Trihydroxybenzoic acid glucoside as a global skin color modulator and photo-protectant

Figures & data

Table 1 Summary of the different parameters related to color assessment

Parameters	Method of determination: direct reading or calculation	Meaning	Value and interpretation
L*	Direct reading	Lightness of the color	From 0 to 100
			L* =0: black
			L* =100: maximum lightness
a*	Direct reading	Chroma of the color	From −128 to +127 corresponding to 256 levels
			− a* = green
			+ a* = red
b*	Direct reading	Chroma of the color	From −128 to +127 corresponding to 256 levels
			− b* = blue
			+ b* = yellow
C*	√ [(a*)^Citation2 + (b*)^Citation2]	Color intensity or color saturation	From 0 to 100
			0= at the center of circle means totally unsaturated
			100= at the edge of the circle high saturation “color purity”
			Higher chroma C* indicates greater intensity
h (hue)°	arctan (b*/a*) or tang^−1 (b*/a*)	Color shading	Colors expressed on 360° grid:
			0°= red; 60°= yellow; 120°= green; 180°= cyan; 240°= blue; 300°= magenta
			Differences in hue angle of 1° are discernible by the human eye
ITA°	arctan [((L*50)/b*)*(180/π)]	Intensity of pigmentation	Dark skin types: lower ITA°
			Light skin types: higher ITA°
			If the ITA° increases, the quantity of melanin decreases

Abbreviation: ITA°, individual typology angle.

Table 2 Color parameters recorded (L*, a*, b*) or calculated (chroma C*, hue angle, and ITA°) from a Chroma-Meter applied on the face skin of 20 volunteers before and after 14, 28, 56, and 84 days of vehicle cream or THBG cream application

Product tested and time		Color parameters Mean ± standard deviation						Average variation parameter vs D0 (%)P-value (significant “s” or non-significant “ns”)
		L*	a*	b*	Chroma C*	Hue angle	ITA°	L*	a*	b*	Chroma C*	Hue angle	ITA°
Vehicle	D0	57.82±2.62	11.55±1.86	19.14±2.23	22.43±2.14	58.82±4.99	22.38±8.1
	D14	57.48±2.75	11.40±2.36	19.22±2.15	22.49±1.85	59.68±5.97	21.25±7.69	−0.7%	−0,4%	+0.14%	0.3%	1.1%	−2.74%
								P=0.795 (ns)	P=0.658 (ns)	P=0.846 (ns)	P=0.766 (ns)	P=0.285 (ns)	P=0.42 (ns)
	D28	57.96±2.69	11.00±1.97	19.56±1.94	22.52±1.92	60.65±5.12	22.20±7.69	0.12%	−3.6%	+2.4%	0.8%	2.8%	−1.95%
								P=0.749 (ns)	P=0.118 (ns)	P=0.938 (ns)	P=0.425 (ns)	P=0.037 (s)	P=0.34 (ns)
	D56	58.13±3.01	11.20±1.83	19.35±2.47	22.45±2.20	58.65±5.32	22.89±8.56	0.30%	−2,8%	+0.4%	−0.4%	−0.3%	−3.3%
								P=0.97 (ns)	P=0.270 (ns)	P=0.878 (ns)	P=0.929 (ns)	P=0.331 (ns)	P=0.34 (ns)
	D84	58.13±3.1	11.44±2.67	19.03±2.57	22.39±2.22	58.98±7.57	22.98±8.35	0.5%	−0,6%	−0.88%	−0.3%	0%	−3.29%
								P=0.76 (ns)	P=0.770 (ns)	P=0.617 (ns)	P=0.865 (ns)	P=0.886 (ns)	P=0.30 (ns)
THBG	D0	57.16±2.10	12.67±2.13	19.03±2.52	23.03±1.67	56.13±7.18	20.82±6.42
	D14	57.27±1.85	12.14±2.57	19.07±2.24	22.8±1.58	57.48±7.69	21.00±5.43	+0.2%	−4.2%	+0.3%	−1%	+2.4%	+0.9%
								P=0.6 (ns)	P=0.128 (ns)	P=0.86 (ns)	P=0.457 (ns)	P=0.117 (ns)	P=0.75 (ns)
	D28	57.71±1.95	11.65±2.21	19.50±2.41	22.89±1.46	58.91±7.31	21.67±5.68	+0.9%	−12.9%	+2.9%	−0.3%	+5.1%	+3.2%
								P=0.06 (ns)	P=0.0035 (s)	P=0.09 (ns)	P=0.779 (ns)	P=0.0024 (s)	P=0.29 (ns)
	D56	58.16±2.22	11.77±1.96	19.23±2.29	22.68±1.63	58.35±6.38	22.99±5.80	+1.8%	−7.3%	+0.5%	−1.5%	+4%	+10.4%
								P=0.001 (s)	P=0.027 (s)	P=0.50 (ns)	P=0.175 (ns)	P=0.045 (s)	P=0.0008 (s)
	D84	58,40±2.21	11.78±2.71	19.42±2.02	22.91±1.29	58.73±7.82	23.20±5.24	+2.2%	−7%	+2.1%	−0.5%	+4.6%	+11.5%
								P=0.0039 (s)	P=0.063 (ns)	P=0.388 (ns)	P=0.780 (ns)	P=0.05 (s)	P=0.034 (s)

Notes: Average variation for each parameter and their statistical significance using Student’s t-test (paired data) was calculated at each study time in comparison to D0. ns means statistically non-significant (P>0.05) and s means statistically significant (P≤0.05). Statistically significant data are represented in bold. Vehicle cream shows no effect on all skin color parameters. THBG shows significant effect on almost all skin color parameters with the exception of b* and chroma C*. Data are presented as mean ± standard deviation.

