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Article

Methodology to Reach Full Spectral Photo-Protection by Selecting the Best Combination of Physical Filters and Antioxidants

by
Alexandra Lan
1,
Yan Lui
1,
Jinhui Zuo
1,
Silke B. Lohan
2,
Sabine Schanzer
2,
Sabrina Wiemann
3,
Cornelia M. Keck
3,
Jürgen Lademann
2 and
Martina C. Meinke
2,*
1
Shanghai Pechoin Daily Chemical Corporation, Shanghai 200063, China
2
Charité—Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Department of Dermatology, Venereology and Allergology, 10117 Berlin, Germany
3
Department of Pharmaceutics and Biopharmaceutics, Philipps-Universität, 35037 Marburg, Germany
*
Author to whom correspondence should be addressed.
Cosmetics 2023, 10(1), 1; https://doi.org/10.3390/cosmetics10010001
Submission received: 16 November 2022 / Revised: 12 December 2022 / Accepted: 13 December 2022 / Published: 20 December 2022
(This article belongs to the Special Issue Feature Papers in Cosmetics in 2022)
Browse Figures
Versions Notes

Abstract

:
Antioxidants can reduce free radical formation in deeper skin layers where typical sunscreen filters may no longer be effective. Here, a general method is presented to pre-select optimum combinations of antioxidants and physical filters. The radical production of selected common physical filters after UV irradiation, the capacity of different antioxidants and the interaction between these compounds was investigated in solution by optical measurement of DPPH scavenging, allowing a theoretical calculation of the antioxidant amount necessary to scavenge UV-induced radicals. Furthermore, the antioxidant capacity and the scattering properties were determined. All physical filters induced different amounts of radicals in suspensions depending on the coating. ZnO coated with polydimethylsiloxane and myristic acid (ZnOpolymyr) showed the lowest radical formation. Epigallocatechin-gallate (EGCG) provided the highest antioxidant capacity. Different formulations with different ratios of selected physical filters and antioxidants were prepared. It turned out that the high radical protection factor (RPF) of cream formulations, which originally did not contain any physical filters, was reduced when such filters were added. The data demonstrates that the addition of physical filters to antioxidant-containing formulations lowers their reduction capacity, but to varying degrees. An optimal combination of physical filters and antioxidants must be pre-selected in order to incorporate them into a formulation and verify their effect on skin.

1. Introduction

Sunscreens are used around the world to prevent sunburn, photo aging and skin cancer. In the past, the focus was geared towards the UV spectral region. Classical ingredients here are physical and chemical UV filters in formulations which locate the filters in the upper layers of the Stratum Corneum (SC) [1]. Chemical filters absorb the UV light, while physical filters (minerals, pigments) mostly reflect and scatter the light on the skin; both filters impede the penetration of UV light into the living dermis [2].
Several investigations have shown that the combination of scattering substances such as physical UV filters, e.g., TiO2 or ZnO with chemical ones increase the sun protection non-linearly. The reason is the enhanced path length in the upper SC, which promotes the absorption by UV filters while inhibiting the penetration into the living epidermis [3,4]. A high degree of protection in the UV spectral region invites prolonged sun exposure, so that the so far unprotected visible (VIS) and near-infrared (NIR) spectral region attracted attention.
During sun exposure, up to 50% of radical formation is observed for skin types I to III in the VIS and NIR spectral region [5]. For darker skin types, this percentage increases [6]. The long stay in the sun increases the radical load in the skin and promotes cell damage, premature skin aging and skin cancer [7,8,9]. In the visible region, no absorber can be used to protect the skin because the sunscreen would be colored [10], which is not acceptable for most consumers.
Instead of absorbers, antioxidants can be applied to scavenge radicals before they promote cell damage [11,12]. Antioxidants have been shown to provide additional value in sunscreens [13,14]. Intuitively, potent antioxidants at high concentrations should provide better protection. However, there is not a universal standard to define the global potency of antioxidants; it depends on the experiments and biomarkers chosen by researchers [15]. In practice, high concentrations of antioxidants usually entail unacceptable color changes in cosmetic products. Physical filters also protect in the VIS and NIR region but with less effect [16]. With increasing wavelengths, the scattering effect decreases [17,18]. The addition of physical filters is limited because of galenic influences and whitening effects [1]. Nevertheless, both protection strategies, physical filters and antioxidants, have shown to preserve the skin by reducing the radical formation, which can be investigated by electron paramagnetic resonance (EPR) spectroscopy [16,19].
Chemical filters and classical physical filters act synergistically in the UV range. But the addition of TiO2 and ZnO nanoparticles in cream formulations containing antioxidants reduces their antioxidant capabilities. This is often not recognized due to lack of antioxidant analysis of the final product. So far, the investigated products with high protection showed either high antioxidant or high scattering properties [19]. Nevertheless, new approaches with alternative physical filters such as colloidal lignin nanoparticles [20,21] or starches and PEG-75 Lanolin [22] led to an increase in both antioxidant capacity and scattering properties.
The question arises how the different antioxidants interact with the various combinations of physical filters and how the optimal composition can be selected.
One assumption is that in a formulation containing physical filters and antioxidants, the physical filters induce free radicals after UV irradiation, which are neutralized by the included antioxidants, attenuating their antioxidant capacity. In general, the selected antioxidants and chosen physical filters fit well. A marginal amount of antioxidants is sufficient to scavenge radicals generated by physical filters under UV irradiation in skin, therefore the impact on antioxidant capacity reduction can be minimized.
The aim of the study at hand was to investigate this phenomenon of interaction in more detail and to develop a methodology to preselect optimum combinations of antioxidants (AO) and physical filters to ensure the best protection effect beyond the UV spectral region. This would be an important step to provide a sunscreen protecting the skin against cell damage and photo-aging throughout the whole spectrum of solar radiation.

