1-s2.0-S0190962210008169-main

8/12/2019 1-s2.0-S0190962210008169-main

1/6

Ex vivo evaluation of radical sun protection factor inpopular sunscreens with antioxidants

Steven Q. Wang, MD,a

Uli Osterwalder,b

and Katinka Jung, PhDc

New York, New York; and Ludwigshafen and Berlin, Germany

Background: UVA induces tissue damage via the production of radical oxygen species. Addingantioxidants to UV filters in sunscreens is a novel photoprotective strategy. The topical application ofantioxidants in sunscreen can potentially neutralize the UVA-induced free radicals.

Objectives: We sought to assess the degree of free radical protection offered by sunscreens withantioxidants and attempted to differentiate the contribution of free radical protection from that of the UVfilters.

Method: Twelve sunscreen products were purchased. The degree of UVA protection (UVA-PF) wasmeasured via an in vitro assay according to a European guideline (Colipa). In addition, an electron spinresonance (ESR) spectroscopy-based assay was used to measure the radical skin protection factor (RSF) andantioxidant power (AP) of each product.

Results:The sun protection factor (SPF) values of the sunscreens ranged from 15 to 55, and the UVA-PFvalues ranged from 2.4 to 28.2. The RSF values ranged from 2.4 to 27.1. There is a high correlation betweenRSF and UVA-PF. The AP values for nearly all the products were 0, and two products (#4 and #9) had verylow AP values of 16 and 12, respectively.

Limitations:The study only evaluated a small number of sunscreen products, and only ex vivo and invitro methods were used to assess the products.

Conclusions:The idea of combining UV filters with antioxidants is appealing. Current sunscreen products

on the market offer free radical protection, but the majority of the radical protection is from UV filters ratherthan antioxidants. ( J Am Acad Dermatol 2011;65:525-30.)

Key words:antioxidant power; radical sun protection factor; sunscreens; UVA protection; UVA protectionfactor.

INTRODUCTIONUltraviolet radiation from the sun is the major

culprit in a number of photodermatoses and skincancers. UVB (290 to 320 nm) is mainly responsiblefor producing sunburn and DNA damages. In con-trast, UVA (320 to 400 nm) penetrates to the deeper

layers of the skin and damages the DNA and tissuevia the production of reactive oxygen species(ROS).1-3 Recognition of the detrimental role ofUVA has prompted an emphasis on broad-

Abbreviations used:

AP: antioxidant powerAU: antioxidative unitsDPPH: diphenyl picryl hydrazilESR: electron spin resonanceORAC: oxygen radical absorbance capacityPPD: persistent pigment darkeningROS: reactive oxygen speciesRSF: radical skin (protection) factorSPF: skin protection factorUVA-PFo: initial UVA protection factor

From Memorial Sloan-Kettering Cancer Center, New York,a BASF

SE, Ludwigshafenb and Gematria Test Lab, Berlin.c

Funding sources: None.

Conflicts of interest: None declared.

Accepted for publication July 6, 2010.

Reprint requests: Steven Q. Wang, MD, Dermatology Service,

Memorial Sloan-Kettering Cancer Center, 136 Mountain View

Blvd, Basking Ridge, NJ 07920. E-mail: [email protected].

Published online May 30, 2011.

0190-9622/$36.00

2010 by the American Academy of Dermatology, Inc.

doi:10.1016/j.jaad.2010.07.009

525
mailto:[email protected]:[email protected]:[email protected]

8/12/2019 1-s2.0-S0190962210008169-main

2/6

spectrum coverage. This shift has led to a number ofinnovative developments in sunscreen products. Incontrast to sunscreens from earlier decades, modernsunscreens, especially those from Australia andEurope, contain new actives that offer superiorUVA protection. Equally important, most of thosesunscreen products are photostable. In additionto the progress achieved insunscreen products, regula-tory agencies around theworld have independentlydeveloped UVA testing crite-ria and labeling guidelines.4-8

Although discrepancies inthese regulations exist,there has been a conver-gence of the standards8

based on the concept that

balanced or uniform UV pro-tection is needed in sun-screen products.

