Research Article Determination of Tannins of Three Common Acacia Species of Sudan Isam Eldin Hussein Elgailani and Christina Yacoub Ishak Department of Chemistry, Faculty of Science, University of Khartoum, P.O Box 321, 11115 Khartoum, Sudan Correspondence should be addressed to Isam Eldin Hussein Elgailani; gailani23@hotmail.com Received 8 June 2014; Accepted 7 September 2014; Published 17 September 2014 Academic Editor: Armando Zarrelli Copyright © 2014 I. E. H. Elgailani and C. Y. Ishak. his is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. he objective of this study is to analyze and compare tannins of three common Acacia species of Sudan, since vegetable tannins are important in leather industry. Acacia nilotica and Acacia seyal samples were collected from Sunt Forest in Khartoum State, while Acacia senegal samples were collected from the Debabat Forest in South Kordofan State. Bark samples from bulk collections of the three Acacia species were extracted with boiled deionized water. he amount of tannins present in these bulk samples was determined by Folin-Denis method for total phenolic materials, followed by precipitation with hide-powder. he diference between the amount of phenolic materials present before and ater addition of hide-powder represents the amount of tannins present. he percentage of tannins in the leaves, bark, and mature and immature fruits of collections of individuals of Acacia species was estimated; mature and immature fruits of Acacia nilotica contain tannins (22.15% and 22.10%, resp.). he leaves of Acacia nilotica and Acacia seyal contain tannins (11.80% and 6.30%, resp.). he barks of Acacia seyal, Acacia nilotica, and Acacia senegal contain tannins (12.15%, 10.47%, and 3.49%, resp.). 1. Introduction Tannins are amorphous, astringent substances occurring widely in the bark, wood, leaves, and resinous exudations of plants [1, 2]. hey are water-soluble phenolic compounds which occur widely in vascular plants [3]. he term was introduced by Seguim in 1796 to describe the substances present in a number of vegetable extracts which possessed the property of converting animal skins into leather [4]. Most authors prefer to speak of “tannin extracts” rather than “tan- nin.” he tannins are colourless and noncrystalline substances which form colloidal solutions in water; these solutions have an astringent taste [5, 6]. he astringency of tannins, that is, their eiciency as precipitants of proteins in the mouth causing the sensation of astringency [7–9], is determined by their reaction with salivary proteins in the oral cavity [10]. Astringency and tanning properties are associated with the higher molecular weight proanthocyanidins (condensed tannins) [11]. Tannins are polymeric phenolic compounds with numerous hydroxyl groups and quite diverse in chemical structure [12, 13]. Hydrolysis of some of the tannins yields the simple, seven-carbon gallic acid and others give ellagic acid or other phenolic acids [14, 15]. Tannins are generally divided into hydrolyzable and condensed tannins. Molecular weight as high as 20,000 has been reported for condensed tannins. he molecular weights of hydrolyzable tannins range from 500 to 5,000 [13, 16–18]. Beside the variation from plant to plant, and from one part of a plant to another, the concentration of tannins in any one organ varies with time [19]. he use of vegetable tannins to tan hides and produce leather predates written history. Hides are usually tanned by either a mineral [20] or vegetable process, depending on the type of animal and the extended use of the leather. In Sudan, approximately 11,400,000 kg of cattle hides and 3,750,000 kg of sheep hides are tanned each year (by both processes). Vegetable tannins consumption in Sudan varies between 350 and 400 tons per year, and a large proportion is locally produced as the Acacia species is more distributed in Sudan (data were obtained from the National Centre for Leather Technology and Khartoum Tannery). One of the best sources of tannins is Acacia species which belong to family of Leguminosae in plant kingdom. here are about 800 species Hindawi Publishing Corporation Advances in Chemistry Volume 2014, Article ID 192708, 5 pages http://dx.doi.org/10.1155/2014/192708