Chapter 1
Potential Resurgence of Natural Dyes in Applied Fields

Shahid Adeel1*, Sana Rafi2, Mahwish Salman2, Fazal-Ur-Rehman2 and Shazia Abrar3

1Department of Chemistry, Government College University Faisalabad, Pakistan

2Department of Biochemistry, Government College University Faisalabad, Pakistan

3Department of Applied Chemistry, Government College University Faisalabad, Pakistan

*Corresponding author: shahidadeel@gcuf.edu.pk

Abstract

Over the past decades, the industries around the globe have been involved in providing sustainable products to its consumers. Their synthesis and application have a much importance owing to their benefits for ecosystem. Plant-derived natural dyes are the substances that are gaining much popularity in the fields of food, pharmaceutical, textile, cosmetics, etc. owing to their health and environmental benefits. Their extraction using novel methods adds more aesthetic value to be used in different fields. This chapter describes the potential efficacy of natural colorants in applied fields. Hopefully, this chapter would satisfy the needs of natural dye reader, researchers, and industrialists who are trying to acquire new sources, their stability, and sustainability in fields other than textiles.

Keywords: Natural dyes, types, extraction, advance technology, fields

1.1 Introduction

Natural dyes are those colorants that are obtained from natural renewable sources such as minerals, plants, animals, and micro-organisms. These are highly environmental friendly and pose no serious threat to human life as well as ecosystem. These different resources are granted with highly colored substances that can be applied and fixed on materials commonly known as substrate and act as dye for textiles. These dyes contain an aromatic ring which have an auxochrome, responsible for resonance, and become able to impart color. Natural dyes were used to dye and print the substrate since the prehistoric times but their application down fall in 1856 with the accident discovery of synthetic dye (mauveine) by W.H. Perkin. Then synthetic dyes become superior over natural one owing to their availability at economical price with bright color, good fastness properties, and their reproducibility [1]. However, studies motivated the revitalization of natural dyes due to the toxic wastes, carcinogenic effects, and skin allergies caused by synthetic dyes [2, 3]. It was confirmed by many researchers that synthetic dyes contain 118 of the azo and benzidine dyes and when are photolytically degraded, their waste products release toxic aromatic amines. Most of the synthetic colorant (about 10-35%) cannot be fixed on the fabric properly and their effluents when become part of ecosystem, disturb the eco-balance [4, 5]. These factors bring awareness and urge many countries especially EU, USA, Canada, Germany, India, Pakistan, and other countries to completely ban on their frequent usage in different applied fields such as textile, food, cosmetics, and flavor [6, 7]. Hence, resurgence of natural dye is being welcomed around the globe.

1.1.1 Types of Natural Dyes

Natural dyes are of two types, i.e.,

1. Substantive dyes
2. Adjective dyes

1. Substantive Dyes

These dyes have good fastness properties and need no additional chemical (mordant) to fix it on materials. Fastness properties may refer to the resistance of the loss of colorant from the substrate. In textile industry color fastness to light, rubbing fastness and washing fastness are considered as effective properties of dyed fabric, while mordant are those chemicals that create strong bonding between fibers and dye molecule e.g., tannic acid [8]. These dyes will not only create affinity between fabric and dye molecule but also give a wide spectrum of color [9, 10].

2. Adjective Dyes

These dyes have poor fastness properties and need mordant to increase fixation of dye on substrate as shown in Figure below. In natural dyeing process, both synthetic (chemical) and biomordant are used. In chemical mordants, salts of aluminum, potassium, copper, iron, tin, etc. and even rare-earth metals are used [11, 12]. Biomordants are those substances that can obtain from natural sources (i.e. plants, animals, etc.) such as myrobolan (Terminalia chebula), tannin, tannic acid, guava, and banana leaves ash. [13]. However, it was suggested by many researchers that biomordant is safer and effective to use than chemical mordant [14]. As biomordants are easily biodegradable and eco-frienldy, while metal mordants such as Cu, Sn, and Cr may pose serious health hazards during handling and dyeing processes [15-17].