In the quest to developbetter sunscreen productsand perhaps to gain market share, manufacturershave also adopted an alternative strategy of addingantioxidants, such as vitamins C and E, to theirsunscreen products. These antioxidant supplementscan potentially boost the bodys natural reserve andneutralize ROS from intrinsic sources (eg, cellularmetabolism) and extrinsic factors (eg, UV damage

and environmental pollution). The idea of aug-menting photoprotection with antioxidants is at-tractive because there may be two layers ofprotection in this new type of sunscreen. First, UVfilters provide passive protection by absorbingand reflecting harmful UV rays from the skin.Second, antioxidants offer active protection byboosting the bodys natural antioxidant reserve toquench any ROS generated from UV that haspassed the UV filters.

Despite the attractive nature of this photopro-tection strategy, it is unclear whether sunscreens

with antioxidants can provide protection againstROS generated from UV exposure. More impor-tantly, the significance of the contribution fromantioxidants in the sunscreen products is notknown. In this study, we first evaluated the degreeof free radical protection offered by products withantioxidants via an assay that measures the radicalskin protection factor (RSF). We then attempted todifferentiate the contribution of free radical pro-tection from the antioxidants from that of the UVfilters by measuring the antioxidant power (AP)and UVA protection factors of these products,

respectively.

METHODSProduct selection

Twelve sunscreen products from well-knownEuropean brands were selected on the basis ofclaims of containing vitamin C, vitamin E, or otherantioxidant substances. The products were pack-aged and labeled only by code numbers and the SPF

label before analysis.

Radical sun protectionfactor (RSF)measurement

This measure is an ex vivotechnique9 for detecting theamount of free radicals gen-erated in the skin with elec-tron spin resonance (ESR)spectroscopy. RSF is the ratioof the number of free radicalsgenerated in the unprotectedskin to that of protected skin,as shown below:

RSFNfree radicalsunprotected skin

Nfree radicalsprotected skin

Briefly, external parts of fresh pig ears werewashed, and subcutaneous fat was removed.A one millimolar solution of nitroxyl substrate2,2,5,5 tetramethylpyrrolidine-N-oxyl PCA (Sigma,Munchen, Germany) in water was allowed to pen-

etrate into the pig skin from the dermal side for 5minutes. PCA reacts with ROS and is widely used asa probe for detection of ROS via ESR spectroscopy.The prepared pig tissues were stored in phosphatebuffer at 48C-88C.

Sunscreen formulations at a concentration of2 mg/cm2 were applied to the epidermal side ofthe pig skin. After 20 minutes, a 4-mm punch biopsyspecimen of the pig skin was taken. The specimenwas then irradiated with a solar simulator (SOL F2,Honle AG, Germany) with UVA 25 mW/cm2 and UVB2.6 mW/cm2. After each irradiation dose, the number

of free radicals produced was detected by ESRspectroscopy until a cumulative applied UV dose of1.2 MED was reached. The ESR measurement wasperformed with the Magnettech MS 300 ElectronSpin Resonance Spectrometer with the followingmeasurement parameters: 8.0 mT sweep range,30-second sweep time, 0.1 second time constant,1 accumulation, 20 dB attenuation, 200 Gain. Forcontrol, untreated skin samples (ie, with no applica-tion of the sunscreen) were treated in the same way.

The RSF factor was calculated by means of acalibration curve, which was constructed using un-

treated skin samples covered with optical density

CAPSULE SUMMARY

d Sunscreens in this study offer significant

protection against free radicals from UV

exposure.

d Radical protection in the tested products

is derived mainly from the sunscreen

UVA filters.

d The low to zero antioxidant activities in

these products suggest that the

antioxidants in these products offer no

contribution for radical protection.

J AMACADDERMATOLSEPTEMBER2011

526 Wang, Osterwalder, and Jung

8/12/2019 1-s2.0-S0190962210008169-main

3/6

filters with PF (protection factors) ranging from 1 to50. The PF of each unknown sunscreen was directlycalculated from this calibration curve.

