LITERATURE REVIEW
2.0 The Quality of Nigerian Cola nut Cola. nitida(red cola nut)
The cultivation of Cola nitidaalso known as red kola nut in Nigeria actually began in the 19th century (Asogwaet al., 2006) and it has been estimated that the country produces about 88% of the world‟s kola nuts with an annual production of 200,000 metric tonnes mostly from South Western Nigeria (Mokwunye., 2009). While the demand is rising, the production remains low because many of the trees in Nigeria are unfruitful or have very low yield due to self and cross incompatibility among trees, partial and total sterility, inefficient natural pollination, old age, field and storage, pests and diseases (Asogwaet al., 2006).
About 90% of the kola nuts produced in Nigeria is consumed in the country while the remaining 10% is exported as sun-dried nuts to other parts of Africa especially neighbouring West African countries where they are used as stimulants or as sources of colorants for cloth dyeing(Akinbode, 1982). C. acuminate is frequently used for social and religious ceremonies in and Middle-belt Nigeria while C. nitidawhich is referred to as “the true kola of commerce” has featured in the internal trade of West Africa for a number of centuries (Jaiyeola, 2001). The crop is important because of its nut that has important pharmacological properties and also contains some active principles found in coffee and cocoa (caffeine, theobromine, kolatin) which prevents sleep, thirst and hunger and also acts as an anti-depressant (Atawodiet al., 2007) (Opeke, 2005) (Mokwunye, 2009). The nuts are the cotyledonous seeds in which the purplish, cartilaginous testa has been removed. The irregular seeds, due to close nesting in the follicle have a compressed triangular shape which have a bitter astringent taste when wet and a faintly aromatic taste when dry (Mokwunye, 2009).
2.1 Properties of kola nut
Family: Malvaceae Juss.
Genus: Cola Schott & Endl.
Botanical name: Cola nitida (Vent.) Schott and Endl.
Cola nitida is a tropical tree from West African rainforests. It is best known for its caffeine-containing seeds, known as kola nuts. Raw seeds are chewed as a stimulant and have a bitter taste. Kola nuts are used in a variety of local ceremonies, to produce kola nut extract, which is an ingredient in some soft drinks and also serve as a source of natural dye(Kulkarni, 2011). The closely related species Cola acuminatais also sometimes known as kola nut, and its seeds are used in the same ways. C. nitidaandC. acuminataare are known as true kolas, yielding superior seeds for chewing. Although seeds of some other Cola species are suitable for chewing, they are of an inferior quality and are known as “false kolas” or “monkey kolas”.
2.1.1 Physical properties of Cola nitida
Cola nitida is an evergreen, tropical tree growing up to about 20 metres tall, with a spreading, open canopy. It has an oval leaves with pointed ends, leathery, with a shiny upper surface, borne alternately on the stem. It is flowers are off-white to cream, star-shaped with five petals and a blotched red-purple centre with a prominent stigma pollinated by flies. The fruits are large (13×7 cm), knobbly, green pods splitting into two equal halves to reveal four to eight, smooth, red or white, seeds of kola nuts(Samanta and Agarwal, 2009).
2.2 Chemical composition of kola nut.
Kola nut is composed of caffeine which is about 2-3%, along with theobromine and kolanin. The kolanin acts as a stimulant, while theobromine helps to promote the cerebral circulation in the body. This nut promotes the level of oxygen in the blood and also enhances concentration power by clearing the mind. It also assists in countering bacterial infections. Other chemical components include: Theophylline, catechin, epicatechin, D-catechin, phenolics, phlobaphens, betaine, protein, starch, fat, thiamine, riboflavin, niacin, ascorbic acid, sugar, gum, cellulose, water, calcium, potassium, iron, beta-carotene and tannic acid.