2. Materials and Methods

2.1. Materials

Compositions and average diameters of the four physical filters investigated for radical formation and interaction with antioxidants in solution are summarized in Table 1.
The base cream formulation contained the following ingredients: Dimethicone (1.5 cs), Dimethicone (10 cs), Cyclopentasiloxane, PEG-9 Polydimethylsiloxyethyl Trimethylsiloxysilicate, Isostearic Acid, Isododecane, Sorbitan Sesquiisostearate, Isopropyl Myristate, Diisopropyl Sebacate, Ethylhexyl Methoxycinnamate, Octocrylene, Diethylamino Hydroxybenzoyl Hexyl Benzoate, Bis-Ethylhexyloxyphenol Methoxyphenyl Triazine, Stearyl Glycyrrhetinate, Menthol, Disteardimonium Hectorite, Methyl Methacrylate Crosspolymer, Polymethylsilsesquioxane, Talc, Fragrance, Zingiber Officinale (Ginger) Root Extract, Water, Disodium EDTA, Sodium Chloride, Glycerin, Butylene Glycol, Alcohol, Phenoxyethanol).
The following antioxidants were included in the base cream formulation: 0.3% Tocopherol (VE), 0.5% EGCG and 0.1% Sodium metabisulfite and 0.2% Carmosine. Prior to investigation, the base cream formulation was complemented by different physical filters according to Table 1.
To counteract the radicals, the following antioxidants were investigated in solution:
  • Epigallocatechin Gallate EGCG (TAIYO KAGAKU CO. LTD, Japan);
  • Alpha-Tocoperol/Vitamin E (VE) (Koninklijke DSM N.V. (Royal DSM, The Nether-lands);
  • Ferulic acid (FA) (Shanghai Lijing Industrial Co, LTD, China);
  • Emblica (Merck KGaA, Germany);
  • Rosmarinic acid (Chengdu Herbpurify Co., Ltd., China);
  • Sodium metabisulfite (SM) (Sinopharm, China).
DPPH was purchased from Tokyo Chemical Industry Co., Ltd. (Japan, purity > 97%).

