LITRATURE REVIEW

2.1 MYCOTOXIN

Mycotoxin is a low molecular weight natural product (i.e. small molecules) produced as secondary metabolites by filamentous fungi. These metabolites constitute a toxigenically and mechanically heterogeneous assemblage that is grouped together only because the membeis can cause diseases and death in human beings and other vertebrates. ( Benneth, 1987). Myco contaminates a wide range of crop plant and fruits before and after harvesting. The most important mycotoxins include: Aflatoxin, Deoxynivalenoi ochratoxin A Fumonisins, Zearaleone, Patulin and T-2 toxin. The acute and chronic impact of mycotoxins on human and animal health is proven scientifically. Mycotoxins contain contamination is recognized as an unavoidable risk because the formation of forngal toxins is weather dependent and effective prevention is impossible (Romer Lab, 2012).

2.2 MAJOR MYCOTOXINS

AFLATOXIN

Aflatoxin are a group of toxins produced by certain species of fungi, these fungi include; Aspergillus Flavus, and Aspergillus parasiticus. The favorite weather conditions of aflotoxins development are hot humid environment with optimal conditions being 330C or more. The crops most susceptible to aflatoxin are maize and groundnut. However bailey, cotton seed, sorghums, wheat, silage, tree nuts, milk, apples, oats, beans and potatoes are also known to be susceptible to contamination (Yun Yun, 2014)

The four major afloxins are called B1, B2, G1, and G2 based on their fluorescence under Ultraviolent light (blue or green) and relative chromatographic mobility during thin-layer chromatography. Aflatoxin B1 is the most potent naturall carcinogen known (squire, 1981) and is usually the major afloxin produced by toxigenic strains.

CITRININ

Citrinin was first isolated from Penicillium citrinum prior to World War II (Helberington et al 1931) subsequently, it was identified in over a dozen species of Penicillium and several species of Aspergillus (e.g Aspergillus terreus and Aspergillus niveus) and Aspergillus oryzae (used to produce sake, miso, and soy sauce). (manabe, 2001). It has also been implicated as a contributor to porcine nephro bathy. Citrinin acts as a nephrotoxin in all animal species tested. Wheat, oats, rye, corn barley and rice have all been reported to contain citrinin (Abrams on et al, 2001).

2.3 ERGOT ALKALOIDS

The ergot alkaloids are among the most fascinating of fungal metabolites. They are classified as indole alkaloids and are derived from a tetracyclic ergoline rings system. Lysergic acid which is a structure common to all ergot alkaloids was first isolated in 1934. The elavines have e.g ergoline as a basis structure but lank peptide components. The Lysergic acid alkaloids include ergotamine and lysergic acid amide.

The compounds are produced as a toxic cocktail of alkaloids in the sclerotia of species of claviceps. The human disease acquired by eating cereals infected with ergot sclerotia, usually in the form of bread made from contaminated flour is called ergotism. Two forms of ergotism are usually recognized, these are “gangrenous” and “ convulsire”. The gangrenous form affects the blood supply to the extremities while convulsire ergotism affects the central nervous system (Bennett, 1991).

2.4 FUMONISINS

Fumonisins were first described and characterized in 1988 (Bezuidenhout et al, 1988). The most aboundantly produced member of the family is fumonisin B1. They are thought to be synthesized by condensation of the umins acid alanine into an acetate derived pprecursor (Sweeney, 1999). Fumonisins are produced by a number of fusanum species, notably fusarium verticilliocldes, fusarium proliferatum and fusarium nygamai as well as alternaria alterata f.sp. lycopersici (marasa et al 2001 and rheeder et al, 2002). These fungi are taxonomically challenging with a complex and rapidly changing nomenclature which has perplexed many non-mycologists and some mycologist too (Leslie, 1996 and Marasas, 1984).

Fusariumm verticilloides grows as acorn endophytes in both vegetative and reproductive tissues without often causing disease symptoms in the plant. However when weather conditions, insect damage and the appropriate fungal and palnt genotype are present it can cause seedling blight, stalk rot and ear rot (Nelson et al 1993). Fumonisins affect animals by causing leukoence phalomalacia (hole in the head syndrome) in equines and rabbits (Buccti et al 1996).It also causes pulmonary eclema and hydro thorax in swine (Harrison et al 1990). In humans there is a probable link with esophageal cancer (Syclenham1991).

