Cyclic tetrapyrrolic photosensitizers from Cladophora patentiramea (Cladophoraceae, Chlorophyta) and Turbinaria conoides (Sargassaceae, Phaeophyta) for photodynamic therapy
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In screening for novel photosensitizers for photodynamic therapy, 14 seaweed samples from Port Dickson in Malaysia were collected. Methanolic extracts of these samples were prepared and evaluated for phototoxicity using a short-term cell viability assay, where promyelocytic leukemia cells, HL60 were incubated with the extracts prior to irradiation with a broad spectrum light at 9.6 J cm−2 (equivalent to 10.5 mW cm−2 for 10 min). Four of the methanolic extracts demonstrated moderate to strong phototoxicity and bioassay-guided isolation of photosensitizers was carried out on two selected seaweeds to yield a total of eight cyclic tetrapyrrolic compounds which are derivatives of chlorophyll-a and -b. Seven of these compounds showed >50% phototoxicity at 5 μg mL−1 while exhibiting minimal cytotoxicity in the dark, which is an important characteristic of an ideal photosensitizer.
KeywordsPhotodynamic therapy Photosensitizer Seaweeds Cyclic tetrapyrroles Chlorophylls
The authors are grateful to the sponsors of Cancer Research Initiatives Foundation (CARIF) for supporting this work and the collaborators for their assistance in taxonomic identification and NMR experiments. The first author thanks the University of Malaya for the research grant (Vot PPP No. PS104/2007B; PS175/2008A) in support of this work.
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