Photophysical properties, singlet oxygen generation efficiency and cytotoxic effects of aloe emodin as a blue light photosensitizer for photodynamic therapy in dermatological treatment

Abstract

Conventional photodynamic therapy (PDT) uses red light for deeper penetration. A natural compound, aloe emodin (AE) with anticancer and photosensitising capabilities, excited by blue light, is proposed to treat superficial diseases. The photophysical properties and singlet oxygen quantum yield (Φ) of AE, as well as the cytotoxic effects of AE on human cells, were investigated. The absorption and emission spectra of AE were analyzed. The Φ of AE was measured by a relative method. In order to study the relationship between Φ and the oxygen concentration, the dependence of Φ on the oxygen concentration was investigated. The cytotoxic effects of AE alone and AE-mediated PDT were compared. The relationship between cells' survival rate and PDT conditions was studied. According to spectral analysis, the energy levels of AE were identified. The maximum absorption peak of AE is in the blue region, which makes AE-mediated PDT suitable for superficial diseases. The Φ of AE was determined to be 0.57(2), which was found to be dependent on the oxygen concentration. The studies under low oxygen concentration proved that there is no type I reaction between AE and the probe for singlet oxygen detection. The effect of AE-mediated PDT was significantly higher than that of AE alone and increased with the concentration of AE or fluence. AE-mediated PDT can provide a new strategy to treat superficial diseases using blue light, thus protecting deeper normal tissues.

Antifungal Effect of Antimicrobial Photodynamic Therapy Mediated by Haematoporphyrin Monomethyl Ether and Aloe Emodin on Malassezia furfur

“…Although HMME has been approved in China for the photodynamic treatment of naevus flammeus, showing high effectiveness and safety ( Mei et al, 2019 ), it is still not expanded in the photodynamic treatment of bacteria or fungi induced skin diseases. AE is a newly discovered natural anthraquinone PS isolated from Chinese traditional herbs, possessing absorption in the blue region (430 nm) and singlet oxygen quantum yield of 0.57, which may be suitable for the treatment of superficial lesions ( Zang et al, 2017 ). It was reported that AE had low cytotoxicity on epidermis and hypodermal cells and it caused no obvious effects on the weight and pathological changes of mice in our previous study ( Wang et al, 2021 ).…”

Does the chemistry of fungal pigments demand the existence of photoactivated defense strategies in basidiomycetes?

“…Numerous AQs are well-known photosensitizers: Emodin (8), physcion (58), and aloe-Emodin (59), just to name a few examples [4]. 8, 58, and 59 produce singlet oxygen, and thus PDT type II-like activities were proposed [106,107] in combination with PDT type I reactivities [108]. In addition to their wide-spread occurrence in the kingdom Plantae, 8 [109] and 58 [109] are chemotaxonomic markers [110] for mushrooms.…”

Aloe‐emodin: A review of its pharmacology, toxicity, and pharmacokinetics

“…The mechanisms underlying this effect might be associated with inhibiting the HIF‐1 α /VEGF signaling pathway (Wu et al, ). Zang et al () reported that aloe‐emodin‐mediated PDT may provide an effective strategy for the treatment of superficial diseases using light sources in the blue region, thus protecting deeper normal tissues from PDT‐induced damage (Zang et al, ). Furthermore, aloe‐emodin could induce the synthesis of matrix proteoglycans, increase the activity of ALP, and enhance the expressions of chondrogenic marker genes such as Collagen II, Collagen X, bone sialoprotein, and runt‐related transcription factor 2 via MAPK and bone morphogenetic protein‐2 signaling pathways, indicating aloe‐emodin may have potential future applications for the treatment of growth disorders (Yang, Li, Heo, & Soh, ).…”