2.2. Methods

2.2.1. Pre-Selection of an Optimal Physical Filter/Antioxidant Ratio

The method comprises three parts: (1) using DPPH as probe to measure radicals generated by four physical filters, (2) determining the capacity of six antioxidants using DPPH, (3) determining each antioxidant’s concentration required to eradicate radicals generated by a chosen physical filter under the condition described in (1), and comparing the concentration of each antioxidant with its “theoretical” value from (2).
  • (1) Radical generation
Six percent (% w/w) of physical filter of Table 1 was dispersed in propylene glycol by homogenizer (Primix Robomix, Tsukishima Kikai Co, Japan). The dispersion was irradiated by a UV source (350–400 nm, 882.59 mW) (Zhongshan Tiandou UV LED, Xiaolan Town, China) for 15 min. Therefore, the lamp was placed into a dark box, the sample was transferred into a glass bottle and was irradiated with UV light for the specified time.
The dispersion was then mixed 1:1 with a DPPH solution (water: ethanol = 2.5:7.5). The final concentration is 2% for physical filter and 0.008% for DPPH. The mixture was stirred for 1 min (1000 mot) and then centrifuged for 5 min at the rate of 4000 r/min (CH80-2, Shanghai Medical Instruments CO., LTD, Shanghai, China). The supernatant was collected and subjected to spectrometric analysis (PerkinElmer, Lambda 750S, Connecticut, USA) for DPPH (517 nm), the value is denoted as A1.
Calculation of the scavenged DPPH:
Ra = 1 − A 1 − A 2 A 0   100 %
Ra = radical generation by physical filters
A2 = A1 without DPPH,
A0 = 0.008% DPPH [propylene glycol/water/ethanol solution].
DPPH reduction without irradiation was considered by subtraction.
  • (2) Determination of the antioxidant capacities of six antioxidants
A propylene glycol/water/ethanol solution was used for antioxidant and DPPH studies (the solvent ratio is the same as shown in (1)). The DPPH concentration was fixed at 0.008% and the antioxidants were added at various concentrations. The calibration curve of each antioxidant against DPPH was plotted at different concentrations by ELISACalc (Shanghai Bluegene Biotech CO.,LTD, Shanghai, China). The IC50 where 50% of the ECGC is consumed was calculated.
  • (3) Ratio finding between physical filters and antioxidants
Preparation and irradiation of pigment dispersion were performed exactly as described in step (1). The dispersed physical filters (without antioxidants) were irradiated to generate radicals. The mixture was then mixed with different concentrations of selected antioxidants solubilized in water/ethanol solution to neutralize the radicals. It was stirred for 10 min at 1000 Mot, then adding DPPH solution (water/ethanol) and stirred for another minute, the final mixture has a solvent that is the same as described in steps (1) and (2). The DPPH concentration was 0.008%. The DPPH solution was introduced to measure the radicals, which had not been neutralized, or excessive antioxidants. The final mixtures were centrifuged for 5 min at the rate of 4000 r/min (CH80-2, Shanghai Medical Instruments CO., LTD, Shanghai, China). The supernatant was collected and subjected to spectrometric analysis (PerkinElmer, Lambda 750S, USA) for DPPH (517 nm), the value is denoted as B1.
Calculation of the scavenged DPPH:
Rb = 1 − B 1 − B 2   B 0   100 %
Rb= radical scavenging
B2 = B1 without DPPH,
B0 = 0.008% DPPH [propylene glycol/water/ethanol solution].
We searched for an Rb inferior to 5% implying the antioxidant concentration is sufficient to almost completely neutralize the radicals generated by a pigment so that less than 5% of DPPH was sacrificed. This value was then compared with the corresponding theoretical value calculated from step (2).
X is defined as the theoretical concentration of an antioxidant that is supposed to completely neutralize radicals generated by a pigment divided by the experimentally obtained concentration when Rb < 5%.
If X = 1, the capacity of an antioxidant to scavenge the radicals generated by a physical filter is in line with expectations.
If X > 1, the capacity of an antioxidant to scavenge the radicals generated by a physical filter outperforms expectations (good for production).
If X < 1 the capacity of an antioxidant to scavenge the radicals generated by a physical filter underperforms expectations.

2.2.2. Measurements of Antioxidant Capacity of the Creams by Radical Protection Factor (RPF)

The radical scavenging activity of the cream formulations including physical filters and antioxidants was analyzed by EPR spectroscopy using again the test radical 2,2-Diphenyl-1-picrylhydrazyl (DPPH) (Sigma-Aldrich, Steinheim, Germany). The number of reduced DPPH represents the radical scavenging activity of the investigated extracts/cream formulation, which is normalized to 1 mg input. The measuring unit of the RPF is 1014 radicals/mg [16,19].
The RPF analysis was performed with an X-band MiniScope MS5000 EPR spectrometer (Magnettech, Freiberg Instruments GmbH, Freiberg, Germany) at a microwave frequency of 9.4 GHz. The method was in principle applied as previously described [16]. The calculation of the spin concentration of the 1 mM ethanolic DPPH solution and the final calculation of the RPF was performed by the MS5000 device control software “ESR Studio” (Freiberg Instruments GmbH, Freiberg, Germany).
For the RPF analysis of the samples, 20 to 500 mg of the formulations were solubilized in 10 mL ethanol, followed by a dilution (1:1) with a 1 mM DPPH ethanol solution. The EPR measurements were performed directly after sample preparation (0 h) and 23 to 28 h after sample incubation, until a stabilization of the DPPH signal was achieved. During the incubation time, the samples were kept dark at room temperature by constant panning. The samples were measured in glass capillaries (Hirschmann Laborgeräte GmbH & Co. KG, Eberstadt, Germany) with the following parameter settings: frequency 9.4 GHz, central magnetic field 338.43 mT, magnetic field sweep width 9.5 mT, modulation frequency 100 kHz, modulation amplitude 0.2 mT attenuation 15 dB, sweep time 20 s.

