Affiliations: [a] Department of Chemical Engineering, School of Chemistry and Chemical Engineering, Chongqing University, Chongqing, PR China | [b] School of Pharmaceutical Sciences, Chongqing University, Chongqing, PR China
Correspondence:
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Corresponding author: Zhiming Zhou and Xiaohua Zhou, Department of Chemical Engineering, School of Chemistry and Chemical Engineering, Chongqing University, Chongqing 401331, PR China. E-mails: [email protected] (Z. Zhou) and [email protected] (X. Zhou).
Abstract: To study the photosensitivity of furocoumarins to proteins, we choose imperatorin (Imp) and Cysteine (Cys), the most active amino acid in proteins, as the experimental subjects. We used UV light to irradiate Imp, Cys and their mixture separately and dedicated from the MS that Cys was weakly oxidized to Cystine, while strongly oxidized to dithiiodipropionic acid hydrate, di-(α-hydroxy-β-dithio sulfoxide) propionic acid, di-(α-keto-β-thithian sulfone) propionic acid and Cystine sulfone disodium salt. The characteristic absorption wavelength of Imp and the mixture were red shifted from 303 nm to 312 nm. This is due to the leaving of isopentenyl moiety at Imp and the lactone bond cleavage under UV light. HPLC analysis showed that two new substances were generated under UV irradiation, and the retention time was 6.3 and 23.4 min respectively. High-resolution MS analysis showed that UV light firstly induced hydrolysis of the lactone, removal of the isopentenyl group in Imp and deamination, dehydrogenation, oxidation of the Cys, and then Imp and its photochemical products chemically reacted with Cys. The product at 6.3 min was purified by a semi-preparative HPLC and successively analyzed by MS and NMR spectroscopy, identified that it was 8-hydroxypsoralen.
