Synthesis of carbamoylethyl Cassia angustifolia seed gum in an aqueous medium

Carbohydrate Polymers 136 (2016) 1259–1264

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Synthesis of carbamoylethyl Cassia angustifolia seed gum in an aqueous medium Gaurav Rajput a,∗ , I.P. Pandey a , H.C. Joshi b a b

Department of Chemistry, D.A.V. (PG) College, Dehradun, Uttarakhand, India Department of Chemistry, S.G.R.R. PG College, Dehradun, Uttarakhand, India

a r t i c l e

i n f o

Article history: Received 4 July 2015 Received in revised form 10 October 2015 Accepted 12 October 2015 Available online 22 October 2015 Keywords: Cassia angustifolia seed gum Carbamoylethylation Nitrogen content Non-Newtonian pseudoplastic behaviour

a b s t r a c t The Cassia angustifolia seed gum (CAG), a galactomannan, isolated from the seeds of C. angustifolia was subjected to the carbamoylethylation which involved the reaction of CAG with acrylamide in an aqueous medium (water) in the presence of alkali (NaOH) as a catalyst. Alkali concentration, acrylamide concentration, liquor:gum ratio as well as reaction temperature and time were found to affect the extent of carbamoylethylation of CAG (expressed in terms of nitrogen content) and so, these were optimized. Degree of substitution (DS) and reaction efficiency was also determined. FTIR revealed the successful carbamoylethylation of CAG and rheological study conducted on 1 and 2% (w/w) solutions of the carbamoylethyl-CAG not only brought out the non-Newtonian pseudoplastic behaviour, but also high stability of carbamoylethyl-CAG solutions in comparison to solutions of the unmodified CAG. © 2015 Elsevier Ltd. All rights reserved.

1. Introduction Galactomannans are naturally occurring bioorganic compounds found in different parts of plants are essentially cheap, biodegradable and environment friendly. Galactomannans finds diverse applications such as thickeners, emulsifiers, viscosifiers, sweeteners, etc. in confectionery, and as binders and drug release modifiers in pharmaceutical dosage forms and so on in number of industries worldwide. However, using the galactomannans in their native forms offers certain limitations which include uncontrolled rates of hydration, pH dependent solubility, thickening, drop in viscosity on storage, and the possibility of microbial contamination (Rana et al., 2011). In order to overcome these drawbacks, the chemical modifications of the galactomannans (via carboxymethylation, cyanoethylation, carbamoylethylation and graft copolymerization) are an efficient as well as an effective technique. Cassia angustifolia is one of the most commonly grown laxative drugs in the eastern and the western nations for the treatment of constipation (Agarwal & Bajpai, 2010). The seeds of C. angustifolia Vahl are a fertile source of galactomannan as the seeds contains 48–52% endosperm (Chaubey & Kapoor, 2001). In the literatures, the systematic works on the structure characterization (Chaubey & Kapoor, 2001), carboxymethylation (Rajput, Pandey, & Joshi, 2015) and cyanoethylation (Rajput, Pandey, Joshi, & Bisht, 2015) of CAG

∗ Corresponding author. E-mail address: gaurav [email protected] (G. Rajput). http://dx.doi.org/10.1016/j.carbpol.2015.10.044 0144-8617/© 2015 Elsevier Ltd. All rights reserved.

have been covered but no study has been done on carbamoylethylation of CAG. So, in this paper, we illustrate the results of our investigation into the optimization of the reaction conditions for carbamoylethylation of CAG. The extent of carbamoylethylation was determined in terms of the nitrogen content in the product. Further, not only the DS and reaction efficiency were calculated, but also rheology of the product was determined. FTIR was used as an evidence for the successful carbamoylethylation of CAG. 2. Material and methods 2.1. Materials 2.1.1. Plant seeds C. angustifolia seeds were obtained from M/S Sindhi Seeds corp., Dehradun Uttarakhand, India. 2.1.2. Chemicals Sodium hydroxide, acetic acid, hydrochloric acid, methanol were of LR grade (S.D. Fine-Chem. Ltd.), acrylamide (AR grade, Rankem, India) and distilled water. 2.2. Methods The experimental methods for the separation of galactomannan gum from the C. angustifolia seeds, along with its carbamoylethylation are briefly described as below.

