EVALUATION OF INSECTICIDAL AND ANTIOXIDANT PROPERTIES OF SELECTED INDIGENOUS SPICES ON Treculia africanaSEED PRODUCTS
Treculia africana seeds, Tribolium castaneum and Sitophilus zeamais insect pests, and Tamarindus indica, Xylopia aethipica, Piper uineense and Monodora myristica spices were procured for the study. Two kilogrammes of Treculia africana seeds and 400g of each of the
spices were dried at 50oC in hot-air oven to about 12.8% moisture content. Dried Treculia africana seeds (2kg) were used for insecticidal properties.
Another 5kg of Treculia africana seeds were parboiled in excess boiling (1000C) water for 15 minutes, drained out of water and
dehulled to produce seed dhals. The seed dhals (4kg) were oven-dried at 50oC to about 12.8% moisture content, and 1.5kg weight of the seed dhal milled into flour. The seed dhals and flour were used for antioxidant study.
Oil was extracted from 200g of each of Piper guineense, Xylopia aethiopica and Monodora myristica fruits with 500ml n-hexane, using
maceration techniques. Fruit pulp was extracted from 200g of Tamarindus indica fruits, using 50ml of distilled water. Ethanolic and water extracts of spices were prepared using 1g of each spice to 20ml of ethanol or distilled water.
Undehulled T. africana seeds (20g each) were treated with different concentrations of each spice oil (0, 0.25, 0.5. 0.75 1.0 ml) or fruit
pulp (0, 1, 2, 3, 5g), and each treatment was infested with ten adults of T. castaneum or S. zeamais and stored for contact (10 days), fumigant (74 hours) and post-exposure (48 hours) toxicity tests Samples (100g) of Treculia africana seed dhals and flour were treated with
different concentrations of spice oils (0, 0.5, 1.0, 1.5, 2.0 ml) or fruit pulp (0, 1, 2, 3, 5g) and stored at 26 + 2oC for 4 months for oxidation study. Ethanolic and water extracts of the spices were screened for total phenolic content, reducing capacity with FeCl3, and scavenging
activity against 1, 1 diphenyl-2- picryl hydrazyl (DPPH). Tamarindus indica fruit pulp did not exhibit insecticidal effect on both Tribolium castaneum and Sitophilus zeamais. Monodora, Xylopia and Piper guineense oils showed dose-dependent insecticidal effects on
T. castaneum and S. zeamais.
Toxicity tests showed that insect mortality increased with storage time and was higher for S. zemais than for T. castaneum at all spice oil
concentrations. Piper guineense oil had the highest mean mortality (%) for both insects, followed by Xylopia oil and then Monodora oil. The spice oils exhibited dose-dependent antioxidant property on Treculia seed dhals and flour as evident from the mean thiobarbituric
acid values which decreased with increasing oil concentrations. Mean thiobarbituric acid (TBA) values for treated seed dhals and flour after 4 months of storage ranged from 2.5 to 3.1 ppm Malonaldehyde while the untreated samples had 4.6 ppm malonaldehyde.
Ethanolic and water extracts of the spices exhibited antioxidant capacity in total phenolics, in reducing power with FeCl3, and in scavenging 1, 1-diplhenyl-2-picryl hydrazyl (DPPH) radical. Tamarindus indica fruit pulp had the highest phenolic content, followed by Monodora myristica, Piper guineense, and Xylopia aethiopica. Antioxidant capacity of the spices was in the order: Piper guineense > Xylopia aethiopica > Tamarindus indica > Monodora myristica. The IC50, final concentrations (mg/ml) of dry spice extracts required to decrease the initial concentration of DPPH to 50% in the corvettes, compared scavenging potency of the extracts with DPPH. Ethanolic extract of Monodora myristica had the least IC50 value of 2.5 while water extract of Xylopia fruit had the highest IC50 value of 154 in scavenging DPPH.
Evidence of malnutrition is increasing in many parts of the world, particularly in developing countries, and unsatisfactory feeding has been shown to be common in such countries (UNICEF, 1989; WHO, 2000). Millions of people, particularly children are affected by inadequate food intake (UNICEF, 1989). Protein- energy malnutrition constitutes the major nutritional problem of these children and this impairs their growth, health, mental capability and productivity (Spur et al., 1979; Martonel, 1992; Bertman and Kawachi, 2000; Ivanovic et al., 2002; Ischara, 2005).
Differences in adaptation of food crops and animals to various agro-ecological regions across the globe and the incessant natural disasters including fire outbreak, flood, draught and pest infestation pose problems of food insecurity worldwide. The world population put at 8.3 billion is increasing at a geometrical progression at the expense of fall in food supply (WHO, 2000). There is therefore the need for adequate storage of food produced at the season of plenty against the period of scarcity; and adequate and regular distribution of food produced from regions of harvest to regions where they are not available.
Regions would be at economic advantage in producing what they have the most favourable conditions for. There would be more food security among nations. Worldwide, effort is currently geared towards massive production, storage and distribution of grains as economically cheap source of proteins (Peace et al., 1988; Nkama and Gbenyi, 2001).
