Structure and Biological Activity of Galactomannans from Seed Pods of Two Crotalaria Species
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STRUCTURE AND BIOLOGICAL ACTIVITY OF GALACTOMANNANS FROM SEED PODS OF TWO Crotalaria SPECIES
F. A. Kodiralieva,1* R. K. Rakhmanberdyeva,1 L. I. Shevchenko,2 and O. B. Shadybekova2
Water-soluble polysaccharides and pectinic substances from seed pods of Crotalaria alata L. (Uzbekistan) and Crotalaria sp. (India) were studied. The water-soluble polysaccharides were found to dominate over pectinic substances. Galactomannan GM-SP with a Man:Gal ratio of 4.4:1 was isolated from Crotalaria sp. seed pods. Its main chain consisted of 1,4-β-bound polymannans with 1,6-α-bound galactopyranose side residues. Sulfated derivatives of galactomannan from C. alata were prepared. The supramolecular structures of the galactomannan and its sulfated derivative were studied using electron microscopy. The galactomannan sulfated derivative exhibited anticoagulant activity. Keywords: Crotalaria, water-soluble polysaccharides, pectinic substances, 13C NMR spectra, galactomannans, sulfated derivatives, anticoagulant activity. Polysaccharides from plants of the bean family (Fabaceae) are now the most studied. Galactomannans (GMs), reserve polysaccharides of the endosperm cell wall tissue, is a common carbohydrate of bean seeds. GMs have broad spectra of biological activity because of their unique physicochemical properties and lack of toxicity. Crotalaria is a large genus among plants of this family that is distributed in tropical and subtropical zones. The isolation and structural characterization of GMs from various Crotalaria species have been reported [1–6]. Previously, the contents of various carbohydrate groups from seeds of C. alata L. were studied by us [2, 4]. The main polysaccharide was shown to be a GM water-soluble polysaccharide (WSPS) [7]. The goals of the present work were to study seed pods of two Crotalaria species growing under various climatic conditions for contents of polysaccharides and their physicochemical parameters, to establish the structure of GM from a Crotalaria sp., and to produce sulfated derivatives with anticoagulant activity from a previously isolated GM from C. alata. Seeds of C. alata (Uzbekistan) and a Crotalaria sp. (India) were studied. WSPS and pectinic substances (PS) were isolated from the seeds using the published method [8] (Table 1). The dominant WSPS in both samples had different yields, molecular masses, viscosities, and galactose:mannose ratios. The monosaccharide composition of WSPS from the Crotalaria sp. included rhamnose (0.38%), arabinose (2.5%), xylose (1.6%), mannose (76.3%), glucose (1.5%), and galactose (17.5%). The PS consisted of neutral monosaccharides and uronic acids. The contents of PS neutral sugars were determined by GC as 13.3% arabinose, 1.7% xylose, 2.8% mannose, and 6.4% galactose. The amount of uronic acids determined by the carbazole method was 75.8%. Aqueous solutions of PS had lower relative viscosities than those from C. alata. The PS had a high degree of esterification (DE) according to titration data, which allowed them to be classified as highly esterified pectins.
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