UVA protection factor (UVA-PF) measurementThe Colipa in vitro Method 20077 was used tomeasure UVA-PF based on the measurement of UVtransmittance through a sunscreen film. Colipa is theEuropean Cosmetic, Toiletry and PerfumeryAssociation. Briefly, the initial UVA protection factor(UVA-PFo) was calculated by using the UV absor-bance spectrum, which was adjusted to the labeledSPF. Sunscreen samples were then exposed to asingle UV dose of 1.23 the UVA-PFo in joules percentimeter squared. The final UVAPF values forthe samples were calculated from the adjustedabsorbance spectrum after irradiation. The ratio ofUVA-PF/SPF was then determined. The EuropeanCommission has recommended a minimumUVAPF/SPF ratio of at least 1:3 for all sunscreenproducts marketed in the European Union.5

Antioxidant power (AP) measurementAntioxidant power measurement is an in vitro

technique10 that measures the capacity and reactiontime of antioxidants in cosmetic and sunscreen for-mulations. Briefly, a 2-mmol solution of the semi-stable test radical diphenyl picryl hydrazil (DPPH)

was freshly prepared in ethanol. Then each sunscreen

formulationwas dissolved in water/ethanol(1:1w/w)at a starting concentration of 100 mg/mL. From thisstock, at least 3 dilutions of each were prepared andmixed with the DPPH solution to a final concentrationof 0.1 mmol DPPH. ESR spectra were then measured

at time intervals for up to 40 minutes. The measuringparameters on the Magnettech MS 300 spectrometerwere the following: 80 G sweep width, 100 Gain, 1 Gmodulation amplitude, 7 mW microwave power,3365G central field. These kinetics were fitted by means ofa mono-exponential algorithm.

The AP was described by the following equation:

APRA3Nspins

wc3 trwhere RA is the constant reduction amplitude(1/e2), Nspinsis the quantity of reduced free radicals

characterized by free electrons (spins) of DPPH, wcis the characteristic weight of the antioxidant pro-duct, and tr is the reduction time. The measuringunit is therefore AP [spins/mg 3 min]. Ascorbic acidwas used as a standard. The AP values are ex-pressed in antioxidative units (AU), where 1 AUcorresponds to the activity of 1 part per million(ppm) of ascorbic acid and 1% vitamin C corre-sponds to 10,000 AU.

RESULTSThe label SPF values and active ingredients of the

12 sunscreen products tested are listed in Tables I

Table I. Description of the 12 sunscreen products studied

Active ingredients (%)

UVB UVB/UVA UVA II

Product No. OC EHMC TiO2 DBT E HT P BSA E HS D TS B EMT Z nO M BBT B MDBM T DSA D HHB Ant ioxida nts

1 5.5 1.5 4.8 Tocopheryl acetate

2 8.1 2.2 3 Tocopheryl acetate3 4.2 2 1.6 2.1 3 4.6 Tocopheryl acetate

4 5.2 Tocopheryl acetate,

tocopherol, ascorbyl

palmitate, plant extracts

5 9.1 2.3 1.5 2.5 0.5 Tocopherol

6 2.3 2.8 1 5 0.5 2 2.5 0.5 Tocopherol

7 10 0.1 2 2 Tocopheryl glucoside

8 10 4 Tocopheryl acetate

9 10 5.9 0.7 7.4 7 Tocopheryl acetate,

tocopherol, ubiquinone,

ascorbyl teraisopalmitate

10 10 2.8 1.5 5.2 Tocopheryl acetate

11 9.1 0.5 1.4 5.2 Tocopheryl acetate12 8 2 0.3 1 2 Tocopheryl acetate

BEMT, Bis-ethylhexyloxyphenol methoxyphenyl triazine; BMDBM, butyl methoxydibenzoylmethane; DBT, diethylhexyl butamido triazone;

DHHB, diethylamino hydroxybenzoyl hexyl benzoate; DTS, drometrizole trisiloxane; EHS, ethylhexyl salicylate; EHMC, ethylhexyl

methocycinnamate; EHT, ethylhexyl triazone; OC, octocrylene; MBBT, methylene bis-benzotriazolyl tetramethylbutylphenol; PBSA, phenyl

benzimidazole sulfonic acid; TDSA, terephtalylidene dicamphor sulfonic acid; TiO2, titanium dioxide; ZnO, zinc oxide.

J AMACADDERMATOLVOLUME65, NUMBER3

Wang, Osterwalder, and Jung 527

8/12/2019 1-s2.0-S0190962210008169-main

4/6

and II. All products were lotions. Labeled SPF valuesranged from 15 (#1) to 55 (#9). Eleven productscontained actives with some degree of UVA protec-tion, and nine (#2-7, 9, 10, and 12) containedinorganic sunscreen ingredients. One product (#4)contained only UVB absorbing active ingredients,and had the lowest UVA-PF and RSF values.

