Characterization of Water-Soluble Polysaccharides from Chamomile Flowers

Abstract

Chamomilla recutita (L.) Rauschert (Asteraceae) is a well-known plant used in medicine, cosmetics, and food industry (1). Due to the content of essential oil and flavonoids, extracts of chamomile flowers exhibit antiphiogistic and antispasmodic activities. In addition, water-soluble polysaccharides have attracted scientific interest, as they are shown to be involved in antiphlogistic effects and might act also as biological response modifiers (2). Therefore the structural features of the water-soluble polysaccharides of chamomile flowers were investigated.Dried flower heads of the chemocultivar DegumilleTM of C. recatita were powdered V 0.2mm), preextracted with methanol and petroleum ether, followed by water extraction (5% w/w) at 25 °C for 8 h. After centrifugation, the polysaccharides were precipitated with ethanol (final concentration 80% v/v), redissolved in water, dialysed (Mr cut-off 3.5 kd) and freeze-dried, yielding 3.2% (w/w of dried flower heads) of a crude polysaccharide fraction (= CPS).By sequential elution of CPS on DEAE-Sephacel with water, 0.25 M and 0.5 M potassium phosphate buffer, three polysaccharide fractions could be obtained: PS I (0.8% w/w dried flower heads), PS 11(0.7%), and PS 111(0.5 %). Allfractions were analysed.Relative molecular mass was determined on GPC with SephacryPTM S 400, SuperdexTM 75 or 200, and SuperoseTM 6 or 12. Neutral sugar composition was determined by GLC of the alditol acetates (3) or alditol trimethylsilyl ethers (4) after hydrolysis with TFA or oxalic acid. Uronic acid content was measured colorimetrically by the hydroxybiphenyl assay (5). The degree of substitntion (DS) with methanol or acetic acid was evaluated photometrically after saponification and formation of 3 ,5-diacetyl-1 ,4-dihydro-2 ,6-dimethylpyridine (6) or of a chelate complex of hydroxamic acid with ferric ions (7).Analysis of sugar linkages was carried out by GLC/MS-analysis of the partially methylated alditol acetates (PMSS) (8). Prior to methylation analysis, a carboxyl reduction with carbodiimide (9) was performed, in the case of acidic polysaccharides.The major polysaccharide component of fraction PS I (85%) was a fructan with a relative molecular mass of 3.5 kd, with a main chain of 1,2-linked fructose and a few branching points (2%) via 1,2,6-fructose. In addition, fraction PS I contained small amounts (15 %) of a neutral arabinogalactan with an identical molecular mass range, mainly consisting of 1,3,6linked galactose, 1,6-linked galactose, and 1,5-linked arabinose in a ratio of 1 :0.9:0.8.Fraction PS II could be separated by GPC into three acidic polysaccharides with molecular masses of 300 kd (PS II A), 83kd (PS II B), and 11 kd (PS II C)in a ratio nfl :3:1. The oronic acid content was determined to be 50.5%, 26.0%, and 37.3%, respectively. PSII A, PSII B, and PSII C also showed differences in the DS with methanol of 52.0%, 42.5%, and 59.7%. backbone of a-1,4-linked galacturonic acid regions and ramified regions with 1, 2,4-rhamnose as branching points and side chains of 1,5-linked arab...