| Home  | About ScienceAsia  | Publication charge  | Advertise with us  | Subscription for printed version  | Contact us  
Editorial Board
Journal Policy
Instructions for Authors
Online submission
Author Login
Reviewer Login
Volume 43 Number 4
Volume 43 Number 3
Volume 43 Number 2
Volume 43 Number 1
Volume 43S Number 1
Volume 42 Number 6
Earlier issues


ScienceAsia 32 Supplement 1 (2006): 011-017 |doi: 10.2306/scienceasia1513-1874.2006.32(s1).011

Physical and Chemical Characterization of Agar Polysaccharides Extracted from the Thai and Japanese Species of Gracilaria

Jantana Praiboon,a* Anong Chirapart,b Yoshihiko Akakabe,c Orapin Bhumibhamond and Tadahiko Kajiwarac

ABSTRACT: Agar polysaccharides extracted from two Thai species of Gracilaria (G. fisheri and G. edulis) and one Japanese species (Gracilaria sp.) were investigated by physical and chemical analysis, and 1H, 13C NMR and FT-IR spectroscopy. Agar with partial 6-O-methylated on 3-linked -D-galactopyranosyl, 2-O-methylated on 4-linked 3,6-anhydro--L -galactopyranosyl and 4-O-methyl--L- galactopyranosyl units attached to the C6 of 3-linked D-galactopyranosyl units were isolated from G. fisheri. The large parts of 6-O-methylated on 3-linked -D-galactopyranosyl units and partial methylation on C2 of 4-linked 3,6-anhydro--L - galactopyranosyl units were observed in the agar extracted from G. edulis which corresponded with higher gelling temperature (>> 60 Co). In contrast, the Japanese agar extracted from Gracilaria sp. showed a typical pattern of agarobiose with partial methylation at C6 of the D-galactopyranosyl units. All agars extracted exhibited sulfate substitution at different positions in the polymers. High sulfate contents were obtained in native agar of G. fisheri (4.56%) and G. edulis (7.54%) that mainly branched at C-4 of the D-galactopyranosyl unit. The presence of this unit was responsible for poor gelling ability of the agar polymers. Alkali treatment was effective both in removing alkali-labile sulfate and increasing the gel strength in Gracilaria sp. (334.5 14.1 g/cm2) whereas only a slight effect was noted on G. fisheri (228.27 48.18 g/cm2) and G. edulis (239.95 28.35 g/cm2). Further investigation may need to determine the constituent sugars and an alternative utilization of the Thai gracilaroids.

Download PDF

a Department of Biotechnology, Faculty of Agro-industry, Kasetsart University, Bangkok 10900, Thailand.
b Department of Fishery Biology, Faculty of Fishery, Kasetsart University, Bangkok 10900, Thailand.
c Department of Biological Chemistry, Faculty of Agriculture, Yamaguchi University, Yamaguchi 753-8515, Japan.
d Schools of Agroindustry, Mae Fah Luang University, Chiang Rai 57100, Thailand.

* Corresponding author, E-mail: juntana_p@yahoo.com