Proximate composition of bungu (Ceratotheca sesamoides Endl.) leaves and seeds

Kola FASAKIN

Faculty of Agricultural Sciences, University of Ado-Ekiti, Ado-Ekiti, Nigeria. E-mail: fasakink@yahoo.com

Received 9 February 2004

Code Number: bk04024

ABSTRACT

Proximate analysis of the leaves of bungu harvested at 7, 8, 9, and 10 weeks after planting and the mature seeds were carried out in respect of the major nutrients. Mean values determined in two cultivars of the crop species indicated that the leaves contain low soluble carbohydrates and fat in addition to substantial amounts of protein (29.35 - 29.85%) and total ash (9.38 - 11.13%). The amounts of these and other nutrients in the leaves varied with age.  The seeds contain appreciable levels of fat (17.25 - 21.00%), suggesting that they are potentially capable of being exploited as source of vegetable oil. So also, the seeds contain high levels of crude protein (21.32 - 22.15%), crude fiber (25.75 - 29.5%), calcium (2.65 -3.15%), and phosphorus (0.53 - 0.54%).  

Key words: Bungu; proximate analysis; major nutrients

INTRODUCTION

Leaf vegetables are known to add taste and flavour, as well as substantial amounts of protein, fiber, minerals, and vitamins to the diet (Oyenuga and Fetuga, 1975; Adeyemi, 1987).  While the amounts of the nutrient constituents in the more commonly used leaf vegetable species in Nigeria have been studied to some extent (Oke, 1966; Oyenuga, 1968; Viyajakumar and Shanmugavelu, 1985; Taylor, 1988), the lesser known regional and local species remain virtually neglected. Lack of information on the specific nutrients in a large number of the native vegetables species with which Nigeria is richly endowed is partly responsible for their under-exploitation especially in areas beyond the traditional localities where they are found and consumed.

Amaranthus spp., Celosia spp., Talinum triangulare, Corchorus olitorius, Telfairia occidentalis, Cucurbita pepo, and Vernonia amygdalina are some of the commonly used leaf vegetable species in Nigeria on which proximate analysis studies have been conducted. Apart from the quantitative determination of specific nutrients in them, it has also been shown that the amount of a particular nutrient is influenced by the plant genotype, climate, soil fertility, age at harvest, and physiological changes during post-harvest handling (Earle and Jones, 1962; Oyenuga, 1968; Kane et. al., 1997).

Bungu, an important member of the family Pedaliaceae to which sesame or beniseed (Sesamum indicum L.) also belongs, is native to the northern parts of West Africa (Irvine, 1969; Zeven and de Wet, 1982). In Nigeria, it is widely distributed in variable forms and consumed as a leaf vegetable in the savanna ecological zones. Its mucilage-containing leaves are cooked directly in the soup, thus there is minimum nutrient loss. However, despite that the leaves and seeds feature prominently in the diet of the indigenous peoples of the savanna zones, published information is scanty on its proximate composition. In order to ascertain the nutritive value of the crop species and thereby stimulate interest in its utilisation beyond the traditional localities, this study was designed to determine the levels of the major nutrients in the leaves and seeds. 

MATERIALS AND METHODS

Edible leaves harvested at 7, 8, 9, and 10 weeks after planting (WAP) and the mature seeds of two bungu cultivars were obtained for proximate analysis from purposely planted plots on the University of Ilorin Teaching and Research Farm in September 1998. The two cultivars (code-named Lrn/09 and Lrn/10) were chosen from among 18 collections from different parts of Nigeria: Lrn/09 represented the tall morphotypes and Lrn/10, the dwarfish types.

Leaf samples were harvested at weekly interval from two randomly selected rows per designated plot beginning at 7 WAP. Seed samples were obtained when about 50% of the fruits on the main stem showed physiological maturity; i.e. changed colour from green to yellow. The samples were oven-dried, in quadruplicate, at 60°C to a constant weight. Shortly before chemical analysis, the dried leaves were ground in an electric grinder and passed through a 2mm-sieve while the seeds were pounded to a fine meal in a small laboratory porcelain mortar. Water content was the difference in weight before and after oven-drying the fresh sample, and dry matter was the oven-dried weight.