The UVA-PF, RSF, and AP values of all the productsare listed inTable II. The UVA-PF values ranged from2.4 to 28.2, and six (#1-2, 5, 7, 9-11) of the productsfulfilled the European Commission guideline of a

minimum UVAPF/SPF ratio of at least 1/3. The RSFvalues ranged from 2.4 to 27.1. The RSF values formost of the products corresponded to the UVA-PF.There was a strong correlation of RSF to UVA-PF(RSF = 1.06 UVA-PF). The AP values for nearly all theproducts were 0, and two products (#4 and #9) hadvery low AP values of 16 and 12, respectively.

DISCUSSIONThe recent focus on UVA protection stems from

the understanding of both the optical properties andthe biological impact of this portion of the UV

spectrum. UVA is not blocked by ozone, and nearly95% ofall UV radiation from the sun is in the UVAregion.11 At longer wavelengths, UVA penetratesdeep into the basal layer of the epidermis and thesuperficial dermis.12 In contrast to UVB radiation thatleads to sunburn and direct DNA damage, UVAinteracts with endogenous and exogenous photo-sensitizers and generates reactive oxygen species(ROS). Subsequently, these ROS damage DNA bases,especially guanine, and other cellular molecules.Accumulation of DNA mutations resulting in abreach of genetic integrity is the basis of skin cancer

development.

1-3,13,14

In addition, UVA damage

mediated by free radicals can accelerate collagenbreakdown and decrease collagen synthesis, result-ing in the clinicalappearance of increased wrinklesand skin fragility.15

Sunscreen is the quasi-exclusive mode of photo-protection.16-18 However, most individuals do not usesunscreen appropriately. Most users only apply onefourth to one half of the recommendedamount andforget to re-apply on a frequent basis.19 Furthermore,many sunscreens do not offer balanced or uniformUVB and UVA protection, with most products tendingto offer significantly higher SPF(primarily UVB) pro-tection, but little UVA protection.8 Sunscreen productswith antioxidant supplements can theoretically offertwo complementary routes of free radical protection.The first line of defense derives from the sunscreenactives (eg, avobenzone or zincoxide) that passivelyabsorb or scatter the UVA rays, thereby diminishing the

total amount of harmful UVA radiation from reachingthe skin. Ideally, the presence of antioxidant supple-ments offers a second line of defense. Topical applica-tion of antioxidants has shown to reduce UV-inducededema, epidermal hyperplasia,and overexpression ofmatrix metalloproteinases.20,21 Combinations of vita-mins C, E, and polyphenolic extracts have been shownto have photoprotective effects in humans andpigs.22-25 The second line of active protection withantioxidants can potentially boost the bodys naturalantioxidantreserve and quenchfree radicals generatedfrom the residual UV rays that have bypassed the

sunscreen filter and reach the skin.A number of in vivo and in vitro assays have been

adopted to measure the degree of UVA protectionoffered by sunscreens. The persistentpigment dark-ening (PPD) test is an in vivo method26 that measuresthe degree of PPD as a clinical endpoint. The theoryof PPD testing is similar to that of SPF testing. Bycontrast, the clinical endpoint for SPF is erythema.PPD does not directly evaluate the degree of freeradical protection; instead it is a physiologic responsethat occurs 2 to 4 hours after the UVA exposure.A number of in vitro testing methodologies have

been adopted around the world.5-7,27

In essence, allthese tests compare the amount and spectrum of UVtransmission through a substrate (eg, quartz plate orPMMA plate) with and without sunscreens. The invitro UVA measurements do not evaluate any clinicalor biological endpoint. In this study, we used theColipa guideline,7 mainly because most of the sun-screen products were from Europe.

In contrast to the aforementioned methods, RSF isan ex vivo technique that directly measures protec-tion against free radicals, one of the direct biologicendpoints from UVA damage. Using ESR spectros-

copy, the amount of free radicals, such as hydroxyl

Table II. Sun protection factor, antioxidant power,and radical skin protection factor values of the 12sunscreen products studied

Product No. SPF UVA-PF RSF AP Colipa

1 15 8.3 10.6 0 Yes

2 20 10.2 16.5 0 Yes3 55 10 6.8 0 No

4 20 2.4 2.4 16 No

5 20 10.9 11.3 0 Yes

6 40 12.1 16.5 0 No

7 20 6.1 13 0 Yes

8 25 5.8 6.3 0 No

9 55 28.2 23.1 12 Yes

10 30 16.4 10.6 0 Yes

11 20 16.3 18.2 0 Yes

12 25 9.9 27 0 No

AP, Antioxidant power; RSF, radical skin protection factor; SPF, sun

protection factor.



