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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.

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.

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.

The paper aims to investigate the feasibility of developing natural dyes from the barks of Araucaria columnaris and leaves of Macaranga peltata, Averrhoa bilimbi. The paper also deals with the application of natural dyes in textile coloration.

Dye extraction was carried out using the aqueous method. The dyeability of the aqueous extract was assessed on cotton, silk and polyester yarns using different mordants (alum, acetic acid, CuSO₄, lemon juice) and without mordant. UV–Visible spectral analysis and pH of different natural dyes were determined. Percent absorption, K/S values, CIELab values and fastness properties of the selected dyed yarns were also assessed.

The percentage values for dye exhaustion differed with various mordants. The K/S values were found to be influenced by the addition of mordants. Different hues were obtained with the usage of different mordants. Fastness results exhibited good to very good grades.

The effective application of aqueous method of dye extraction in the study avoids solvent toxicity. The current results proved that the dyeing could be achieved at room temperature for different yarns (cotton, silk, polyester). At present, no report exists in the literature of research work on the extraction of natural dyes from the leaves of M. peltata, A. bilimbi and their dyeing potential on cotton, silk and polyester.

The present work offers new environment-friendly dye as well as simple dyeing method. Barks and leaves are promising sources of dye. Enormous availability of barks and leaves avoids the exploitation of the plant parts for the extraction of natural dyes.

The important feature of this study was the effective dyeing of natural and synthetic fibers at room temperature. The novel sources of natural dyes would contribute significantly to the existing knowledge of dyeing, and the natural dyes reduce the environmental impact of synthetic dyes.

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.

The purpose of this paper is to evaluate the efficacy and kinetics along with diffusion properties of a new source of natural dye obtained from leaves and fine stems of the Sesbania aculeata plant, using metallic mordants for cotton dyeing.

The approach followed in this work is to conduct experiments with the application of the natural dye obtained from Sesbania aculeata plant and to study the kinetics, dye uptake and the diffusion properties of this dye.

Sesbania aculeata with simultaneous mordanting with different metal mordants imparted shades which varied from cream to light brown to dark brown in case of aqueous extract. The different mordants used not only changed the hue colour and K/S values but also L* and brightness index values. The results of fastness properties of the dyes were found to vary from fair to good. The percentage dye exhaustion values varied with different mordants. The dye uptake value increased with time and reached its saturation limit after 4 hours of dyeing. In the absence of mordants, the diffusion coefficient values increased with increase in the temperature. In the presence of mordants, the diffusion process appears to slow down, which could be attributed to the binding effects of mordants.

The extraction and dyeing process of Sesbania aculeata plant is less tedious and time consuming compared to the other sources of natural dyes.

Sesbania aculeata is relatively easier to grow and does not require much tending operations. Thus, it promises to be an affordable source of natural dye. If this dye is commercialised, it will help to generate sustainable employment and income for the farmers in rural and sub-urban areas. This could be both for dyeing and for non-food crop farming.

An advantageous feature of this plant, in contrast to the other natural dyes based on vegetable and fruit sources, is that its usage in making the natural dye does not result in any wastage of an otherwise highly commercial product. The current experimental study on a new source of natural dye would be a significant contribution to the existing database of knowledge regarding the kinetics and diffusion properties of natural dyes. There are several reported studies in the literature pertaining to the application of natural colourants and evaluation of their dyeing properties on various fibers. However, relatively fewer studies exist on the kinetic and exhaustion aspects. Thus, the current study would help to develop a set of predictable settings for application of natural dyes on various textiles.

Everyone is extremely concerned about environmental protection and health safety due to the rise in living standards. Plant-derived natural dyes have garnered much industrial attention in food, pharmaceutical, textile, cosmetics, etc. owing to their health and environmental benefits. The present study aims to focus on the elimination of the use of synthetic dyes and provides brief information about natural dyes, their sources, extraction procedures with characterization and various advantages and disadvantages.

In producing natural colors, extraction and purification are essential steps. Various conventional methods used till date have a low yield, as these consume a lot of solvent volume, time, labor and energy or may destroy the coloring behavior of the actual molecules. The establishment of proper characterization and certification protocols for natural dyes would improve the yielding of natural dyes and benefit both producers and users.

However, scientists have found modern extraction methods to obtain maximum color yield. They are also modifying the fabric surface to appraise its uptake behavior of color. Various extraction techniques such as solvent, aqueous, enzymatic and fermentation and extraction with microwave or ultrasonic energy, supercritical fluid extraction and alkaline or acid extraction are currently available for these natural dyes and are summarized in the present review article.

If natural dye availability can be increased by the different extraction measures and the cost of purified dyes can be brought down with a proper certification mechanism, there is a wide scope for the adoption of these dyes by small-scale dyeing units.

The purpose of this paper is to evaluate the efficiency of ultrasonication on new natural dye obtained from leaves extract of Acer pectinatum Wallich using metal mordant for good cotton dyeing prospects.

For effective natural dyeing with leaves extract of Acer pectinatum Wallich, both conventional and sonication methods of dyeing were carried out using metal mordants. The purpose of using sonication was for improvement of dye uptake, improved dye adherence and good wash and light fastnesses. Results show marked improvement by the chosen dyeing method.

The superiority of sonicator dyeing over conventional dyeing in terms of enhanced resource productivity and, as a result, reduced wastes establishes it as the best available technique in the natural dyeing industry. Use of sonicator shows marked enhancement for cotton dyed fabric. 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, respectively, 30 and 50 per cent. The cycle time for dyeing was also reduced by 50 per cent and this would make possible more tonnage of fabric per unit time and lower waste generation for the dyeing process. This would also result in improved capacity utilisation leading to enhanced productivity levels in the dyehouses.

Although metal mordanting with copper sulphate and potassium dichromate is not ecofriendly, yet only 2 per cent of these metal salts have been used to prepare different shades with leaves extract of Acer pectinatum Wallich.

The method developed for natural dyeing of cotton fabric using sonication in conjunction with metal mordanting has shown marked improvement.

The method developed for natural dyeing of cotton fabric using 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.

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 evaluate the dyeing potentials of Melastoma malabathricum whose fruit pulp showed high dye contents. It is an abundantly available shrub in the north eastern forests of India.

Dye extraction was carried out by conventional heating and sonicator. The dyebility of the aqueous extract of melastoma was evaluated for dyeing cotton fabric by two methods – sonication and conventional heating. The purpose of using sonication was for betterment of dye uptake, improved dye adherence and good wash and light fastnesses.

The test results showed that choosing this dyeing method produced improved results. 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. Use of sonicator shows marked enhancement for cotton dyed fabric. 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, respectively, 30 and 50 percent.

Although natural dyeing has its limitations of fastness, we have tried to overcome this limitation by using sonicator.

The method developed for natural dyeing of cotton fabric using sonication in conjunction with metal mordanting has shown marked improvement.

The method developed for natural dyeing of cotton fabric using fruit pulp of Melastoma malabathricum under sonication in conjunction with metal mordanting using has shown marked improvement in terms of dye adherence and fastness properties and can thus be recommended for industrial application.