Upgrading suncreens to optimal UVA-performance and photostability

Transcription

1 Upgrading suncreens to optimal UVA-performance and photostability Thierry Baldecchi Technology & Application Network Functionals Europe South Seminario Solari SICC; 26 e 27 febbraio 2015

2 Sunscreen regulations for UVA protection Determination of the UVA protection level EU USA J/Aus UVA Prot. Factor in vivo (PPD method) Colipa in vitro UVA PF Critical wavelength FDA UVA labelling Final enforcement of the 2007 monograph (in 2012) Japan PA+, ++, +++ & ++++ Australian Standard (in vitro) A number of different methods Different requirements for the relation UVA-PF : SPF Colipa ratio in EU UVA protection level should be at least 1/3 of the SPF level USA in vitro UVA protection factor assessment needed to get the broad spectrum claim protection critical wavelength (only) 2

3 Sunscreen regulation in Europe UVA protection as valid since September 2006 UVA protection level should be at least 1/3 of the SPF level (Colipa ratio) Colipa recommendation no. 20: UVA protection level should be determined preferably according to an in vitro UVA PF (or according to the in vivo PPD method) In addition, the critical wavelength crit should be >/= 370 nm c 290nm 400nm A( )* ( ) 0.9* A( )* ( ) 290nm crit = area ratio 10% : 90% the bigger crit, the better (or broader) the UVA protection 3

4 UVB filters ctocrylene Phenylbenzimidazole Sulfonic Acid /Ensulizole [PBSA] Ethyhexyl Methoxycinnamate / ctinoxate [MC] Ethylhexyl Dimethyl PABA / Padimate Ethylhexyl Salicylate / ctisalate [S] Homosalate [HMS] Isoamyl p-methoxycinnamate Ethylhexyl Triazone [EHT] Diethylhexyl Butamido Triazone Methylene Bis-Benzotriazolyl Tetramethylbutylphenol [MBBT] Benzylidene Malonate Polysiloxane/Polysilicone-15 4-Methylbenzylidene Camphor 4

5 UVA filters Butyl Methoxydibenzoylmethane / Avobenzone [BMDBM] Disodium Phenyl Dibenzimidazole Tetrasulfonate Diethylamino Hydroxybenzoyl Hexyl Benzoate [DHHB] Zn * UVA/B filters Benzophenone-3 / xybenzone [B-3] Benzophenone-4 Bis-Ethylhexyloxyphenol Methoxyphenol Triazine [BEMT] Titanium Dioxide 5

6 Differences between UV filters Protection range Power State of aggregation Solubility Compatibility with cosmetic raws Regulatory status Reputation Price UVB; UVA; broadband extinction coefficient solid; liquid water; polar oils e.g. inorganic filters and gel formers EU; USA, J, etc. e.g. PABA-phobia in USA Patent restrictions e.g. triple combination BMDBM + CR + EHT protected from L réal Stability vs sunlight 6

7 Photoreactions Common mechanism of UV filters UV-rays electronic excitation energy UV Filter Heat vibrational energy transferred to environment 7

8 ther photoreactions of UV filters Reversible Photoreactions photoketonisation (Avobenzone/BMDBM) intramolecular H-transfer (xybenzone/benzophenone-3) trans-cis photoisomerization (ctinoxate/mc): ctinoxate-e C 8 H 17 max (MeH)[nm] = 309 ( = 24550) h * h * ctinoxate-z max (MeH)[nm] = 304 ( = 13500) C 8 H 17 8

9 Irreversible Photoreactions Result in a loss of UV absorbing properties due to loss of the conjugated system of the filter or due due to cleavage of the molecules Examples: 2+2-homo-photocycloaddition (ctinoxate/mc) Norrish-type-I cleavage (Avobenzone/BMDBM) 2+2-hetero-photocycloaddition (MC + BMDBM) BMDBM and MC show undesired photoreactions as single UV filters The photo stability of the combination of BMDBM + MC is even worse 9

10 Irreversible Photoreactions 2+2 photocycloaddition of ctinoxate ctinoxate H 3 CPh CC 8 H 17 CC 8 H 17 H 3 CPh CC 8 H 17 Dimer H 3 CPh H 3 CPh CC 8 H 17 ctinoxate 10

11 Irreversible Photoreactions Norrish-Type-I cleavage of Avobenzone H Photoketonisation h * t-butyl t-butyl Avobenzone h * -cleavage derived Photoproducts t-butyl 11

12 Irreversible Photoreactions 2+2 photocycloaddition H t-butylph PhCH 3 Avobenzone H 3 CPh CC 8 H 17 H t-butylph PhCH 3 CC 8 H 17 Dimer H 3 CPh ctinoxate t-butylph PhCH 3 H 3 CPh CC 8 H 17 12

13 Photosensitive UV filters as singles Ethyhexyl methoxycinnamate (ctinoxate/mc) Butyl Methoxydibenzoylmethane (Avobenzone/BMDBM) Dosis: 250 kj/m 2 (unweighted total UVB+A); applied quantity: 2 mg/cm 2 ) While ¾ of MC remain, just 1/10 of BMDBM is available for UVA protection 13

14 Abs Photosensitive UV filter combination MC/BMDBM 2,5 2 Typical curves of BMDBM/MC prior 1,5 1 and after irradiation 0, wavelength [nm] both UV filters exhibit a poor stability under UV light the stability is even worse in combination! 14

