







































Highlights in Bioscience;


 
Highlights in BioScience             

ISSN: 2682-4043 

DOI:10.36462/H.BioSci.20206                                                                                                          
 

 

Highlights in BioScience                                                                                                                                                                           June 2020| Volume 3 

http://bioscience.highlightsin.org/ 

Page 1 of 4 

                                               

 

Research Article 

 

 

Open Access 

 
 

 

 

 

 

1Chemistry Department, College of Science, 

Sudan University of Science and Technology, 

Sudan. 

 

 

Contacts of Authors  

 

 

* To whom correspondence should be 

addressed: Mohammed Sulieman Ali 

Eltoum 

 

 

Citation: Eltoum M S A, Elfaki A A M (2020). 

Extraction, characterization, and usage of 

Turmeric Curcumin for color coating of 

metronidazole tablets. Highlights in BioScience 

Volume 3. Article ID 20206. dio:10.36462/ 

H.BioSci.20206 

 

Received:  May 20, 2020 

 

Accepted:  June 27, 2020 

 

Published: June 30, 2020 

 
 

Copyright: © 2020 Eltoum and Elfaki .This is 

an open access article distributed under the 

terms of the Creative Commons Attribution 

License, which permits unrestricted use, 

distribution, and reproduction in any medium, 

provided the original author and source are 

credited. 

 

 

Data Availability Statement: All relevant data 

are within the paper and supplementary 

materials 

 

 

Funding: The authors have no support or 

funding to report. 

 

 

Competing interests: The authors declare that 

they have no competing interests. 

 

 

 

Extraction, Characterization, and Usage of Turmeric 

Curcumin for Color Coating of Metronidazole Tablets 

 
Mohammed Sulieman Ali Eltoum*

1
, ALMustafa Ahmed Mohamed Elfaki

1
 

 

Abstract 

      Curcumin is a chemical compound produced by Curcuma longa 

plants that is widely used as a coloring agent and a dietary supplement 

and has some therapeutic activity. Our aim is to evaluate the use of 

curcumin as color coating material for metronidazole tablets. Curcumin 

was extracted at higher yields from three different samples of turmeric 

plants. The extract obtained was characterized by Infrared Red 

Spectroscopy (IR), Thin Layer Chromatography (TLC) and ash content 

and melting point (MP). The curcumin produced has an MP content 

ranging from 182 ° C to 184 ° C and an ash content ranging from 1.5 to 

3.17 %. Curcumin material was used as a colorful agent for the coating of 

metronidazole tablet pills using spray coating technology. Experimental 

results have shown that curcumin-coated metronidazole tablets exhibit 

strong color stability even at higher temperatures, and that the taste of 

bitterness in metronidazole pills has been reduced or has disappeared 

entirely.   

 

Keywords: Curcumin, Turmeric, Color-coating, Metronidazole tablets, 

Pharmaceutical.  

 

Introduction  

Scientific research on color chemistry is needed to improve and maintain 

color stability. Natural coloring additives are generally considered to be coloring 

additives derived from plant or animal sources by extraction or other physical 

processing[1,2]. Examples of natural colorants include carmine, annatto extract, 

grape skin extract, turmeric, saffron and beta-carotene, which are the major 

natural color additives used in food products. Synthetic coloring additives include 

chemically synthesized substances such as tartrazine, erythrosine and indigo 

carmine. Natural or vegetable colors are less in use because they are expensive or 

difficult to extract [1, 2]. Curcumin (synonyms: turmeric yellow, kurkum, INS 

No. 100(i)) is an orange-yellow crystalline powder.  

The standards of the Joint Expert Committee on Food Additives (JECFA) 

define only curcumin extracted from natural source materials. It may also be 

produced by chemical synthesis, which is not used as a food additive [3]. The 

chemical structure of curcumin is shown in Figure 1. The yellow coloring 

components (curcuminoids) and the primary coloring pigment are curcumin 

(CurI), along with two additional minor curcuminoids, demethoxycurcumin 

(CurII) and bisdemethoxycurcumin (CurIII), which are the key active constituents 

of the turmeric (Figure 2). Curcumin is a major secondary metabolite of the 

perennial Asian plant turmeric (Curcuma longa L). Curcumin was identified as 

the active principle of turmeric in 1815 and its structure was determined after 

crystallization in 1870 [4]. Turmeric is only one representative of more than 80 

species of turmeric in the ginger family, Zingiberaceae [5].



