Masakuni Tako^1,, Hiyori Taba^{1, 2}, Keiko Uechi¹, Yukihiro Tamaki^{1, 3}, Teruko Konishi¹

Unusually branched pectin was isolated from leaves of a traditional medicine, Artemisia indica Willd. var. indica that was grown in Okinawa, Japan. D-Galacturonic acid, L-arabinose, D-galactose, L-galactose, L-rhamnose, D-xylose, acetic acid, methyl ether and methyl ester were identified via chemical, HPAEC and NMR analyses. The molecular mass was 18.5 kDa. The polysaccharide was fractionated on DEAE chromatography and divided into neutral and acidic fraction. Almost D-galacturonic acid residues were moved into acidic fraction and all of the carbon atoms (C1-C6) on ¹³C-NMR spectrum were assigned to double (coupling) signals suggesting that long D-galacturonic acid side-chains (homogalacturonan) were involved. By methylation analysis, (1→4)-linked α-D-GalpA (major), terminal, (1→5)-, (1→2,3)-, (1→2,5)-, and (1→3,5)-linked α-L-Araf were identified. Terminal, (1→6)- and (1→3,6)-linked β-D-Galp, (1→2)- and (1→2,4)-linked α-L-Rhap, (1→4)-linked α-D-Xylp, and (1→4)-linked β-D-GlcpA were also identified. The pectin was consisted of homogalactouronan main-chain, rhamnogalacruronan main-chain, double galacturonan side-chains, arabinogalactan side-chain, and galactoglucuronoxylose side-chain. This study is the first to report on involving double homogalacturonan side-chains. The pectin molecules seem to cross-linking each other between carboxyl groups of D-GalpA residues through cations, such as B³⁺, Ca²⁺ and Mg²⁺, to hold nutrients, inorganic matters, and water in the cell walls and intercellular areas of leaves of Artemisia indica Wild var. indica.

unusually branched pectin, Altemisia indica, medicinal food, NMR analysis, methylation analysis, chemical structure