Tannin-Mordant Coloration with Matcha (Camelia Sinensis) and Iron(II)-Lactate on Human Hair Tresses

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Article Tannin-Mordant Coloration with Matcha (camelia sinensis) and Iron(II)-Lactate on Human Hair Tresses

Lusine Sargsyan 1,2,*, Thomas Hippe 1, Hartmut Manneck 1 and Volkmar Vill 2

1 R&D Hair Color Level 3, Henkel AG & Co KGaA, Hohenzollernring 125-127, 22763 Hamburg, Germany; [email protected] (T.H.); [email protected] (H.M.) 2 Department of Chemistry, University of Hamburg, Martin-Luther-Kingplatz 6, 20146 Hamburg, Germany; [email protected] * Correspondence: [email protected]; Tel.: +49-8824-2410

Abstract: The aim of this work was to optimize our natural hair dyeing system which we described in our previous work and to compare with other dyeing systems. Therefore, we investigated concentration limits of matcha and mordant and compared this new dyeing method with commercial permanent systems on the market. Completely unpigmented hair tresses were dyed with matcha powder (camelia sinensis) and iron(II)-lactate. To investigate the wash fastness and concentration limits, the differently dyed hair tresses were spectrophotometrically measured. The comparison of the damage potential for which cysteic acid is an indicator was measured by NIR. The concentration of matcha and mordant are responsible for the intensity of the color results. The higher the matcha or the mordant concentration, the darker the color results of the dyed hair tresses. Hair damage of

matcha mordant dyeing is comparable with results of commercial permanent hair coloration systems. Moreover, the results of wash fastness of matcha mordant dyed hair tresses is comparable and even

Citation: Sargsyan, L.; Hippe, T.; better by tendency to permanent colored hair tresses. Manneck, H.; Vill, V. Tannin-Mordant Coloration with Matcha (camelia Keywords: tannin-mordant-complex; natural hair coloration; matcha; ∆E-values; wash fastness sinensis) and Iron(II)-Lactate on Human Hair Tresses. Molecules 2021, 26, 829. https://doi.org/10.3390/ molecules26040829 1. Introduction One of the most desirable goals in the hair dye industry is to develop a color that Academic Editors: will permanently dye the hair without damaging, while still providing long-lasting color Teresa Escribano-Bailón and intensity. The interest in natural and renewable raw materials as an alternative source Ignacio García-Estévez has increased in many areas. [1] Natural hair dyeing colorants such as henna are widely Received: 4 December 2020 used in natural cosmetics. The main coloring agent in henna leaves is lawsone (2-hydroxy- Accepted: 2 February 2021 1,4-naphthoquinone), also known as CI Natural Orange 6, which is responsible for the Published: 5 February 2021 coloration of the hair fibers and leads to red-orange color results. [2,3]. Natural colorants such as iron-gall inks have been used for thousands of years. They Publisher’s Note: MDPI stays neutral represent a colored tannin-iron complex. They have been used to dye leather, fabrics, and with regard to jurisdictional claims in published maps and institutional affil- other materials, whereby different plants provide different tanning agents, thus creating a iations. wide variety of colors [4]. There are many categories of synthetic hair dyes, which are differentiated by their ability to penetrate the surface or deeper parts of the hair shaft and the longevity of the color after washing. The two most used types of hair dyes are temporary and permanent colorations. Temporary dyes damage the hair less than permanent dyes and are not capable Copyright: © 2021 by the authors. to reach the cortex. [3] The lastingness of this intensive colors is limited to 5–8 hair washes. Licensee MDPI, Basel, Switzerland. An alternative method instead of henna and synthetic coloration could be a dyeing This article is an open access article distributed under the terms and system with polyphenolic compounds of natural origin and mordants with other color conditions of the Creative Commons results than reddish ones. Attribution (CC BY) license (https:// While the polyphenolic compound itself has only a low substantivity to the hair creativecommons.org/licenses/by/ fiber, it is necessary to use metal salts as mordants to increase the affinity by formation 4.0/).

Molecules 2021, 26, 829. https://doi.org/10.3390/molecules26040829 https://www.mdpi.com/journal/molecules Molecules 2021, 26, 829 2 of 12

