Naphthoquinone colorants from Arnebia nobilis Rech.f

Naphthoquinone colorants from Arnebianobilis Rech.f

Anjali Arora,a,* Deepti Gupta,b Deepali Rastogia

and Mohan Gulrajanib

aDepartment of Fabric and Apparel Science, Lady Irwin College, Delhi University, NewDelhi 110001, IndiaEmail: [email protected]

bDepartment of Textile Technology, Indian Institute of Technology, Hauz Khas, New Delhi

110016, India

Received: 12 May 2010; Accepted: 16 December 2011

The roots of Arnebia nobilis have traditionally been used as a colorant in food and cosmeticpreparations. The deep red colour obtained is attributed to the presence of shikonin and its isomeralkannin and their derivatives. In this study, five colouring components were extracted from the roots ofA. nobilis. These were separated and purified chromatographically and characterised using variousspectrophotometric techniques. Three of the five components were identified. The major component wasfound to be alkannin b, b-dimethylacrylate [5,8-dihydroxy-2-(1¢-b, b-dimethylacryloxy-4¢-methylpent-3¢-enyl)-1,4-naphthoquinone], accounting for nearly 25% of the total colouring matter. Alkannin acetate[2-(1¢-acetoxy-4¢-methylpent-3¢-enyl)-5,8-dihydroxy-1,4-naphthoquinone] made up ca. 8% and shikonin[(5,8-dihydroxy-4¢-methylpent-3¢-enyl)-1,4-naphthoquinone] contributed ca. 6% of the colouring matter.Polyester was dyed pink, nylon was dyed blue and all other substrates acquired a purple hue undersimilar dyeing conditions. The dyed fabrics showed excellent wash, rub and perspiration fastness;however, light fastness was found to be poor.

IntroductionNaphthoquinones constitute a structurally diverse class of

phenolic compounds with wide applications in the fields of

pharmacy and medicine [1]. Pharmacological studies have

shown that these have anti-inflammatory, antibacterial,

anti-fungal, antiviral and anti-tumor properties [2,3]. There

is also a long history of utilisation of naphthoquinones as

strongly coloured pigments in food and cosmetics [4].

Cosmetics made with these pigments have the advantages

of strong, stable colouring properties in addition to being

antibacterial and antiviral. Light absorption by

naphthoquinone dyes depends on their skeleton and is

strongly influenced by the presence of various substituents.

The introduction of a substituent, especially a free or

methylated hydroxyl group, may bring about a

bathochromic shift (shift to the red end) of the absorption

band [5]. Naphthoquinone pigments demonstrate variable

colours as a result of change in pH [6].

Some investigations have been reported on the dyeing

of textiles with natural quinonoid dyes. Two

naphthoquinone-based isomeric dyes; lawsone (CI

no. 75480) and juglone (CI no. 75500) (2-hydroxy and 5-

hydroxy naphthoquinone, respectively) were found to

have remarkable substantivity for both hydrophilic and

hydrophobic fibres (wool, human hair, silk, nylon and

polyester). Both these colorants are also used as a

colouring agent in hair-colouring formulations [5–9].

Red colorants based on the anthraquinone molecule

have been separated, purified and characterised from the

roots of Rubia cordifolia (Indian madder). Dyeing studies

conducted with the purified components showed that the

dye had structural characteristics similar to those of

disperse dyes and the dye gave clear and deep shades on

hydrophobic fibres – nylon and polyester [10,11].

Another source of natural red colorant based on a

naphthoquinone molecule is Arnebia nobilis Rech.f.,

commonly known as ‘Ratanjot’ in India. This plant is a

source of enantiomeric naphthoquinones, shikonin (CI

no. 75535) and alkannin (CI no. 75530) and their

isohexenylnaphthazarin derivatives. Biological investi-

gations over the last decades have proved these colorants

to be potent pharmaceutical substances with a well-

established and wide spectrum of medicinal properties

[12–23]. The colour-yielding property and therapeutic

efficacy of this plant is attributed to the presence of these

napthoquinones [17]. Earlier studies have shown that dye

extracted from Ratanjot yields deep and fast colours on

nylon and polyester fibres [24,25].

Despite this dye being so well known for its brilliant red

colour, it was found that limited work has been reported in

the literature on the systematic investigation of this dye. As

the structural features of the dyes are responsible for their

colour and dyeing properties, it is of interest to understand

and structurally identify the colorants. In this study, the

processes for extraction and separation of these naphtho-

quinones reported in the literature were used[18,20,21,26–

32,34–36]; however, none of these yielded the purified

colorants. Therefore, extraction, separation, chromatographic

purification and spectroscopic characterisation of the major

coloured constituents of the root were undertaken here.