Crude protein, fat (Ether Extract), crude fiber, and total ash contents were determined using the methods described by AOAC (1990). Carbohydrate (Nitrogen Free Extract) was determined by difference; i.e. the sum of the percentages of crude protein, fat, crude fiber, and total ash deducted from 100. Calcium was determined by the EDTA titration method (Hildebrand and Reilley, 1957) and phosphorous by the Ascorbic acid method (Jackson, 1969; Aldrich, 1986). The values determined were statistically analysed for variance and significantly different treatment means determined at 5% level using Duncan multiple range test (DMRT).

Table 1: Percent Proximate Composition of the Edible Leaves of two Cultivars of Ceratotheca sesamoides

RESULTS AND DISCUSSION

The proximate analysis results in respect of the edible leaves are presented in Table 1. The ages mentioned in the text are the lengths of time from sowing to harvesting. Variation with age in the levels of the nutrients determined indicate that the percentages of crude protein, crude fat, and total ash in the leaves of the two cultivars were significantly higher at 7 than 8, 9, and 10 weeks. Conversely, dry matter, soluble carbohydrates, crude fiber, calcium, and phosphorous contents increased with age, their mean values being higher at 10 than 7 weeks. The decline in the levels of the major nutrients after 7 weeks may be attributed to the phenomenon, which Hewitt and Marrush (1986) described as assimilate remobilisation from the leaves to the reproductive organs during flowering and fruiting. In bungu, flowering in the two cultivars studied was observed to have started at about 8 weeks, reaching 50% stage at 9 - 10 weeks.

Table 2   Percent Proximate Composition of the Mature Seeds of two Cultivars of Ceratotheca sesamoides

Mean proximate composition of the leaves, also shown in Table 1, was derived from the values determined at 7, 8, 9, and 10 weeks. Between the two cultivars, there were no significant differences in their content of water, dry matter, crude fat, crude fiber, calcium, and phosphorus whereas Lrn/09 had lower total ash but slightly higher soluble carbohydrates and crude protein than Lrn/10. When these results are compared with those reported for the more commonly used leaf vegetables in Nigeria (Oke, 1966; Oyenuga, 1968; Taylor, 1988), bungu is not inferior as far as protein and mineral nutrients in the leaves are concerned.

Generally, the mean values indicate that the leaves contain low calories (soluble carbohydrates and fat) as well as high levels of protein (29.35 - 29.85%) and two of the elemental nutrients needed in large amounts by the human body, i.e. calcium (2.60 - 2.62%) and phosphorus (0.25 - 0.27%). The vegetable is, therefore, a potent supplement to the starchy staple foods with which it is traditionally consumed. Mohan and Janardhanan (1995) opined that the prohibitive cost of animal protein in developing countries (of which Nigeria is one) calls for extensive exploitation of plant protein sources, which are often economically cheaper. It is noteworthy that although the calcium content of bungu leaves is relatively high, its availability to the human body needs to be investigated. Oke (1966) observed   that calcium bioavailability could be lower than expected due to its usual occurrence as insoluble oxalates and phytates.

Table 2 shows that the mature seeds of the two cultivars are similar in respect of percentage composition of crude protein, calcium, and phosphorus. Lrn/09 seeds had higher contents of dry matter, crude fat, and crude fiber while Lrn/10 seeds were superior in respect of water, soluble carbohydrates, and total ash contents. When compared with the proximate composition reported for some of the conventional oil-yielding seeds, such as sesame, soyabean, cotton, and olive (Oyenuga, 1968; Nayar and Mehra, 1970), bungu seeds can be said to contain appreciable levels of oil (17.25 - 21.00%), crude protein (21.32 - 22.15%), crude fiber (25.75 - 29.75%), calcium (2.65 - 3.15%), and phosphorus (0.53 - 0.54%).

These results suggest that the seeds are potentially capable of being exploited as commercial source of vegetable oil and the extracted meal as vital source of protein and minerals for livestock feeds, subject to tests confirming the presence or absence of anti-nutritional factors in it.  It may be concluded that the consumption of bungu leaves should be promoted, especially in families that can ill-afford the prohibitive cost of animal protein.

REFERENCES 

© 2004 Nigerian Society for Experimental Biology