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2.2.1. Extraction of CAG from the seeds of C. angustifolia Vahl The CAG was extracted from the C. angustifolia seeds as per the method reported by Soni and Pal (1996) for such gums in which the seeds were heated for few minutes in a hot air oven and the endosperm was isolated by removing seed coat and germ by impact grinding using high speed domestic grinder. Germ and seed coat from the endosperm were separated by sifting. Endosperm was tempered to 37.5% moisture by steam and flaked by passage through smooth roller. The flaked endosperm was made to flour C. angustifolia gum (100 mesh) using milcent flour mill. 2.2.2. Carbamoylethylation of C. angustifolia gum The carbamoylethylation of C. angustifolia gum was performed as follows. In a 500 ml stoppered conical flask equipped with magnetic stirring bar CAG (0.03 mol as AGU) was dispersed in aqueous alkaline (0.050–0.150 mol, NaOH) solution varying liquor/gum ratio (v/w; 20:1, 40:1, 60:1 and 80:1). After 15 min, acrylamide (0.03–0.150 mol) was added drop wise with continuous stirring. At this end the reaction is allowed to proceed for desired reaction temperature (20–60 ◦ C) and reaction time (60–240 min) the reaction mixture was cooled and neutralized with dil. acetic acid (1:1, v/v) and precipitated by pouring the reaction contents in the ethanol with stirring. The precipitated product was centrifuged, filtered and washed twice with aqueous methanol followed by pure methanol. The product was initially dried at room temperature and then in an electric oven at about 60 ± 2 ◦ C.

3.4. Evidence of cyanoethylation The infra-red (IR) spectra of CM-CAG was taken as KBr pellets using (JASCO FT/IR-5300) spectrophotometer in the range 650–4000 cm−1 . 4. Result and discussion Carbamoylethylation of CAG was carried out by reacting it with acrylamide in the presence of sodium hydroxide under a variety of conditions. The variables studied were concentrations of sodium hydroxide and acrylamide, gum–liquor ratio as well as temperature and duration of reaction. Like cyanoethylation, the carbamoylethylation reaction is a Michael-type, nucleophilic addition reaction may be depicted as in Eq. (1). El-Molla, Abdel Rahman, and Abd El-Thalouth (1998), Khalil, Bayazeed, Farag, and Hebeish (1987) and Moe, Miller, and Buckley (1952) have reported that along with carbamoylethylation following side reactions (Eqs. (2)–(6)) also occur and that their extent could be controlled by employing suitable reaction conditions. CAG-OH + CH2 CH CONH2 aq. NaOH

−→ CAG-O CH2 CH2 CONH2 . . .

CAG-O CH2 CH2 CONH2 NaOH

3. Analysis and measurements 3.1. Estimation of nitrogen content in carbamoylethyl-CAG

−→ CAG-O CH2 CH2 COO− Na+ + NH3 . . . NaOH

CH2 CH CONH2 −→ CH2 CH COO− Na+ + NH3 . . . NaOH

The estimation of the nitrogen content in the modified gum (i.e. carbamoylethyl C. angustifolia gum) was done by Kjeldhal’s method (Jeffery et al., 1989).

CH2 CH CONH2 + H2 O −→ HO CH2 CH2 CONH2 . . .

−→ H2 NOC CH2 CH2 O CH2 CH2 CONH2 . . .

