ABSTRACT
The exudate of Eucalyptus citriodora. (family) which was initially thought to be a gum
was found to contain mainly tannins using 5% aqueous FeCI3. Such tannin containing exudates
that issue from the trunks of Eucalyptus and other trees are referred to as “kino”. The exudate
was collected from four identified trees throughout the investigation at a plantation behind the
settlement. Laying Zomo, opposite the premises of the Nigerian College of Aviation Technology,
Zaria
The reagents that were used to establish the nature of the “kino” included 5% Ferric
Chloride, 5% gelatin solution, bromine water, ferric ammonium citrate, formalin, sodium nitrite
and lime. The reagents indicated that the “kino” contained mainly hydrolysable tannins whose
main constituents are gallotannins and ellagic tannins but with traces of condensed tannins
otherwise known as catechol tannins or catechins. It is worthy of note that inspite of the different
periods of collection of the kino, the 1R spectral properties of the various samples were identical.
This further indicated that the same spectrum of tannins as stated above were present.
A solution of the kino in water was spotted against solutions of tannic and gallic acids on
cellulose paper and chromatographed. The presence of free gallic acid in both the “kino” and
tannic acid was confirmed. Free ellagic acid was, however, absent. The exudate was then
hydrolysed with 2N hydrochloric acid and again chromatographed with tannic acid and gallic acid.
The presence of gallic was further confirmed. There was also a strong indication of
anthocyanidins as shown from the red colour of the hydrolysate. Alkaline hydrolysis (2N NaOH)
of the exudate, subsequent chromatography and the use of appropriate detective methods, UV
(X max) 366 nm before and alter exposure to NH3, suggested that one of the probable components
of catechol tannins was kaempferol
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Quantitative analyses of the exudate showed that it contained an average of 50% tannins
which compares well with all known commercial sources of tannins. Subsequent tanning trials
and leather analyses (both physical and chemical) showed the leather to be of good resulting in
the good quality leather products. These are the shrinkage temperature, 58°C, load at crack,
250NM2, distention at crack, 6.7, waterproofness, 42.7gm, tensile strength, 212.03 NM2, %
Elongation at break average, 73NM”, pH of unfiltered extract, 3.10, pH of 10 x dilution, 3.7,
Difference Figure, 0.6, substance extractable by Dichloromethane, 4.57, volatile matter, 8.46 and
Degree of Tannage, 39.50.
It was concluded that the exudate (“kino”) contains mainly gallotannins and ellagitannins
with traces of catechin tannins. It was established that the leather produced was of high quality as
attested to by physical appearance and physical and chemical tests.
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