8/12/2019 1-s2.0-S0190962210008169-main

5/6

radicals (dOH), the superoxide anion radical (O2-d)and lipid radicals, generated from UV exposures canbe captured and measured. The concept of RSF issimilar to that of SPF; RSF is derived from the ratio ofthe number of free radicals generated in unprotectedskinversus the number of free radicals in protectedskin.9 Our results indicate that sunscreens offersignificant protection against free radicals from UVexposure, and the RSF values of these products rangefrom 2.4 to 27. More importantly, there is a significantcorrelation between UVA-PF and RSF of the testedproducts (ie, RSF = 1.06 UVA-PF), indicating that aproduct with a high UVA-PF blocks or absorbs moreharmful radiation from the UVA spectrum andthereby reduces the total amount of free radicalsgenerated in the skin.

In an attempt to differentiate the contribution offree radical protection from the UVA sunscreen filters

versus antioxidants, we further measured the anti-oxidant power (AP) units in these products. The APmeasurements from 10 tested products were 0, andthe remaining 2 had very low AP values. The APassay used in this study is also an ESR spectroscopy-based methodology characterizing a substance or amixtures capacity to remove a certain number of freeradicals in a certain time intervals. The test is stan-dardized to ascorbic acid (ie, 1% vitamin C corre-sponds to 10,000 AU). A substance with the capacityto remove a large number of radicals in a short timeinterval has a high AP value. The low to zero AP

values in these products suggest that the antioxidantsin these products offer no significant contribution tofree radical protection. Our results indicate that mostof the free radical protection (RSF value) from thetested products is derived from the sunscreen UVAfilters, not from the antioxidants.

Our findings should not be used as a justificationfor abandoning the strategy of incorporating antiox-idants in sunscreens; rather, they point out thechallenges from both technical and regulatory per-spectives. To ensure the efficacy of antioxidants inthe final products, a number of technical require-

ments must be fulfilled: the antioxidants need (1) tohave a very high antioxidative capacity and reactiv-ity, (2) to be present in high concentration, (3) to bestable in the final formulation, and (4) to penetratethe skin barrier. In our tested products, we were notable to determine the final concentration of eachantioxidant compound. Most products containedtocopheryl acetate (ie, stabilized forms of tocopherol[Vit E]) and ascorbyl palmitate (ie, a stabilized form ofascorbic acid [Vit C]). Both forms have very lowbiological activity. Hence, it is no surprise that the APmeasurements from these products were zero. The

low AP values may be attributed to failure in fulfilling

any or all of the 4 criteria stated above. Currently,there is no regulatory requirement for cosmeticmanufacturers to substantiate claims, and companiesoften include vitamin E or C on the product label togain market share. As dermatologists, we need toeducate the public about the importance of focusingon photoprotection from sunscreen actives and for-mulation, rather than being enticed by the claims ofadditional antioxidants in the product.

Our study has a number of limitations. First, thestudy included a small number of samples. Second,the RSF measurement is an ex vivo assay with pigskin as the substrate. Ex vivo human skin fromdiscarded tissue could provide more accurate pre-diction of the free radical protection. Ideally, an invivo assay provides the most accurate assessment,but currently an in vivo assay that can reliablymeasure free radical protection is not available.

Third, the AP measurement used in evaluating theantioxidant capacity of these sunscreens is an in vitrotechnique. The AP values only indicate the antioxi-dant potential in the bottles of sunscreen products,but the efficacy of these antioxidants when appliedto the skin may be dramatically altered. In our study,the AP values were virtually nonexistent for nearly allthe products. Fourth, the commercial products stud-ied contained predominantly tocopherol and itsesters. Only 2 products contained additional antiox-idants combined with tocopherol esters, and bothdemonstrated very low level antioxidant activity. The

concentrations of these materials were not disclosed,and they were probably present in very low concen-trations. The potential for developing formulationswith effective levels of antioxidants remains to bedetermined. Lastly, it is important to understand thataccurate quantification of free radicals and antioxi-dant capacity is a challenging task. Currently, there isno single assay available that can sufficiently meetthis task. A number of assays (eg, lipid peroxidation,oxygen radical absorbance capacity [ORAC] and totaloxygen radical absorbance capacity [TORAC]) havealso been described. ORAC is awell-known antiox-

