A general analysis of bark and leave of some indigenous wood species was carried out with the aim of establishing whether their percentage tannin content is high enough to be of commercial value. The results obtained from the four species examined, show the percentage tannin to be 12.7%, 7.1%, 5.3% and 8.4% for the bark of four species pterocarpus osun, pterocoupus soyaixii, Burkea Africans and khaya senegacensis respectively. Also from the leaves, the percentages obtained where 3.2, 2.8, 4.4 for pterocarpus osun, pterocarpus soyauxii and khaya senegacensis respectively. These results are comparable with the empirical data and so are enough to be of commercial value.
The tissue of wood, bark and leaves of trees contain a great variety of chemical substances of considerably scientific interest and some of the practical values. Tannin is a generic name for widely occurring group of substances of vegetable origin.
Tannins from the bark, wood and leaves of certain species of plants is one of the most important commercial extractives which also form the basis of some important industries. The main local source of obtaining industrial vegetable tannin in Acacia nilotica pods, obtained principally around Kano and Maiduguir. Due to ever increasing demand for this materials by the producers of particle boards and leathers, there has grown a scarcity which normally manifest itself in the cost of materials.
Even in the southern parts of Nigeria where new leather industries are developing, the problem of obtaining transporting and storing these pods cannot for too long be over – looked there is therefore the need for a search into other alternatives in order to avoid a heavy drain on foreign exchange because of the importation of synthan (synthetic phenolic polymers).
Again the mangrove (Rhizophora species) found largely in most tropical coast lines contain reasonable amount of tannin. But when used in the heavy tanning industries. They a re known to produce an extract which has the major set back because of its hard red colour, which is prone to further darkening on exposure to sunlight during drying Fasina (1974) suggested that after full tannage is achieved, that the leather or particle board is bleached and then retanned using a light coloured fast penetrating vegetable tannin extract. But one cannot over look here, the cost factor, since an industry is usually profit motivated.
This project is therefore an investigation carried out the determine other sources of vegetable tannin of commercial importance and which can sustain the available tanners industries in the country that is the species (bark and leaves) investigated were Pterocarpus Osun Pterocarpus Soyaureii. Burkea africana and Khaya senegalensis.
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