Waste and Biomass Valorization https://doi.org/10.1007/s12649-021-01443-9 REVIEW Natural Quinone Dyes: A Review on Structure, Extraction Techniques, Analysis and Application Potential Benson Dulo1,3 · Kim Phan1 · John Githaiga2 · Katleen Raes3 · Steven De Meester1 Received: 19 September 2020 / Accepted: 13 April 2021 © The Author(s) 2021 Abstract Synthetic dyes are by far the most widely applied colourants in industry. However, environmental and sustainability con- siderations have led to an increasing eforts to substitute them with safer and more sustainable equivalents. One promising class of alternatives is the natural quinones; these are class of cyclic organic compounds characterized by a saturated (C6) ring that contains two oxygen atoms that are bonded to carbonyls and have sufcient conjugation to show color. Therefore, this study looks at the potential of isolating and applying quinone dye molecules from a sustainable source as a possible replacement for synthetic dyes. It presents an in-depth description of the three main classes of quinoid compounds in terms of their structure, occurrence biogenesis and toxicology. Extraction and purifcation strategies, as well as analytical methods, are then discussed. Finally, current dyeing applications are summarised. The literature review shows that natural quinone dye compounds are ubiquitous, albeit in moderate quantities, but all have a possibility of enhanced production. They also display better dyeability, stability, brightness and fastness compared to other alternative natural dyes, such as anthocyanins and carotenoids. Furthermore, they are safer for the environment than are many synthetic counterparts. Their extraction, purifcation and analysis are simple and fast, making them potential substitutes for their synthetic equivalents. Graphic Abstract Keywords Natural dye · Extraction · Characterisation · Quinone · Sustainability · Biomass Statement of Novelty This paper evaluates natural quinone dyes as potential sub- * Steven De Meester stitute for their synthetic equivalents. Sustainability and [email protected] environmental safety will be achieved by the use of these Extended author information available on the last page of the article dye extracts. Earlier studies concentrated on favonoids and Vol.:(0123456789)1 3 Waste and Biomass Valorization carotenoids whereas quinoids have not received similar The most abundant natural dyes are the carotenoids, fa- attention, despite being at least as promising as the other vonoids and quinones [15]. Of these, the carotenoids and two sources. The paper also presents an up-to-date over- favonoids have been extensively studied and reviews are view of chemical analysis techniques and the use of natural available [16–19]. By contrast, quinones have not been given quinone dyes. similar attention, despite being at least as promising as the other two sources, since they can be considered the natural analogues of the more established synthetic quinone dyes. Introduction This review, therefore, aims to provide some insight into the potential of natural quinoid dyes. It gives a brief overview Dyes can generally be categorised as either synthetic or of the structure, occurrence, biogenesis, uses and toxico- natural. While synthetic dyes are typically synthesised logical analysis of these class of dyes. It also delves into from petrochemical sources, natural colourants are abun- quinone extraction, purifcation, identifcation, quantifca- dantly available in nature and can be obtained from plants, tion and application in the context of dyeing. To ensure an microorganisms, animals or minerals. Of these sources, exhaustive review, literature materials, such as text books, plants can potentially be a more sustainable source since articles, abstracts and peer-reviewed publications listed in plants biomass is more abundant in nature and contains Web-of Science and Google scholar, were searched using the dye molecules in higher quantities [1, 2]. These dyes have phrases “quinone dyes”, “natural quinone”, “natural dyes”, been used for centuries for colouration of natural fbres, “quinone compound”, “natural anthraquinone”, “natural such as cotton, silk, and wool, as well as for other sub- naphthoquinone” and “natural benzoquinone” within the strates like leather, skin, hair, shoe polish, paper, wood, period 1998–2019. cane, candles and food [3]. However, in the beginning of the twentieth century, the introduction of synthetic dyes resulted in a drastic decline in the use of natural dyes due Structure, Occurrence, Use and Biogenesis to the low cost, availability, simplicity of application, col- of Natural Quinones our range, shade reproducibility and superior colour fast- ness of the synthetics [4]. Nevertheless, in the past two Though