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Resveratrol
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@zwapp has any research been done on the effect of radical chain terminators, e.g. BHT or benzophenone derivatives?
(since photoisomerisation occurs via a radical mechanism, chain terminators could in principle halt the reaction before it starts)
also, I’m surprised that photoisomerisation favours the cis form; unless they’re macrocyclic or physically constrained in some other way (which resveratrol isn’t) the trans form is usually favoured where stilbene-type molecules are concerned
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@zwapp I think your intuition is wrong and it’s more likely that it’s protected than not, depends the kinetics of degradation and skin penetration. Here’s one study showing how retinol is very well protected in a sunscreen formula exposed to daylight https://www.ncbi.nlm.nih.gov/pubmed/18405792 and this doesn’t even account for skin penetration.
You might not need any protecting factors if it penetrates the skin quickly and deeply enough.“photoisomerization yield is reported as a function of 260 nm excitation time. 330 min continuous excitation led to ~60% isomerization yield.” https://www.ncbi.nlm.nih.gov/pubmed/21494846 seems to slow to be of much concern in a topical. I also noticed there’s a patent describing UV protection of tres.
At the end of the day you’d have to measure it.
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First, I read the abstract to your link about induced isomerization of resveratrol. It looks to be irrelevant to the sunscreens questions because the wavelength tested was 260 nm, which is UVC range that doesn’t reach earth’s surface. UVC light is what’s used for germicidal irradiation, and it’s in the range of 100-280 nm.
“trans-resveratrol has two absorption peaks
at 304 nm and 316 nm” right in the UV-B range where sunscreens typically protect the skin very well. UV-A is lower energy too.Here’s an experiment with trans resveratrol exposed to actual sunlight, it took 2 hours to cause a ~36% conversion, in vivo it’ll only be exposed to direct sunlight for a few seconds as it goes through the stratum corneum and since UV-B transmittance of the stratum corneum at these wavelength is only around 10-20%, I highly doubt it will be an issue in a formula with a few SPF points.
https://www.researchgate.net/publication/23802677_Simple_spectrophotometric_assessment_of_the_trans-cis-resveratrol_ratio_in_aqueous_solutionshttp://www.dnva.no/geomed/solarpdf/Nr_3_Nielsen.pdf
SPF 15 sunscreen blocks ~95% of UV-B. So 5% gets through, then 15% of that gets through the stratum corneum, then there is absorption by other components in the epidermis etc. Not all sunscreen ingredients degrade significantly either, definitely not mineral sunscreens. Overall this is an easy thing to solve, and I don’t think any experiments are warranted.
Also, you could still use mineral sunscreen actives in a non-sunscreen formula, so this definitely applies. Don’t waste your time solving a problem that doesn’t need solving.
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@Zinc Hi I dont mean to jump in out of nowhere, but hey hi! Just reading and thought I could give you some solid info on pine bark extract and oil. Its contains oligemeric proanthocyanidin compounds which as you know are “super antioxidants” property compounds. Its readily available, im a aromatheraphy Essential Oil practitioner. As well as formulater .
Chow! -
Also french maritime pinebark is clinicaly shown to contain photoprotective properties against uv rays. Also anti- aging and anti-bacterial. However even topically it can be unsafe for immune system suppresion needs, and as an anti-coagulative sooo…
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@zwapp Yes in case of resveratrol it’s fairly clear that we don’t need stabilized version for sunscreen formulas, the obvious thing to do to verify this is to test it. If anyone is working on this problem, they should do that verification first. It’s not unusual to see scientists missing out on obvious experiments.
I’m aware of the phototoxicity of TiO2/ZnO, this is why you use silane coating to make extra sure it’s not an issue, but even without, there’s no real evidence of danger or skin cancer correlation according to SCCP: http://ec.europa.eu/health/ph_risk/committees/sccp/documents/out135_en.pdf
Yes I read the articles I cite, but it’s hard to respond to you when you do not cite what you refer to. Why do you think UVA matters for resveratrol when it’s absorbance peak in in the UVB range? When the sunlight experiment demonstrated 36% conversion after 2 hours exposed to direct sunlight with no photoprotection, which as I explained would not be the case for in vivo application. If you do the math I’d estimate (again, needs to be measured) that more than 90% would remain in tRes form in vivo with topical application.
Sorry if I was a bit flippant, I was hoping it would get you to pull out some references! (still hoping
)@NoHypeCosmetics thx! do share info here or through PM
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