Competing photochemical reactions of bis-naphthols and their photoinduced antiproliferative activity. Issue 5 (1st March 2019)

• Record Type: Journal Article
• Authors: Sambol, Matija; Ester, Katja; Landgraf, Stephan; Mihaljević, Branka; Cindrić, Mario; Kralj, Marijeta; Basarić, Nikola
• Is Part Of: Photochemical & photobiological sciences. Volume 18:Issue 5(2019)
• Page Start: 1197
• Page End: 1211
• Publication Date: 2019-03-01
• Subjects: Photochemistry -- Periodicals; Photobiology -- Periodicals; 541.35
• DOI: 10.1039/c8pp00532j
• Languages: English
• ISSNs: 1474-905X

Abstract

Abstract : Bis-naphthols4 in aqueous solution undergo three competing photochemical reactions: photodehydration delivering quinone methides, symmetry breaking charge separation and excited state proton transfer. Abstract : The photophysical properties and photochemical reactivities of a series of bis-naphthols4a–4e and bis-anthrols5a and5e were investigated by preparative irradiation in CH3 OH, fluorescence spectroscopy and laser flash photolysis (LFP). Methanolysis taking place via photodehydration (bis-naphthols: Φ R = 0.04–0.05) is in competition with symmetry breaking charge separation (SB-CS). The SB-CS gave rise to radical ions that were detected for4a and4e by LFP. Photodehydration gave quinone methides (QMs) that were also detected by LFP ( λ max = 350 nm, τ ≈ 1–2 ms). In the aqueous solvent, excited state proton transfer (ESPT) competes with the abovementioned processes, giving rise to naphtholates, but the process is inefficient and can only be observed in the buffered aqueous solution at pH > 7. Since the dehydration of bis-naphthols delivers QMs, their potential antiproliferative activity was investigated by an MTT test on three human cancer cell lines (NCI-H1299, lung carcinoma; MCF-7, breast adenocarcinoma; and SUM159, pleomorphic breast carcinoma). Cells were treated with4 or5 with or without irradiation (350 nm). An enhancement of the activity (up to 10-fold) was observed upon irradiation, which may be associated with QM formation. However, these QMs do not cross-link DNA. The activity is most likely associated with the alkylation of proteins present in the cell cytoplasm, as evidenced by photoinduced alkylation of bovine and human serum albumins by4a .