Compositional analysis and rheological properties of gum kondagogu (Cochlospermum gossypium): a tree gum from India.
Gum kondagogu ( Cochlospermum gossypium) is a tree exudate gum that belongs to the family Bixaceae. Compositional analysis of the gum by HPLC and LC-MS revealed uronic acids to be the major component of the polymer ( approximately 26 mol %). Furthermore, analysis of the gum by GC-MS indicated the presence of sugars such as arabinose (2.52 mol %), mannose (8.30 mol %), alpha- d-glucose (2.48 mol %), beta- d-glucose (2.52 mol %), rhamnose (12.85 mol %), galactose (18.95 mol %), d-glucuronic acid (19.26 mol %), beta- d-galactouronic acid (13.22 mol %), and alpha- d-galacturonic acid (11.22 mol %). Gum kondagogu, being rich in rhamnose, galactose, and uronic acids, can be categorized on the basis of its sugar composition as a rhamnogalacturonan type of gum. The rheological measurements performed on the gum suggest that above 0.6% (w/v) it shows a Newtonian behavior and shear rate thinning behavior as a function of gum concentration. The viscoelastic behavior of gum kondagogu solutions (1 and 2%) in aqueous as well as in 100 mM NaCl solution exhibits a typical gel-like system. The G' (viscous modulus)/ G'' (elastic modulus) ratios of native gum kondagogu (1 and 2%) in aqueous solution were found to be 1.89 and 1.85 and those in 100 mM NaCl to be 1.54 and 2.2, respectively, suggesting a weak gel-like property of the polymer. Crossover values of G' and G'' were observed to be at frequencies of 0.432 Hz for 1% and 1.2 Hz for 2% for native gum in aqueous condition, indicating a predominantly liquid- to solid-like behavior, whereas crossover values of 2.1 Hz for 1% and 1.68 Hz for 2% gum in 100 mM NaCl solution suggest a larger elastic contribution.
Vinod
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VT
Jonaki, Board of Radiation and Isotope Technology, CCMB Campus, Uppal Road, Hyderabad 500 007, Andhra Pradesh, India.
Sashidhar
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RB
Sarma
V U M
VU
Vijaya Saradhi
U V R
UV
D031212:Bixaceae / Q000737:chemistry*; D002241:Carbohydrates / Q000032:analysis; D002851:Chromatography, High Pressure Liquid; D005690:Galactose / Q000032:analysis; D008401:Gas Chromatography-Mass Spectrometry; D007194:India; D011134:Polysaccharides / Q000737:chemistry*; D012210:Rhamnose / Q000032:analysis; D012212:Rheology; D014574:Uronic Acids / Q000032:analysis
D002241:Carbohydrates; D011134:Polysaccharides; D014574:Uronic Acids; D012210:Rhamnose; D005690:Galactose