The DS and RE were calculated by using following formulae: DS =

Mo × %N (MN × 100) − (MAM × %N)

RE =

N1 × 100% N2

where %N is the nitrogen content (in percent) in the modified gum (product), N1 is the weight of acrylamide reacted, N2 is the initial weight of acrylamide, Mo (=162) is the molecular weight of AGU (anhydro glucose unit), MAM (=71) is the molecular weight of acrylamide, MN (=14) is the molecular weight of nitrogen. 3.3. Determination of the rheological properties of carbamoylethyl-CAG The rheological properties were determined using Brookfield Digital Viscometer model “RVTD”, Stoughton, USA by utilizing Spindle-27 and varying shear rates from 2.5 to 25.0 s−1 at temperature 25 ± 1 ◦ C. The apparent viscosity () in centipoise (cps) was calculated by using formula. =

 S

where  is shear stress (Dyne/cm2 ), and; S is shear rate (s−1 ).

(2) (3) (4)

CH2 CH CONH2 + HO CH2 CH2 CONH2 NaOH

3.2. Calculation of degree of substitution (DS) and reaction efficiency (RE)

(1)

NaOH

CAG-O CH2 CH2 CONH2 −→ CAG-OH+CH2 CH CONH2 . . .

(5) (6)

The carbamoylethylation of CAG was optimized with respect to “nitrogen content and the DS” of the product (i.e. carbamoylethylated C. angustifolia seed gum, CE-CAG) and the observations recorded are shown graphically as in Fig. 1. 4.1. Effect of NaOH concentration on carbamoylethylation of CAG The effect of changing the NaOH concentration from 0.050 to 0.150 mol on the extent of carbamoylethylation of CAG (measured as nitrogen content, %N) under the following reaction conditions: 0.030 mol (as AGU) of CAG, and 0.075 mol of acrylamide and a liquor–gum ratio of 40:1 for duration of 60 min and at 60 ◦ C. The results are depicted in Table 1 and Fig. 1(a). From the results it was seen that up to 0.100 mol NaOH concentration, the extent of carbamoylethylation of CAG increases considerably as the concentration of NaOH is increased but decreases as concentration of NaOH exceeds 0.100 mol The increase in the extent of carbamoylethylation up to a NaOH concentration of 0.100 mol may be assigned to the following two desired functions of NaOH: (a) Swelling of CAG, and (b) Catalyzation reaction of NaOH by deprotonating CAG-OH that are prevailing more. Further, the decrease in the nitrogen content at concentrations of NaOH higher than 0.100 mol may be attributed to the undesired hydrolysis of amide groups in acrylamide and carbamoylethyl-CAG (Eqs. (2) and (3)) and the cleavage of the ether linkage in carbamoylethyl-CAG (Eq. (6)) that becomes more prominent at NaOH concentrations

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Fig. 1. Effect of different reaction parameters on the carbamoylethylation of CAG: (a) NaOH concentration; (b) acrylamide concentration; (c) reaction temperature; (d) reaction time; and (e) liquor/gum ratio. Table 1 Effect of variation of NaOH concentration on carbamoylethylation of CAG.

4.2. Effect of acrylamide (AM) concentrations on carbamoylethylation of CAG

Concentration of NaOH (mol)

Nitrogen content (%N)

DS

RE (%)

0.050 0.075 0.100 0.125 0.150

1.52 1.83 2.68 1.82 1.80

0.190 0.233 0.359 0.232 0.229

7.71 9.28 13.59 9.23 9.13

Reaction conditions: CAG concentration = 0.03 mol (as AGU), acrylamide concentration = 0.075 mol, reaction temperature = 60 ◦ C, reaction time = 60 min, liquor/gum ratio = 40:1.

higher than 0.100 mol Similar, observations have been reported in literatures by El-Molla et al. (1998), Sharma, Kumar, and Soni (2003), and Sharma, Kumar, and Soni (2004).

