The present invention relates to a novel process for the extraction and purification of cesalin, a proteinaceous substance exhibiting antitumor activity, which can be extracted from the seeds of the plant Caesalpinia gilliesii (Wall), a glandular shrub found in the Southwestern United States, particularly in Arizona.
The seeds of many plants have been the source of proteins and glycoproteins which affect the growth and division of cells. They have been used as a probe for the components of cell surfaces, for the stimulation of cell division, and in studies of cytotoxic effects.
Cesalin is an oligomeric protein of undetermined structure, having a molecular weight of about 110,000. Hence it may be regarded broadly as a biopolymer. Several types of biopolymers that exhibit antitumor activity have been derived from plant materials. They may be polysaccharides, such as lentinan, a glycan isolated from Lentinus edodes, scleroglucan isolated from Sclerotium glucanicum, or proteins, such as cesalin.
A process for the extraction and purification of cesalin derived from the plant Caesalpinia gilliesii (Wall) is described in an article by A. Ulubelen, et al., J. Pharm. Sciences, Vol. 56, No. 7, pages 914-916 (July 1967). The cesalin obtained by these authors displayed activity against Walker carcinosarcoma 256 in rats and sarcoma 180 in mice. It was obtained by extracting the dry pods (whole seeds) with water at room temperature, lyophilizing the aqueous extract to obtain a crude powder which was redissolved in water, defatted with ether, and precipitated with ethanol, dialyzed against water, and the resulting dialysate lyophilized to yield a product having antitumor activity. Fractions were separated by column chromatography using ion exchange resins and synthetic dextran derivatives (Sephadex G-200) as chromatographic supports. Six fractions were subjected to paper electrophoresis, and their saccharide content detected by paper chromatography. Various protein peaks were observed, indicating that the original extract comprised a mixture of several proteins and/or glycoproteins differing in their content and distribution of amino acids, thus representing a partially purified cesalin, which was only moderately active against Walker 256 carcinosarcoma and sarcoma 180.