of stable colored complexes. [5] Iron salts, especially iron(II)-lactate, form intensive coloration in combination with polyphenolic compounds in comparison to other metal salts as investigated in our previous work [6]. Tannic substances can be extracted from different parts of plants as barks and leaves and also from tea to use it for hair dyeing methods. [5] All investigations in this work were done with matcha tea powder (camelia sinensis) itself because of the tannic and catechine compounds which are present in the powder. In our previous work, we could achieve intensive coloration on pre-bleached hair tresses. [6] In this current work, the investigations were carried out on unpigmented hair tresses to determine whether intensive color results can also be achieved on untreated hair tresses. In addition, the wash fastness and the damage potential were compared to commercially available permanent dyeing systems. The examination of hair tresses using near-Infrared (NIR)-spectroscopy has become an established method regarding the detection of cysteic acid. For instance, Pande and Yang examined hair tresses damaged by oxidative treatment using NIR spectroscopy. [7]. Miyamae et al. applied partial least squares (PLS) regression to NIR-DR spectra of human hair after mean centering (MC), standard normal variate (SNV), and ﬁrst derivative (1d) or second derivative (2d) analysis to develop calibration models that predict physical properties of human hair [8]. Thus, the cysteic acid determination in our studies was also carried out by NIR spectroscopy and determined by creating a calibration set and a validation set.

2. Results and Discussion 2.1. Investigation of the Concentration of Matcha To investigate the dependence of the concentration of the tanning agent, herein matcha, and the color intensity, the color change values were determined and presented as box plots in Figure1. The abscissa represents the concentration of matcha and the ordinate represents the color change as ∆E-value after each treatment. The ∆E-value describes absolute color differences calculated by the Euclidean color distance formula as described in Section 4.5 in Formula (1). Moreover, the color coordinates L, a, b, and ∆E are listed in Table1. Compared to the reference, which is the untreated hair tress, all ∆E-values of the hair tresses treated with 1–30 wt% matcha and then treated with mordant differ statistically significantly with (p ≤ 0.001). No more significant differences (p = 1) are identifiable between the ∆E-values of hair tresses dyed with 20 wt% and 30 wt% matcha and then with 1 wt% iron(II)-lactate. Despite significant differences with (p ≤ 0.001) between hair tresses, which where dyed with 10 wt% and 20 wt% matcha and afterwards with 1 wt% iron(II)-lactate, the ∆E-values only raise low. Higher concentration of matcha tends to result in more intense colors. From these investigations, it is evident that the color intensity correlates with the concentration of matcha. An optimal color result can be expected at a concentration of 10 wt% matcha or more. Molecules 2021, 26, 829 3 of 12

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 20

0 mean 0 1 10 20 30 mean ± SE Concentration of Matcha [%] mean ± 1.96*SE

Figure 1. Box andFigure whisker 1. Box plotand ofwhisker color changeplot of ∆colorE-value change of dyed E-value hair tressesof dyed with hair differenttresses with concentrations different con- of matcha in combination withcentrations 1 wt% iron(II)-lactate of matcha in combination and the corresponding with 1 wt% photographs iron(II)-lactate of theand hair the tressescorresponding (n = 10). photo- SE: standard error. graphs of the hair tresses (n = 10). SE: standard error. Table 1. Color coordinates, L, a, b, and ∆E of hair tresses dyed with different concentrations of Table 1. Colormatcha coordinates, in combination L, a, b, and with E 1of wt% hair iron(II)-lactate tresses dyed with (n = different 10). SD: standardconcentrations deviation. of matcha in combination with 1 wt% iron(II)-lactate (n = 10). SD: standard deviation. Concentration of Matcha Concentration of Matcha Color Color Coordi- 0 SD 1 SD 10 SD 20 SD 30 SD Coordinates0 SD 1 SD 10 SD 20 SD 30 SD nates L 76.98 ± 0.41 49.33 ± 0.87 42.22 ± 1.15 40.81 ± 1.24 41.15 ± 0.72 L a76.98 ± 0.41 0.42 ±49.330.12 ± 0.87 0.81 42.22± 0.1 ± 1.15 1.140.81± 0.12 ± 1.24 1.1841.15± 0.11 ± 0.72 1.07 ± 0.08 a b0.42 ± 0.12 19.51 ±0.810.54 ± 0.1 2.75 ±1.10,47 ± 0.12 0.11.18± 0.42 ± 0.11 −0.371.07± ±0.46 0.08 −0.98 ± 0.42 b ∆E19.51 ± 0.54 2.01 ±2.750.55 ± 0,47 31.23 ±0.10.88 ± 0.42 38.76−0.37± 1.18 ± 0.46 40.23−0.98± 1.27± 0.42 40.2 ± 0.82 E 2.01 ± 0.55 31.23 ± 0.88 38.76 ± 1.18 40.23 ± 1.27 40.2 ± 0.82 2.2. Investigation of the Concentration of Iron(II)-Lactate Compared toTo the investigate reference, thewhich dependence is the untreated of the concentrationhair tress, all  ofE-values the mordant, of the hair herein iron(II)- tresses treatedlactate, with and1–30 the wt color% matcha intensity, and thethen color treated change with values mordant were differ determined statistically and presented as significantlybox with plots (p ≤ in0.001) Figure. 2. The abscissa represents the concentration of iron(II)-lactate and the No moreordinate significant represents differences the color (p = change1) are identifiable as ∆E-value between after each the treatment. E-values Moreover,of hair the color tresses dyedcoordinates with 20 wt% L, and a, b, 30 and wt∆%E m areatcha listed and in then Table with2. 1 wt% iron(II)-lactate. Despite significant differences with (p ≤ 0.001) between hair tresses, which where dyed with 10 wt% and 20 wt% matcha and afterwards with 1 wt% iron(II)-lactate , the E- values only raise low. Higher concentration of matcha tends to result in more intense colors. From these investigations, it is evident that the color intensity correlates with the concentration of matcha. An optimal color result can be expected at a concentration of 10 wt% matcha or more.