2.2.1 Health Benefits of Kola nut
• Kola nuts may possess antimicrobial properties (Lowe etal., 2014) suggesting that the kola nut shows promising results against microbes. The fruits showed antimicrobial activity against Bacillus subtilis, Staphylococcus aureus, Escherichia coli, Klebsiellapneumonae, Pseudomonas aeruginosa and Candida albicanswhen compared with antibiotics and antifungals gentamicin and nystatin. Although more research is still being conducted, kola nuts have been used to treat malaria, fever, ringworm, scabies, gonorrhea and dysentery (Solipurametal., 2009).
• Kola nuts may help fight cancer: Measured the chemoprotective properties of kola nuts, which contained phytoestrogens and phytoandrogens. These non-steroidal chemicals mimic or disrupt sex-linked hormones like estradiol anddihydrotestosterone to prevent hormone-dependent cancers like breast and prostate cancers (Solipurametal., 2009).
• Kola nuts help improve mental well-being: Kola nuts are comprised of 2% caffeine, a stimulant. This psychoactive substance is absorbed into the bloodstream and travels to the brain to block an inhibitory transmitter named adenosine. Once that occurs, brain cells increase in firing rate because of the build-up of excitatory neurotransmitters like norepinephrine and dopamine. This process could help improve memory, boost energy levels, and increase reaction times(Solipurametal., 2009).
• Kola nuts could help burn fat: A basal metabolic rate is the minimal rate of energy your body burns when not exercising or moving around. The amount of energy burned is measured in calories. When ones metabolic rate increases, one burns more calories at rest. One of the main ingredients in fat burning supplements is caffeine. Research shows that caffeine can help boost ones metabolic rate by 3-11% (Solipurametal., 2009).
• Kola nuts can be used as a diuretic: Theobromine, formerly known as xantheose, is another abundant stimulant in kola nuts. This bitter chemical increase urine production which can help treat heart failure, liver cirrhosis, hypertension, influenza, water poisoning, and certain kidney diseases.
• Kola nuts can help improve blood circulation in the body: Caffeine, theobromine, and kolanin can stimulate the heart rate, thus increasing circulation. This action can help boost oxygenation to certain parts of the body like the skin, organs, and brain. Increased oxygen levels in the brain have been linked with increased concentrating and higher cognition.
2.2.2 Applications of kola nut
Kola nut is use in industries, Pharmaceutical, Beverages, Dye and colorante.t.c.
Pharmaceutical: kola nut has a significant importance in medicinal industries due to a wide range of beneficial properties(Solipurametal., 2009).
Beverages: kola nut is use as a flavoring agent that is why it gain popularity in commercial industries. kola nut has a long history of use in the preparation of beverages in Africa and Muslim cultures, John Pemberton, a 19th century American pharmacist, was inspired to combine kola with cocoa, sugar and carbonate water, giving the world the soft drink aptly named Coca-Cola(Solipurametal., 2009).
Dye and Colorant: kola nut is use in the production of dye naturally.
2.3 Dyes
A dye is a coloured substance, normally used in solution and has an affinity to the substrate which is being applied to. It is also defined as the compound which contains chromophore and auxochrome groups. The chomophore group is responsible for dye colour due to their unsaturation, while the auxochrome group is responsible for the dye fibre reaction.
2.3.1 Sources of dyes
Natural dyes are dyes or colorants derived from plants, invertebrate, or minerals. The majority are vegetable dyes from plant sources (roots, berries, bark, leaves, and wood) and other biological sources such as fungi and lichens. Most natural dyes come from dye plants, the best known ones are woad, weld, and madder from Europe, and brazilwood, logwood and indigo from the tropics. Some, such as cochineal, come from insect and a small number, including iron and copper salts, come from mineral sources (Dattaet al., 2013).
2.3.2 Types of dyes
1. Natural dyes
Natural dyes are simply dye substances extracted from natural sources. Although the main source of dyes for early times, they have largely been replaced by synthetic dyes, which are usually more reliable, cheaper and can be supplied more readily. Natural dyes still in use include haematoxylin, carmine and orcein. Colouring materials have been used for many thousands of years by man. Leather, cloth, food, pottery and housing have all been modified in this way.
Some of our most common dyes are still derived from natural sources. These are termed natural dyes. The Colour Index uses this as a classification and naming system(Brown, 1978). Each dye is named according to the pattern: Natural + base colour + number.
