Light-Mediated Toxicity of Porphyrin-Like Pigments from a Marine Polychaeta

Porphyrins and derivatives form one of the most abundant classes of biochromes. They result from the breakdown of heme and have crucial physiological functions. Bilins are well-known representatives of this group that, besides significant antioxidant and anti-mutagenic properties, are also photosensitizers for photodynamic therapies. Recently, we demonstrated that the Polychaeta Eulalia viridis, common in the Portuguese rocky intertidal, holds a high variety of novel greenish and yellowish porphyrinoid pigments, stored as granules in the chromocytes of several organs. On the follow-up of this study, we chemically characterized pigment extracts from the worm’s skin and proboscis using HPLC and evaluated their light and dark toxicity in vivo and ex vivo using Daphnia and mussel gill tissue as models, respectively. The findings showed that the skin and proboscis have distinct patterns of hydrophilic or even amphiphilic porphyrinoids, with some substances in common. The combination of the two bioassays demonstrated that the extracts from the skin exert higher dark toxicity, whereas those from the proboscis rapidly exert light toxicity, then becoming exhausted. One particular yellow pigment that is highly abundant in the proboscis shows highly promising properties as a natural photosensitizer, revealing that porphyrinoids from marine invertebrates are important sources of these high-prized bioproducts.

LMCT transition-based red-light photochemotherapy using a tumour-selective ferrocenyl iron(iii) coumarin conjugate

A mitochondria-targeted ferrocenyl iron(iii) coumarin complex shows red-light toxicity against cancer cells but remains harmless in the dark and to normal cells.

Brine shrimp (Artemia salina Leach) bioassay of extracts from Lychnophoriopsis candelabrum and different Lychnophora species

The present study aimed to evaluate on Artemia salina the citotoxicity of twenty-two extracts from five species of the genus Lychnophora and one species of the genus Lychnophoriopsis. The extracts solubilized in DMSO and prepared at the final concentrations of 100, 250, 375, 500 and 600 μg mL-1 were added to tubes containing Artemia salina nauplii (10 units each) and filled to 5 mL total volume with artificial salt water. Lapachol and 5% DMSO were used as positive and negative controls, respectively. The samples were kept under light and dead larvae were counted after 24 hours of contact. LC50 was calculated by using Probit software. The crude ethanol extracts from five species showed low lethality in the following order: Lychnophora trichocarpha (LC50 = 672.38 μg mL-1) > Lychnophora pinaster (LC50 = 678.73 μg mL-1) > Lychnophora ericoides (LC50 = 738.09 μg mL-1) > Lychnophoriopsis candelabrum (LC50 = 812.57 μg mL-1) > Lychnophora passerina (LC50 = 921.78 μg mL-1). All tested extracts from L. candelabrum and chloroform extract from L. staavioides showed light toxicity on A. salina. Results indicated that there are substances with potential pharmacological activity in all tested species.