I have recently been introduced to the measurement of skin carotenoids level by the Pharmanex patented device using the Raman spectroscopy method. I scored 49 000, which is great. I tried to look into it and critically examine the relevance, despite a lot of research was done, for which I do not have much time to go through at the moment. I have found that this method assesses the content of carotenoids in the top layer of the skin, the dead keratin layer, which represents the past exposure to the carotenoids, hence not necessarily the current state in the body and the current diet. I would like to ask what layer of the skin the HPLC method uses (if not examining the blood plasma, of course), as they also mentioned that they once examined the level of carotenoids in the abdominal skin tissue during the operation of some patients. Does anybody know?
My concern is that if the HPLC method liquidified the skin with its deeper layers and assessed the carotenoid levels and these agreed with the Raman method, this might have been a coincidence as these people had a constant/ habitual exposure to these carotenoids. In other scenario, when people had abundance of the carotenoids several weeks ago, which translated into the rich content in their stratum corneum (the top layer of the skin), while currently having a poor diet, the Raman assessment might be misleading. This also applies to associated aspect as they found out that smokers and those exposed to higher UV radiation had lower carotenoids concentrations in their skin regardless of their dietary intake - the oxidative stress can also vary in time and low carotenoids in the top layer of the skin may not be an accurate measurement of the current oxidative stress in that person...
Can anybody comment on that?
Article Xanthophyll Esters in Human Skin
Dear Dagmar,
I can not help you with the HPLC part of your problem as it is outside my expertise. If you want more information on the location of the cartenoids you may consider in vivo Confocal Raman. With a depth resoluton of ~4 micron you may be able to penetrate the skin several tens of microns. giving you a depth profile of the cartenoids. This profile will help you to asses the history of cartenoids intake and/or depletion. You will also be able to get the concentration in the epidermis and top layers of the dermis. Such an instrument is commercially available from RiverD located in the Netherlands (no commercial interest from my side) You could contact Dr. Puppels or Peter Caspers for more information. In my opinion they are the leaders in biomedical applications of Raman spectroscopy in skin research.
Best Regards,
Rolf
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