The effect of changing the acrylamide concentration from 0.030 to 0.120 mol on the extent of carbamoylethylation of CAG under the following reaction conditions: 0.030 mol (as AGU) of CAG, and 0.100 mol of NaOH concentration and a liquor–gum ratio of 40:1 for duration of 60 min and at 60 ◦ C. The results are depicted in Table 2 and Fig. 1(b). The result shows that the %N and DS increases predominantly as the acrylamide concentration is increased from 0.030 to 0.075 mol but decreases as the concentration is increased beyond 0.075 mol. The increase in the extent of carbamoylethylation of CAG may be attributed to the higher availability of acrylamide in the vicinity of the immobile hydroxyl groups of CAG. Further the decrease in the

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Table 2 Effect of variation of acrylamide concentration on carbamoylethylation of CAG.

Table 4 Effect of variation of reaction time on carbamoylethylation of CAG.

Acrylamide concentrations (mol)

Nitrogen content (%N)

DS

RE (%)

Reaction time (min)

Nitrogen content (%N)

DS

RE (%)

0.030 0.045 0.060 0.075 0.090 0.105 0.120

1.43 1.67 1.83 2.68 2.31 2.10 1.95

0.178 0.211 0.233 0.359 0.303 0.272 0.250

7.25 8.47 9.28 13.59 11.72 10.65 9.89

30 60 90 120 150

1.83 2.68 2.42 2.34 2.03

0.233 0.359 0.319 0.307 0.262

9.28 13.59 12.27 11.87 10.30

Reaction conditions: CAG concentration = 0.030 mol (as AGU), NaOH concentration = 0.100 mol, reaction temperature = 60 ◦ C, reaction time = 60 min, liquor/gum ratio = 40:1.

Table 3 Effect of variation of reaction temperature on carbamoylethylation of CAG.

Reaction conditions: CAG concentration = 0.03 mol (as AGU), acrylamide concentration = 0.075 mol, NaOH concentration = 0.100 mol, reaction temperature = 60 ◦ C, liquor/gum ratio = 40:1.

Table 5 Effect of variation of liquor/Gum ratio on carbamoylethylation of CAG. Liquor/gum ratio (ml/g)

Reaction temperature (◦ C)

Nitrogen content (%N)

DS

RE (%)

30 45 60 75 90

1.73 2.10 2.68 1.05 0.95

0.219 0.272 0.359 0.128 0.115

8.77 10.65 13.59 5.33 4.82

Reaction conditions: CAG concentration = 0.03 mol (as AGU), acrylamide concentration = 0.075 mol, NaOH concentration = 0.100 mol, reaction time = 60 min, liquor/gum ratio = 40:1.

%N on increasing the acrylamide concentration beyond 0.075 mol might be associated with conditions becoming favourable for the side reactions (Eqs. (3)–(5)) as a result of the less availability of the acrylamide for the carbamoylethylation of CAG. These observations are in compliance with the observations of Hebeish and Khalil (1988), Sharma et al. (2004) and El-Molla et al. (1998). 4.3. Effect of reaction temperature on carbamoylethylation of CAG The effect of changing reaction temperature from 30 to 90 ◦ C on the extent of carbamoylethylation of CAG under the following reaction conditions: 0.030 mol (as AGU) of CAG, and 0.075 mol of acrylonitrile, 0.100 mol of NaOH concentration and a liquor–gum ratio of 40:1 for duration of 60 min. The results are depicted in Table 3 and Fig. 1(c). From the above results it was seen that the %N increases from 1.73 to 2.68% as the reaction temperature is raised from 30 to 60 ◦ C. However, when the reaction temperature is increased beyond 60 ◦ C a significant lowering of %N is observed. The increment in the %N occurred on increasing the reaction temperature indicates that the carbamoylethylation reaction (Eq. (1)) prevails over the side reaction (Eqs. (2)–(6)). Further, the decrease on increasing the temperature above 60 ◦ C might be associated with conversion of CONH2 groups of acrylamide and carbamoylethyl-CAG (Eqs. (2) and (3)) and fission of the ether linkage in carbamoylethyl-CAG (Eq. (6)) occurring more predominantly. Similar observations have been

20:1 40:1 60:1 80:1

Nitrogen content (%)