Molecules 2020, 25, x FOR PEER REVIEW 4 of 12

2.2. Investigation of the Concentration of Iron(II)-Lactate To investigate the dependence of the concentration of the mordant, herein iron(II)- lactate, and the color intensity, the color change values were determined and presented Molecules 2021, 26, 829as box plots in Figure 2. The abscissa represents the concentration of iron(II)-lactate and 4 of 12 the ordinate represents the color change as E-value after each treatment. Moreover, the color coordinates L, a, b, and E are listed in Table 2.

E 20

mean  0 mean ± SE 0 0.001 0.01 0.1 1 mean ± 1.96*SE Concentration of Iron [%]

Figure 2. BoxFigure and whisker 2. Box and plot whisker of color plot change of color∆E-value change of dyedE-value hair tressesof dyed with hair different tresses with concentrations different con- of iron(II)-lactate in combinationcentrations with 10 wt%of iron(II) matcha-lactate and thein combination corresponding with photographs 10 wt% matcha of the and hair the tresses corresponding (n = 10). SE: photo- standard error. graphs of the hair tresses (n = 10). SE: standard error. Table 2. Color coordinates, L, a, b, and ∆E of hair tresses dyed with different concentrations of Table 2. Color coordinates,iron(II)-lactate L, a, in b combination, and E of hair with tresses 10 wt% dyed matcha with (n different = 10). SD: concentrations standard deviation. of iron(II)-lactate in combination with 10 wt% matcha (n = 10). SD: standard deviation. Concentration of Iron(II)-Lactate Concentration of Iron(II)-Lactate Color 0 SD 0.001 SD 0.010 SD 0.1 SD 1 SD Color CoordinatesCoordinates 0 SD 0.001 SD 0.010 SD 0.1 SD 1 SD L 76.60 ± 0.74 62.67 ± 1.41 43.56 ± 0.74 43.1 ± 0.81 70.17 ± 0.86 L 76.60 ± 0.74 62.67 ± 1.41 43.56 ± 0.74 43.1 ± 0.81 70.17 ± 0.86 a 0.41a ± 0.23 0.410.57± 0.23 ± 0.14 0.571.1± 0.14± 0.06 1.10.94± 0.06 ± 0.1 0.942.05± ±0.1 0.3 2.05 ± 0.3 b 18.08b ± 0.71 18.08 7.51± 0.71 ± 1.05 7.51−0.84± 1.05 ± 0.3 −−1.160.84 ± ±0.3 0.42 −18.091.16 ± ±0.42 0.75 18.09 ± 0.75 E ∆1.24E ± 0.62 1.2418.28± 0.62 ± 1.72 18.2838.92± 1.72 ± 0.73 38.9239.47± 0.73± 0.76 39.477.55± ± 0.760.88 7.55 ± 0.88

As in the studyAs of in the the concentration study of the concentrationof the tanning ofagent the, tanning Figure 2 agent, also shows Figure that2 also all shows that all E-values of the∆E-values treated hair of the tresses treated differ hair statistically tresses differ significantly statistically with signiﬁcantly (p ≤ 0.001 with) from (p ≤ 0.001) from the E-value ofthe the∆ E-valueuntreated of hair the untreatedtress, which hair is tress,the reference. which is the reference. The delta ∆E-values of hair tresses treated with 0.01 wt% iron(II)-lactate and matcha do not show statistically signiﬁcant differences (p = 1) compared to the ∆E-values treated with 0.1 wt% or 1 wt% iron(II)-lactate. Intensive color results can be achieved at concentrations as low as 0.01 wt% iron(II)- lactate. From these investigations, it is evident that the color intensity correlates with the concentration of iron(II)-lactate as mordant. An optimal color result can be expected at a concentration of 0.01 wt% of iron(II)-lactate or more. Molecules 2020, 25, x FOR PEER REVIEW 5 of 12

The delta E-values of hair tresses treated with 0.01 wt% iron(II)-lactate and matcha do not show statistically significant differences (p = 1) compared to the E-values treated with 0.1 wt% or 1 wt% iron(II)-lactate. Intensive color results can be achieved at concentrations as low as 0.01 wt% iron(II)- lactate. From these investigations, it is evident that the color intensity correlates with the Molecules 2021, 26, 829 concentration of iron(II)-lactate as mordant. An optimal color result can be expected5 ofat 12 a concentration of 0.01 wt% of iron(II)-lactate or more.