Natural dyes are often negatively charged. Positively charged natural dyes do exist, but are not common. In other words, the coloured part of the molecule is usually the anion. Although the molecular charge is often shown on a specific atom in structural formulae, it is the whole molecule that is charged. Many, but by no means all, natural dyes require the use of a mordan(Brown, 1978).
2.3.3 Types of natural dyes
• Haematoxylin: Haematoxylin is a compound extracted from the heartwood of the logwood tree (Heamatoxylumcampachianum). It is the most important and most used dye in histochemistry laboratories (Brown, 1978). It is especially used in Erhlich'shaematoxylin and eosin technique for the demonstration of general tissue structures where it stains tissue in shades of blue, pink and red enabling recognition of malignant and non-malignant cells as well as several intracellular and extracellular substances necessary for diagnosis of disease conditions in tissues and cells (Brown, 1978).
.Orcein: Orcein is a reddish-brown dye extracted from several species of lichen, commonlyknown as “Orchella weeds,” found in various parts of the world (Beecken, 2003). It is used as a stain in microscopy to visualize elastic fibers, Hepatitis B, surface antigens and copper associated proteins. It is a mixture of phenoxazone derivates - hydroxyorceins, aminoorceins, and aminoorceinimines.
• Carmine: Carmine is a pigment of bright-red color obtained from the aluminium salt of carminic acid. Carminic acid is a general term for a particularly deep-red colour (Dapson, 2007). The pigment is produced from some scale insects such as the cochineal scale and certain Porphyrophora species (Armenian cochineal and Polish cochineal). Carmine is used in the manufacture of artificial flowers, paints, crimson ink, rouge and other cosmetics, and some medications. It is routinely added to food products such as yoghurt, candy and certain brands of juice, the most.
2 Synthetic dyes
Dyes derived from organic or inorganic compound are known as synthetic dyes. Examples of this class of dyes are direct dyes, acid dyes, basic dyes, reactive dyes, metal complex dyes, vat dyes, sulphur dyes, and disperse dyes etc. Synthetic dyes over the years quickly replaced the traditional natural dyes. They cost less, they offer a vast range of new colors, and they imparted better properties to the dyed materials. Dyes are now classified according to how they are used in the dyeing process.
2.4 Types of synthetic dyes
• Acid dyes: Acid dyes are water-soluble anionic dyes, containing one or more sulfonic acid substituents or other acidic groups. An example of the class is Acid Yellow 36. Acid dyes are applied to fibers such as silk, wool, nylon and modified acrylic fibers using neutral to acid dye baths. Acid dyes are not substantive to cellulosic fibers. Most synthetic food colors fall in this category. The dyeing process is reversible and may be described as follow (Beecken, 2003).
• Basic or cationic dye: This group was the first of the synthetic dyes to be taken out of coal-tar derivatives. As textile dyes, they have been largely replaced by later developments. They are still used in discharge printing, and for preparing leather, paper, wood, and straw. More recently they have been successfully used with some readymade fibers. An example of cationic dye is basic brown 1 (Beecken, 2003).
Basic brown 1
• Direct Dye: These are the dyes which can be applied directly to the fabrics from an aqueous solution. These are most useful for fabrics which can form hydrogen bonds with the dye. The direct dyes were widely hailed because they made it unnecessary to use a mordant or binder in dyeing cotton. Direct dyes can be used on cotton, linen, rayon, wool, silk and nylon. These dyes usually have an azo linkage –N=N-. Direct orange 26 is a typical example of direct dyes (Beecken, 2003).
• Azoic dye: Azo dyes contain at least one azo group (-N=N-) attached to one or often two aromatic rings. These dyes are used primarily for bright red shades in dyeing and printing since most other classes of fast dyes are lacking in good red dyes. Azoic dyes are called Naphthols in the industry. An example is the bluish red azoic dye (Beecken, 2003).