Abbreviations: ITA°, individual typology angle; THBG, 3,4,5-trihydroxybenzoic acid glucoside; D, day.

Table 3 Melanin content quantification by SIAscope™ applied on the face skin of 20 volunteers at the beginning of the study (D0) and after 14, 28, 56, and 84 days of vehicle and THBG treatment

Parameters	Vehicle		THBG at 2%
	Melanin quantity (mean ± standard deviation) (arbitrary unit)	Average variation vs D0 (%) P-value	Melanin quantity (mean ± standard deviation) (arbitrary unit)	Average variation vs D0 (%) P-value	THBG vs vehicle (% and P-value)
D0	337.45±39.02		347.23±37.81
D14	331.98±40.56	−1.6%	332.00±30.48	−4.4%
		P=0.0796 (ns)		P=0.0214 (s)
D28	323.00±44.01	−4.2%	328.90±34.13	−5.3%
		P=0.0299 (s)		P=0.0073 (s)
D56	327.54±42.64	−3%	329.41±39.32	−5.1%
		P=0.0058 (s)		P=0.0174 (s)
D84	327.40±38.51	−3%	321.36±33.04	−7.5%	−150%
		P=0.0008 (s)		P=0.0017 (s)	P=0.04 (s)

Notes: Each measurement was done in triplicate, s and ns mean respectively the significant (P≤0.05) and non-significant (P>0.05) effect seen using Student’s t-test (paired data). Statistically significant data are represented in bold. Melanin quantity decreases in both conditions but the effect seen is more pronounced with THBG. THBG quickly and continuously decreases melanin content of skin (effect observed after 14 days and continues until 84 days). Data are presented as mean ± standard deviation.

Abbreviations: THBG, 3,4,5-trihydroxybenzoic acid glucoside; D, day.

Figure 1 Melanin content visualization at D0 and after 14, 28, 56, and 84 days of placebo and THBG treatments (SIAscope™ tool, selection of two volunteers).

Notes: Melanin content is not decreased or slightly decreased in vehicle cream treated side in comparison to THBG treatment where a clear decrease of melanin content is seen in spot area (represented by the dark spot “black color”) and normal area (represented by “gray color”).
Abbreviations: THBG, 3,4,5-trihydroxybenzoic acid glucoside; n°, number; D, day.

Figure 2 Macrophotographies taken under visible or UV light from one volunteer before and after vehicle cream or THBG cream application for 84 days.

Note: UV photographs show UV spots (black spots on the pictures) non-visible under visible light.
Abbreviations: UV, ultraviolet; THBG, 3,4,5-trihydroxybenzoic acid glucoside; D, day.

Table 4 UV spots parameters quantification

Parameters	Placebo		THBG at 2%
	UV spots (mean ± standard deviation) (arbitrary unit)	Average variation vs D0 (%) (P-value)	UV spots (mean ± standard deviation) (arbitrary unit)	Average variation vs D0 (%) P-value	THBG vs placebo (fold) (P-value)
D0	0.213±0.060		0.209+0.070
D14	0.212±0.063	−0.4%	0.203±0.064	−2.9%
		(P=0.8825) (ns)		(P=0.4788) (ns)
D28	0.228±0.074	+6.8%	0.193±0.060	−7.9%	×16
		(P=0.0809) (ns)		(P=0.0630) (ns)	(P=0.0101) (s)
D56	0.226±0.065	+3.3%	0.194±0.058	−7.4%	×12
		(P=0.521) (ns)		(P=0.0336) (s)	(P=0.07) (ns)
D84	0.233±0.075	+9.3%	0.194±0.064	−7.5%	×18
		(P=0.0188) (s)		(P=0.05) (s)	(P=0.0020) (s)

Note: ns means non-significant and s means significant effect seen with P≤0.05, Student’s t-test, paired data, and VISIA-CR™ tool analysis. Statistically significant data are represented in bold. Data are presented as mean ± standard deviation.

Abbreviations: UV, ultraviolet; THBG, 3,4,5-trihydroxybenzoic acid glucoside; D, day.

Figure 3 Macrophotographies taken using visible light from three volunteers before and after vehicle cream or THBG cream application for 84 days.

Note: Decrease of skin redness is visible on these three volunteers, whereas no or slight improvement is seen with vehicle cream application.
Abbreviations: THBG, 3,4,5-trihydroxybenzoic acid glucoside; D, day.

Figure 4 Absorption spectra of THBG pure or diluted in a formulation cream.

Abbreviation: THBG, 3,4,5-trihydroxybenzoic acid glucoside.

Figure 5 Visualization of melanin content in skin explants cultured in presence or not of THBG at 2% and kojic acid at 1% (histological analysis, Fontana Masson staining).

Abbreviations: THBG, 3,4,5-trihydroxybenzoic acid glucoside; D, day.

Figure 6 Visualization of melanin content in skin explants cultured after irradiation and in presence or not of THBG at 2% (histological analysis, Fontana Masson staining).

Abbreviations: THBG, 3,4,5-trihydroxybenzoic acid glucoside; UV, ultraviolet; D, day.

RuizDEgeaJTomas-BarberanFAGilMICarotenoids from new apricot (Prunus armeniaca L.) varieties and their relationship with flesh and skin colorJ Agric Food Chem200553166368637416076120

 PubMed Web of Science ®Google Scholar