2.3. NIR-Measurement of Cysteic Acid Amount of Matcha and Mordant and Dove Grey Dyed 2.3.Hair NIR-Measurement Tresses of Cysteic Acid Amount of Matcha and Mordant and Dove Grey Dyed Hair Tresses To obtain information on the damage potential of the tanning and mordant dyeing, To obtain information on the damage potential of the tanning and mordant dyeing, the cysteic acid amount was determined using NIR measurements. The relevant NIR- the cysteic acid amount was determined using NIR measurements. The relevant NIR- range for the analysis were the range of the wavelength 7300 to 4020 cm-1 as shown in range for the analysis were the range of the wavelength 7300 to 4020 cm−1 as shown in Figures 3 and 4. The abscissa represents each treatment and the ordinate represents the Figures3 and4 . The abscissa represents each treatment and the ordinate represents the amount of cysteic acid after each treatment as shown in Figure 5. amount of cysteic acid after each treatment as shown in Figure5.

MoleculesFigureFigure 2020 3.3., 2First First5, x FOR derivation derivation PEER REVIEW of of FT-NIR-spectra FT -NIR-spectra of hairof hair tresses tresses after after 3 times 3 times bleaching bleaching and dyedand dyed with matchawith m andatcha iron-(II)-lactate and iron-(II)-6 of 12 withlactate n =with 5. n = 5.

FigureFigure 4. 4.First First derivation derivation FT-NIR-spectra FT-NIR-spectra of of hair hair tresses tresses after after 3 3 times times bleaching bleaching and and dyed dyed with with Dove Dove Grey Grey with with n n = = 5. 5.

6.6

6.4

6.2

6.0

5.8

5.6

Amount of cysteic acid [%] acid of cysteic Amount

5.4

5.2

5.0 mean Reference Matcha Dove Grey mean ± SE Treatment mean ± 1.96* SE

Figure 5. Box and whisker plot of comparison to untreated hair tresses as reference of the amount of cysteic acid amount of hair tresses treated with 10 wt% matcha in combination with 1 %wt iron(II)-lactate and hair tresses dyed with Dove Grey with the corresponding photographs of the hair tresses (n = 5). SE: standard error.

Molecules 2020, 25, x FOR PEER REVIEW 6 of 12

Molecules 2021, 26, 829 6 of 12

Figure 4. First derivation FT-NIR-spectra of hair tresses after 3 times bleaching and dyed with Dove Grey with n = 5.

6.6

6.4

6.2

6.0

5.8

5.6

Amount of cysteic acid [%] acid of cysteic Amount

5.4

5.2

5.0 mean Reference Matcha Dove Grey mean ± SE Treatment mean ± 1.96* SE

Figure 5. Figure 5. Box and whisker plotplot ofof comparisoncomparison toto untreated untreated hair hair tresses tresses as as reference reference of of the the amount amount of of cysteic cysteic acid acid amount amount of hairof hair tresses tresses treated treated with with 10 wt%10 wt% matcha matcha in combination in combination with with 1 wt% 1 %wt iron(II)-lactate iron(II)-lactate and hairand tresseshair tresses dyed dyed with Dovewith D Greyove withGrey thewith corresponding the corresponding photographs photographs of the of hair the tresses hair tresses (n = 5). (n SE: = 5). standard SE: standard error. error.

The product of oxidative treatments is cysteic acid, which is an indicator of damage to the hair structure. The higher the cysteic acid content, the more serious the damage [9]. No statistical differences (p = 1) can be observed between the 3 times bleached hair tress, which is the reference, and both dyed hair tresses. A higher number of samples or a conﬁdence level of 10 wt% would probably lead to signiﬁcant differences between the cysteic acid amount of the reference and the cysteic acid amount of Dove Grey (Igora Royal Absolutes Silverwhite, Schwarzkopf) treated hair tresses. Statistical differences with (p ≤ 0.001) between the cysteic acid amount of matcha and iron(II)-lactate dyed and Dove Grey treated hair tresses are visible. The cysteic acid amount of Dove Grey dyed hair tresses is higher by tendency as shown in Figure5. The potential to damage the hair is low or almost non-existent in both treatments. Thus, the hair coloration by using tanning agents and mordants is comparable and even better by tendency to a permanent hair coloration system.