Different textile substrates have been dyed with the dye

extract and assessed for their colour value.

ExperimentalMaterials

Dried root material of A. nobilis Rech.f. was procured from

Nature and Nurture Healthcare Pvt Ltd (India). Taxonomic

doi: 10.1111/j.1478-4408.2012.00383.x

ª 2012 The Authors. Coloration Technology ª 2012 Society of Dyers and Colourists, Color. Technol., 128, 1–6 1

ColorationTechnology

Society of Dyers and Colourists

identification was carried out by the National Institute of

Science Communication and Information Resources

(NISCAIR) at the Indian Council of Agricultural Research

(ICAR). The chemical reference substance, shikonin (S,

517-89-5), isolated from Lithospermum erythrorhizon, was

procured from Merck (USA).

Analytical grade n-hexane and ethyl acetate (Qualigens,

India) were used. High-performance liquid chroma-

tography (HPLC) grade acetonitrile and water (Rankem,

India) was used for HPLC analysis. All solvents were

filtered through a 0.22-lm membrane filter prior to use.

For the dyeing, polyester (74 g ⁄ m2, warp 98 epi, weft

74 ppi), nylon (68 g ⁄ m2, warp 144 epi, weft 84 ppi), silk

(42.9 g ⁄ m2, warp 116 epi, weft 74 ppi), wool (179.9 g ⁄ m2,

warp 66 epi, weft 60 ppi) and cotton (122.6 g ⁄ m2, warp

104 epi, weft 86 ppi) were used. Acrylic yarn with a

radius of 0.001175 cm, measured using a Leica

microscope, was used. A high-temperature, high-pressure

beaker dyeing machine (R B Electronic and Engineering

Pvt. Ltd, India) was used to carry out all dyeing studies.

Colorimetric measurements of the dyed samples were

performed on a Color-Eye 7000A computer colour-

matching system (Gretag Macbeth, USA).

For thin-layer chromatography (TLC), Kieselgel 60 F254

silica gel pre-coated plates were procured from Merck. A

glass column (600 · 250 mm internal diameter) was used

for preparative column chromatography with silica gel of

mesh size (60–120) (Qualigens, India) as the adsorbent.

Methods

Extraction of colorants

The roots of A. nobilis were ground to a coarse powder

and extracted in a single cycle lasting 8.5 h using n-

hexane in a Soxhlet apparatus (Scientific Glass Creations,

India). A deep red viscous residue amounting to ca. 5%

on the dry weight basis of the roots was obtained after

evaporation of the solvent. This residue contains a

mixture of colouring compounds.

Chromatographic separation of colorants

Solvent systems comprising of benzene, chloroform,

methanol, n-hexane, acetone and ethyl acetate, and their

respective mixtures, were used for separation of

components of A. nobilis through TLC analysis

[17,18,20,26–31].

The optimised solvent system obtained from the TLC

analysis was used for preparative column

chromatography. The ratio of crude dye to silica gel in

the column was 1:300 (w ⁄ w). Purity of the eluted

fractions was determined by TLC analysis. The

percentage quantity of each component obtained through

the column was estimated in grams of component

obtained ⁄ grams of dye · 100.

Crude extract, purified components and the standard

were submitted for HPLC analysis using water (H2O,

eluent A) and acetonitrile (eluent B). The eluent was fed at

a rate of 1.00 ml ⁄ min and component samples were

introduced in the form of solution in water:acetonitrile

(25:75 v ⁄ v) at a concentration of 100 ppm.

Chromatographic analysis was carried out using the linear

gradient shown in Table 1. The column temperature was

set at ambient and the injection volume was 20 ll.

Characterisation of separated colorants

High-performance liquid chromatography was performed

on a 200-series (PerkinElmer Inc., USA) HPLC system

equipped with a vacuum degasser, a binary pump fitted

with a 20-ll sample loop and an ultraviolet–visible (UV–

vis) detector. The chromatographic system was controlled

by the TCNav chromatography data system (PerkinElmer,

USA). Chromatographic separations of the coloured

compounds were achieved on a reverse-phase Microsorb

C18 column (150 · 3.9 mm i.d., 4 lm particle) (Waters,

USA).