Bluish red azoic dye
• Nitro Dye: Nitro dyes are polynitro derivatives of phenols containing at least one nitro group ortho or para to the hydroxyl group. It is used to dye wool. It consists of two or more aromatic rings (benzene, naphthalene). An example of nitro dye is maritus yellow (Beecken, 2003).
Maritus Yellow
• Disperse Dye: Disperse dyes were originally developed for dyeing secondary cellulose acetate fibers. These dyes are relatively insoluble in water and are prepared for dyeing by being ground into relatively fine powder in the presence of dispersing agents. In the dye bath, a suspension of the dye particle dispersion produces a very dilute solution of the dyes, which are then absorbed by the fibers. This dye class is used to dye polyester, nylon, acetate and triacetate fibers. Disperse yellow 3, Disperse Red 4, and Disperse Blue 27 are good examples of disperse dyes (Beecken, 2003).
Disperse dye
• Vat Dye: The vat dyes are insoluble complex polycyclic molecules based on the quinone structure (ketoforms). The term vat comes from the old indigo method dyeing in a vat: indigo had to be reduced to light form. Vat dyes are made from indigo, anthraquinone and carbazole. They are successfully used on cotton, linen, rayon, wool, silk, and sometimes nylon. Vat dyes are also used in the continuous piece of dyeing process sometimes called the pigment application process. The dyeings produced in this way have high wash and light fastness. An example of a vat dye is Vat Blue 4 (Indanthrene) (Beecken, 2003).
Vat dye
2.4.1 Advantages and Disadvantages of Natural Dyes and Synthetic Dyes
To make the right choice between natural and synthetic dyes, one needs to understand their advantages and disadvantages.
Advantages of Natural Dyes
. Natural dyes are derived from plants, animals, fruits, insects, minerals and other natural resources.
. They are usually perceived as harmless and safe for the environment. However, that is not the case all the time. (Dapson, 2007).
Disadvantages of Natural Dyes
• Some natural dye sources such as logwood and bloodroot can be toxic. Logwood can produce a range of colors, but the active ingredients in it, which are hematein and hematoxylin, can be harmful when it enters the body through inhalation, ingestion, or skin absorption. Meanwhile, bloodroot can also be harmful because it may cause irritation and inflammation when inhaled.
• Natural dyes can be toxic due to the mordant used for their application. Mordants are substances used to make the natural dye stick to fabrics such as aluminum, copper, iron and chrome.
• Natural dyes are scarce and expensive, because producing it requires a vast area of land. Sustainability is also an issue because their pigment may wash off overtime.
Advantages of Synthetic Dyes
• Synthetic dyes became popular because of its lasting color pay-off and wide range of color choices.
Disadvantages of Synthetic Dyes
• Synthetic dyes have harmful effects on the environment and human beings. First off, synthetic dyes are made up of chemical compounds that can be harmful to humans, especially those who work in their production.
• Some of the chemicals found in synthetic dyes are mercury, lead, chromium, copper, sodium chloride, toluene, and benzene. Exposure to large doses of these substances can be toxic and can have severe effects in the human body.
• Water pollution can also result from manufacturing synthetic dyes when untreated dye effluent is dumped directly on bodies of water.
CONCLUSION
Research has shown that dyes, both natural and synthetic have wide range of applications and are important for textile demands. These demand however is accompanied with certain demerits and environmental problems to man. Natural dyes obtain from natural sources like C. nitida are suitable for application, but imposes little to no harmful effects. Synthetic dyes on the other hand could be harmful, health threatening to those rapidly exposed to it due to the bulk of chemicals involved in it making.
RECOMMENDATIONS
The research of the study reveals that red kola nut yields more dye extracts with increase quantity of powdered red kola nut compared to white and bitter kola produces little quantity of dye extract even with increased quantity of powdered nut during extraction. However dyeing the fabrics with red kola nut dye extract by simultaneous mordanting produces more promising fastness properties result whereas poor to fair fastness properties was obtained with white and bitter kola nut dye extract. The research suggests that red kola nut dye could have prospect in large scale dyeing of cotton and polyester fabrics.