2.4. Wash Fastness of Matcha and Mordant and Dove Grey Dyed Hair Tresses To test the wash fastness, matcha and iron(II)-lactate treated hair tresses and Dove Grey dyed hair tresses were hand washed up to 30 times and measured spectrophotometrically. The abscissa represents each number of hair washing (HW) and the product which was used for the treatment. The ordinate represents the ∆E-values after of each treatment after Molecules 2020, 25, x FOR PEER REVIEW 7 of 12

The product of oxidative treatments is cysteic acid, which is an indicator of damage to the hair structure. The higher the cysteic acid content, the more serious the damage [9]. No statistical differences (p = 1) can be observed between the 3 times bleached hair tress, which is the reference, and both dyed hair tresses. A higher number of samples or a confidence level of 10 wt% would probably lead to significant differences between the cysteic acid amount of the reference and the cysteic acid amount of Dove Grey (Igora Royal Ab- solutes Silverwhite, Schwarzkopf) treated hair tresses. Statistical differences with (p ≤ 0.001) between the cysteic acid amount of matcha and iron(II)-lactate dyed and Dove Grey treated hair tresses are visible. The cysteic acid amount of Dove Grey dyed hair tresses is higher by tendency as shown in Figure 5. The potential to damage the hair is low or almost non-existent in both treatments. Thus, the hair coloration by using tanning agents and mordants is comparable and even better by tendency to a permanent hair coloration system.

2.4. Wash Fastness of Matcha and Mordant and Dove Grey Dyed Hair Tresses Molecules 2021, 26, 829 To test the wash fastness, matcha and iron(II)-lactate treated hair tresses and Dove 7 of 12 Grey dyed hair tresses were hand washed up to 30 times and measured spectrophotometrically. The abscissa represents each number of hair washing (HW) and the product which was used for the treatment. The ordinate represents the E-values after of each treatment the number of hair washings as shown in Figure6. Moreover, the color coordinates L, a, b, after the number of hair washings as shown in Figure 6. Moreover, the color coordinates and ∆E are listed in Tables3 and4. L, a, b, and E are listed in Tables 3 and 4.

0HW to 30HW 0HW to 30HW



2 mean 6 12 18 24 30 6 12 18 24 30 mean ± SE Product: Matcha Product: Dove Grey mean ± 1.96* SE Number of washing

Figure 6. Box and whisker plots of color change ∆E—values after washing numbers of 6 to 30 of dyed hair tresses with 10 wt%Fi matchagure 6. Box in combination and whisker with plots 1 of wt% color iron(II)-lactate change E— comparedvalues after to washing hairs tresses numbers dyed of with 6 to Dove30 of Grey and the correspondingdyed photographs hair tresses of with the 10 hair wt% tresses matcha from in the combination reference 0 with hair washes1 wt% i toron(II) 30 hair-lactate washes compared (n = 5). SE:to standard error. hairs tresses dyed with Dove Grey and the corresponding photographs of the hair tresses from the reference 0 hair washes to 30 hair washes (n = 5). SE: standard error. Table 3. Color coordinates, L, a, b, and ∆E of hair tresses dyed with commercial hair color Igora Royal Silverwhite Dove Grey (n = 5). SD: standard deviation.

Number of Hair Washes of Dove Grey Color 6 SD 12 SD 18 SD 24 SD 30 SD Coordinates L 45.59 ± 0.37 49.47 ± 0.93 49.6 ± 1.2 50.01 ± 0.76 50.28 ± 1.12 a 1.4 ± 0.08 1.7 ± 0.1 1.69 ± 0.15 1.72 ± 0.09 1.84 ± 0.05 b 5.7 ± 0.24 7.59 ± 0.19 7.89 ± 0.22 8.26 ± 0.31 8.31 ± 0.29 ∆E 5.92 ± 0.4 10.24 ± 0.8 10.49 ± 1.08 11.01 ± 0.64 11.2 ± 1.03 Molecules 2021, 26, 829 8 of 12

Table 4. Color coordinates, L, a, b, and ∆E of hair tresses dyed with iron(II)-lactate in combination with 10 wt% matcha (n = 5). SD: standard deviation.

Number of Hair Washes of Matcha and Iron(II)-lactate Color 6 SD 12 SD 18 SD 24 SD 30 SD Coordinates L 44.09 ± 2.12 48.03 ± 1.82 48.83 ± 1.3 49.36 ± 1.51 51.03 ± 1.31 a 0.93 ± 0.07 1.48 ± 0.13 1.51 ± 0.12 1.71 ± 0.78 1.53 ± 0.06 b 3.53 ± 0.76 7.05 ± 0.41 7.7 ± 0.37 8.54 ± 0.22 8.98 ± 0.36 ∆E 4.35 ± 1.65 7.34 ± 1.64 8.35 ± 1.14 9.92 ± 1.28 10.88 ± 1.25

