Isolation and Characterization of a Pentasaccharide from Stellaria media

While classic raffinose family oligosaccharides (RFOs) such as raffinose and stachyose are common in plants, stachyose is absent in the Caryophyllaceae. Instead the tetrasaccharide lychnose alpha-D-Gal-(1 -> 6)alpha-D-Glc-(1 -> 2)beta-D-Fru-(1 -> 1)alpha-D-Gal can accumulate. Stellaria media, a representative member of this family, was used to isolate alpha-D-Gal-(1 -> 6)-[alpha-D-Gal-(1 -> 4)]alpha-D-Glc-(1 -> 2)beta-D-Fru-(1 -> 1)alpha-D-Gal, a novel pentasaccharide with a lychnose backbone. Complete NMR characterization using COSY, HSQC, HSQC-TOCSY, HMBC, and NOESY experiments was performed to unequivocally resolve its structure. This is the first report of a natural compound containing a Gal alpha(1 -> 4)Glc linkage. The trivial name stellariose is proposed for this new pentasaccharide.