idant assay, developed in 199328-30

and used in thefood industry to measure the antioxidant potential offoods.31 The assay measures the fluorescence of aprobe (eg, fluorescein) that is susceptible to oxida-tion by free radicals. The ORAC result is normalizedto Trolox, a water-soluble derivative of tocopherol.For our study, the ESR spectroscopy based assay waschosen over other assays, because ESR spectroscopyquantifies both the antioxidant capacity and thekinetic parameter (ie, reaction time). Other assaysignore the kinetics parameter. Furthermore, theassays discussed above require both a detector (eg,

fluorescent probe) and a reagent (ie, free radicals).

J AMACADDERMATOLVOLUME65, NUMBER3

Wang, Osterwalder, and Jung 529

8/12/2019 1-s2.0-S0190962210008169-main

6/6

This approach creates a competitive reaction wherethe free radicals can react with both the antioxidantsand the detection molecule, yielding less accuratemeasurement of the antioxidant capacity. The ESRspectroscopy based technology uses only one sub-stance that serves both as the reagent and thedetection probe.32

In summary, broad-spectrum protection, espe-cially in the UVA range, is important for prevention offree radical formation. The idea of combining pas-sive protection with UV filters and active protec-tion with antioxidants is appealing. However,examination of current products on the marketindicates that more work is needed. By using ESRspectroscopy, it is possible to measure free radicalprotection as a clinical endpoint with the RSF valueand assess the antioxidant capacity using AP values.These two additional assays can potentially provide

much-needed accountability and authentication inthe development of future sunscreen products.

We thank Joe Stanfield for editorial assistance of thismanuscript.

REFERENCES1. Ley RD. Ultraviolet radiation A-induced precursors of cutane-

ous melanoma in Monodelphis domestica. Cancer Res 1997;

57:3682-4.

2. Setlow RB, Grist E, Thompson K, Woodhead AD. Wavelengths

effective in induction of malignant melanoma. Proc Natl Acad

Sci U S A 1993;90:6666-70.

3. Staberg B, Wulf H, Klemp P, Poulsen T, Brodhagen H. The

carcinogenic effect of UVA irradiation. J Invest Dermatol 1983;81:517-9.

4. Standards Australian/Standards New Zealand, #AS/NA 2604:

Sunscreen products: Evaluation and classification.1993

5. The Commission of the European Communities. Commission

Recommendation of 22 September 2006 on the efficacy of

sunscreen products and the claims made relating thereto.

Official Journal of the European Union, L265/39, 26.9.2006.

6. U. S. Food and Drug Administration. Sunscreen Drug Products

for Over-the-Counter Human Use; Proposed Amendment of

Final Monograph; Proposed Rule; 21CRF Parts 347 and 352.

Federal Register 72 (165) August 27, 2007. 49070-49122.

7. Colipa In Vitro Photoprotection Methods Task Force. Method

for the in vitro determination of UVA protection provided by

sunscreen products. Guideline 2007a.

8. Wang SQ, Stanfield JW, Osterwalder U. In vitro assessments of

UVA protection by popular sunscreens available in the United

States. J Am Acad Dermatol 2008;59:934-42.

9. Herrling T, Jung K, Fuchs J. Measurements of UV-generated

free radicals/reactive oxygen species (ROS) in skin. Spectro-

chim Acta A Mol Biomol Spectrosc 2006;63:840-5.

10. Jung K, Richter J, Kabrodt K, Lucke IM, Schellenberg I, Herrling

T. The antioxidative power APeA new quantitative time

dependent (2D) parameter for the determination of the

antioxidant capacity and reactivity of different plants. Spec-

trochim Acta A Mol Biomol Spectrosc 2006;63:846-50.

11. Miller SA, Hamilton SL, Wester UG, Cyr WH. An analysis of UVA

emissions from sunlamps and the potential importance for

melanoma. Photochem Photobiol 1998;68:63-70.

12. Kochevar I, Pathak M, Parrish J. Photophysics, photochemistry

and photobiology. In: Freedberg I, Eisen A, Wolff K, et al,

editors. Dermatology in general medicine. New York: McGraw-

Hill; 1999. pp. 220-9.

