Photo- and Sono-Active Food Colorants Inactivating Bacteria.

Food colorants are commonly used as excipients in pharmaceutical and nutraceutical fields, but they have a wide range of other potential applications, for instance, as cytotoxic drugs or mediators of physical antimicrobial treatments. The photodynamic antibacterial activity of several edible food colorants is reported here, including E127, E129, E124, E122, E133, and E150a, alongside Rhein, a natural lipophilic antibacterial and anticancer compound found in medicinal plants. Minimal inhibitory concentration (MIC) values for S. aureus and E. coli showed that E127 and Rhein were effective against both bacteria, while other colorants exhibited low activity against E. coli. In some cases, dark pre-incubation of the colorants with Gram-positive S. aureus increased their photodynamic activity. Adding Rhein to E127 increased the photodynamic activity of the latter in a supportive mode. Optional sensing mechanism pathways of combined E127/Rhein action were suggested. The antibacterial activity of the studied colorants can be ranged as follows: E127/Rhein >> E127 >> E150a > E122 > E124 >> E129 ≈ E133. E127 was also found to exhibit photodynamic properties. Short ultrasonic treatment before illumination caused intensification of E127 photodynamic activity against E. coli when applied alone and especially in combination with Rhein. Food colorants exhibiting photo- and sonodynamic properties may have good potential in food preservation.

Phyto-Photodynamic Therapy of Prostate Cancer Cells Mediated by Yemenite 'Etrog' Leave Extracts.

Cancer therapy, from malignant tumor inhibition to cellular eradication treatment, remains a challenge, especially regarding reduced side effects and low energy consumption during treatment. Hence, phytochemicals as cytotoxic sensitizers or photosensitizers deserve special attention. The dark and photo-response of Yemenite 'Etrog' leaf extracts applied to prostate PC3 cancer cells is reported here. An XTT cell viability assay along with light microscope observations revealed pronounced cytotoxic activity of the extract for long exposure times of 72 h upon concentrations of 175 µg/mL and 87.5 µg/mL, while phototoxic effect was obtained even at low concentration of 10.93 µg/mL and a short introduction period of 1.5 h. For the longest time incubation of 72 h and for the highest extract concentration of 175 µg/mL, relative cell survival decreased by up to 60% (below the IC50). In combined phyto-photodynamic therapy, a reduction of 63% compared to unirradiated controls was obtained. The concentration of extract in cells versus the accumulation time was inversely related to fluorescence emission intensity readings. Extracellular ROS production was also shown. Based on an ATR-FTIR analysis of the powdered leaves and their liquid ethanolic extract, biochemical fingerprints of both polar and non-polar phyto-constituents were identified, thereby suggesting their implementation as phyto-medicine and phyto-photomedicine.