Determination and Characterization of Tannin Material Extract From Three Common Acacia Species in Sudan

Abstract

This research is dealing with the analysis and comparative studies of tannins

of three common Acacia species of Sudan. Since vegetab1e tannins are important

for leather industry, A. nilotica and A. seyal samples were collected from Sunut forest

in Khartoum State while A. tomentosa, samples were collected from the shmbata

Forest.

Bark samples From collections of the three acacia species ,were extracted

with distilled water, 80% methanol and 70% acetone ;two sets of extraction were

made, one by boiling, and the other by shaking the samples in the respective solvent

for eight hours at room temperature. Although the amount of material extracted by

these two procedures did not differ greatly , 70% acetone was a more efficient solvent

than either water or 80% methanol.

Qualitative analysis showed that the fruits (garad) contain tannins materials,

flavinoid coumarins, and quantitative analysis showed that the fruits (pods) contain a

higher percentage of tanning materials, that can be used commercially, barks contain

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low tannin content compared with fruits. Also it was found that the unripe fruits give

the highest percentage of the tannins content.

Rotary system (with extraction changing in size of powder, rate of solvent to

the fruits weight, and solvent temperatures), enabled access to extracts with high

concentration when using crushed fruits, water at 70°C and ratio of (3:1) of water to

fruits weight.

Sodium fluoride and a mixture of oxalic acid and sodium sulphite showed high

efficiency as antifungal reagents. With the mixture of acid - sulphite was found to be

the best bleaching agent compared with sodium fluoride

The amount of tannins present in the bulk samples was determined by folindenis

method for total phenolic materials, followed by precipitation with hide-powder.

The difference between the amount of phenolic materials present before and after

addition of hide-powder represent the amount of tannins present. The extracts of the

bark of A. nilotica A. seyal and A. tomentosa, contain (80.45% ,59.9% and 33.5%)

tannins respectively.

The amount of iron content of the extracts and samples of Acacia species was

determined since the Iron hinders the process of retanning leather of Iron content was

determined by atomic absorption spectrophotometry. The iron content of bark extracts

of A nilotica, A tomentosa and A seyal is 0.0044%, 0.0040% and 0.0029%

respectively. In contrast, the iron content of bark extract of the three species of Acacia

had lower percentage compared to that of Mimosa (0.00475%), which is imported

from Kenya.

The tannins of a mixture of powder of Acacia nilotica and bark of the acacia

seyal were identified by using thin layer chromatography (TLC), ultraviolet and

infrared spectroscopy. Comparisons of the absorption spectra and TLC of the

reference tannins and some phenolics with that of a mixture extracts revealed the

presence of both condensed and hydrolysable tannins, since it consists of catechin,

tannin and gallic acids.

The leaching materials were powdered using spray drier. They exhabited excellent

properties, when used for tannage of leather. Better physical and chemical properties

of leather were achieved compared with leather tanned using mimosa powder.