UV–vis spectra of the isolated components were

recorded in n-hexane. Structures of the coloured

naphthoquinones were confirmed by Fourier Transform–

infrared (FTIR) and proton nuclear magnetic resonance

(1H-NMR) spectroscopy. UV–visible spectra were recorded

in n-hexane on a Lambda 25 spectrometer (PerkinElmer

Inc.). FTIR spectra were recorded on a BX FTIR spectro-

photometer (PerkinElmer Inc.) using potassium bromide

(KBr) discs. 1H-NMR spectra were measured on a Spectro-

spin 300 machine (Bruker, India) in CDCl3 at 300 MHz

using trimethylsilane (TMS) as an internal standard.

Fabric preparation

Fabrics were thoroughly scoured using a solution of 1 gpl

nonionic detergent (Lissapol N) for 1 h at 100 �C for

polyester, at 90 �C for nylon, silk, cotton and acrylic, and

at 50 �C for wool. The material ⁄ liquor ratio was kept as

1:30. This was followed by repeated rinsing in hot and

cold water followed by drying at room temperature.

Dyeing studies

Different substrates were dyed with crude dye extract at a

pH value of 4.5 (adjusted with sodium acetate buffer) and

a liquor ⁄ goods ratio of 30:1. The substrates were dyed

with 0.5% (owf) shade for 60 min. Polyester was dyed at

100 and 130 �C. Cotton, nylon, wool, silk and acrylic

were dyed at 80 �C. The dyed samples were then cold

rinsed and soaped with 0.5 gpl Lissapol N for 20 min

followed by rinsing.

Determination of depth of shade

The depth of shade was determined in terms of K ⁄ Svalues calculated from reflectance data according to the

Kubelka–Munk equation:

K=S ¼ ð1� RÞ2=2R

where K is the absorption coefficient, S is the scattering

coefficient and R is the reflectance of the dyed fabric at

the wavelength of maximum absorption.

Fastness tests

For assessing the fastness to light, washing, rubbing and

perspiration, fabrics were dyed at pH 4.5 with 0.5% (owf)

Table 1 Parameters for gradient elution

Time (min) % H2O % acetonitrile Flow rate (ml min)1)

0.5 80 20 1.0030 0 100 1.00

Arora et al. Naphthoquinone colorants from Arnebia nobilis

2 ª 2012 The Authors. Coloration Technology ª 2012 Society of Dyers and Colourists, Color. Technol., 128, 1–6

shade. Light fastness was assessed in accordance with

AATCC 16-2004 on a Xenotest Alpha High Energy light

fastness tester (SDL Atlas, USA). Colour fastness to

washing was assessed in a Launder-O-Meter (R B

Electronic and Engineering Pvt. Ltd, India) in accordance

with the method prescribed in ISO: 3361-1984 (ISO-II)

[38]. Colour fastness to rubbing was assessed on a

crockmeter as per AATCC 8-2007. Colour fastness to

perspiration was assessed on a perspirometer in

accordance with the method prescribed in AATCC 15-

2007.

Results and DiscussionChromatographic analysis

TLC and column chromatography

Different solvent systems were tried, but the best

separation of components of n-hexane-extracted dye was

obtained with an n-hexane:ethyl acetate (80:20 v ⁄ v)

mixture by TLC analysis. Five spots (A–E) bluish–red in

colour were observed at Rf values of 0.98, 0.93, 0.77, 0.5

and 0.21, respectively. It was observed that component B

formed the major colorant in the extract. Components A

and E are present in very small amounts. It was observed

that each component spot was followed by a tail and a

distinct spot could not be obtained for these colorants by

TLC. This may be because all the naphthoquinone

colorants are very similar in structure and hence could

not be separated until a high level of purity was reached.

The Rf value of component D (0.5) was found to match

that of a standard sample of shikonin. When benzene

(C6H6) was used as the mobile phase, the Rf value of

component B was found to be 0.80 and that of

component C was found to be 0.56. These values

correspond to values reported for alkannin b, b-

dimethylacrylate and alkannin acetate, respectively, by

Shukla et al. [26]. Alkannin b, b-dimethylacrylate and

alkannin acetate have also been confirmed for their

activity against Walker carcinosarcoma in rats [26].

Hence, three of the major components could be identified

from the TLC analysis. The structures of these

components are depicted in Figure 1.