2.2.3. Evaluation of the Optical Properties of the Creams by UV-VIS Spectroscopy

The double integrating sphere technique combined with inverse Monte Carlo simulation (iMCS) was used to determine the optical parameters absorption µa and effective scattering coefficient µs’ of the different cream formulations [23]. The method was performed as previously described in detail [24]. An integrating sphere spectrometer (Lambda 1050, PerkinElmer, Rodgau-Jügesheim, Germany) was used for the measurements. The cuvette can be fixed in a defined position at a constant distance from the sphere opening in front of or behind the integrating sphere to measure the transmission (TtM) or reflection (RtM) spectra. For the measurement of Tt, the reflectance port was closed with a diffuse reflecting Spectralon® standard. Rt was measured relative to the reflectance standard by replacing the special Spectralon® standard by the sample, which is inclined at an angle of 8° to the incident light.
In order to obtain reproducible reflectance and transmittance measurements, a homogeneous sample distribution was ensured. The measurement inaccuracy of repeated measurements was less than 2%. The optical parameters µa and µs’ were calculated by inverse Monte Carlo simulation (iMCS) as previously described [23,24]. Thereby, the iMCS uses forward Monte Carlo simulations iteratively to calculate the optical parameters µa and µs’ on the basis of a given phase function and the experimentally measured values for reflection and transmission (RtM and TtM). By systematic variation of μa and μs’ the deviation of the simulated RtSand TtSvalues from the ones measured is minimized until a set of optical parameters is found, where the deviations are within an error threshold of 0.20%.

3. Results and Discussion

First, radical production of selected common physical filters after UV irradiation and the antioxidant capacity of various antioxidants were measured in solution under standardized conditions. Second, the interaction of selected physical filters and antioxidants (AO) was investigated with the same method.
One promising AO mixture was selected and combined with different physical filters in cream formulations. From these cream formulations, the antioxidant capacity using RPF technology and the scattering properties were determined.

3.1. Radical Generation by Physical Filters under UV Irradiation

As shown in Table 2 (first line) different physical filters have different capacities to generate radicals during UV irradiation. The higher the scavenged DPPH, the more radicals were generated by a pigment under the same experimental condition.
Zinc oxide and ZnOpolymyr showed the lowest radical-generating capacity and ZnOtriet25 the most. This may be due to pigment size and its coating. Small physical filters are more difficult to be uniformly coated [25] and the type of coating is also of importance [26].

3.2. Antioxidant Capacities of Various Antioxidants in Solution

The capacities of six antioxidants against DPPH are summarized in Table 3. Their IC50 and fitting curves were calculated (Figure 1). Comparing their IC50 against DPPH, we found that EGCG > ferulic acid > rosmarinic acid > vitamin E > emblica > metabisulfite. In addition, their theoretical values for each pigment can be obtained from the fitting curve. For example, TiO2-AlOH scavenged 45% of DPPH, and the corresponding IC45 for EGCG is 0.000047%. Consequently, 0.000047% of EGCG is supposed to neutralize all the radicals generated by the TiO2-AlOH under the described condition.
The measured DPPH IC50 values confirm the action of antioxidants in the literature. EGCG, from green tea extract, providing the lowest IC50 value, has been shown to attenuate UV-induced erythema [27]; as a potent antioxidant, only a low amount of EGCG is necessary to counteract the radicals formed by physical filters; rosmarinic acid belongs to the hydroxycinnamic acid esters found in Boraginaceae and Lamiaceae plants. In addition to its ability to scavenge radicals, rosmarinic acid can reduce UVB-induced protein carbonylation [28] and Poly(I:C)-induced inflammation [29]. Ferulic acid, another hydroxycinnamic acid derivative, is a natural UV absorber and antioxidant [30]; emblica is the Phyllanthus Emblica fruit extract from Merck. The extract is rich in emblicanins which are metal iron chelators. Irons are known to catalyse the Fenton reaction, which generates reactive hydroxyl radicals [31].

