DECLARATION 1 PLAGIARISM
1.10 The present study
1.10.2 Species under investigation in this study
In terms of distribution, there are about 200 – 300 species of Trichilia, native to, and concentrated in America with few in Africa (about 14 – 18 species) and Madagascar (about six species) (Philips, 1926; Dyer, 1975; Grundy and Campbell, 1993; Maroyi, 2007). T. dregeana is found in the high rainfall evergreen coastal forests of KwaZulu- Natal and Eastern Cape; Mpumalanga and Limpopo provinces of South Africa. It also occurs in Swaziland, Zimbabwe, and northward to tropical Africa (Angola, Democratic Republic of Congo, Congo, Cameroon, Côte d’Ivoire, Guinea and Ethiopia (Pooley, 1993; Maroyi, 2007)). It may however be found in many countries, outside its natural habitat, where it is planted for ornamental purposes.
Altitudinal variations typify the distribution of T. dregeana across Africa. It is found in similar vegetation (i.e. transitional vegetation zone between savanna-mosaic forest and moist, evergreen forest) in West Africa and DR Congo, but at altitudes 800 – 1,600 m in West Africa and below 500 m in the DR Congo. It is found in Ethiopia where the average annual rainfall is 1,500 – 2,500 mm and at altitude of 1,350 – 2,000 m, whereas it is found at lower altitude in Uganda and Tanzania. The altitude gradually reduces toward southern Africa, and it is found close to sea-level near Durban (Maroyi, 2007).
Virtually every part of T. dregeana is useful for humans and animals. It has similar usefulness to T. emetica. Butterflies and bees feed on the flowers of these plant species while the fruits are eaten by human and birds (Pooley, 1993). The aril serves as food for baboons. Although the seed coat is poisonous, boiled seeds are edible after the removal of the seed coat. The aril is also edible; can be eaten or made into a drink or sauce. Poultices made from the leaves can be used to treat bruises and eczema. The leaves are also believed to induce sleep and hot infusions from the leaves can be soothing when applied to bruises. In addition, the leaves can also be used in the treatment of lumbago, rectal ulcer and dysentery. In Nigeria, leaves are used for the treatment of syphilis and can be eaten for the treatment/relief of gonorrhea. Decoctions made from the roots are consumed as tonic and can be used against fever. It is also useful as purgative. Daily consumption of the bark decoctions and hot infusions can be used to treat diarrhea. The bark decoction is also useful in the treatment of back pain that results from kidney problems. Other
medicinal uses are the treatment of stomachache, fever, scabies as well as a purgative in form of enema and as a blood purifier. The bark can also be used to make fish poison (Palgrave, 1977; Grace et al., 2003; Eldeen et al., 2005; Krief et al., 2005 Maroyi, 2007).
Medicinal use of the tree especially in Africa also includes treatment of inflammatory problems such as kidney pain, sore back/back ache and inflammation of the bronchus (Eldeen et al., 2007).
The wood is used for furniture, carving, household equipments, shelving and construction. The wood is also used to repair ships and canoes, as well as for firewood and charcoal. The tree is planted for ornamental purposes in cities, parks and gardens. It is also grown as a shade tree for coffee in Ethiopia. The trees serve as breeding sites for some butterfly species (Pooley, 1993; Maroyi, 2007).
One of the most important components of the seeds that contribute to their usefulness is the seed oil. T. dregeana seeds are rich in oil; comprising 55% - 65% of the seeds and they can produce as much oil as many other oil-rich dicotyledonous seeds. The approximate composition of the fatty acid in the oil is: plamitic acid 34%; stearic acid 3%; oleic acid 51% and 11% of linoleic acid. One kilogram of fresh seeds can produce 308 ml of oil. Thus it can serve as potential source of income to the rural people (Grundy and Campbell, 1993; Maroyi, 2007). The oil is used to make candles, soap and cosmetics and can be used for cooking. The residue after the extraction of oil is used as fertilizer as well as animal feed. It can be used to hasten the healing of a fractured limb when rubbed into a cut made in the skin; used as massage oil or consumed internally for the treatment/relief of rheumatism and also useful as general body ointment (Palgrave, 1977;
Pooley, 1993; Maroyi, 2007). The oil provides good finish on wooden surfaces (Grundy and Campbell, 1993).
Various phytochemical compounds have been extracted from the different parts of T.
dregeana and these extracts have been shown to be biologically active; having anti- microbial and anti-inflammatory activities. Examples are the extractions of cycloart-23- ene-3,25-diol from the leaves by Eldeen et al., (2007) and limonoids (which include
evodulone and prieurianin derivatives, dregeanin, dregeana 1-5 and rohituka 7 in T.
dregeana) from the seeds and the seed coats (Maroyi, 2007). Apart from having anti- microbial and anti-inflammatory properties, limonoids (which are commonly found in the Meliaceae) are also known as antifeedants and growth regulators of insects, thus can serve as potent insecticides (Maroyi, 2007; Wheeler et al., 2001). Limonoids also show cell-adhesion inhibitory properties. Extracts from the bark (as well as leaves and roots) have anti-bacterial properties. They also inhibit prostaglandin synthesis which is useful in the suppression of pain and inflammation (Eldeen et al., 2005; Maroyi, 2007). It is therefore convenient to suggest that T. dregeana can be a potential source for the production of pharmaceutical products.
In terms of yield, one or two years of abundant seed yield may be followed by year(s) of low yield. The species is easily propagated by the seeds, especially fresh seeds. T.
dregeana is frost-sensitive. The wood is susceptible to borer attack, thus must be treated against insects. The seeds have also been categorised as showing recalcitrant post-harvest behaviour (Maroyi, 2007). T. dregeana is not considered as being threatened because of its abundant existence and wide distribution. Although there is no record of evidence to substantiate this, it is assumed that wild populations of the species may be compromised locally, because common trees found are those planted in cities, parks and gardens for ornamental purposes (Pooley, 1993; Kioko, J.I; 2002; Pammenter et al., 2003; Maroyi, 2007).
Figure 1.2: Trichilia dregeana tree.
Source: http://www.plantzafrica.com/planttuv/trichildreg.htm
Figure 1. 3: Trichilia dregeana open fruits with seeds. Photo taken by Prof. Berjak, P.
Figure 1. 4: Trichilia dregeana seeds from the four provenances. Photo taken by Prof.
Berjak, P.