2.5 OCHRATOXIN

Ochratoxin was discovered as a metabolite of Aspergillus ochraceus in 1965 during a large screen of fungal metabolites that was designed to identify new mycotoxins ( Van der Merwe et al 1965) members of ochratoxin family have been found as metabolites of many different species of Aspergillus including Aspergillus alliaceus, Aspergillus glaucus, Aspergillus auricomus, Aspergillus carbonarius, Aspergillus niger and Aspergillus melleus,(Abarca et al, 1994, and Baymen et al 2002 and Legler et al, 1971). As other mycotoxins the substrate on which the mould grow well in influences the level of toxin produced. Orchratox in A has been found in Barley, oats, rye, wheat, coffee, beans and other plant products ( Margua rat et al.,1992, and pitt 2000 and Van Egmond et al, 1994). Of the Aspergillus toxins only ochratoxins is potentially as important as the aflatoxins, the kidney is the primary target and they are involved in the human disease called endemic Balkan nephropathy (Hult et al, 1982).

2.6 ZEARALENONE

Zearalenone is a secondary metabolite from fusarium graminearum and was given the trivial name zearalenone as a combination of Zeae for “resorcyclic acid lactone-ene for the presence of C-1 and C-2 double bone and one for the C-6 ketone (Urry et al, 1996). The word toxin in zearalenone is misnormer because it is hardly a toxin rather it resembles 17B-estradivl which is the principal hormone produced by human ovary; which allows it to bind to estrogen receptors in mammalian target cells ( Kuiper Roodman, 1987).

2.7 ARACHIS HYPOGEA

ORIGIN

Groundnut which is a member of the legume family is an important food and oil crop. It is currently grown on an approximately 42 million acres worldwide. It is the third major oil seed of the world after soya bean and cotton (FAO, 1990). India, China and the United States have been the leading producers for over the last25 years ant they grow about 70% of the world’s crop. Groundnut originated in South America. The Portuguese took it from Brazil to West Africa. The Spaniards introduced groundnuts to the Philippines from where they spread throughout tropical and sub tropical Asia and indeed the world.

2.8 BOTANY OF ARACHIS HYPOGEA

Groundnut is an annual herbaceous plant that grows to a maximum height of 60cm. it is characterized by fruits that develop and mature underground. Fertilization of the ovary results in the development of an elongated stalk which grows down ward and carries the ovary into the soil to a depth of 2 – 7cm. The stalk can attain a length of 15 – 30cm.once penetration of the soil surface has occurred, fruit enlargement proceeds at the stalk tip with eventual formation of the groundnut pod, the pods can contain 1-6 seeds (Anonymous, 2015)

2.9 DISTRIBUTION OF ARACHIS HYPOGEA

Native to South America: now widely cultivated in warm countries throughout the world. It was introduced in pre Columbian times to West Indies and Mexico, in early Post-Columbian times to Africa and Eastern Asia and during the colonial period to Atlantic North America known only in cultivation (Duke 1981).

2.10 CULTIVATION OF ARACHIS HYPOGAEA

All commercial groundnuts are propagated from seed. The seed bed should be prepared, either on a flat or wide ridged. Seeds often treated with anti fungal dressing before planting. In countries of advance agriculture, groundnuts are often grown in monoculture and mechanized means. In many countries, they are cultivated by hands and sometimes in mixed culture. The spacing and seed rate varies with growth habits and production methods. The weeds are controlled by cultivation and by pre – and post-planting application of selective herbicides.(Duke 1981).

2.11 HARVESTING OF ARACHIS HYPOGAEA

Although flowering may commence in 30 days, 80-150 days or more are required for fruit maturation. In hand-harvest, plants are pulled up and turned over on the ground or stacked or placed on racks to cure. Pods are picked and allowed to complete drying in depths of 5cm or less on trays, or spread in the sun in the dry season tropics. In a case of fully mechanized harvesting, a single operation pulls up, inverts and windows the plants where they remain a few days for preliminary drying. The pods are removed by combine machines and elevated into the baskets attached to the combine or blown directly into trailing drying wagons which when full may be towed to a dry station where warm or ambient air is forced through the load of groundnut.(Ratnam,1979).

2.12 USES OF ARACHIS HYPOGEA

Seeds yield non-drying, edible oil used in cooking, margarines, salads, canning for deep frying, for shortening in pastry and bread, and for pharmaceuticals, soaps, cold creams, pomades, and lubricants, emulsion for insect control and fuel for diesel engines. The oil cake which is a high protein livestock feed may be used for human consumption. Other products include dyes, ice cream, massage oil, plants, paints, and peanut milk. The seeds are eaten raw, whole roasted and salted or chopped in confectioneries or ground into peanut butter. Young pods may be consumed as vegetables. Young leaves and tips are suitable as a cooked green vegetable(Martin and Roberte, 1975). Scorched seeds are used as coffee substitute. Peanut hulls are used for Furfural, fuel, as a filler for fertilizers and for livestock feed or sweeping compounds(Duke, 1981).