13. Drobetsky EA, Turcotte J, Chateauneuf A. A role forultravioletA

in solar mutagenesis. Proc Natl Acad Sci U S A 1995;92:2350-4.

14. Kvam E, Tyrrell RM. Induction of oxidative DNA base damage

in human skin cells by UV and near visible radiation. Carcino-

genesis 1997;18:2379-84.

15. Fisher GJ, Kang S, Varani J, Bata-Csorgo Z, Wan Y, Datta S, et al.

Mechanisms of photoaging and chronological skin aging. Arch

Dermatol 2002;138:1462-70.

16. Robinson JK, Rademaker AW. Sun protection by families at the

beach. Arch Pediatr Adolesc Med 1998;152:466-70.

17. ORiordan DL, Steffen AD, Lunde KB, Gies P. A day at the beach

while on tropical vacation: sun protection practices in a high-

risk setting for UV radiation exposure. Arch Dermatol 2008;

144:1449-55.

18. Wang SQ, Dusza SW. Assessment of sunscreen knowledge: a

pilot survey. Br J Dermatol 2009;161(Suppl. 3):28-32.

19. Faurschou A, Wulf HC. The relation between sun protection

factor and amount of sunscreen applied in vivo. Br J Dermatol2007;156:716-9.

20. Vayalil PK, Mittal A, Hara Y, Elmets CA, Katiyar SK. Green tea

polyphenols prevent ultraviolet light-induced oxidative dam-

age and matrix metalloproteinases expression in mouse skin.

J Invest Dermatol 2004;122:1480-7.

21. Katiyar SK, Elmets CA, Agarwal R, Mukhtar H. Protection

against ultraviolet-B radiation-induced local and systemic

suppression of contact hypersensitivity and edema responses

in C3H/HeN mice by green tea polyphenols. Photochem

Photobiol 1995;62:855-61.

22. Elmets CA, Singh D, Tubesing K, Matsui M, Katiyar S, Mukhtar

H. Cutaneous photoprotection from ultraviolet injury by green

tea polyphenols. J Am Acad Dermatol 2001;44:425-32.

23. Lin FH, Lin JY, Gupta RD, Tournas JA, Burch JA, Selim M, et al.

Ferulicacidstabilizes a solution of vitamins C andE anddoublesits photoprotection of skin. J Invest Dermatol 2005;125:826-32.

24. Li YH, Wu Y, Wei HC, Xu YY, Jia LL, Chen J, et al. Protective

effects of green tea extracts on photoaging and photo-

immunosuppression. Skin Res Technol 2009;15:338-45.

25. Camouse MM, Domingo DS, Swain FR, Conrad EP, Matsui MS,

Maes D, et al. Topical application of green and white tea

extracts provides protection from solar-simulated ultraviolet

light in human skin. Exp Dermatol 2009;18:522-6.

26. Japan Cosmetic Industry Association. JCIA measurement

standard for UVA protection efficacy. JCIA, 9-14, Toranomon

2-chome, Minato-Ku Tokyo 1995;105.

27. Measurement of UVA: UVB ratio according to the Boots Star

rating system (2008 revision). Nottingham (UK): Boots UK Ltd.

NG2 3AA. January 2008.

28. Cao G, Alessio HM, Cutler RG. Oxygen-radical absorbance capac-

ity assay for antioxidants. Free Radic Biol Med 1993;14:303-11.

29. Prior RL, Cao G. In vivo total antioxidant capacity: comparison of

differentanalytical methods. FreeRadic Biol Med 1999;27:1173-81.

30. Cao G, Prior RL. Measurement of oxygen radical absorbance

capacity in biological samples.Methods Enzymol1999;299:50-62.

31. U.S. Department of Agriculture, Agricultural Research Service.

Oxygen radical absorbance capacity (ORAC) of selected foods,

Release 1. Available at:http://www.ars.usda.gov/nutrientdata/

orac 2007. Accessed December, 2009.

32. Halliwell B, Whiteman M. Measuring reactive species and

oxidative damage in vivo and in cell culture: how should you

do it and what do the results mean? Br J Pharmacol 2004;142:

231-55.


http://www.ars.usda.gov/nutrientdata/orachttp://www.ars.usda.gov/nutrientdata/orachttp://www.ars.usda.gov/nutrientdata/orachttp://www.ars.usda.gov/nutrientdata/orac

Documents

1-s2.0-S0190962210008169-main