 

 

Eltoum M S A, Elfaki A A M. 2020                                                                               Usage of Turmeric Curcumin for color coating of metronidazole tablets 

 

 

Highlights in BioScience                                                                                                                                                                           June 2020| Volume 3 

http://bioscience.highlightsin.org/ 

Page 2 of 4 

 

 

Figure 1:  The chemical structure of curcumin. 

 

 

 

 

 

 

Figure 2: Structure of the minor curcuminoids. 

 

Turmeric is widely cultivated in many Asian countries, 

particularly India, where it is mainly grown for dietary use 

and is a major component of the spice curry. In addition, 

turmeric is recognized for its medicinal properties and has 

been used for centuries in the treatment of a variety of 

diseases including eczema, arthritis, ulcers, asthma, anemia 

and many others [6]. As a result of extensive studies over 

the last few decades, curcumin has emerged as a promising 

anti-cancer agent and has been shown to target multiple and 

diverse pathways of disease causation and progression [4]. 

The attractiveness of curcumin as a therapeutic agent is 

enhanced by its safety, affordability, and history of long-

term use [7]. Molecular formula of C21H20O6, 

corresponding to a molecular weight of 368.37.  

Curcumin is a yellow-orange crystalline powder with 

maximum absorbance at430 nm and melting point of 183 °C 

[6]. Curcumin exhibits hydrophobic and (slight) hydrophilic 

properties owing to its aliphatic heptadienone linker and 

polar β-dicarbonyl and phenolic groups, respectively [8].  

Curcumin is sparingly soluble in water, but shows greater 

solubility in some organic solvents such as acetone, ethyl 

acetate, acetonitrile and ethanol. Its reported partition 

coefficient (Log P) ranges from 2.5 to 3.3 [9]. Curcumin is a 

bis-α,β-unsaturated β- diketone and exists in equilibrium 

with its enol tautomer [10]. Studies involving 1H, C NMR, 

and infrared spectroscopy have shown that the enolate form 

predominates in alkaline solution [11].  

No previous literature has introduced the use of 

curcumin as a color coating for metronidazole tablets. The 

aim of this study is to extract and characterize curcumin 

obtained from the turmeric plant using different analytical 

techniques and to evaluate the use of turmeric powder as a 

coating material for metronidazole tablets. In addition, we 
studied the effect of this coat material on some of the 

properties of the metronidazole tables. 

 

Materials and Methods 

Turmeric samples were collated from Sudanese local 

market. 

Curcumin extraction: Twenty grams of ground turmeric in 

50 mL of dichloromethane was magnetically stirred and 

heated at the reflux condenser for 1 h. The mixture was then 

suction-filtered and the filtrate was concentrated in a hot 

water bath maintained at 50°C. The reddish yellow oily 

residue was treated with 20 ml hexane and the resulting 

solid was collected by suction filtration [3]. The obtained 

yield was calculated as follow: Yield = Wpr/WtheoX100 

Where:  Wpr = practical weight, Wtheo = theoretical weight 

 

Fourier Transform Infrared Spectroscopy (FT –I R): 

Two milligrams of curcumin were mixed with 300 mg of 

dried potassium bromide. Carefully, the mixture was 

grinded, spread evenly in an appropriate die and subjected 

to a pressure of approximately 800 MPa (8 t·cm
-2

). In the 

case of substances that were unstable under normal 

atmospheric conditions, the disc was pressed into a vacuum.  

A disc was rejected if visual examination had been show 

lack of uniform transparency or when transmittance at 2000 

cm
-1

 (5 µm) in the absence of a specific absorption band was 

less than 60 per cent without compensation, unless otherwise 

prescribed. Samples were prepared by the same procedure 

and the spectrum was recorded between 4000- 400 cm
-1 

(2.5-15.4 µm) under the same operational conditions. The 

transmission minima (absorption maxima) in the spectrum 

was obtained with the substance to be examined correspond 

in position and relative size to those in the spectrum 

obtained with the reference substance [12]. 

 

Thin Layer Chromatography (TLC): The solvent system 

which was used to characterize of curcumin powder was 

prepared by mixed of (3% methanol and 97% 

dichloromethane). The diameter of TLC plate had 10X20 

cm
2
 [3]. 

 

Melting point (MP): A sufficient quantity of curcumin was 

introduced into the capillary tube to give a compact column 

of 4 mm to 6 mm in height. The temperature of the bath was 

increased to about 10°C below the assumed melting point 

and the heating rate was adjusted to about 1° C/min. When 

the temperature was 5°C below the assumed melting point, 

the capillary tube was introduced into the instrument. In the 

case of the apparatus described above, the capillary tube was 

immersed in such a way that the closed end is near the 

center of the thermometer bulb, the immersion mark of 

which is at the surface level of the liquid. The temperature at 

which the last particle was transferred to the liquid phase 

was recorded [12]. 