DS

RE (%)

2.36 2.68 1.30 1.25

0.301 0.359 0.161 0.154

11.97 13.59 6.59 6.34

Reaction conditions: CAG concentration = 0.03 mol (as AGU), acrylamide concentration = 0.075, NaOH concentration = 0.100 mol, reaction temperature = 60 ◦ C, reaction time = 60 min.

reported in the works of Gupta, Sharma, and Soni (2005), Khalil, Beliakova, and Aly (2001), and Sharma et al. (2003). 4.4. Effect of reaction time on carbamoylethylation of CAG The effect of varying the reaction from 30 to 150 min on the extent of carbamoylethylation of CAG under the following reaction conditions: 0.030 mol (as AGU) of CAG, 0.100 mol of NaOH and 0.075 mol of acrylonitrile and a liquor–gum ratio of 40:1 at 60 ◦ C. The results are depicted in Table 4 and Fig. 1(d). From the results in Table 4, it is clearly seen that the extent of carbamoylethylation of CAG is time dependent. It was noticed that as the reaction time is increased from 30 to 60 min %N increases quite significantly from 1.83 to 2.68% suggesting that the carbamoylethylation of CAG (Eq. (1)) is favoured more under the reaction condition employed. However on further increasing the reaction time, lowering in the %N is seen. This decrease in the %N might be attributed to the side reaction represented by Eqs. (2) and (6) starts predominating over carbamoylethylation reaction (Eq. (1)). These observations are in agreement with observations reported in literatures (Khalil et al., 1987; Khalil et al., 2001). 4.5. Effect of liquor/gum ratio on carbamoylethylation of CAG The effect of changing the liquor/gum ratio from 20:1 to 80:1 on the extent of carbamoylethylation of CAG (measured as nitrogen content, %N) under the following reaction conditions: 0.030 mol (as AGU) of CAG, 0.100 mol of NaOH and 0.075 mol of acrylonitrile for duration of 60 min and at 60 ◦ C. The results are depicted in Table 5 and Fig. 1(e).

Table 6 Effect of shear rate and storage on apparent viscosity of 1% and 2% solutions of unmodified CAG sample and carbamoylethyl-CAG samples at 25 ± 1 ◦ C. Shear rates

Apparent viscosity () in centipoise at 25 ± 1 ◦ C, Spindle-27 Unmodified CAG 3h

2.5 5.0 12.5 25.0

Carbamoylethyl-CAG (%N = 6.36, DS = 0.969) 24 h

3h

1% solution

2% solution

1% solution

2% solution

240 210 165 150

270 220 170 155

Degradation

Degradation

24 h

48 h

72 h

1% solution

2% solution

1% solution

2% solution

1% solution

2% solution

22,300 20,100 13,600 8600

35,400 24,600 15,960 9860

23,400 20,870 14,250 9030

36,200 27,300 16,680 9910

21,700 19,800 13,170 8450

31,700 22,600 13,220 8600

1% solution

2% solution

2520 2130 1530 1370

4800 3650 3180 2400

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Fig. 2. IR spectra of: (a) unmodified CAG and (b) carbamoylethyl-CAG.

The results obtained shows that a maximum %N value of 2.68% is obtained at liquor/gum ratio of 40:1 which connotes the significance of the volume of liquor in the carbamoylethylation of CAG. At this liquor/gum ratio CAG swells significantly as consequence of which diffusion, absorption and effective collision of acrylamide

molecules in the vicinity of CAG is facilitated which in turn results in higher extent of carbamoylethylation of CAG. However, at higher liquor to gum ratios the chances of effective collision probability of the CAG and acrylamide reduces and side reactions depicted in Eqs. (2)–(6) are favoured more over the main reaction. Various similar

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studies in the related polysaccharides that have been reported are in support of our observations (Gupta et al., 2005; Sharma et al., 2004).

values. This provides a valid evidence of successful carbamoylethylation of CAG. 5. Conclusion

