Chemical composition of agars from a newly reported Japanese agarophyte, Gracilariopsis lemaneiformis

The chemical composition of agars from Gracilariopsis lemaneiformis, newly reported from Japan, was investigated. Native agars were isolated by a sequential extraction of plants in water at 22 degree C and 100 degree C, and in boiling 20, 40 and 60% ethanol. Agars in each extract were analyzed by chemical methods, super(1)H, super(13)C NMR; and IR spectroscopy. The highest yield of agar (total carbohydrate) was obtained from the 40% ethanol extract (55%). Highest sulfate content was attained in non-alkali treated agars extracted with hot water (4.81%, DS 0.2). The 3,6-anhydrogalactose content was highest in the 40% ethanol extract (36.1% in non-alkali treatment, 40.3% in alkali treatment). The highest methoxyl content (6.51%, DS 0.66) was obtained in the 60% ethanol extract. The G. lemaneiformis agar is composed of the biological precursor to agarobiose repeating units and agarobiose containing 6-O-methyl agarobiose and a small amount of 2-O-methyl- alpha -L-galactopyranose residues. Alkali treatment improved the chemical quality of the agar fractions, which was comparable with Japanese commercial agar and agarose.