Carbohydrates from Solidago caucasica herb

Abstract

Solidago caucasica Kem.-Nath. is a goldenrod of the family Asteraceae and is an unstudied species endemic to the Caucasus although other species of the genus Solidago are widely used worldwide to treat diseases of the urogenital system. We previously detected in S. caucasica herb flavonoids (rutin, vicenin, hesperidin), coumarins (umbelliferone, esculetin, dihydrocoumarin), phenolcarboxylic acids (gallic, chicoric, chlorogenic, and caffeic acids) [1], organic acids (citric, malic, and succinic) [2], 15 amino acids, 5 macroelements, and 16 microelements [3]. We studied the carbohydrate composition of S. caucasica herb collected in subalpine meadows of the western Caucasus (Daut Gorge of Karachay-Cherkessia Republic). Raw material (30.0 g of S. caucasica herb) was extracted with CHCl 3 (2 100 mL) and dried. The remaining raw material was extracted twice with refluxing EtOH (82°C) in order to isolate sugars soluble in alcohol (SSA). The resulting extracts were evaporated and chromatographed on Filtrak FN 7,12 paper (PC) using BuOH–Py–H 2 O (6:4:3). SSA according to PC were glucose, galactose (anilinium biphthalate detector), fructose, and sucrose (5% urea detector). Next, polysaccharides were isolated by successive extraction of water-soluble polysaccharides (WSPS) with H 2 O, pectinic substances (PS) with oxalic acid and ammonium oxalate solutions (0.5%), and hemicellulose (HMC) with base solution (5%). The monosaccharide composition of the carbohydrates was established by acid hydrolysis [4]. Neutral sugars were identified by GC. Samples were analyzed by GC on a Chrom-5 chromatograph with a flame-ionization detector, glass column (1.5 m 0.3 m) with 5% Silicone XE-60 on Chromaton NAW (0.200–0.250 mesh), 210°C, He carrier gas at 30 mL/min, and aldononitrile acetates [4]. Table 1 presents the results. The isolated WSPS and PS were assigned according to the amount of component monosaccharides as galactans; HMC, xylans. The greatest amount of galactose was observed in PS fractions. The PS and HMC fractions were the main ones with respect to content. Uronic acids were identified in all fractions. The amount of uronic acids was determined by a photoelectrocolorimetric method using the reaction with carbazole in H 2 SO 4 solution [5]. The greatest amount of uronic acids was detected in PS. The accumulation of these components was responsible for the prospective pharmaceutical use of the carbohydrates. WSPS were a dark-brown powder with relative viscosity 3.0 (c 1%, H 2 O). The content of free carboxylic acids (Cf) was established by titration as 1.98%; of esterified carboxylic acids (Ce), 4.6%; the degree of esterification (), 69.9%. Therefore, WSPS were highly esterified compounds. This allowed them to be recommended for use as excipients for manufacturing drug forms as gel-formers, thickeners, stabilizers, etc. PS were a dark-brown powder that dissolved in H 2 O with heating to form viscous solutions of relative viscosity 10.17 (c 1%, H 2 O). The content of Cf was 6.75%; Ce, 3.78%; 35.89%. Therefore, PS were low-esterified compounds. The rather high content of free carboxylic acids made this plant a promising subject for isolating PS with pronounced sorption properties, especially with respect to metal ions. HMC was a friable light-brown powder that dissolved in base. IR spectra of samples were taken in pressed KBr pellets on a Model 2000 IR-Fourier spectrometer (PerkinElmer) using 100 scans. The following conclusion could be made based on an analysis of the found characteristic IR absorption bands of the carbohydrates.