Although components B and C could be identified after

employing benzene as the mobile phase, it was found

that better separation was obtained on n-hexane:ethyl

acetate (80:20 v ⁄ v) as compared with benzene. Moreover,

only four components could be identified using benzene

as compared with five components in the case of n-

hexane:ethyl acetate (80:20 v ⁄ v) as the solvent system.

Therefore, n-hexane:ethyl acetate (80:20 v ⁄ v) was

optimised as the solvent system for further analysis.

The components were further purified through

preparative columns over silica gel. Findings from the

analysis are summarised in Table 2. It was found that

component B, the most abundant colorant in the extract

of Arnebia roots, constitutes almost 25% of the total dye

extract, followed by component C which constituted

ca. 8% of the dye extract. An interesting finding was that

shikonin (component D) made up a very small fraction of

the colouring matter (ca. 6%). It must be noted that the

percentage of contents given for the three principal

components (25, 8 and 6%) are only rough estimates,

because two processes have been employed that may

have distorted the figures (hexane extraction; column

chromatographic separation). A different extraction

technique and variations in chromatography may give

other figures.

It is also interesting to note that different amounts of

these naphthoquinones have been reported to be present

in A. nobilis. Shukla et al. [26] extracted the dye with n-

hexane and separated alkannin b, b-dimethylacrylate and

alkannin acetate to the extent of 15 and 3%, respectively

in A. nobilis using hexane–benzene (3:1 and 1:1,

respectively) as the solvent system. Much smaller

amounts of alkannin b, b-dimethylacrylate and alkannin

acetate have been reported by Chauhan et al. [20] at 2.8

and 1.8%, respectively. These compounds were

chromatographically separated using n-hexane and n-

hexane–benzene, respectively, as the solvent systems.

Khatoon et al. carried out TLC with 0.5% methanol–

benzene and quantitatively assessed the components

through fluorescence spectroscopy. The study reported

the presence of 9.37% of the major component and

10.53% of alkannin acetate in A. nobilis [27].

1. Alkannin β, β-dimethylacrylate

2. Alkannin acetate

3. Shikonin

R= CH. CH2. CH

R= CH. CH2. CH

R= CH. CH2. CH

CMe2

CMe2

CMe2

O. CO. CH

O. CO. CH3

CMe2

OH O

O

H

R

OH

OH

Figure 1 Structures of the major naphthoquinones present inA. nobilis Rech.f.

Table 2 Analysis of n-hexane extract by column chromatography

Spot EluantComposition(w ⁄ w) (%)

Thin-layerchromatography(Rf)

A 1% ethyl acetate:n-hexane 4.2 0.98B 2% ethyl acetate:n-hexane 24.6 0.93C 3% ethyl acetate:n-hexane 8.2 0.77D 4% ethyl acetate:n-hexane 6.1 0.5E 14% ethyl acetate:n-hexane 2.05 0.21



Optimisation of detection wavelength for HPLC

On the basis of the UV–vis spectrum of the

naphthoquinone derivatives, two wavelengths of 215 and

234 nm were chosen for HPLC analysis. The best

separation of the components was observed at 215 nm,

thus it was selected as the optimal detection wavelength

for use in HPLC analysis.

HPLC analysis

The crude extract, shikonin (standard) and each

separated fraction were analysed by HPLC. The

chromatogram of n-hexane extract obtained under

optimised conditions is shown in Figure 2. The

developed chromatographic procedure was found to be

adequate for the separation of three major analytes, i.e.

components B, C and D. The time taken for the analysis

was 30 min and peaks at retention times of 18, 14.12 and

11.37 min were obtained, respectively. Distinct peaks

were not observed for components A and E, which might

be attributable to their very low concentration in the

extract. Injections of blank samples after component

analysis showed that there were no carry-over effects.

In order to estimate the proportion of respective

components present in the n-hexane extract of A. nobilis

Rech.f., the percentage area under the peak for each

derivative was calculated from the chromatogram and

estimated at 215 nm. Peaks were assigned by spiking the

samples with the purified components and the reference

substance. HPLC analysis showed that peak 3 (at

11.37 min) corresponded to shikonin as well as

component D, thus confirming its identity.

Spectroscopic analysis

FTIR and 1H-NMR spectra of all the purified components

were analysed and compared with published data.