 



 

 

Eltoum M S A, Elfaki A A M. 2020                                                                               Usage of Turmeric Curcumin for color coating of metronidazole tablets 

 

 

Highlights in BioScience                                                                                                                                                                           June 2020| Volume 3 

http://bioscience.highlightsin.org/ 

Page 3 of 4 

Ash content: The porcelain crucible was ignited at 600 ± 50 

°C for 30 min and then allowed to cool over the silica gel in 

the desiccators. The prescribed amount of curcumin was 

placed in the crucible and weighed, after it had been gently 

heated to low temperatures as practicable, until the sample 

had been thoroughly charred, until white fumes had ceased 

to develop and ignited at 600 ± 50 °C until the residue had 

been completely incinerated. The crucible was allowed to 

cool over the silica gel in the desiccator, was weighed again 

and the percentage yield was calculated [12]. 

 

Percentage of whiteness: The sample powder was placed 

in dishes, regularly highlighted and then the color was 

measured against the white color standard and the 

percentage was finally recorded. 

 

Coating of metronidazole tablets with curcumin: A total 

of 25 g of Opadry white was dissolved in 500 ml of ethanol 

with stirring during 30 min. and 1 g of curcumin powder was 

added during 10 min. The spray coating process for 

metronidazole tablets began by placing the tablets in the 

coating machine chamber, and then the main unit button was 

pressed.The exhaust was operated until the powder was 

removed from the tablets and the hot air was operated until 

the temperature of the tablet reached 50°C. The temperature 

control key was operated with hot air to control the 

temperature of the coating. The spray stage was then 

operated, and the turn sprayers were opened until the tablets 

were completely coated. And after coating, the other keys 

were turned off until the tablets had dried. The coating 

machine was stopped; the tablets were removed [12]. 

Results and Discussion 

The turmeric plant can be identified both by its 

characteristic tuberous root and by the leaves which 

extend upward from the erect, thick stems of the root. 

Turmeric root has a fragrant aroma and a slightly bitter, 

peppery, biting taste reminiscent of ginger. When eaten, it 

colors the saliva yellow and leaves a warm feeling in the 

mouth. The curcumin yields obtained for the different 

samples are shown in Table 1 and the resulting compounds 

were finely soft, clear yellow powder. The yield of the 

samples was consistent with the method described by 

Andrew et al, [3], and the appearance of the powder was as 

clear as the standard colour. 

 

Table 1: The Curcumin yield (CY), Melting point (MP), 

Ash Content (AC) and Percentage of Whiteness (PW) of the 

studied tumeric samples. 

Figures 3 show the absorption of samples. These Figures 

contain the following characteristic peaks: the broad band of 

the three OH groups at 3250-3500 cm
−1

, sharp peak Stretch 

of C- H aliphatic system less than 3000cm
−1

, weak peak of 

C-H aromatic system around 3050cm, sharp peak of C═O at 

1510 cm
−1

, medium peak of C-O at 1300cm
−1

, and sharp 

peak of C=C of aromatic system at about 1510cm
−1

. Figure 

4 shows the TLC plate of the compound. The chromatogram 

obtained showed that curcumin was divided into three 

distinct compounds. Clearly, this result is in agreement with 

Andrew et al., [3]. 

 

Figure 3: IR spectrum analysis results of curcumin for 

samples 1 (A), 2 (B) and 3 (C). 

Figure 4: TLC of curcumin sample. 

The melting point determined by the capillary method 

and it is the temperature at which the last solid particle of a 

compact column of a substance in a tube passes into the 

liquid phase. The results of the three samples are shown in 

Table 1. The melting point of curcumin is 183°C 

(BP2012)[12]. The ash content obtained of the samples 

ranges from 1.5 to 3.17 % (Table 1). In summary, from the 

three samples above, the percentage of Ash in curcumin was 

good. The percentage of whiteness of the three samples 

obtained ranges from 51.08% to 53.03% (Table 1).  