Complex formation among dye (pelargonidin), fabric (silk), and mordant (Al)

1.2 History

Natural dyes have been used extensively since long periods. Excavation and written records shows the interest of ancient people toward natural dye. They used natural colorant from soil, plants, animal, insects, and minerals. Some of these historical examples are given below:

1. People of Stone Age used metal to color their body and hair during hunting to gain magic power.
2. Firstly, they protect themselves with severe weather using tanned skin and later they used textiles.
3. Ancient Egyptian cuneiform texts also confirm the usage of natural organic colorant in their cloth dyeing.
4. People of Phoenicians Ages used purple dye from murex shells and this dye was so costly that Asiatic rulers can only wear purple colors. And after 17th century when Turks conquered Byzantium, the use of purple went declines and kermes were the only choice to dye their clothes.
5. Until the discovery of America kermes was used as a source of red color however, later it was replaced with cochineal.
6. Similarly, saffron was a good source of golden color used by Arabian and Chinese people [18].
7. Indigo dye (blue dye source) has been used since 640-320 BC and was only used for painting by Roman and Greeks.
8. Egyptian people used alizarin from madder for dyeing purpose.
9. Fustic in past was used to dye wool fabric.
10. Cotton textile industry used such cheap natural dyes since medieval period.

1.3 Advantages of Natural Dyes

Natural dyes contain numerous beneficial characteristics that make it superior again over synthetic dyes. Some of these advantages are mentioned below:

1. Handling of natural dyes is safer and noncarcinogenic during its application and processes.
2. Natural dyes have better biodegradability and generally have higher compatibility with the environment.
3. These dyes are nontoxic, nonallergic to skin, and noncarcinogenic [19].
4. They are renewable and sustainable product [20].
5. These dyes have wide range of shades depends on the part of plant used and type of mordant applied [21].
6. Most of natural dyes adsorb the industrial toxic wastes that help to clean the environment from pollution [22].
7. These dyes are a big source of income for poor through viable harvesting and sales of these plants that also provide rich and different sources of dyestuff.
8. Natural dyes are bestowed with numerous beneficial properties such as insect repellent, deodorants, and flame retardant [23].
9. These dyes also exhibit UV protection [24] fluorescence [25, 26], and antimicrobial properties as well as antioxidant properties [27].
10. Such dyes generate more attractive and highly functional value added products [28].
11. Application of the waste materials as sources of natural dye can help in the preservation of the environment and also reduce the cost of natural dyeing [29].
12. Natural dyes have wide range of applications such as food, cosmetics, agriculture, textile, pH indicator, and DSSC (dye-sanitized solar cells).

1.4 Classification

Natural dyes are identified on the basis of their

• Structure
• Color
• Application

Here, we will discuss the classification basis on structure.

1.4.1 Structure Base

1. Flavonoids

Flavonoid is the major structural class of the natural dye plant and has been further divided into seven classes such as flavones, flavanones (e.g., citrus fruit), flavonols, isoflavones (e.g., pulses), anthocyanins, anthocyanidins, and proanthocyanidins (e.g., black tea, green tea, apple, and blackberry). This is responsible for imparting yellow color to the substrate. Weld (Reseda luteola) and woadwaxen (Genista tinctoria) are also examples of flavonoids group.

2. Tannin

Tannin is considered to be the most important components that are essential for dyeing with natural dyes, especially to obtain brown shades of color. Babool (A.nilotica), pomegranate rind, and gallnut (Quercus infectoria) contain ellagic acid (tannin) [30]. Albizia coriaria plant species have shown the presence of tannin moieties in their molecular structure [31]. Due to the presence of polyphenolic group, this can be employed as safer biomordant.

3. Alkaloids

The main chemical constituent present in Adhatoda vasica is a bitter quinazoline alkaloid Vasicine and has high therapeutic value. It gives light yellow color with copper sulphate and gray with ferrous sulfate [32].

4. Indigoid

Indigoid being the source of blue color is an oldest natural colorant. In plant, it is in the form of water-soluble...