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Natural dyes are mostly used for dyeing of natural fibre textiles to improve their eco-friendly features. For successful commercial use of natural dyes, the appropriate and standardized dyeing techniques need to be adopted. Appropriate scientific techniques or procedures need to be derived from scientific studies on dyeing methods, dyeing process variables, dyeing kinetics and compatibility of selective natural dyes with minimal use of hazardous chemicals.

In the present study, different enzymes (protease, amylase, xylanase, pectinase, phytase) were used efficiently with Rubia dye by using simultaneous and two-step processes; both the processes were developed with an aim for conservation of time and energy, for the ease of industrial use. The highlights of the study are twofold: eco-friendly natural dyeing by using enzyme replacing metal mordant and room temperature dyeing, which is a completely new concept.

Experiments showed that enzymatic treatment can give good colour strength to silk fabric using Rubia as a dye source and has good potential for commercial dyeing. It is a non-toxic dye. Use of enzymes were a deliberate attempt to avoid metal mordanting in silk dyeing, as it would make textile dyeing eco-friendlier. The order of reactivity of enzymes in one-step process was found to be protease > phytase > xylanase > amylase > pectinase. Similarly, for two-step dyeing process, the order of reactivity of enzymes observed was protease > amylase > xylanase = pectinase > phytase. Protease enzyme was the best option in both the cases. Overall, it can be concluded that in the case of enzymatic treatment, the two-step process was better in terms of larger K/S values, colour coordinate values and dye adherence.

A new domain of room temperature dyeing technique has been introduced.

In the present study, different enzymes (protease, amylase, xylanase, pectinase, phytase) were used efficiently with Rubia dye by using simultaneous and two-step processes; both the processes were developed with an aim for conservation of time and energy, for the ease of industrial use. The highlights of the research are twofold: eco-friendly natural dyeing by using enzyme replacing metal mordant and room temperature dyeing, which is a completely new concept. Overall, the ease of use for industrial application. Rubia dye from Sri Lanka has been used in conjunction with different enzymes to show that metal mordanting can be easily replaced by the use of eco-friendly and biodegradable enzymes. The most attractive feature of this study is the low-temperature dyeing at 30-40°C. For any dyeing house, this process can be easily adapted on jigger, winch or even in continuous padding machine. Good fastness properties and dye adherence have been the other highlights of this study.

The purpose of this study is to check the effectivity of plasma in the natural dyeing of polyester fabric using four natural dyes – Turkey red, Lac, Turmeric and Catechu using plasma and alum mordant. The surface modification on the polyester fabric by plasma along with the use of benign mordant alum is studied. The enhancement of dyeability in polyester fabric with natural dyes is the main focus. Due to surface modification, the wettability increases, which leads to better dye uptake. Better dye uptake and better dye adherence are the main objectives.

Plasma-mediated natural dyeing is the main design of this research work. The effect of plasma treatment on surface modification of synthetic fabric polyester and its subsequent effects on their dyeing with different natural dyes, namely, Turkey red, Lac, Turmeric and Catechu are studied. The dyeability was further enhanced by the use of alum as mordant. The main focus is on the betterment of natural dyeing of polyester fabric using sustainable natural dyes resources for dyeing and to reduce wastewater contamination from the usage of toxic additive chemicals for cleaner production.

Plasma-mediated and alum-mordanted dyeing method facilitated very good dyeability of all the four natural dyes, namely, Turkey red, Lac, Turmeric and Catechu. Color strength (K/S) values and fastness properties of plasma-treated samples were far better than untreated samples. The synergistic effect of plasma and alum mordanting has made natural dyeing of polyester very easy with very good fastness results. Natural dyeing of polyester after 2 min of plasma treatment showed excellent and desirable results. The process is also easy to be adapted by industries.

As polyester is hydrophobic, natural dyeing of polyester fabric is not very easy, but with plasma-mediated natural dyeing, it becomes a very facile dyeing method; thus, there are no limitations. Use of plasma has reduced the need for any chemical additives which are usually added during the dyeing process.

