Photodynamic activity of natural anthraquinones on fibroblasts

Abstract

Natural anthraquinones (AQs) isolated from Heterophyllaea lycioides (Rusby) Sandwith (Rubiaceae) demonstrated to have photodynamic properties: soranjididol (Sor), 5-Chlorosoranjidiol (5-ClSor), bisoranjidiol (Bisor), 7- Chlorobisoranjidiol (7-ClBisor) and lycionine (Lyc). Sor, 5-ClSor and Bisor exhibited photodynamic inactivation on bacteria and parasites. As they could be used in topical application, the aim of this work was to study their photodynamic activity on fibroblasts. AQs were tested at 2.5 μM in darkness and under irradiation conditions. They were photoactivated with violet-blue LED (λ = 410 ± 10 nm; fluence rate =50 mW/cm2) and exposure time corresponded to a fluence of 27 J/cm2. Negative and positive control (–C and +C, respectively) were included. Mitochondrial activity was determined by using MTT assay that is a measure of the cell viability and it was expressed as a percentage respect to –C (% CV). Results showed that AQs in darkness conditions showed similar metabolic activity as –C, except for 5-ClSor (about 75% CV). Under irradiation, AQs exhibited dissimilar results. Sor and 7-ClBisor maintained cell viability at approximately 100%, Bisor and Lyc around 70%, whereas 5-ClSor reduced cell viability by 90%. Taken together, our results suggest that Sor could mediate photodynamic therapy (PDT) in cutaneous infections since no toxicity was observed in fibroblasts. On the other hand, 5-ClSor could be used for topical PDT of keloids and hypertrophic scars.