Chemical, molecular, and structural characterization of alkali extractable nonstarch polysaccharides from Job's tears.
The polished Job's tears ( Coix lachryma-jobi L.) seeds, dark and white husk types, were sequentially extracted by hot water (75 degrees C) and 0.5 M NaOH solution. Nonstarch polysaccharides were not found in the water extract but were present in the alkali extract. The major components of the alkali extract from both Job's tears were protein, ash, and nonstarch polysaccharides, mainly arabinoxylans. The high arabinose to xylose ratio of 1.25 and 1.24 indicated a highly substituted structure. The average molecular weight (MW) of arabinoxylans of the dark and white husk types were 741,000 Da (Pd 1.5) and 1,449,000 Da (Pd 2.6), respectively, and their average MW reduced after treatment with protease. The alkali extractable arabinoxylans were elucidated to have a (1,4)-linked beta- d-xylan main chain highly substituted with single arabinose units. The results showed that the alpha- l-arabinofuranosyl residues (Ara f) were attached to the main chain mostly at O-3, followed by both O-2 and O-3 of xylopyranosyl residues (Xyl p).
Apirattananusorn
Supaporn
S
School of Food Technology, Suranaree University of Technology, Nakhon Ratchasima, Thailand 30000.
Tongta
Sunanta
S
Cui
Steve W
SW
Wang
Qi
Q
D001089:Arabinose / Q000032:analysis; D031742:Coix / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D009682:Magnetic Resonance Spectroscopy; D010936:Plant Extracts / Q000737:chemistry*; D011134:Polysaccharides / Q000032:analysis* / Q000737:chemistry; D012212:Rheology; D012639:Seeds / Q000737:chemistry*; D014990:Xylans / Q000032:analysis / Q000737:chemistry; D014994:Xylose / Q000032:analysis
D010936:Plant Extracts; D011134:Polysaccharides; D014990:Xylans; C085118:arabinoxylan; D014994:Xylose; D001089:Arabinose