4.6. Rheological properties of carbamoylethyl-CAG To analyze any gum, hydrocolloids and/or their derivatives for their industrial viability and feasibility, viscosity assessment is generally considered as one of the parameter to judge the performance of the said gum(s) in a particular industry. So, in order to examine the potential of our modified CAG gum i.e. carbamoylethyl-CAG the 1% (w/v) and 2% (w/v) solutions of both the unmodified CAG as well as carbamoylethyl-CAG (optimized, %N = 2.68, DS = 0.359) were prepared and their rheological study via viscosity measurement were conducted. The results of the viscosity assessment obtained are shown in Table 6. The results in Table 6 clearly indicated that (a) Solutions of the carbamoylethyl-CAG are more viscous than the solutions of unmodified CAG prepared under similar conditions, (b) Solutions of the carbamoylethyl-CAG are highly stable in comparison to the solutions of unmodified CAG similar storage conditions, and (c) Both 1% and 2% solutions of the carbamoylethyl-CAG are characterized by a non-Newtonian pseudoplastic behaviour. These inferences are in agreement with the observations reported in literatures for the carbamoylethyl derivatives of other galactomannans like Cassia tora gum (Sharma et al., 2003), Guar gum (Sharma et al., 2004) and Cassia occidentalis seed gum (Gupta et al., 2005). 4.7. Evidence of carbamoylethylation FT/IR analysis has been utilized as an evidence of carbamoylethylation of CAG. For this purpose the IR spectra of unmodified CAG & carbamoylethyl-CAG were recorded in the range 4000–450 cm−1 with the help of Bruker tensor 27 spectrophotometer using KBr pellet. In the IR spectra of unmodified CAG (Fig. 2(a)) the presence of a strong and broad absorption band at 3400 cm−1 was due to OH stretching while the sharp absorption band at 2926 cm−1 attributed to CH stretching. The absorption band appearing at 1653 cm−1 was corresponding to the OH bond of water molecules (moisture). The absorption band at 1437 cm−1 belongs to CH2 group bending while the presence of strong peak 1024 cm−1 was observed due to the bending H2 C O CH2 bond. The peaks at 869 and 813 cm−1 were related with the presence of glycosidic linkages and anomeric configurations (␣- and ␤-conformers), attributed to two sugar units, respectively (Figueiro, Góes, Moreira, & Sombra, 2004; Prado, Kim, Özen, & Mauer, 2005; Rajput, Pandey, & Joshi, 2015; Rajput, Pandey, Joshi, & Bisht, 2015; Yuen, Choi, Phillips, & Ma, 2009). In the IR spectra of carbamoylethyl-CAG (Fig. 2(b)) shows an absorption band at 1669.39 cm−1 which is attributed to the amide I band of carbonyl stretching vibrations (Ren, Peng, & Sun, 2008) and a broad absorption band at 3434.68 cm−1 belonging to OH group stretching vibrations and symmetrical and asymmetrical N H stretching vibrations, which are merged with OH group stretching vibrations. The rest of the IR peaks absorbed at their respective