Coated tablets are tablets containing one or more layers of 

mixtures of different substances, such as natural or synthetic 

resins, gums, gelatin, inactive and insoluble fillers, sugars, 

plasticizers, polyols and waxes. Coloring matter authorized 

by the competent authority and sometimes flavorings and 

Samples 

Number 

CY MP AC PW 

1 86.36% 183°C 1.50% 52.04% 

2 81.81% 184°C 3.09% 53.03% 

3 82.72% 182°C 3.17% 51.08% 



 

 

Eltoum M S A, Elfaki A A M. 2020                                                                               Usage of Turmeric Curcumin for color coating of metronidazole tablets 

 

 

Highlights in BioScience                                                                                                                                                                           June 2020| Volume 3 

http://bioscience.highlightsin.org/ 

Page 4 of 4 

active substances. The mean weight and disintegration time 

of metronidazole tablets prior to coating with curcumin was 

323.0 mg and 23 sec and 22 sec respectively. However, the 

average weight and disintegration time after coating was 

324.74 mg and 120 sec, 93 sec and 114 sec respectively 

(Figure 5). 

 
Figure 5: Metronidazole tablets before (A) and after 

blistering. 

Conclusion 

The primary purpose of the study in this study is to 

study the isolation of curcumin from turmeric and also to 

characterize curcumin as a color-coating martial for 

metronidazole tablet in pharmaceuticals. Curcumin was 

extracted from the turmeric in a simple and easy way using 

dichloromethane and triturated with hexane, and the 

extraction yield was finely soft yellow powder. 

Experimental results have shown that curcumin-coated 

metronidazole tablets exhibit strong color stability even at 

higher temperatures, and that the taste of bitterness in 

metronidazole pills has been reduced or has disappeared 

entirely. 

Acknowledgments  

We would like to thank the Climax Factory for the 

Drugs and Medicines Industry-Khartoum for giving us the 

opportunity to carry out the practical work of this research 

in their different laboratories, and we would also like to 

thank the Sudan University of Science for accepting this 

work as part of the complementary research on the 

requirements of the M.Sc. in Chemistry [13]. 

References  

1. Allen L, Ansel HC. Ansel's pharmaceutical dosage forms 

and drug delivery systems. Lippincott Williams & 

Wilkins; 2013 Dec 23. 

2. Carter SJ. Cooper and Gunn's Dispensing for 

Pharmaceutical Students (12th Edn) Publisher. 47-50 

3. Anderson AM, Mitchell MS, Mohan RS. Isolation of 

curcumin from turmeric. Journal of chemical education. 

2000 Mar;77(3):359 

4. Aggarwal BB, Harikumar KB. Potential therapeutic 

effects of curcumin, the anti-inflammatory agent, against 

neurodegenerative, cardiovascular, pulmonary, metabolic, 

autoimmune and neoplastic diseases. The international 

journal of biochemistry & cell biology. 2009 Jan 1; 41(1): 

40-59. 

5. Leong-Škorničková J, Šída O, Jarolímová V, Sabu M, Fér 

T, Trávníček P, Suda J. Chromosome numbers and 

genome size variation in Indian species of Curcuma 

(Zingiberaceae). Annals of Botany. 2007 Sep 1; 100 (3): 

505-26. 

6. Goel A, Kunnumakkara AB, Aggarwal BB. Curcumin as 

“Curecumin”: from kitchen to clinic. Biochemical 

pharmacology. 2008 Feb 15; 75 (4):787-809. 

7. Chandran B, Goel A. A randomized, pilot study to assess 

the efficacy and safety of curcumin in patients with active 

rheumatoid arthritis. Phytotherapy research. 2012 Nov; 26 

(11):1719-25. 

8. Balasubramanian K. Molecular orbital basis for yellow 

curry spice curcumin's prevention of Alzheimer's disease. 

Journal of agricultural and food chemistry. 2006 May 17; 

54 (10):3512-20. 

9. Grynkiewicz G, Ślifirski P. Curcumin and curcuminoids 

in quest for medicinal status. Acta Biochimica Polonica. 

2012 May 14; 59 (2). 

10. Chignell CF, Bilskj P, Reszka KJ, Motten AG, Sik RH, 

Dahl TA. Spectral and photochemical properties of 

curcumin. Photochemistry and photobiology. 1994 Mar; 

59(3):295-302. 

11. Sun YM, Wang RX, Yuan SL, Lin XJ, Liu CB. 

Theoretical study on the antioxidant activity of curcumin. 

Chinese Journal of Chemistry. 2004 Aug; 22(8):827-30. 

12. BP. The British pharmacopoeia 2012. 

13. http://repository.sustech.edu/handle/123456789/13398?sh

ow=full 

 

 

 

 

 

 

 

 

  


