Photodynamic Inactivation of Human Coronaviruses.

Photodynamic inactivation (PDI) employs a photosensitizer, light, and oxygen to create a local burst of reactive oxygen species (ROS) that can inactivate microorganisms. The botanical extract PhytoQuinTM is a powerful photosensitizer with antimicrobial properties. We previously demonstrated that photoactivated PhytoQuin also has antiviral properties against herpes simplex viruses and adenoviruses in a dose-dependent manner across a broad range of sub-cytotoxic concentrations. Here, we report that human coronaviruses (HCoVs) are also susceptible to photodynamic inactivation. Photoactivated-PhytoQuin inhibited the replication of the alphacoronavirus HCoV-229E and the betacoronavirus HCoV-OC43 in cultured cells across a range of sub-cytotoxic doses. This antiviral effect was light-dependent, as we observed minimal antiviral effect of PhytoQuin in the absence of photoactivation. Using RNase protection assays, we observed that PDI disrupted HCoV particle integrity allowing for the digestion of viral RNA by exogenous ribonucleases. Using lentiviruses pseudotyped with the SARS-CoV-2 Spike (S) protein, we once again observed a strong, light-dependent antiviral effect of PhytoQuin, which prevented S-mediated entry into human cells. We also observed that PhytoQuin PDI altered S protein electrophoretic mobility. The PhytoQuin constituent emodin displayed equivalent light-dependent antiviral activity to PhytoQuin in matched-dose experiments, indicating that it plays a central role in PhytoQuin PDI against CoVs. Together, these findings demonstrate that HCoV lipid envelopes and proteins are damaged by PhytoQuin PDI and expands the list of susceptible viruses.

Deeper insights into the drug defense of glioma cells against hydrophobic molecules.

By means of fluorescence microscopy the intracellular distribution of fluorescent drugs with different hydrophobicity (quinizarin, emodin and hypericin) was studied. Selective photoactivation of these drugs in precisely defined position (nuclear envelope) allowed moderately hydrophobic emodin enter the nucleus. Highly hydrophobic hypericin was predominantly kept in the membranes with no fluorescence observed in the nucleus. The redistribution of quinizarin, emodin and hypericin between lipids, proteins and DNA was studied in solutions and cells. Based on these results was proposed theoretical model of hydrophobic drugs' nuclear internalization after photo-activation. Molecular docking models showed that hypericin has the strongest affinity to P-glycoprotein involved in the cell detoxification. Presence of 10 µM quinizarin, emodin or hypericin increased P-glycoprotein function in U87 MG cells. Moreover, emodin pretreatment allowed quinizarin nuclear internalization without photo-activation, which was not the case for hypericin. The synergy of such pretreatment and photo-activation should lessen the drug doses with simultaneous increase of drug efficacy triggering cell apoptosis/necrosis.

Photo-irradiation of Aloe vera by UVA--formation of free radicals, singlet oxygen, superoxide, and induction of lipid peroxidation.

Aloe vera whole leaf extracts are incorporated into a wide variety of topically applied commercial products. Aloe vera whole leaf extracts may contain anthraquinones, which have been shown to generate reactive oxygen species in the presence of ultraviolet A (UVA) light. Exposure to UVA light alone can also generate reactive oxygen species and is associated with photo-damaged and photo-aged skin in humans. This paper examines the photochemical properties of two Aloe vera whole leaf extracts that differed in their anthraquinone content. In the presence of methyl linoleate, the UVA irradiation of Aloe vera leaf extracts induced lipid peroxidation. The amounts of lipid peroxides formed were higher in the Aloe vera leaf extract that contained lower amounts of anthraquinones. Superoxide dismutase and sodium azide inhibited and deuterium oxide enhanced the formation of lipid peroxides, suggesting that singlet oxygen and superoxide were involved in the mechanism. Spin trapping electron spin resonance (ESR) spectroscopy was used to investigate the generation of free radicals by the UVA photo-irradiated Aloe vera plant extracts. ESR measurements indicated that the UVA photo-irradiation of Aloe vera plant extracts produced carbon-centered free radicals. These results suggest that humans exposed to products that contain Aloe vera whole leaf extracts may have enhanced sensitivity to ultraviolet light.

Studies on the photostability and phototoxicity of aloe-emodin, emodin and rhein.

Aloe-emodin (1), emodin (2) and rhein (3) were found to be photolabile by visible (390-500 nm) light under aerobic conditions. The drugs 1, 2 and 3 were phototoxic in vitro when examined by the photohemolysis test under both oxygen and argon atmospheres, although the photohemolysis rate was markedly lower under anaerobic conditions. The experiments were also carried out in the presence of butylated hydroxyanisole (BHA), reduced glutathione (GSH), sodium azide (NaN3) and superoxide dismutase (SOD). Based on the inhibition of this process on addition of BHA, GSH, SOD and NaN3, there would seem to be involvement of free radicals (type I mechanism) and singlet oxygen in the process (type II mechanism). The in vitro phototoxicity of this anthraquinone series was also verified in a lipid-photoperoxidation test with linoleic acid. In summary, this anthraquinone series is phototoxic in vitro. This behavior can be explained through the involvement of singlet oxygen and stable photoproducts.