official Anal. Chem.,Arlington, VA.
- Booth, S., R. Bressani, and T. Johns. 1992. Nutrient content of selectedindigenous leafy vegetable consumed by Kekchi people of Alta Verapaz,Guatamela. J. Food Compos. Anal. 5:25-34.
- Bonner-Weir, S., D.F. Trent, R.N. Honey, and G.C. Weir. 1981. Responses ofneonatal rat islets to streptozotocin-limited ß-cell regeneration andhyperglycemia. Diabetes 30:64-69.
- Breckon, G.J. 1979. Studies in Cnidoscolus (Euphorbiaceae). Brittonia31:125-148.
- Brise, H. and L. Hallberg. 1962. Effect of ascorbic acid on iron absorption.Acta Med. Scand. Suppl. 171:51-58.
- Diaz-Bolio, J. 1975. Chaya (Cnidoscolus chayamansa, Euphorbiaceae), amarvellous food (in spanish). Tierra 30:407-408, 427-428.
- FAO. 1987. Promoting under-exploited food plants in Africa.: A brief for policymarkers. Food and Agriculture Organization, Food Policy & Nutrition Div.,Rome.
- Grubben, G.J.H. 1978. Tropical vegetables and their genetic resources. Int.Board Plant Genetic Resource, FAO-UN, Rome Italy.
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- Hodges, R.E., H.E. Sauberlich, J.E. Canham, D.L. Wallace, R.B. Rucker, L.A.Mejia, and M. Mohanram. 1978. Hematopoietic studies in vitamin A deficiency.Am. J. Clin. Nutr. 31:876-885.
- Levander, O.A. 1990. Fruit and vegetable contribution to dietary mineral intakein human health and disease. HortScience 25:1486-1488.
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| Component | chaya | spinachz |
| Water (%) | 85.3 | 90.7 |
| Protein (%) | 5.7 | 3.2 |
| Fat (%) | 0.4 | 0.3 |
| Crude fiber (%) | 1.9 | 0.9 |
| Total CHO (%) | 4.2 | 3.8 |
| Ash (%) | 2.2 | 1.8 |
| Calcium (mg/100g) | 199.4 | 101.3 |
| Phosphorus (mg/100g) | 39.0 | 30.0 |
| Potassium (mg/100g) | 217.2 | 146.5 |
| Iiron (mg/100g) | 11.4 | 5.7 |
| Ascorbic acid (mg/100g) | 164.7 | 48.1 |
| Carotenoids (mg/100g) | 0.085 | 0.014 |
| Average nutritive valuey | 14.94 | 6.38 |
yAverage nutritive value according to Grubben emprical formula(1978).Table 2. Effect of Cnidoscolus chayamansa leaf extract ("chaya"tea) on blood glucose levels of non-diabetic and streptozoctocin-induceddiabetic rabbits.
| Blood glucose level (mg/dL)z | ||||
| Non-diabetic | Diabetic | |||
| Time (h) | water | "chaya" | water | "chaya" |
| 0.0 | 87±3.1 | 85±2.5 | 112±8.3 | 118±13.2 |
| 1.0 | 86±2.7 | 91±3.9 | 138±4.6 | 114±7.3 |
| 2.0 | 87±2.6 | 99±4.3 | 143±6.4 | 103±8.7 |
| 3.0 | 87±3.1 | 82±1.6 | 139±8.0 | 96±9.3 |
| 4.0 | 88±3.0 | 85±2.1 | 153±6.3 | 92±5.8 |
| 5.0 | 87±4.7 | 84±4.2 | 158±7.4 | 89±3.6 |
| 6.0 | 87±3.1 | 82±2.7 | 162±9.0 | 87±2.7 |
Fig. 1. A potted chaya plant. The young leaves and shoots are edibleafter being boiled in water.
Fig. 2. Proximate fat, protein, carbohydrate and crude fibercompositions of raw and cooked chaya leaves.
Fig. 3. Proximate mineral macronutrient (calcium, phosphorus, potassiumand iron) compositions of raw and cooked chaya leaves.
Last update August 24, 1997aw