Component B (alkannin b, b-dimethylacrylate)

The UV–vis spectrum showed absorption peaks at 214,

275, 489, 523, 546 and 562 nm. The infrared spectrum of

component B showed mmax at 3480 and 3419 cm)1

(phenolic OH), 2965 and 1413 cm)1 (free and bonded

OH), 1638 cm)1 (isolated double bond), 1619 cm)1

(bonded carbonyl), 1262 cm)1 (ether linkage), 1096 cm)1

(typical of secondary alcohol), 1454 and 803 cm)1

(aromatic nature). The 1H-NMR chemical shifts of

component B were observed at d: 1.50 and 1.61 (doublet,

6H for the methyl protons of the isopropylidene group),

1.86 (6H for the methyl groups in the angelic acid

moiety), 2.52 (doublet, 2H for the allylic methylene

protons), 5.05 (singlet, 1H for the vinylic proton next to

the methylene group), 5.96 (singlet, 2H for the vinylic

proton of the angelic acid moiety and proton a to the

oxygen), 7.10 (triplet, 1H for the proton on the quinone

ring and 2H for the protons on the benzene ring) and

12.34 and 12.50 (singlets, 2H for the two perihydroxyl

groups). For the TLC analysis, the 1H-NMR signals were

found to conform to those reported for alkannin b,

b-dimethylacrylate [5,8-dihydroxy-2-(1¢-b,b-dimethylacryloxy-

4¢-methylpent-3¢-enyl)-1,4-naphthoquinone] [32,35]. Some

additional peaks were also observed that might be

attributable to the impurities in the sample.

Component C (alkannin acetate)

The UV–vis spectrum showed peaks at 202, 214, 275,

489, 523, 546 and 563 nm. The infrared spectrum of

component C showed mmax at 3418 cm)1 (phenolic OH),

2964 and 1417 cm)1 (free and bonded OH), 1616 cm)1

(chelated quinoid carbonyl), 1635 cm)1 ()C = C)),

1377 cm)1 (CH3)2–C, 1573, 1456 and 801 cm)1 (aromatic

nature). The component had bands at 1742 and

1262 cm)1, indicating the presence of an acetyl group, as

reported by Shukla et al. [28]. The 1H-NMR chemical

shifts of component C were observed at d: 1.51 and 1.63

(doublet, 6H for the methyl protons of the isopropylidene

group), 2.07 (singlet, 3H for the acetyl proton), 2.58 (2H

for the allylic methylene protons), 5.05 (singlet, 1H for

the vinylic proton), 5.95 (singlet, 1H for the proton a to

quinone ring), 6.92 (singlet, 1H for the proton on the

quinone ring), 7.19 (doublet, 2H for the protons on the

benzene ring), 12.36 and 12.5 (singlets, 2H for the two

perihydroxyl groups). The 1H-NMR signals were found to

be characteristic of alkannin acetate [2-(1¢-acetoxy-4¢-methylpent-3¢-enyl)-5,8-dihydroxy-1,4-naphthoquinone]

[32,35].

Component D (shikonin)

The UV–vis spectrum of component D showed absorption

peaks at 234, 259, 489, 521 and 559 nm. The infrared

spectrum of component D had mmax at 3234, 1730, 1618,

1262, 1225, 1097 and 1022 cm)1, which were attributed

to the presence of OH stretching, ester carbonyl, chelated

quinoid carbonyl, ether linkage, C–O stretch, secondary

alcohol and an additional CO group, respectively. A

comparison of component D with standard shikonin

showed similar peaks. However, the standard sample

showed additional peaks in the region of 980–830 cm)1,

which were attributed to substituted alkenes. These peaks

were found to be absent in component D. This may be

because the purity of both the samples varies. The 1H-

NMR chemical shifts of component D were observed at d:

1.5–1.7 (triplet, 6H for methyl protons), 2.4–2.6 (doublet,

2H for the CH2 group), 4.92 (singlet, 1H for the proton ato quinoid ring), 5.21 (singlet, 2H for the vinylic proton

60

50

40

30

Res

pons

e, m

V

11.3

7

Com

pone

nt C C

ompo

nent

B

Com

pone

nt D

14.1

2

17.8

20

10

00 4 8 12

Time, min16 20 24 28

Figure 2 High-performance liquid chromatogram of n-hexaneextract of the roots of A. nobilis Rech.f.



and the secondary hydroxyl proton), 7.2 (triplet for 3H

for protons on the benzene ring and the quinine ring),

12.6 and 12.5 (singlets, 2H for the two perihydroxyl

groups). The 1H-NMR chemical shifts of component D

[(5,8-dihydroxy-4¢-methylpent-3¢-enyl)-1,4-naphthoquinone]

corresponded with the standard shikonin sample and the

values in the literature, thus confirming its identity

[33,36].