This process of natural dyeing of polyester fabric can be scaled up to industrial dyeing with natural dyes. Plasma pretreatment of the fabric followed by premordanting with alum has facilitated the natural dyeing well.

Use of plasma in place of chemical modifiers can be a green and environmentally friendly approach for sustainable coloration of polyester fabric, providing a clean wet processing for textiles dyeing.

The synergistic effect of plasma-mediated and alum-mordanted natural dyeing of polyester has not been attempted by any researcher. To the best of the authors’ knowledge, this is for the first time that pretreatment with atmospheric plasma followed by alum mordanting of polyester fabric has shown very good dye uptake and fastness properties as the dye molecules could penetrate well after 2 min of the plasma treatment.

Replacing conventional mordants by benign mordants, rare earth (RE) salts have been used in the process of natural dyeing with annatto seed extract. The purpose was threefold – first, to increase the dye uptake through these new mordants; second, to have better fastness properties of dyed swatches and third, to have lesser effluent pollution, as the new RE mordants are used in one-tenth quantities only.

Sustainable natural dyeing was attained by using RE salts as mordant in one-tenth quantity, for natural dyeing, replacing the conventional mordants such as alum and ferrous sulphate. Annatto extract has been used as natural dye.

Through the study, it was inferred that the natural dyeing using annatto seed extract gives very good colour depth on the dyed swatches and also shows marked improvement in fastness properties.

Research implication is that often it is expected that any new chemical used in the textile processing adds on to the effluent load; however, contrary to that, this study found that the use of RE salt is very beneficial as it is used in smaller quantities, but gives far better dyeing results.

RE salts can be used in natural dyeing without causing any harm to the environment and dyers.

Use of RE salts in natural dyeing is a new concept. It is a very safe technology and can be used without causing any harm to the environment and the dyers.

This study is unique as it focuses on the use of RE salts in natural dyeing replacing the conventional mordants, which are used ten times more in quantity.

This paper aims to study carotenoids as a natural food colorant from Canna flowers. There is a growing demand for eco-friendly and non-toxic colorants, specifically for health-sensitive applications such as colours of food and textiles. Red Canna variety can be grown in normal garden situations and gives ample of flowers yielding good amount of natural colorant for both the purposes.

In the present work, ultrasound extraction of natural colorant from Canna indica flowers has been studied. The use of ultrasound is found to have a significant improvement in the extraction efficiency of colorants obtained from dry and fresh Canna flowers in different mediums. Ultrasonic cavitational processing has twofold advantages, it is an eco-friendly and cost-effective process.

The total carotenoid content in dry and fresh flower extract was found to be between 136.56 and 978.89 mg/kg. The assessment of antioxidant activity (AOA) in dry and fresh flower extract was found to be 5.78-78.33 per cent assayed by scavenging 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical and identified by electron paramagnetic resonance (EPR) studies.

The use of ultrasonication for the extraction of colorant has been the main feature and a step towards technological advancement in the area of finding newer method of efficient extraction of the colorant.

The ease of extraction due to ultrasound waves has been the highlight.

It is for the first time that the phytochemical data of red Canna flower and has been studied, the total carotenoid content and antioxidant activities of different extracts of Canna were measured. The extraction of natural dye from C. indica flowers using ultrasound has been found to have significant improvement in the extraction efficiency of the colorant obtained from flowers.

Illicium griffithii (local name - Lissi) belongs to the family Illiaceae. It produces yellow colored natural dye from its stem and leaves, which has been used to dye textiles for the first time here. In the present study, innovative dyeing with Illicium griffithii has been shown to give good dyeing results. Pre-mordanting with 1-2% metal mordants viz. alum, copper sulphate, ferrous sulphate, potassium dichromate, stannous chloride and stannic chloride, and using 5% (o.w.f.) of plant aqueous solution of the extract, is found to be satisfactory and shows very good fastness properties for cotton, wool and silk fabrics. The innovative solvent extraction of the dry stem-leaves of Illicium griffithii is an easy process; the solvent is removed/recovered and the aqueous extract is used for dyeing. The CIELab and color strength (K/S) of the dyed fabrics are also evaluated. The superiority of solvent extraction over conventional extraction has been established through this study.