Carbamoylethylation of C. angustifolia seed gum was successfully performed with acrylamide using alkali (sodium hydroxide) as a catalyst. The optimum condition for preparing carbamoylethylCAG with maximum %N = 2.68% and DS = 0.359 with RE of 13.59% could be obtained employing following reaction conditions: 0.03 mol of CAG (as AGU, anhydro glucose unit), 0.100 mol NaOH, 0.075 mol acrylamide and liquor/gum ratio (v/w) of 40:1 at a reaction temperature of 60 ◦ C and reaction time of 60 min. Also, the rheological study revealed that the paste quality, cold water solubility and stability of 1% and 2% (w/v) solutions of carbamoylethyl-CAG was significantly more than that of the 1% and 2% solutions of unmodified CAG and that the solutions of carbamoylethyl-CAG showed non-Newtonian pseudoplastic behaviour. References Agarwal, V., & Bajpai, M. (2010). Pharmacognostical and biological studies on senna & its products: An overview. International Journal of Pharma and Bio Sciences, 1(2), 1–10. Chaubey, M., & Kapoor, V. P. (2001). Structure of a galactomannan from the seeds of Cassia angustifolia Vahl. Carbohydrate Research, 332(4), 439–444. El-Molla, M. M., Abdel Rahman, A. A., & Abd El-Thalouth, I. (1998). Chemical modification of Fenugreek gum. Part I: Carbamoylethylation. American Dyestuff Reporter, 87(9), 56–62. Figueiro, S. D., Góes, J. C., Moreira, R. A., & Sombra, A. S. B. (2004). On the physico-chemical and dielectric properties of glutaraldehyde crosslinked galactomannan-collagen films. Carbohydrate Polymers, 56(3), 313–320. Gupta, S., Sharma, P., & Soni, P. L. (2005). Chemical modification of Cassia occidentalis seed gum: Carbamoylethylation. Carbohydrate Polymers, 59(4), 501–506. Hebeish, A., & Khalil, M. I. (1988). Characterization of the reaction products for starch and acrylonitrile. Starch–Stärke, 40(3), 104–107. Jeffery, G. H., Bassett, J., Mendham, J., & Denney, R. C. (1989). Vogel’s textbook of quantitative chemical analysis (5th ed., pp. 302–303). Essex: Addison Wesley Longman Limited. Khalil, M. I., Bayazeed, A., Farag, S., & Hebeish, A. (1987). Chemical modification of starch via reaction with acrylamide. Starch–Stärke, 39(9), 311–318. Khalil, M. I., Beliakova, M. K., & Aly, A. A. (2001). Preparation of some starch ethers using the semi-dry state process. Carbohydrate Polymers, 46(3), 217–226. Moe, O. A., Miller, S. E., & Buckley, M. I. (1952). Investigation of the reserve carbohydrates of leguminous seeds. II. Derivatives. Journal of the American Chemical Society, 74(5), 1325–1327. Prado, B. M., Kim, S., Özen, B. F., & Mauer, L. J. (2005). Differentiation of carbohydrate gums and mixtures using Fourier transform infrared spectroscopy and chemometrics. Journal of Agricultural and Food Chemistry, 53(8), 2823–2829. Rajput, G., Pandey, I. P., & Joshi, G. (2015). Carboxymethylation of Cassia angustifolia seed gum: Synthesis and rheological study. Carbohydrate Polymers, 117, 494–500. Rajput, G., Pandey, I. P., Joshi, G., & Bisht, S. S. (2015). Cyanoethylation of Cassia angustifolia seed gum in aqueous medium. Journal of the Indian Academy of Wood Science, 12(1), 1–8. Rana, V., Rai, P., Tiwary, A. K., Singh, R. S., Kennedy, J. F., & Knill, C. J. (2011). Modified gums: Approaches and applications in drug delivery. Carbohydrate Polymers, 83(3), 1031–1047. Ren, J. L., Peng, F., & Sun, R. C. (2008). Preparation and characterization of hemicellulosic derivatives containing carbamoylethyl and carboxyethyl groups. Carbohydrate Research, 343(16), 2776–2782. Sharma, B. R., Kumar, V., & Soni, P. L. (2003). Carbamoylethylation of Cassia tora gum. Carbohydrate Polymers, 54(2), 143–147. Sharma, B. R., Kumar, V., & Soni, P. L. (2004). Carbamoylethylation of guar gum. Carbohydrate Polymers, 58(4), 449–453. Soni, P. L., & Pal, R. (1996). Industrial gum from Cassia tora seeds. Trends in Carbohydrate Chemistry, 2, 33–44. Yuen, S. N., Choi, S. M., Phillips, D. L., & Ma, C. Y. (2009). Raman and FTIR spectroscopic study of carboxymethylated non-starch polysaccharides. Food Chemistry, 114(3), 1091–1098.