3.3. Determination of Theoretical and Real Amount of Antioxidants to Counteract Radical Production by Physical Filters

The calculated amounts of each AO to neutralize the amount of radical formed by the irradiated physical filters are given as ICx in Table 3 for investigated antioxidants. Furthermore, the used amount of AO and the factor X between calculated and used amount is given. We have to conclude that the theoretical value is almost not reached in the experimental determination of the radical scavenging amount. For the TiO2-AlOH, EGCG at the concentration of IC45 can almost scavenge all the radicals generated by TiO2-AlOH (XEGCG = 0.9). For the TiO2-AlOH, sodium metabisulfite outperforms its theoretical value by a factor of 5.4 (XSM = 5.4); however, ferulic acid remarkably underperforms its expectation, which suggest much more ferulic acid than calculated is required to eliminate TiO2-AlOH-generated radicals. For the ZnOtriet25, EGCG, emblica and rosmarinic acid exceed all expectations, suggesting that they are good counterparts for this pigment.
The reason why the experimental data did not match the theoretical data illustrate that the mechanism of interaction between radical formation by physical filters and counteraction by AO is complex and that not all effects are considered in the theory. Nevertheless, this data should be used to select combinations of physical filters and AO to provide good scattering parameters and antioxidant capacity.
The selection of the best combinations is influenced by the following parameters:
  • Low radical formation of physical filters during irradiation;
  • Low amount of consumption of AO;
  • Low costs of antioxidants;
  • High availability and reproducibility of production of AO;
  • Various chemical properties (hydrophilic/lipophilic/protein for optimal combinations).
Based on these considerations, three AO were selected to be combined into a cream formulation. EGCG as its AO properties are outstanding and only a low amount is necessary to counteract the radicals formed by all investigated physical filters. VE as a strong lipophilic antioxidant is easily available, reproducible and helps to stabilize the formulation, thus providing protection from oxidative damage both during storage and after application to the skin. For example, it can protect the squalene from UV-induced degradation [25]. SM is a low-cost, yet effective antioxidant; it can sometimes prevent color changes in some formulas. Carnosine, a dipeptide, was added to the sunscreen because of its anti-oxidant and anti-glycation properties [30].
The above described combination was added to a cream containing three different physical filters: ZnOtriet, ZnOpolymyr and the mixture of TiO2AlOH+ZnOtriet. They were selected because TiO2-OH and ZnOtriet provide very good scattering parameters and are used very frequently. ZnOpolymyr produces the lowest radical load.
The cream formulations were investigated by EPR spectroscopy which has the advantage that scattering events do not influence the results of DPPH measurements.

3.4. Antioxidant Capacity in the Cream Formulation

The RPF data are presented in Table 4, first column. The RPF method works without irradiation. Only the antioxidant capacity is measured, but in presence of physical filters.
All samples (Appendix A) of Table 4 provide high RPF values. C1-No-pigm, which contains no physical filters, provided the highest RPF of 360, which represents a very high value. This high value is reduced by addition of different physical filters (C4-ZnOtriet25) down to 160, which is still a high value for a sunscreen. C5-ZnOpolymyr reduced the RPF only by 33% to 240.

3.5. Optical Properties of the Creams

All creams were prepared two times and each sample was measured three times. The spectra for each sample were averaged and independently simulated and the optical properties are shown in Figure 2. The measurements and simulations could be performed with low errors, with the exception of ZnOtriet25 which has a low viscosity and could not be applied easily.
The absorption in the visible wavelength range is very low for all samples. The scattering properties vary from very low for the sample without physical filters, and increase for the ones with particles µs’ by a factor of 6 to 7 at 400 nm (Table 4). µs’ decreases with increasing wavelength which is typical for particles of this size. The sample TiO2AlOH + ZnOtriet containing scattering particles with a concentration of 14% provide the highest µs’, closely followed by ZNOtriet25 using only 10% of physical filters. Thus, the addition of 4% TiO2AlOH is not detectable in the cream. At 800 nm the differences are low (with exception of the one using no physical filters as shown in Table 4).
To investigate a possibly existing negative correlation between the RPF and the scattering properties for samples containing the same antioxidants, a correlation plot is shown in Figure 3. The data for µs’ at 400 nm show clear the negative correlation. Thus, an addition of the used physical filters independent of their nature reduce the RPF.