The purpose of this paper is to carry out phytochemical investigations of different extracts of Eucalyptus globulus bark such as aqueous, methanolic and supercritical carbon dioxide fluid extract (SCFE) with ethyl acetate as entrainer. Three fractions (Eu 8, 9 and 10) containing steroidal δ‐lactone were isolated from SCF extract and the structure of Eu‐10 was earlier determined on the basis of NMR, HPLC‐MS, X‐Ray crystallography.

Column chromatography led to the isolation of flavonoids, tannins, steroids, etc. in different solvent systems. Isolated steroidal lactone (Eu‐8,9&10) of Withanolide series were tested for the presence of total phenolic content, total flavonoid content and the results were expressed as gGAE/100 g (TPC), and gQE/100 g (TFC), respectively. The antioxidant capacity was evaluated based on their ability to scavenge free radicals generated from ABTS, DPPH, FRAP and H₂O₂ by spectrophotometric method.

The result of the present study showed that different extracts of E. globulus bark and the isolated fractions, exhibited different antioxidant activity. This was due to the fact that they contained different amounts of flavonoid and phenolic compounds as per their ability to solubilize these compounds; the high scavenging property of E. globulus may be attributed to hydroxyl groups existing in the phenolic compounds. All the samples exhibited different extent of antioxidant activity (AOA) and showed higher potency when compared with BHT in scavenging action of DPPH free radical. Comparative data analysis showed SCF extract to be better than methanolic and aqueous extracts, both in terms of yield and AOA, while Eu‐10 was the best amongst purified fractions.

The present research has serious implications on identification of natural antioxidants from E. globulus. Natural antioxidants with better structure‐activity relationship are under investigation. Isolation of withanolide from Eucalyptus bark has opened newer horizon for its use.

Collection of Eucalyptus bark from the forest (a forest waste) by women folk can be a source of revenue generation and thus has social implication as well. It is an important agro product.

The steroidal lactone (Eu‐10) showed highest radical scavenging effect even at IC50, thus the isolated lactone proved to be the best potential scavenger of free radicals amongst all crude extracts and the isolated fractions.

The purpose of this paper is to study the structure‐activity correlation of four medicinal plants – Ocimum basilicum L., Piper betle L., Grewia asiatica L., Lantana camara L. in crude methanolic extract. These plants have been used in Ayurvedic preparation as alternative medicine. The contents of phenolic compounds (flavonoids, anthocyanin) and antioxidant capacities were evaluated.

Folin‐Ciocalteu method was used for the analysis of the phenolic compounds. Total flavonoids were also evaluated. DPPH, ABTS+, FRAP and H₂O₂ assays were used to evaluate antioxidant activity. Most of the assays were determined spectrometrically.

O. basilicum L. had the highest of total phenolics content (305.11 mg GAE/g), highest content of anthocyanins (15.427 mg/Kg) and total flavonoids (9.692 QE mg/g). The DPPH, ABTS+, FRAP and H₂O₂ assay indicated that these plants possessed considerable antioxidant activities.

The results also showed that O. basilicum and L. camara from red colored cultivars possessed high contents of phenolic compounds. FRAP assay showed AOA in the following sequence – Lantana camara>Ocimum basilicum>Piper betle>Grewia asiatica. Since L. camara showed highest antioxidant capacity thus it can be a potential resource for commercial antioxidant.

Artocarpus heterophyllus Lam (local name jackfruit) belongs to the family of Moraceae. It produces natural dye from the bark of the tree which has been shown as a prospective natural dye source for textiles. In the present study, innovative extraction of yellow colorants using ultrasound energy is shown. Dyeing with jackfruit bark extract has been shown to give good dyeing results. Pretreatment with 1 % metal mordant and 4 % of bark extract (owf) was found to be suitable and showed very good fastness properties for cotton, wool and silk dyed fabrics with hue colors ranging from light brown to greenish to brown. The dye uptake by cotton fabric ranged from 55-62%, 68-70% for silk and 59-73% for wool with different mordants. The effectiveness of metal mordant-artocarpus in better dye uptake appears to be an improved process resulting in good dye adherence and good fastness properties.