Actually grains are wide and are nutritiously rich (Pascual, 1978) but are adversely affected by pest infestation both in the fields and in stores after harvest. Also most legumes and oilseeds, because of their high oil contents, when processed become rancid on storage due to autoxidation (Attman et al., 1986). Common pests of grains in store include microorganisms, rodents, mites and insects. Insect damage in stored cereals and pulses may account for up to 10 to 40% in countries where modern storage technologies have not been introduced (Shaaya et al., 1997) Currently, the measures to control autoxidation and pest infestation in grain and dry food products rely heavily on the use of gaseous and liquid synthetic Pesticides, which pose health hazards (to warm blooded animals) and a risk of environmental contamination (Snelson, 1984).
Recently, chemicals in use for insect control have decreased drastically as problems of insect resistance have intensified and mounting social pressures against the use of toxic chemicals have limited the introduction of new compounds (Nakakita and Winks, 1981; Lale,
1995; Shaaya, 1997). At present methyl bromide and phosphine are still in use but methyl bromide has been identified as a major contributor to ozone depletion which cast doubt on its future use for insect control (WHO, 1995). Also there has been a repeated indication that certain insects have developed resistance to phosphine, which is widely used today (Nakakita and Winks, 1981; Mills, 1983; Tyler et al., 1983).
Application of antioxidants is one of the technically simplest ways of reducing autoxidation of lipids (Karpinska et al., 2001). The antioxidants can be of synthetic and natural origin. Some synthetic antioxidants including BHA and BHT might be dangerous for
living organisms (Attmann et al., 1986). Naturally derived antioxidants are considered better and safer than synthetics (Dorko, 1994).
There is the need to develop ecologically friendly methods, which will use natural compounds, and yet be simple and convenient to use. A wide variety of higher plants may provide new sources of natural antioxidants (Dorko, 1994; Madsen and Bertelson, 1995), pesticides and antifeedants (Grainge and Ahmed, 1988; Arnason et al., 1989; Ananthakrishnan, 1992). Among the many plant derived substances studied are spices and extracts of spices which have various effects on insect pests, including stored-product insects (Grainage and Ahmed, 1988; Jacobson, 1989; Shaaya et al., 1991).
Insect control agents of plants origin are broad spectrum in action, safe to apply, nonpersistent and easily processed (Talukder and Howse, 1995). The same is true of antioxidants of plant origin. Several studies have shown that they offer good prospects for protection of stored products against rancidity development and damage by pests (Nawrot et al., 1986, Sharaby, 1988; Khanam et al., 1990, Serit et al., 1992; Telukder and Howse, 1994). In view of the various activities of powders, extracts and oils of spices against rancidity development and some insect pests of stored grains, pulp powder and oil extracts from the fruits of tamarind, Ethiopian pepper, African black pepper and African nutmeg were screened for antioxidant and insecticidal properties on the seeds of African breadfruit (Treculia africana).
These four spices are indigenous spices in Nigeria. Tamarind is popular in the North while the other three are more popularly used in the Eastern and Western parts of the country. These spices have been reported (Iwu, 1993) to have many medicinal values apart from their flavouring effects. The pulp of the fruits of tamarind is used in traditional flavouring while the entire fruit of African nutmeg is also used for food flavouring.
African breadfruit (Treculia africana) is native to tropical region and produces abundant quantity of fruits. The seeds are of high nutritional value and are currently a potential source of nutrient in the diet of many Nigerians (Iwe and Ngoddy, 2001). The flour is also a good complement to wheat flour in bakery products (Giami et al., 2004).
Unfortunately the seeds (dehulled and undehulled) and flour deteriorate easily on storage, due partly to oxidation of lipids, lipolytic moulds and insect pests, namely Tribolium casteneum and Sitaphilus orizae (Adindu and Williams, 2003). A preliminary study here in the tropics,
in the laboratory, revealed that Sitophilus zeamais ferociously attacked the seeds instead of sitophilus orizae, a temperate pest. This causes a lot of losses of the product and reduces its supply.
Attempts were made in this work to evaluate the insecticidal and antioxidant properties of pulp powder and oil extracts of tamarind, Ethiopian pepper, African black pepper and African nutmeg fruits on African breadfruit. Two primary insect pests, Tribolium castanuem and Sitophilus zeamais, of stored Treculia African Decne were used for the insecticidal study.
EVALUATION OF INSECTICIDAL AND ANTIOXIDANT PROPERTIES OF SELECTED INDIGENOUS SPICES ON Treculia africanaSEED PRODUCTS
1.2 Statement of the problem
Common grains in use for food are becoming too expensive and scarce. Alternative food sources from some, unconventional grains which are lost periodically to insect infestation need to be protected on prolonged storage for more exploitation for food use. This would also increase the use of such grains globally.
Treculia Africana Decne (African breadfruit) seed is one of such less common oilseeds that are periodically being lost to insect pest infestation and also become rancid on storage. It is, therefore, necessary to exploit some spice materials to protect this grain legume from insect infestation and autoxidation.
1.3 Justification for the Study
There is the need to increase food supply from under-utilized food crops such as Treculia africana Decne seeds in the tropics. Treculia africana is a good source of protein, readily available, though not cheap but easily becomes rancid, and gets damaged by insect
pests on storage. The seeds are seasonal in supply. The undehulled and dehulled seeds need to be protected against storage insect pests while the dehulled seeds and seed flour need to be protected from rancidity development to extend its shelf life for more food application across the globe.
1.4 Significance of the study
This work will improve storage and utilization of whole, dhal and flour of Treculia africana seeds in homes and industries. It will facilitate exportation and industrial uses of the food crop within and outside the tropics. It will create employment opportunities for many people; and will lead to the development of new products based on Treculia africana seed.