Abstract:
The objective of this research is to introduce new green, nontoxic, cost effective
derivatives of guar gum (GG-1). Guar gum is one of the important naturally occurring
non-ionic polysaccharide which has incredible applications due to its rheological
modifying properties in medicinal, pharmaceutical, food, textile, cosmetics, water
treatment, mining, drilling, explosives, confectioneries and scores of other industrial and
commercial sectors. Guar gum, also called guaran, is a galactomannan. It is primarily the
ground endosperm of guar beans. The guar seeds are dehusked, milled and screened to
obtain the guar gum. It is typically produced as a free-flowing, off-white powder.The
adaptation of physical properties of GG-1 & GG-2 can improve and diversify its
commercial applications.
GUAR GUM
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In this project, novel and efficient synthesis of five different new derivatives (120-124) of
guar gum were done by insitu activation of cinnamic acid, ferulic acid, caffeic acid,
coumaric acid and hydrocinnamic acid by coupling with dicyclohexylcarbodiimide
(DCC) and N, N-dimethylaminopyridine (DMAP). Effect of temperature, concentration
of reactants and time interval plays important role for determining DS value of guar
esters. Reaction conditions were optimized for each reaction. Antioxidant potential was
examined by DPPH method.
A rapid method for protecting the hydroxyl group in sterically hindered gum has been
developed by using microwave assisted synthesis (MAS). A novel and efficient synthesis
of different guar gum derivatives (126-133) such as acetate, butyrate propionate, maleate,
succinate, phthalate, citraconate and glutarate have been developed by microwave
irradiation. The maximum ester formation was successfully achieved in 15minutes at
600W by using iodine and DMAP as a reaction promoter. Gum ester formation was
obtained by concentration variation at different time intervals. The products were
characterized by IR and NMR spectroscopy and SEM. Moreover, degree of substitution
was also calculated for each experiment by titration method.
First time fatty acid esters (C5-C18) were formulated (136-145) via acid chloride route.
Reaction proceeded in two steps. First step involves conventional synthesis of fatty acid
chlorides (135a-135j) by reacting corresponding acid with slight excess of thionyl
chloride (134). Second step involves esterification of free hydroxyl group of GG-2 with
acid chloride; as a result novel derivatives (136-145) with fascinating thickening and
emulsifying properties were obtained which might be promising candidate for cosmetic
and food industry.
Physical properties were examined like solubility, surface morphological study, swelling
behavior, gelation index etc. Different spectroscopic techniques were used for structure
elucidation. In situ hydrolysis of guar esters were done in DCl during NMR experiments
due to the poor solubility of guar derivatives. Guar derivatives with variable degree of
substitution (DS) were prepared and were confirmed by FT-IR spectroscopy, presence of
carbonyl signal confirmed the formation of guar ester. Further structural elucidation was
done by 1H-NMR .Surface morphological study of guar esters was done by scanning
electron microscopy (SEM) which showed networking in guar derivatives which
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enhanced when degree of substitution increased. Degree of substitution was determined
quantitatively by titration method for each derivative.