The purpose of this paper is to evaluate the efficiency of dyeing on cotton wool and silk fabrics with natural dye obtained from kitchen waste of dry skin extract of Allium cepa.

The dry skin of onion produces natural dye which has been used for dyeing textiles. In the present study, innovative dyeing with onion has been shown to give good dyeing results. Pretreatment with 2 per cent metal mordant and using 5 per cent of plant extract (owf) was found to be optimum and showed very good fastness properties for cotton, wool and silk dyed fabrics. For effective natural dyeing with dry skin extract of Allium cepa, conventional method of dyeing was carried out using metal mordants. The purpose of using this source was with an idea to produce value addition dyed product from kitchen waste as the dye has very good potential of uptake, adherence to the fabric and has good wash and light fastnesses. Results show very attractive hue colours.

The preference of using easily and cheaply available material for dyeing by conventional dyeing lowers the cost of natural dyeing and enhances resource productivity and as a result, reduces waste. This makes onion scale one of the easily available materials for natural dyeing industry.

Although metal mordanting with copper sulphate and potassium dichromate are not ecofriendly but we have used only 2 per cent of these metal salts to prepare different shades with dry scales of Allium cepa extract.

The method developed for natural dyeing of cotton, silk and wool fabrics using skin extract of allium in conjunction with metal mordanting has shown very deep coloration. The stepwise dyeing of cotton fabric with metal mordant by the natural dye Allium cepa showed that the stepwise dyeing process gave very good result. The dye uptake in case of stepwise dyeing was from 65‐68 per cent in the case of cotton, 70‐74 per cent in silk and 78‐82 per cent in wool with different mordants.

The method developed for natural dyeing of cotton, silk and wool fabrics using skin extract of allium in conjunction with metal mordanting has shown marked improvement in terms of dye adherence and fastness properties and can thus be recommended for industrial application.

The purpose of this paper is to evaluate the efficiency of ultrasonication on new natural dye obtained from leaves and stem extracts of Daphne papyraceae using metal mordant for good cotton, silk and wool dyeing prospects. It also proposes to effect the characterisation of the colorant.

For effective natural dyeing with leaves and stem extracts of D. papyraceae, both conventional and sonication methods for cotton, silk and wool dyeing were carried out using metal mordants. The purpose of using sonication was for betterment of dye uptake, improved dye adherence and good wash and light fastnesses. Results show marked improvement by the chosen dyeing method. Simultaneously, chemical characterisation of the colorant was carried out by first column chromatographic separation of the crude extract, followed by spectral analysis of the isolated products.

The superiority of sonicator dyeing over conventional dyeing in terms of enhanced resource productivity and, as a result, reduced wastes makes it the established best available technique in the natural dyeing industry. This fact has been examined for several natural dyes. Use of sonicator shows marked enhancement for cotton‐, silk‐ and wool‐dyed fabrics. Typical bath liquor to fabric ratio for conventional dyeing varies from 20:1 to 15:1 and for sonicator dyeing from only 12:1 to 10:1, thereby reducing specific water and energy consumption by 30 and 50 per cent, respectively. The cycle time for dyeing was also reduced by 50 per cent and this would benefit the dyeing process with more tonnage of fabric per unit time and with lower waste generation. This would also result in improved capacity utilization leading to enhanced productivity levels in the dyeing houses.

Although metal mordanting with copper sulphate and potassium dichromate is not ecofriendly, only 2 per cent of these metal salts has been used to prepare different shades with leaves and stem extracts of D. papyraceae for cotton, silk and wool fabrics.

The method developed for natural dyeing of cotton, silk and wool fabrics using sonication in conjunction with metal mordanting has shown marked improvement. The chemical composition of the crude extract shows the presence of flavonoids and other specific natural pigments.

The method developed for natural dyeing of cotton, silk and wool fabrics using stem and leaves extracts of D. papyraceae under sonication in conjunction with metal mordanting has shown marked improvement in terms of dye adherence and fastness properties and can thus be recommended for industrial application. This is a new source of natural dye.