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. Author manuscript; available in PMC: 2018 Jul 1.
Published in final edited form as: Exp Dermatol. 2017 Mar 23;26(7):563–568. doi: 10.1111/exd.13208

Figure 3.

Figure 3

Hydroxymetabolites of melatonin detected in human epidermis.

Epidermis was extracted with 75% acetonitrile after homogenizing and applied to qTOF LC-MS (EIC) at m/z=249.1 [M+H]+ for hydroxymelatonin as described previously (8). Peak corresponding to 6(OH)M is confirmed by identical retention time as the corresponding 6-hydroxymelatonin standard and additional m/z=287.1 [M+K]+. The additional hydroxymelatonin (OH)M most likely corresponds to 2-hydroxymelatonin, also showing m/z=190.1 [M+H-NH2COCH3]+, because it was detected in HaCaT keratinocytes (7) and has a different retention time from 6-hydroxymelatonin.