It can be observed that the removal of hair color is even when the hair tresses are dyed with matcha and iron(II)-lactate. When coloring with matcha and iron(II)-lactate, the ∆E-values of the hair tresses, which were washed up to 6 times, differ statistically significant with (p ≤ 0.001) from all other hair washes up to 30 times. Significant differences with (p ≤ 0.001) can be noticed between the ∆E-values of the hair tresses which were washed up to 12 times and the hair tresses washed up to 30 times after dyed with matcha and iron(II)-lactate. Therefore, the color will not change statistically significant after more than 12 hair washes, when hair tresses are dyed with matcha and iron(II)-lactate. When coloring with Dove Grey, the ∆E-values of the hair tresses, only which were washed up to 6 times, differ statistically significant with (p ≤ 0.001) from all other hair washes up to 30 times. Therefore, the color will not change statistically significant after more than 6 hair washes, when hair tresses are dyed with Dove Grey. The ∆E-values of matcha and iron(II)-lactate dyed hair tresses and Dove Grey dyed hair tresses are comparable after 30 hair washes. This means that the new dyeing system with matcha and iron(II)-lactate can also keep up with the tests of wash fastness with a permanent hair dye as Dove Grey.

2.5. Possible Chemical Bonds on the Hair Fibre after Tannin and Mordant Dyeing According to the investigations of Covington A. D., the protein tannin interactions are based on various types of bonds as hydrogen bonds, salt links between amino side chains and carboxylic acid groups, or hydrophobic interactions [10]. The following Figure7 shows possible bonds and interactions of the hair fiber with ingredients of matcha, here a flavonoid, and iron. The mesomeric effect and the complex bonds that can be formed from the iron ion to the hydroxy groups of the flavonols are shown. It can be seen that the iron can be in a boundary state as an anion covalently bound with the charge −3 or coordinately bound with the charge +3. Furthermore, Figure7 shows the ionic bond between a negative charged oxygen of the flavonol and a positive charged amino side chain group. Numerous hydrogen bonds can also be formed between the hydroxy groups of flavonol and keratinous hair structure. Molecules 2021, 26, 829 9 of 12

Molecules 2020, 25, x FOR PEER REVIEW 9 of 12

Figure 7. PossiblePossible interactions interactions between between hair hair fiber ﬁberss and andflavono ﬂavonoll compounds compounds of matcha of matcha and the and mesomeric the mesomeric effect of effectiron(II) of- lactate where R=-H, -CH, or -OH. iron(II)-lactate where R=-H, -CH, or -OH.

3. Conclusions 3. ConclusionsThese studies show the potential of the hair dye system developed here to compete in theThese hair dye studies industry. show The the potentialinvestigations of the of hair the dye damage system potential developed and here the wash to compete fastness in withthe hair a permanent dye industry. coloring The investigations product on the of themarket damage show potential that this and system the wash provides fastness compa- with rablea permanent and better coloring results. product To confirm on the our market obtained show results, that this further system investigations provides comparable are necessary.and better For example, results. other To conﬁrm parameters our obtained can also results, be investigated further investigations before in vivo are experiments necessary. canFor be example, performed. other In parameters addition, the can exposure also be times investigated can still beforebe optimized,in vivo andexperiments the sequence can ofbe the performed. procedure In can addition, be varied. the exposureFurther investigations times can still with be optimized,different tanning and the agents sequence and mordantsof the procedure should canbe carried be varied. out Furtherto generate investigations additional color with differentshades. tanning agents and mordants should be carried out to generate additional color shades. 4. Materials and Methods 4. Materials and Methods Hair tresses were obtained from the leading manufacturer Kerling International Hair tresses were obtained from the leading manufacturer Kerling International Haar- Haarfabrik GmbH (Backnang, Germany) with a total length of 10 cm of which 8 cm in- fabrik GmbH (Backnang, Germany) with a total length of 10 cm of which 8 cm include hair clude hair fibers. Completely unpigmented hair tresses from Caucasians with 0.45 ± 0.05 ﬁbers. Completely unpigmented hair tresses from Caucasians with 0.45 ± 0.05 g weight, g weight, excluding glue bond, are used for the investigations in this work. excluding glue bond, are used for the investigations in this work.

4.1. Application of Permanent Coloration To compare vegetable tannin coloration with commercially available permanent hair color for for professional professional hairdressing hairdressing needs, needs, Igora Igora Royal Royal Absolutes Absolutes Silverwhite Silverwhite with thewith color the colordirection direction Dove GreyDove(Schwarzkopf Grey (Schwarzkopf Professional, Professional Düsseldorf,, Düsseldorf Germany), Germany) was used. was Ratio used. of Ratiocolor creamof color to cream developer to developer is 1:1 with is an1:1 application with an application time of 20 time min of and 20 3% min developer. and 3% devel- After oper.mixing After of developer mixing of and developer color cream and color 9 g for cream one hair9 g for tress one was hair used. tress was used.

