Novel anthraquinone photosensitizers: Synthesis, photoactivity, and 3D-QSAR studies

In this study, three-dimensional quantitative conformational relationship (3D-QSAR) analysis was conducted on 38 known anthraquinone derivatives. Additionally, five pH-responsive anthraquinone photosensitizers (A1 to A5) were designed and synthesized through addition, elimination, and substitution mechanisms using the anthraquinone derivative chrysophanol as the raw material. The structures of the products were characterized using 1HNMR, 13CNMR , LCMS, and the UV–Vis absorption spectra and fluorescent spectra at different pH values were obtained. To investigate the photodynamic antibacterial activity of the compounds, their inhibitory activities against Pseudomonas aeruginosa and Staphylococcus aureus were tested in vitro under different light and pH conditions. The results showed that the compounds exhibited good photodynamic antibacterial activity and selectivity in light and weak acid environments. MTT experiments were conducted to evaluate the cytotoxicity of the compounds on the human cancer cell line HeLa. It was found that the phototoxicity and dark toxicity effects of compound A3 at concentrations of 0.625 μM and lower were similar to those of the reference photosensitizer Chlorin e6 (Ce6). However, the amount of singlet oxygen produced by A3 was approximately 7.6 times that produced by Ce6, indicating its potential for application in the photodynamic therapy of tumours and providing a reference for research on anthraquinone photosensitizers.