Irvingia gabonensis(Ogbono)

Irvingia gabonensis is a specie of African trees in the genus Irvingia, sometimes known by the common names which are wild mango, African mango, bush mango, ogbono. They bear edible mango like fruits and are especially valued for their fat and protein rich nuts. Irvingia is a nutritional important non-timber wood plant with edible parts such as fruits, nut and kernel (Ladipo, 1996).

2.13 DISTRIBUTION AND HABITAT OF Irvingia gabonensis

Irvingia gabonensis is indigenous to the humid forest zone from the Northern tip of Angola, including Congo, Nigeria, Cote d’ ivoire and South-Western Uganda(World Agro Forestry center, 2014). It is planted in parts of this area for example in Southern Western Nigeria and Southern Cameroon and also Cote d’iviore, Ghana, Togo and Benin.

The tree is present in the tropical wet and dry climate zone. Dika grows naturally in canopied jungle, gallery forest and semi deciduous forest. It grows at altitudes from 200-800m with annual rainfalls from 1200-1500mm(Agro forestry center, 2014). Supported temperature ranges from 20 degree to 38 degree under slightly shaded to very bright clear skies. Deep soil with more than 150cm is needed with a moderate fertility and good drainage with pH of 4.5 to 7.5(Food and agriculture organization, 2007).

2.14 BOTANY OF Irvingia gabonensis

Irvingia gabonensis grows straight up to a height of 40metres(130ft) and 1metre(3ft 3in) in diameter(World Agro forestry Centre, 2014). It has buttresses to a height of 3metres(9.8ft). The outer bark is smooth to scaly with grey to yellow to grey colour. The crown is evergreen, spherical and dense. The leaves are elliptic, one margin is often a little rounder than the other, accliminate, dark green and glossy on the upside. Flowers are yellow to green to green is to white in small panicles(World Agro forestry center,2014). The flowers are bisexual,the fruit is nearly spherical, green when ripe with a bright orange pulp. The seed is woody and contains one seed, the seedling germinates epigeally.

2.15 PROPAGATION AND PLANTING OF OGBONO (Irvingia gabonensis)

Irvingia gabonensis is mainly propagated by seed. When farmers plant it, they choose seed from selected trees on their own farm, from neighbours or from the market. The criteria for selection are large fruit size, good taste,high yield, regular production every year, early maturity, good sliminess and drawability of kernels and easy kernel extraction. Transplanting of wildlings and Retainment and protection of wildlings when cleaning land for agriculture are common.

Germination of Irvingia gabonensis seeds takes more than 14days and they should first be extracted from the fruit and dried for at least 2days. A germination rate of 80% can be reached in this way. Methods of vegetative propagation through rooting of leafy stem cuttings under mist have been developed and micro propagation, grafting, and marcoting experiments are in progress. Preliminary results show that plant from bush mango marcots can fruit for 2-2.5 years after transplanting(Aubry Lecomte ex o’Rorke, 2012).

2.16 HARVESTING OF OGBON (Irvingia gabonensis)

Irvingia gabonensis fruits are mostly gathered from the ground around each tree or harvested by climbing when the tree is not tall. The next step consists of extracting the kernels from seed which is split in halves with cutlass and the kernel is removed with the help of a knife. The kernel are then dried in the sun or on bamboo drying racks over the fire place (Aubry-Lecomte ex o’Rorte, 2012).

2.17 USES OF OGBON (Irvingia gabonensis)

Kernels of the fruits of Irvingia gabonensis called ‘”Ugiri” in Igbo and “apon” in Yoruba yield important food additives popularly in West and Central Africa. They are processed by grinding and crushing and then used to thicken soups and stews. The kernels are also made into a cake called dika bread or “odika bread” for year round preservation and easy use.

An edible oil is extracted from the seed that is used in cooking. As it is solid at ambient temperature, it has been used as a substitute for cocoa butter and for soap making. The press cake is suitable for thickening soup and is a good cattle feed. Unlike the fruit pulp of most other Irvingia spp which are bitter. The pulp of the fruit of Irvingia gabonensis is juicy and sweet and is eaten fresh. It can be used for the preservation of juicy and sweet and is eaten fresh. It can be used for the preservation of juice, jelly, jam and wine. The pulp has also been used to prepare a black dye for cloth.