4. Conclusions

The results provide sound scientific evidence that physical filters can act as generators of free radicals. These free radicals are released in the formulation where they can oxidize other ingredients, mainly antioxidants and/or other compounds with low redox potential. Hence, physical filters must be considered as oxidizing agents that can reduce the antioxidative potential of formulations or even render them pro-oxidative. If the formulation becomes pro-oxidative the formulation will lose its beneficial effect on skin, too. The pro-oxidative effects and the degradation of ingredients can be circumvented by adding powerful antioxidants. The influence of physical filters on the anti-oxidative potential of formulations can be assessed ex vivo by EPR spectroscopy. A simple in vitro method is also available. A validation of this new method that allows for a complete in vitro—ex vivo correlation is now needed.

Author Contributions

A.L., Y.L., J.Z., C.M.K., J.L. and M.C.M. conceived and designed the concept of the study and methodology, S.S., S.B.L. and S.W. performed the experimental investigations, data analysis and interpretation of the data was done by A.L., Y.L., J.Z., C.M.K., J.L., M.C.M. and S.B.L., M.C.M., C.M.K. and S.B.L. prepare the original draft. All authors have read and agreed to the published version of the manuscript.

Funding

The investigation has been supported by Shanghai Pechoin Daily Chemical Corporation, Shanghai, China and by the Foundation of Skin Physiology, which is incorporated in the Donor Association for the Promotion of Sciences and Humanities in Germany.

Data Availability Statement

The data presented in this study are available on request from the corresponding author.

Conflicts of Interest

The authors declare no conflict of interest. This basic research is methodology driven and did not include any final products from Pechoin.

Appendix A

Cosmetics 10 00001 g0a1 550
Figure A1. Photo of the used cream formulations.
Figure A1. Photo of the used cream formulations.
Cosmetics 10 00001 g0a1