quinone compounds are structurally the most varied decades, an upsurge has occurred in the use of natural dye molecules [5, 20], they all share some features, sources, dyes because of their potential eco-friendliness, biodeg- usage and biosynthesis pathways as described below. radability, renewability and lower toxicity to humans and the environment [5–7]. Structure Natural dyes can be classifed based on the dye source, application method and chemical structure. However, clas- Quinones are coloured compounds with a basic benzoqui- sifcation based on the chemical structure might be more none chromophore (Fig. 1a) consisting of two carbonyl appropriate since the structure uniquely identifes dyes groups with two carbon–carbon double bonds. The quinone belonging to a certain chemical group with specifc prop- dyes are fused benzenoid quinoid ring systems with suf- erties [5, 8]. On this basis, natural dyes are further grouped cient conjugation to achieve colour. The three main classes as indigoids, pyridine-based, carotenoids, quinoids, favo- of quinones are benzoquinones (Fig. 1a), naphthoquinones noids, betalains, tannins and dihydropyrans [4, 5]. Of these (Fig. 1b) and anthraquinones (Fig. 1c), which contains 1, 2 groups, the quinoids, which include benzoquinones, naph- and 3 ring structures respectively. thoquinones and anthraquinones are of particular interest Benzoquinone (Fig. 1a) is the basic subunit of quinone since they resemble synthetic dyes [9] and may therefore compounds [21]. Chemically, 1,4-benzoquinone (also called be potential substitutes for the synthetic equivalents. para-benzoquinone) is a non-aromatic compound which is Synthetic dyes mainly consist of two major classes; easily converted into hydroquinone on reduction [22]. Ben- azo dyes and anthraquinones dyes. The azo dyes, despite zoquinone units serve as building blocks in quinone syn- having many functional advantages, are now considered thesis and provide important moieties for the biosynthesis hazardous [10]. In fact, they are banned in many countries, of active biological compounds [21]. Compounds with such as the United States of America (U.S.A), India, and para-benzoquinones attached to one more benzene ring at the European Union (E.U), among others [11, 12]. Many position 2,3-C (carbon), are called naphthoquinones. The synthetic anthraquinones dyes, such as Disperse Blue 3, naphthoquinone structure (Fig. 1b) has two carbonyl groups 2-aminoanthraquinone, and many others, have also been on one benzene ring, normally at the o- or p- orientation found to be highly toxic to humans and to the environment [23]. Naphthoquinones also have α- and β-unsaturated car- [13, 14]. bonyls. The extended electron delocalisation through the double bonds and the carbonyl groups gives rise to intense 1 3 Waste and Biomass Valorization Fig. 1 Chemical structure of a benzoquinone, b naphthoquinone and c anthraquinone colouration in the visible region [24]. The third class of Leguminosae, Polygonaceae, Bignoniaceae, Verbenaceae, quinones known as anthraquinones, are compounds con- Scrophulariaceae, and Liliaceae plant families. These com- taining the anthracene nucleus with two carbonyl groups, pounds have been reported to exist in almost all parts of normally on the B-ring. They are derived from the basic plants tissues and organs, such as leaves, stems, pods, seed structure 9,10-dioxoanthracene (C 14H8O2) (Fig. 1c), a tri- coats, fruits, nut shells, fowers, tubers, leaf glands, root cyclic aromatic organic compound. The parent structure bark and heartwood [20, 31]. The most commonly occur- is also referred to as 9,10-anthracenedione, anthradione, ring anthraquinone is emodin, due to its presence in moulds, 9,10-anthrachinon, anthracene-9–10 quinone, 9,10-dihi- lichens, higher fungi, fowering plants and insects as well dro-9, or 10-dioxoanthracene. Since quinone structures [20]. Anthraquinones may also be hydroxylated and may allow diferent substitution patterns, hundreds of derivatives occur in vivo in free (aglycone) forms, or in combined (gly- exist in nature, especially for anthraquinones. Hydroxyan- coside) forms, or in reduced forms [32]. In plants, anthraqui- thraquinoids absorb visible light and are therefore coloured nones are mostly present as glycosides, which makes them [25]. Generally, the colour of a quinone compound depends water soluble and gives them a lower chemical reactivity on the position, nature and number of hydroxyl and electron- towards other plant cell compounds [33]. Normally, the agly- donating/accepting constituents, also called auxochromes, cone forms are converted into glycoside anthraquinones by on the diferent rings impacting on intra-molecular hydrogen β-glycosidase activity or through an oxidative process [26]. bonding