4.2. Method of Matcha and Mordant Dyeing All investigations investigations according according to tomordant mordant coloration coloration where where done done with withmatcha matcha tea pow- tea powderder and andiron(II) iron(II)-lactate.-lactate. The The matcha matcha tea teaused used in inthis this work work was was obtained obtained from from The The Tea Company GmbHGmbH && Co.Co. KG KG (Neu (Neu Wulmstorf, Wulmstorf, Germany) Germany) with with 100% 100% origin origin in Japanin Japan and and the Articlethe Article No. 174077.No. 174077. Tencha Tencha (camellia (camellia sinensis) sinensis) is the originis the productorigin product of which of the which matcha the matcha powder is manufactured by stonegrounds. [11] As shown in Figure 8, the flowchart of the complete tannin-mordant dyeing method is listed and will be described

Molecules 2021, 26, 829 10 of 12

Molecules 2020, 25, x FOR PEERpowder REVIEW is manufactured by stonegrounds. [11] As shown in Figure8, the ﬂowchart of the 10 of 12 complete tannin-mordant dyeing method is listed and will be described more precise in the following.more precise Matcha in solutions the following. of 1 wt%, Matcha 10 wt%, solutions 20 wt%, of and1 wt 30%, wt%,10 wt whereby%, 20 wt% 1, wt% and 30 wt%, matcha solutionwhereby contains 1 wt% m aboutatcha 0.3solution wt% polyphenols,contains about were 0.3 wt% prepared polyphenols, in a buffer were system prepared in a of pH =buffer 5. (Gentle system to theof pH hair, = 5. as (Gentle the ISP to ofthe the hair, hair as isthe about ISP of pH the 4.6). hair Theis about hair pH tresses 4.6). The hair were eachtresses treated were for 30each min treated in the for respective 30 min in solution the respective (100 mL/g) solution and (10 then0 mL rinsed/g) and under then rinsed runningunder deionized running water deionized for 1 min water under for 20 1 times min combing.under 20 times Afterwards, combing the. Afterwards, hair braids the hair were driedbraids with were a commercially dried with availablea commercially hair dryer available at a deﬁned hair dryer distance at a defined and temperature distance and tem- ◦ (T = 80 ±perature5 C; d =(T 10 = cm)80 ± under5 °C; d 20-fold = 10 cm) combing. under 20-fold combing.

Untreated hair Pre-cleansing tress

Drying

Tanning

Drying

Mordanting

Tannin-mordant Drying dyed hair tress

FigureFigure 8. 8.Flowchart Flowchart of of complete complete dyeing dyeing method. method.

Subsequently,Subsequently, 0.001–1 wt%0.001 metal–1 wt% salt metal solutions salt solutions were prepared. were prepared. The tannin-treated The tannin-treated hair tresseshair were tresses each were treated each for treated 30 min for in 30 the min respective in the respective solution (100solution mL/g) (10 and0 mL then/g) and then rinsed underrinsed running under deionizedrunning deionized water for water 1 min for under 1 min 20-fold under combing. 20-fold combing. Afterwards, Afterwards, the the hair tresseshair were tresses dried were with dried a commercially with a commercially available available hair dryer hair at adryer defined at a distancedefined anddistance and ◦ temperaturetemperature (T = 80 ± (T5 =C; 80d ± =5 10°C; cm) d = under10 cm) 20-fold under 20 combing.-fold combing. 4.3. Method of Wash Fastness 4.3. Method of Wash Fastness The hair strands were washed under deionized running water with a volume flow The hair strands were washed under deionized running water with a volume flow of of V = 40 ± 20 mL/s (T = 33 ± 2 ◦C) for 1 min to remove coarse contaminants first. To V ̇ = 40 ± 20 mL/s (T = 33 ± 2 °C) for 1 min to remove coarse contaminants first. To review review the wash fastness of the color, the wet hair tresses were washed up to 30 times the wash fastness of the color, the wet hair tresses were washed up to 30 times by hand by hand using 0.5 ± 0.02 g/hair commercially available shampoo (Schauma 7 Kräuter, using 0.5 ± 0.02 g/hair commercially available shampoo (Schauma 7 Kräuter, Schwarz- Schwarzkopf). The 7 Herbs Shampoo was massaged in 10 times with a 5-fold circular kopf). The 7 Herbs Shampoo was massaged in 10 times with a 5-fold circular motion with motion with the thumb and forefinger and constant pressure from the adhesive bond to the thumb and forefinger and constant pressure from the adhesive bond to the tip of the the tip of the hair. After incorporation of the shampoo, the hair tresses were rinsed out hair. After incorporation of the shampoo, the hair tresses were rinsed out under running under running deionized water under deionized running water with a volume flow of deionized water under deionized running water with a volume flow of V = 40 ± 20 mL/s V = 40 ± 20 mL/s (T = 33 ± 2 ◦C) for 1 min. After rinsing, the hair tresses were detangled (T = 33 ± 2 °C) for 1 min. After rinsing, the hair tresses were detangled by combing them 20 times, starting from the adhesive bond up to the tip of the hair. After cleaning and combing, the hair tresses were dried with a commercially available hair dryer at a defined

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by combing them 20 times, starting from the adhesive bond up to the tip of the hair. After cleaning and combing, the hair tresses were dried with a commercially available hair dryer at a deﬁned distance and temperature (T = 80 ± 5 ◦C; d = 10 cm). This process was repeated up to 30 hair washes.

