Carbohydrates from seeds of Raphanus sativus and Brassica napus

Abstract

Various radish varieties are well known as vegetables. The chemical composition of their roots is rather well studied. However, seeds are included as medicinal raw material in the Chinese and Japanese pharmacopoeias as diuretics, sedatives, and expectorants. Several cultivated oil crops also have great agricultural significance. The most prolific oil plant of these is rape, seeds of which contain up to 50% oil. Rape is at present the principal oil crop in 28 countries. Its seeds are raw material for producing the preparation Braguzol, a lipase inhibitor [1]. Herein we communicate results on the isolation and general characterization of carbohydrates from seeds of two common radish varieties, black and white [Raphanus sativus L. var. niger J. Kern. and R. sativus L. ssp. acathiformis (Blanch.)Stank.], and common rape (Brassica napus L. ssp. oleifera Metzg.). These are highly interesting because their chemistry is poorly studied. We studied air-dried ground seeds of plants cultivated in Stavropol Territory (Russia). Polysaccharide fractions were isolated from ground raw material (50.0 g) by treatment with CHCl3 to remove colored compounds and non-carbohydrate components. The remaining raw material was extracted (2 ) with refluxing (82°C) EtOH. The raw material was dried. The EtOH extracts were combined, evaporated, and chromatographed on Filtrak FN 7 and 12 paper. Paper chromatography (PC) identified in the EtOH extracts of seeds from these plants sucrose and two fructooligosaccharides (urea detector) in addition to insignificant amounts of glucose and galactose (anilinium biphthalate detector). Then, we isolated successively water-soluble polysaccharides (WSPS) by extraction with cold and hot water; pectinic substances (PS), by a mixture of oxalic acid and ammonium oxalate solutions (0.5%); and hemicellulose (HMC), base solution (5%). The carbohydrates underwent acid hydrolysis in order to establish the monosaccharide composition [2]. The qualitative and quantitative monosaccharide composition was determined by PC (n-BuOH:Py:H2O, 6:4:3; anilinium biphthalate detector) and GC. PC of the hydrolysates identified the monosaccharides (arabinose, galactose) given in Table 1 and insignificant amounts of glucose and xylose in all samples. GC analyses were performed on a Chrom-5 chromatograph with a flame-ionization detector with a glass column (1.5 m 3 mm) and 5% Silicone XE-60 on Chromaton NAW (0.200–0.250 mesh) at 210°C with He carrier gas (30 mL/min) as the aldonitrile acetates [3]. All isolated WSPS and HMC were mainly galactoarabans. Therefore, we give the ratio of monosaccharides arabinose and galactose. The greatest amount of arabinose was detected in common rape seeds in the PS and WSPS fractions. The accumulation of these components is responsible for the potential pharmaceutical use of the carbohydrates. The HMC fraction was the principal one with respect to content in all studied samples. Uronic acids were identified only in the PS fraction.