Coagulants of Moringa Oleifera Lam. seeds : purification & characterisation

Water has been declared a human right by the United Nations, thus urging countries who have ratified the International Covenant on Economic, Social and Cultural Rights to ensure supply with drinking water for their populations1. However, supply of drinking water in developing countries underlies different constraints than those met in industrialized countries. An example is the dependency on treatment chemicals that may pose problems in these countries regarding importation and distribution2. In pioneering work in the Darfur region (Sudan) S.A.A. Jahn has instructed rural people how to use local natural coagulants, that had been used traditionally by parts of the population, for the preparation of water for household use with special emphasis on the seeds of the Moringa oleifera tree3. The implementation of water supply for the population on the other hand demands centralized water treatment for villages and cities and thus traditional techniques will reach their limitations. The present work tries to identify and characterise the coagulating principle present in the seeds and press-cake of M.oleifera, in order to produce quantities of a standardized coagulant that could be used in small treatment works. Therefore, different extraction methods, reported in the literature, are compared regarding extraction efficiency and composition. All extracts contained a large proteinaceous moiety, which differed from proteins described before as Mo 2.1 (flocculating proteins4) in the way that two proteins were detected under reducing conditions, both not co-migrating with a synthetic protein having the amino acid sequence of Mo 2.1. Moreover a different group of proteins with higher molecular weight was only present during the first two days of storage of the liquid extract. An optimized extraction procedure is presented, resulting in a total protein yield of 40g/L. Separation of proteinaceous components present in the seed and press-cake extracts lead to the determination of relative molecular masses of two protein components present (4 and 8 kDa) which form a 12 kDa heterodimer under non-reducing conditions, such as those found in the raw extracts. Further evidence is presented that the number of different proteins present in the extracts using the reported techniques may be an artifact due to sample degradation, oxidation and reaction with non-proteinaceous substances present in the extracts. The presence of glucosinolates and of their derivatives that belong to the reactive group of isothiocyanates was show in the extracts of M.oleifera seeds and press-cake, thus increasing the risk of protein stability problems during storage of the potential product. Furthermore, a method for protein isolation which reduces interference of isothiocyanates has been developed for extraction from M.oleifera. In order to compare the coagulating activities of different components present in fractions after separation of the seed extracts a miniaturized assay has been develop