Lamiaceae carbohydrates. VII. Glucoarabinogalactan from Panzerina lanata

Abstract

In continuation of research on polysaccharides from plants of the family Lamiaceae [1-3], we studied water-soluble polysaccharides from the aerial part of Panzerina lanata (L.) Sojak.The aerial part of P. lanata was collected in August 2008 near the village of Atsagat (Buryatiya, Russia). Optical rotation was determined on an SM-3 polarimeter (Zagorsk Optico-Mechanical Plant). Spectrophotometric studies were performed on a UV-Vis-mini spectrophotometer (Shimadzu). IR spectra were recorded from films on KRS-5 plates in the range 4000-450 cm -1 on a Spectrum 100 Fourier-IR spectrometer (Perkin-Elmer). 13 C NMR spectra were recorded on a VXR 500S NMR spectrometer (Varian) at operating frequency 125.7 MHz. Spectra were taken from solutions (1%) in DMSO-d 6 . GC-MS analysis of methylated monosaccharides was carried out in a 5973 N GC-MS (Agilent Technologies) with a 6890N mass-selective detector (Agilent Technologies) with a diffusion pump and PH-Innowax capillary column (30 m/250 μm/0.50 μm), temperature gradient 150-250°C, heating rate 2°C/min, He carrier gas, flow rate 1 mL/min. Carbohydrate content was determined by the anthrone method [4]; acetyl groups, using hydroxylamine [5] and IR spectroscopy methods [6]. Total hydrolysis of polysaccharides was carried out in TFA (2 M, 120°C, 2 h). Quantitative monosaccharide composition was determined by HPTLC [1]. Gel chromatography was performed on Sephadex G-100 (1.5 × 90 cm, Pharmacia), NaCl (0.3%) eluent, flow rate 0.1 mL/min, detection of products by phenol-H 2 SO 4 [7]. Oxidation of polysaccharides by CrO 3 was performed after preliminary acetylation by the literature method [8]. Periodate oxidation, Smith degradation, and deacetylation were carried out as before [3]. Methylation was carried out by the literature method [9] with monitoring of the process by IR spectroscopy. Then formolysis and hydrolysis of the permethylate [1] and analysis by GC-MS were performed.Water-soluble polysaccharides were isolated from raw material (200 g) by preliminary extraction with EtOH (80%, 1:10, 100°C, 10 × 1.5 h). The pulp was treated successively with water (1:20) at 20 and 100°C until the reaction for carbohydrates was negative (phenol-H 2 SO 4 method). Aqueous extracts were concentrated separately, demineralized over a column of KU-2-8 cation-exchanger (H + -form, Reakhim, 50 × 300 mm, water eluent). Effluents were neutralized with AV-17-8 anionexchanger (HCO 3 --form, Biolar), concentrated to 100 mL, precipitated with acetone (1:6), and centrifuged (3000 g, 15 min) after 1 h. The resulting precipitates were washed with acetone and dried to afford two fractions of water-soluble polysaccharides that were soluble in cold (PLW C ) and hot (PLW H ) water in 0.54 and 5.54% yields of raw material mass, respectively.