Re: Phylloerythrin. Mechanisms for cellular uptake and location, photosensitisation and spectroscopic evaluation

The paper by E Scheie, A Flaoyen, J Moan and K Berg published in the New Zealand Veterinary Journal 50, 104–110, 2002, entitled, “Phylloerythrin. Mechanisms for cellular uptake and location, photosensitisation and spectroscopic evaluation” contained an error in the structure of phylloerythrin in Figure 1; a double bond was inadvertently left out of the structure shown. The correct chemical structure is shown here. In response to queries about the solubility of phylloerythrin at a concentration of 1 mg/ml, E Scheie and A Flaoyen responded as follows: “Dimethylsulphoxide (DMSO) is a good solvent for amphiphilic compounds such as phylloerythrin. It is, however, important to ensure that the pH is not too low, to ensure that the carboxyl group is ionised. Additionally, an ultrasound bath must be used for a few seconds, shortly after adding the solvent. It is doubtful it would be possible to dissolve phylloerythrin at 1 mg/ml in DMSO without the ultrasound treatment. Other photosensitisers resembling phylloerythrin, such as 2-(1-hexyloxethyl)-2-devinyl pyropheophorbide-a, are dissolved at >1 mg/ml. The very hydrophobic meso-tetra(hydroxyphenyl)chlorin is used clinically at 4 mg/ml (in ethanol + polyethyleneglycol). Furthermore, protoporphyrin IX is easily dissolved in ethanolic solutions at 2.5 mM. Thus, although the concentration of 1 mg/ml in the stock solution as described in this paper by Scheie et al. (2002, 2003) is correct, we omitted to mention use of the ultrasound bath.”