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Cosmetics 10 00001 g001 550
Figure 1. DPPH reduction depending on various EGCG concentrations with the best fit. The x-axis represents the concentration of antioxidants (in %); the y-axis represents the portion of DPPH reduced by oxidants, where 0 means no DPPH is reduced and 1 means all the DPPH molecules are reduced.
Figure 1. DPPH reduction depending on various EGCG concentrations with the best fit. The x-axis represents the concentration of antioxidants (in %); the y-axis represents the portion of DPPH reduced by oxidants, where 0 means no DPPH is reduced and 1 means all the DPPH molecules are reduced.
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Cosmetics 10 00001 g002 550
Figure 2. µa and µs‘ for all creams without error bars for better comparison. The scale for µa is logarithmic.
Figure 2. µa and µs‘ for all creams without error bars for better comparison. The scale for µa is logarithmic.
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Cosmetics 10 00001 g003 550
Figure 3. Correlation of RPF with µs‘ for scattering coefficients at 400 nm (R2 = 0.98).
Figure 3. Correlation of RPF with µs‘ for scattering coefficients at 400 nm (R2 = 0.98).
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Table
Table 1. Cream formulations codes with implemented physical filters in % and the size of the physical filters.
Table 1. Cream formulations codes with implemented physical filters in % and the size of the physical filters.
Cream Code/Physical filtersTiO2-AlOH
Titanium Dioxide,
Aluminum Hydroxide, Isostearic Acid		ZnOtriet25
Zinc Oxide, Triethoxycaprylylsilane 		ZnOtriet45
Zinc Oxide, Triethoxycaprylylsilane 		ZnOpolymyr
Zinc Oxide, Polydimethyl-siloxane, Myristic Acid
Diameter in nm *10252535
C1-No-pigm0000
C4-ZnOtriet 10
C5-ZnOpolymyr 10
P6-TiO2AlOH+ZnOtriet410
* according to the supplier Huzhou Luxon Fine Chemical Co., Ltd., China.
Table
Table 2. Scavenged DPPH in % by different physical filters during UV irradiation in solution, theoretically calculated amount of selected antioxidants ICx to counteract this radical formation, used amount of selected antioxidants to counteract the radical formation and the factor X between calculated and used amount of selected antioxidants (EGCG = Epigallocatechin Gallate, VE = Alpha-Tocoperol/Vitamin E, SM = Sodium metabisulfite).
Table 2. Scavenged DPPH in % by different physical filters during UV irradiation in solution, theoretically calculated amount of selected antioxidants ICx to counteract this radical formation, used amount of selected antioxidants to counteract the radical formation and the factor X between calculated and used amount of selected antioxidants (EGCG = Epigallocatechin Gallate, VE = Alpha-Tocoperol/Vitamin E, SM = Sodium metabisulfite).
PigmentTiO2-AlOH
Titanium Dioxide, Aluminum Hydroxide, Isostearic Acid		ZnOtriet25
Zinc Oxide, Triethoxycaprylylsilane 		ZnOtriet45
Zinc Oxide, Triethoxycaprylylsilane 		ZnOpolymyr
Zinc Oxide, Polydimethyl-siloxane, Myristic Acid
Scavenged DPPH (%)45534223
EGCG ICx%0.0000470.0000620.0000430.000018
EGCG used %0.0000500.0000100.0000150.000250
XEGCG0.906.202.900.10
VE Icx %0.0007920.0014010.0006810.000224
VE used %0.000.000.000.001
XVE1.01.40.90.2
SM Icx %0.040680.053830.036690.01287
SM used %0.00750.050.00250.025
XSM5.41.114.70.5
Table
Table 3. DPPH IC50 values for the respective AO and its curve fittings including r2 (EGCG = Epigallocatechin Gallate, VE = Alpha-Tocoperol/Vitamin E, FA= Ferulic acid, SM= Sodium Metabisulfite).
Table 3. DPPH IC50 values for the respective AO and its curve fittings including r2 (EGCG = Epigallocatechin Gallate, VE = Alpha-Tocoperol/Vitamin E, FA= Ferulic acid, SM= Sodium Metabisulfite).
A.O.DPPH IC50 (w.t. %)Curve-FittingR2
EGCG0.000057y = 0.03069 + 0.73277 [1 − [e (−18094.2851*x)]]0.99
VE0.001107y = 0.0596 + 0.5012 [1 − [e (−1906.1098*x)]]0.96
FA0.000227y = 0.02585 + 0.6568 [1 − [e (−6571.7067*x)]]0.99
Emblica0.001597y = 0.09510 + 1.03919 [1 − [e (−309.1062*x)]]0.99
Rosmarinic acid0.000461y = 0.09875 + 0.84752 [1 − [e (−1391.6724*x)]]0.98
SM0.04905y = 0.1013 + 0.7953 [1 − [e (−14.1852*x)]]0.95
Table
Table 4. Determination of the RPF of different cream formulations and the scattering coefficient µs’ at 400 and 800 nm of the investigated formulation.
Table 4. Determination of the RPF of different cream formulations and the scattering coefficient µs’ at 400 and 800 nm of the investigated formulation.
Formulation RPF in 1014 Radicals/mgµs’ at 400 nm in 1/mmµs’ at 800 nm in 1/mm
C1-No-pigm360 ± 144.23.4
C4-ZnOtriet160 ± 941.116.3
C5-ZnOpolymyr240 ± 230.415.5
C6-TiO2 + AlOH + ZnOtriet180 ± 1343.015.5
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Lan, A.; Lui, Y.; Zuo, J.; Lohan, S.B.; Schanzer, S.; Wiemann, S.; Keck, C.M.; Lademann, J.; Meinke, M.C. Methodology to Reach Full Spectral Photo-Protection by Selecting the Best Combination of Physical Filters and Antioxidants. Cosmetics 2023, 10, 1. https://doi.org/10.3390/cosmetics10010001

AMA Style

Lan A, Lui Y, Zuo J, Lohan SB, Schanzer S, Wiemann S, Keck CM, Lademann J, Meinke MC. Methodology to Reach Full Spectral Photo-Protection by Selecting the Best Combination of Physical Filters and Antioxidants. Cosmetics. 2023; 10(1):1. https://doi.org/10.3390/cosmetics10010001

Chicago/Turabian Style

Lan, Alexandra, Yan Lui, Jinhui Zuo, Silke B. Lohan, Sabine Schanzer, Sabrina Wiemann, Cornelia M. Keck, Jürgen Lademann, and Martina C. Meinke. 2023. "Methodology to Reach Full Spectral Photo-Protection by Selecting the Best Combination of Physical Filters and Antioxidants" Cosmetics 10, no. 1: 1. https://doi.org/10.3390/cosmetics10010001

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