15 Residual amount of BMDBM [%] after 5 MED Photostabilisation of Avobenzone 1) Triplet quenchers inhibit Norrish-Type-I cleavage of Avobenzone e.g. Diethylhexyl syringylidene malonate (xynex ST Liquid) e.g. ctocrylene e.g. [xygen] fold increase in photo stability : 0 1 : 4.5 The typical combination of 2 % BMDBM and 10 % CR ensures high photo stability of BMDBM Ratio BMDBM : CR

16 Abs CR a photostabilizer for BMDBM 1,4 1,2 1 Typical curves of BMDBM/CR prior and after irradiation 0,8 0,6 0,4 0, Wavelength [nm] 16

17 Photostabilisation of Avobenzone 2) Polar (cosmetic) solvents inhibit Norrish-Type-I cleavage of Avobenzone Cyclohexene Paraffin Alkyl Benzoates Alkyl -Hydroxyalkylcarboxylates Ethanol zero stability total stability Relevance depending strongly on formulation basis 17

18 Degraded MC Degraded BMDBM Photostabilisation of BMDBM and MC 3) Specific anti-oxidants inhibit undesired photoreactions and neutralize photoproducts of the filters Bis-Ethylhexyl HydroxyDimethoxy BenzylMalonate (RonaCare AP) 25% 20% 15% 10% 5% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% 5% MC 5% MC + 2 % HDBM 0% 2% BMDBM 2% BMDBM + 1 % HDBM Loss can be reduced by half with both MC and BMDBM In each case the double filter amount is available for protection 18

19 Photostabilization of Avobenzone/ BMDBM C CH 2 C (CH 3 ) 3 C CH 3 Triplet energy quenchers (e.g. ctocrylene or xynex ST Liquid) high polarity of surrounding matrix (ideal medium is ethanol) specific antioxidants like RonaCare AP Possibilities to oppose the weak photo stability of Avobenzone in combination with MC? 19

20 Residual amount of BMDBM [%] after 5 MED Photostabilization of Avobenzone/ BMDBM Can CR stabilize Avobenzone in the presence of MC? : 0 : 0 1 : 4.5 : 0 1 : 4.5 : 2.5 Ratio BMDBM : CR : MC Loss of stabilizing performance of CR, when MC is present!! 20

21 Photostabilization of Avobenzone and MC 2+2 photocycloaddition of ctinoxate with BMDBM 4) Spacial separation of reactants by encapsulation of MC inhibits photocycloaddition Eusolex UV-Pearls capsule with UV filters in the core Filter capsules dispersed in aqueous basis 21

22 Residual BMDBM [%] Spacial separation of reactants Encapsulation of MC UV filters in /W emulsions 3 % BMDBM / 7.5 % MC as Eusolex UV-Pearls % BMDBM / 7.5 % free MC UV irradiation [min] 22 The spacial separation of BMDBM (in oil phase) and MC (in water phase) prevents side effects and leads to an improved photo stability of the combination MC/BMDBM

23 Remaining BMDBM after irradiation [%] k Photostabilisation of Avobenzone 5) Positive influence of Titanium Dioxide % BMDBM 2 % BMDBM 10 % CR 2 % BMDBM 10 % CR 2 % T-AV 2 % BMDBM 10 % CR 5 % T-AV Irradiation dosis = 250 kj/m 2 (5 MED) 23

24 Photostabilization of Avobenzone/ BMDBM C CH 2 C (CH 3 ) 3 C CH 3 Triplet energy quenchers (e.g. ctocrylene) high polarity of surrounding matrix (ideal medium is ethanol) specific antioxidants like RonaCare AP spacial separation of reactants by encapsulation The presence of (suitable) inorganic UV filters has a beneficial effect on photostability 24

25 Filter combinations in the regions USA Small number of UV filters vs EU New UVA regulation still has to be yet reflected in market products New UVA regulations make Avobenzone essential The prohibited combination of Avobenzone/Ti 2 forces the formulator to use organic UV filters, and leaves just a few options to use the inorganic UV filters. EU Broad choice of regulated UV filters New UVA regulation established in the market (e.g. Austr. Std. has disappeared since then) New UVA regulations require strong UVA filters (e.g. Avobenzone) How are the regional variations reflected in the market products? 25

26 European Sun Care Market UV Filters (Jan2013-June2014) 60% 48% 45% % Variants per UV Filter 40% 33% 32% 30% 20% 21% 24% 15% 13% 11% 0% 26 Totally: 1049 product launches

27 Asian Sun Care Market UV Filters (Jan2013-June2014) 60% 50% 40% 30% 20% 10% 0% 27

28 The relevance of photostable filter combinations in the regions Filters loose their efficacy to protect from UV The protecting efficacy of the formulation drops Low return on investment! UVB filters UVA filters a number of photostable products available in all regions low choice (esp. in the USA as xybenzone is too weak) just one organic UVA filter regulated world-wide Avobenzone Photostabilized Avobenzone becomes essential as the new UVA regulations in the USA and in Europe imply stringent irradiation steps 28

29 Summary & Conclusion The practical implementation in market formulations is strongly depending on the approved UV filters in the regions. New UVA regulations take photostable formulations for granted and push Avobenzone in the spotlight in Europe and USA Photostable formulations with Avobenzone can be obtained by several measures - Triplet energy quenching molecules like ctocrylene - High polarity of surrounding solvents (ethanol) - Specific antioxidants to neutralize the BMDBM mediated reactive oxygen species (e.g. Bis-Ethylhexyl Hydroxydimethoxy Benzylmalonate/RonaCare AP) - Spacial separation from MC by means of Eusolex UV-Pearls - Inorganic UV filters 29