Stability and ultraviolet A photostability of silymarin polyphenols and its consequences for practical use in dermatology

• Published in: Journal of photochemistry and photobiology. A, Chemistry. Vol. 429; p. 113897
• Main Authors: Kosina, Pavel, Ryšavá, Alena, Vostálová, Jitka, Papoušková, Barbora, Biedermann, David, Ulrichová, Jitka, Rajnochová Svobodová, Alena
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.08.2022
• Subjects: Flavonoid; Flavonolignan; Photodecomposition products; Photostability; Silybum marianum; Stability; UHPLC-HRMS; Stability; Silybum marianum; HPLC-MS; Flavonolignan; TA; Flavonoid; SB; DS; SC; SD; QE; Photostability; ISB; SM; Photodecomposition products
• ISSN: 1010-6030; 1873-2666
• DOI: 10.1016/j.jphotochem.2022.113897

[Display omitted] •Quercetin and 2,3-dehydrosilybin are unstable in aqueous solutions.•Quercetin and 2,3-dehydrosilybin undergo UVA dose-dependent photodegradation.•Putative structure of main 2,3-dehydrosilybińs photoproduct was proposed.•Same structural motif in 2,3-dehydrosilybin and quercetin's photoproduct was found. Silymarin (SM), a complex mixture of polyphenols, flavonolignans and flavonoids, isolated from milk thistle seeds (Silybum marianum L. Gaertn., Asteraceae), is widely accepted as a phytomedicine for the treatment of numerous diseases of various etiology. Thanks to its manifold biological properties, i.e. anti-oxidant, anti-inflammatory, immunomodulatory, and regenerative attributes, SM is of interest for dermatological applications. The stability of SM components for dermal use in aqueous environments of varying pH, as well as their photostability after UVA irradiation, were studied here using UV/VIS spectroscopy and HPLC-MS. Isosilybin, silychristin and silydianin were found to be stable and UVA photostable. Silybin and mainly taxifolin were unstable in aqueous solutions but both were UVA photostable. Quercetin and 2,3-dehydrosilybin were unstable and dose-dependent UVA-induced degradation was also found. The main UVA-induced degradation product of 2,3-dehydrosilybin (C24H19O10, m/z 467.0978) in aqueous solutions was detected by UHPLC-HRMS analysis and MSE spectra. The main UVA photodegradation product of 2,3-dehydrosilybin has a similar structural motif to the minor quercetin photoproduct (C14H9O7, m/z 289.0348), newly identified in this study.