4.4. Cysteic Acid Measurement with NIR-Spectroscopy Additionally, the samples were measured near infrared (NIR) spectroscopically with the integrating sphere module at 6 different sample positions in diffuse reflection. The spectra were recorded with a MPATM FT-NIR spectrometer from Bruker Optik GmbH. The NIR-range covers the wavenumber range from 12,500 to 4000 cm−1 and is characteristic for overtone and combination oscillations of e.g., CH-, OH-, and NH- groups. The measurements of the samples were performed in transmission at a resolution of 16 cm−1 and a scan number of 64. The relevant NIR-range for the analysis were the range 7300 to 4020 cm−1. A partial least squares (PLS) regression of spectroscopic data and corresponding concentration values of the individual components was used to create a calibration model. The basis of the calibration work was a set of reference samples with defined concentrations. The PLS-model is improved by changing the frequency range, mathematical data pre-treatment (first derivation), selecting the appropriate number of factors and automatic outlier detection. Here, the factor number is equal to the number of PLS-factors. The concentration and spectral data matrix were decomposed into scores and loading vectors by the PLS algorithm. The model created in each case was validated by the chemometric method.

4.5. Spectrophotometric Measurement with Data Color The matcha and iron(II)-lactate hair tresses were measured spectrophotometrically using a Datacolor SF600 Spectraflash device. A D65 illuminant and diffuse/8◦ optical configuration were used for the spectrophotometer measurements. The spectral reflectance data for each sample from 380 to 700 nm were converted into colorimetric data using the DCI Color software. Reflectance measurements were recorded for each hair sample using an average of 4 measurements. In 1976, CIE introduced the CIE-Lab three-dimensional color space. An important reason for the introduction was to standardize formulas for measuring color differences. Color distances should correspond as closely as possible to the perceived differences. Thus, the system is intended to create visual uniformity in the evaluation of color differences [12]. Hair color is expressed in terms of the L*, a*, b* color coordinates, where L* corre- sponds to the lightness (0 = black, 100 = white), a* to the red-green coordinate (−delta e green, +delta e red), and b* to the yellow-blue coordinate (−delta e = blue, +delta e = yellow) of a sample identifies a point in the 3D CIELAB color space that describes the color of the hair sample [13]. The color changes after each wash cycle were measured as ∆E. Abso- lute color differences are measured with the following, Euclidean color distance formula calculated as described in DIN 6174 as in formula (1) [14]: q ∆E = ∆L2 + ∆a2 + ∆b2 . (1)

4.6. Statistical Analysis All data analyses were conducted using the software Statistica 13.0 (StatSoft Inc., Tulsa, OK, USA). One-way ANOVA and post-hoc Tukey test were conducted if the dataset was normal distributed and homogeneity of variance was given. If one of the abovementioned assumptions is not fulfilled the nonparametric Kruskal–Wallis test and afterwards the Dwass–Steel–Critchlow–Fligner test is conducted. All results are presented as box–whisker plots. The box defined by the mean ± standard error (SE) and the whiskers represent the mean ±1.96* standard error, which give the limits of the confidence interval on 95% confidence level. Molecules 2021, 26, 829 12 of 12

5. Patents Patent resulting from this manuscript with the following Number: DE102020214790.6.

Author Contributions: Conceptualization: L.S., T.H., H.M., V.V. Methodology: L.S., T.H., V.V., H.M. Formal analysis: L.S., H.M., T.H. Investigation: L.S. Data curation: L.S. Software: L.S., H.M. Writing— original draft preparation: L.S. Writing—review and editing: L.S. Visualization: L.S. Supervision: V.V., T.H., H.M. All authors have read and agreed to the published version of the manuscript. Funding: This research was funded by Henkel AG&Co KGaA. Institutional Review Board Statement: Not applicable. Informed Consent Statement: Not applicable. Data Availability Statement: The data presented in this study are available on request from the corresponding author. Acknowledgments: We are grateful to all R&D members of the hair color level 3 department (Henkel AG&Co KGaA, Germany) and the perfect cooperation with the University of Hamburg. Conﬂicts of Interest: The authors declare no conﬂict of interest. Sample Availability: Samples of the compounds are available from the authors.

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