Dyeing studies

Different fibres were dyed with the extracted dye. The

depth of shade obtained in each case was determined

spectrophotometrically (see Table 3). A very low depth of

shade was obtained on cotton fabric. As the dye

components present in Arnebia are hydrophobic in

nature, they are not expected to have any affinity for

cotton, which can only be dyed with anionic dyes that

have long, linear and planar geometry. Better shade depth

was obtained on wool (K ⁄ S = 4.4) as compared with silk

(K ⁄ S = 1.4). This is because wool is highly amorphous in

nature and takes up very large amounts of dye as

compared with the highly crystalline silk fibre. Acrylic

also showed good dye uptake (K ⁄ S = 5.5).

The colouring matter extracted from A. nobilis

comprises low molecular weight dyes with a largely

hydrophobic molecule. Theoretically, such molecules are

expected to behave as disperse dyes [25]. Polyester was

found to have a lower dye uptake (a K ⁄ S value of 2.1)

when dyed at 130 �C as compared with that dyed at

100 �C (K ⁄ S = 2.7). This slight decrease in dye uptake on

polyester at 130 �C may be attributed to the low thermal

stability of the dye at higher temperature. The dye uptake

on polyester dyed at 100 �C was found to be comparable

with that of nylon (K ⁄ S = 2.1). Also it was observed that

the nylon sample showed a blue colour, whereas the

polyester fabric was dyed a pink colour. This can be

explained by a higher b* value obtained on nylon

(b* = )13.2) than on the polyester sample dyed at 100 �C(b* = )4.08) and at 130 �C (b* = )3.87). The polyester

sample dyed at 130 �C showed a significantly higher a*

value, making the colour of the sample appear pink. This

may be attributable to different dye–fibre interactions.

Colour fastness properties

The colour fastness ratings of the dyed substrates were

determined. Light fastness on all substrates was found to

be 1–2. Colour change and staining ratings on all

substrates for wash and rub fastness as well as acid and

alkaline perspiration tests were determined to be 4 ⁄ 5–5. It

was interesting to note that, although the dye exhibited

acute sensitivity to different pH solutions, there was no

change in hue of the dyed fabrics in the acidic and

alkaline perspiration solutions.

ConclusionsDetailed chromatographic analysis of the n-hexane root

extract of Arnebia nobilis was carried out in this study. A

protocol for the extraction of naphthoquinone colorants

from Arnebia nobilis and characterisation of the major

components has been proposed. Three coloured

components present in the extract could be successfully

isolated using water–acetonitrile as the mobile phase in

reversed-phase high-performance liquid chromatography

in less than 20 min of elution time. The components

appear to be closely related in structure and colour.

Alkannin b, b-dimethylacrylate [5,8-dihydroxy-2-(1¢-b, b-

dimethylacryloxy-4¢-methylpent-3¢-enyl)-1,4-naphthoquinone]

was identified as the major component, followed by

alkannin acetate [2-(1¢-acetoxy-4¢-methylpent-3¢-enyl)-5,8-

dihydroxy-1,4-naphthoquinone] and shikonin [(5,8-

dihydroxy-4¢-methylpent-3¢-enyl)-1,4-naphthoquinone].

Although the dyeing conditions were similar, the shade

obtained on nylon was blue while that on polyester was

pink because of the nature of the dye–fibre interactions.

Light fastness of the dyed substrates was found to be

poor, whereas wash, rub and perspiration fastness were

found to be excellent.

AcknowledgementThe authors are grateful to the Department of

Biotechnology, Government of India for providing the

financial aid to carry out this study.

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Table 3 Colorimetric data of the dyed fabrics

Fabric pH L* a* b* C* h� K ⁄ S

Polyester (100 �C) 4.5 49.62 17.13 )4.08 17.61 346.6 2.7Polyester (130 �C) 4.5 53.2 18.76 )3.87 19.16 348.35 2.1Nylon 4.5 53.06 4.61 )13.2 13.98 289.24 2.1Wool 4.5 39.55 12.3 )2.93 12.65 346.6 4.4Silk 4.5 55.82 7.46 )3.95 8.44 332.1 1.4Acrylic 4.5 37.93 6.94 )7.75 10.4 311.83 5.5Cotton 4.5 60.77 3.62 )4.43 5.72 309.27 0.9



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