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J. Cosmet. Sci., 74.4, 200–215 (July/August 2023)
*Address all correspondence to Min Yang, 2578973180@qq.com
Polyphenol-Metal Complex With Dopamine for Dyeing
Natural White Hair
HAI ZHANG, DAN MA, ANRU LIAO AND MIN YANG
School of Pharmaceutical Sciences, Guizhou University, Guiyang, 550025, China (H.Z., D.M., A.L., M.Y.)
Accepted for publication August 9, 2023.
Synopsis
Hair becomes white due to melanin deficiency, and hair dye can be used to restore hair color. Currently,
commercial hair dyes are dominated by p-phenylenediamine (PPD) hair dyes, although PPD has been
suspected of being carcinogenic. Natural plant polyphenols, when complexed with metals, produce a variety
of colors that can be used for hair coloration. Gallic acid and ferrous ions self-assemble to form a network
structure, and the addition of dopamine results in a composite hair dye. By using ethanolamine to unfold
the natural white hair scales, dye molecules can penetrate through the hair scales to the hair cortex, and the
dopamine oxidative self-polymerization in the hair dye forms an adhesion film in the hair cortex layer, thereby
fixing the dye molecules. A hair washability test showed that the color difference value remained unchanged
after 40 washes. Scanning electron microscope (SEM) analysis of the hair after dyeing showed that the hair
dye did not destroy the hair structure. Additionally, results from hair stretch tests displayed good stretch
resistance to the hair. This study shows that hair dye based on a polyphenol-metal complexes containing
dopamine could be used as an alternative to PPD-based hair dyes.
INTRODUCTION
Natural melanins are important pigments found throughout living organisms, including
microorganisms, plants, animals, as well as in human eyes, skin, and hair.1,2 Melanin has
several biological functions, such as UV protection, free radical scavenging, antibiotic function,
and neuroprotection.3,4 Natural hair color is derived from the presence of melanin in the
cortex,5 with its abundance and relative concentration determining hair color. A deficiency
of melanin is believed to be responsible for graying or whitening hair, and white hair can
be restored to color using hair dyes.5,6 Modern hair dyes are classified as oxidative or non-
oxidative oxidative hair dye products are often referred to as permanent or semi-permanent,
while non-oxidative hair dye products are considered temporary or semi-permanent.7
A variety of new, permanent oxidative chemical hair dyes dominate the global hair dye
market. Permanent hair dyes have the highest market share of all modern hair dyes in Asia,
the Americas, and Europe.8 However, most commercial permanent hair coloring products
contain hydrogen peroxide and PPD or PPD-derived compounds as key ingredients. These
substances undergo chemical reactions both on the hair’s surface and internally, resulting in

201 Polyphenol-metal Complex With Dopamine
a permanent alteration of hair color.5 However, such compounds are sometimes allergenic,
toxic, and potentially carcinogenic to humans. For example, PPD, despite being deemed safe
for cosmetic use by the Cosmetic Ingredient Review, has been shown to readily cross the
skin barrier and has been considered a human allergen and carcinogen.9 In addition, in situ,
oxidation reactions in the presence of such compounds may damage hair and scalp,10 and
some alternative hair coloring methods have been proposed to address the potential human
health hazards of the aforementioned oxidative permanent hair dyes. For example, hair dyes
based on graphene sheets utilize graphene oxide (GO) and its reduced form, r-GO, to create
water-based formulations that form a smooth and continuous coating on the hair to achieve a
dyeing effect.11 Another approach involves inducing melanin-like polydopamine (PDA) and
brown melanin-like PDA/cysteine co-deposited coatings on the hair’s surface using sodium
periodate. This process yields melanin-mimicking multicolor hair dyeing with low toxicity.12
To achieve dyeing, the metal chelation-assisted deposition of polydopamine on human hair
results in black coloration of human keratin hairs.13 This rapid hair coloring of natural white
hair is achieved through the formation of metal-phenolic networks (MPNs).14 Polymerization
by laccase-mediated in situ oxidation of dopamine produces intensely pigmented polymers
and is used for the biological coloration of human hair.15
In addition, gallic acid (GA) has been studied for hair coloring. GA is a phenolic compound
found in large quantities in quince and pomegranate skins and is used as a food additive.16,17
GA is also a very important benzoic acid with anti-ulcer, antibacterial, antifungal, and
antioxidant properties.16,18 It has been reported that GA can be complexed with metal ions
to form multi-colored dyes for hair dyeing applications. GA has been polymerized with
CuCl
2 in aqueous sodium chloride solution to form oligomers to produce polyphenolic hair
dyes. These dyes result in a dark brown color to the hair. Meanwhile, Cu(II) ions complex
with hydroxyl groups to form Cu-O couplings, which can form an ion-channel coating on
the surface of the hair to protect the hair. However, hair dye has the problem of thickening
the hair and reducing hair stretch.19 Based on the property that laccase can catalyze the
polymerization of phenolic structures to form dimers, Jeon et al. used laccase to catalyze
the reaction of GA to produce a brown dye and for coloring white hair.20 Varsha Panwar et
al., used a heat-resistant bacterial laccase from Puccinia agalactiae to react with GA in a
coupling reaction to produce hair color, which can be used to dye bleached hair to a dark
brown color.21 Deepak Kumar et al. used a laccase from Bacillus subtilis DS to react with
GA to produce a golden yellow dye, which can be used as an alternative to synthetic dyes
(such as PPD) for hair coloring.22 In addition to being prepared as a dye for hair coloring,
GA was combined with GA and tannic caffeic acid to prepare a hair-coating polyphenol
complex that was able to provide UV radiation protection to the hair by coating the hair
cuticle, minimizing the electrostatic effect and improving the mechanical strength of the
hair.23 In addition, GA was prepared as a hair supplement for its antioxidant effect on
hair.24 As mentioned earlier, commercial hair dyes (such as PPD) are allergenic, so it is
also a matter of consideration when exploring GA for dyeing gray hair. However, GA has
been reported to have potent antioxidant, anti-inflammatory, antibacterial, and anticancer
activities,16, 18, 25 and even in studies applied to cosmetics, GA has been reported to have
anti-inflammatory, antioxidant, and anti-aging activities.26-28 Swan et al. reported that a
patient with PPD allergy used pure henna, black tea, and indigo powder as an alternative
hair dye, but the patient still experienced allergic symptoms. It is well known that pure
henna and black tea contain GA, so Swan et al. tested patients and 10 controls for GA
allergy, and the results were all negative.29 Therefore, there’s no need for excessive concern
about allergies when using GA in hair dye.