Irvingia gabonensis is commonly preserved on farms to provide shade for crops especially cocoa and coffe. The medicinal use of Irvingia spp are many but it is difficult to assign them to an individual species. The preparations from the bark are rubbed on the body to relieve pains and are applied to sores and wounds and against toothache. They are also taken to treat diarrhea, the bark are used to treat hernia and yellow fever and also an antidote for poisoning and to treat diabetes.

The wood is used locally for heavy construction work and for making ship deck, paving blocks, and planking. Young trees are used for poles and stakes while branches are made into walking sticksor thatched roof support(Aubry-Lecomte ex o’Rorke, 2012).

2.18 Colocynihis citrullus (EGUSI)

ORIGIN AND GEOGRAPHICAL DISTRIBUTION OF EGUSI

Egusi (Colocynihis Citrullus) known as melon is originated from western Kalahari region and Botswana where it can be found in wild diversity of forms together with other citrullus species (Grubben et al, 2004). According to Adebowale (2002), it occurs as wild from Guinea Bissau east to Southern Sudan and Uganda and South Angola.( Grubben et al, 2004) reported that Colocynthis citrullus was first domesticated in the southern Sahel zone or in region surrounding the Kalahari desert. Al-mmer et al (2006) noted that the plant is an annual wild plant procumbent herb with simple tendril that grows fast in the sandy soil and wide spread in different part of Saudi-Arabia. According to Oyolu, (1997). The people of Namibia and Botswana still harvest most of their seed from the wild, but some land races have been selected specially for their rich oil-seed.

2.19 BOTANY OF Colochytis citrullus (EGUSI)

Egusi is an herbaceous annual, prostrate or climbing often scabrous with trichomes containing photolyth stem typically five angled, characterized anatomically by bicellateral vascular bundles often arranged in two concentric rings(Beta et al,2001). Pandey (2004) stated that Egusi leaves are simple, palmately bobbed usually stipules, large and long petiole. He also stated that the arrangement of the stem is alternate. According to Jeffery,(2005) the fruit is a berry, usually globules to oblong or ellipsoid, sometimes ovoid. Lloyd (1998) stated that the flower are monoecious, the stamen and pistils being borne indifferent flower on the same plant. Pandey (2004) reported that seedlings develop by means of epigeal germination and has cotyledon which are large and leafy often rounded to oblong.

2.20 CULTIVATION OF Colochytis citrullus (EGUSI)

Egusi is cultivated in Middle East, western Africa (Nigeria, Ghana, Togo and Benin) and other Africa countries (Emergies, 2010). It is cultivated mostly in the tropics (Ekundayo 1987; Pandey 2007). Egusi is cultivated for the food in the seed and as a crop inter planted with maize, cassava and yam (Emergies, 2010). In Nigeria, it is cultivated in an area over361000 ha with a production figure of 347,000 tonne (as seed) in 2002 (Grubben et al; 2004: Energies, 2010). It is planted with early rainfall in March to April but some localities in south, the crop is grown in the late rain (Komolafe et al, 1985) According to Philip (1977), After maturity, they are gathered into heap and left until the flesh begins to breakdown and the seed is then extracted, washed and dried.

2.22 USES OF Colochytis citrullus

In traditional farming system, Egusi melon Canopy is used to control weed and run-off in new cultivated posts (Agba, 2004). Olufemi and Salami,(2006) reported that egusi is easily identifiable with the complex mixed cropping system of the humid and the sub-humid tropical zone of Nigeria as the trailing nature of its vine, alternating arranged and pinnately disserted leave allow inter-planting at distance detected by the humble, sequence, type and combination of crop in the mixture. Agba et al (2009), reported that the seed is commonly consumed in Nigeria as a thickening agent for sauce and soup and also eaten as a snack. Vegetable oil is extracted from the seed while the grounded seed is used to prepare delicacy (Yusuf et al,(2008). The roasted seed is grounded with salt and is taken with warm water or porridge to prevent vomiting (Ugwuumba, 2008). According to Schipper (2000), Egusi melon is important for seed in Sudan and Ethiopia and the extracted yellow oil is high in demand. Gill(1922) reported that the fruit without seed, when cut into pieces and mixed with root of Anthroceleista spp and salt and cooked together and drank every morning, it serves as an anti-fertility agent. Egusi serves as an important source of herbal medicine.