Phytochemical profiles of marine phytoplanktons: an evaluation of their in vitro antioxidant and anti-proliferative activities.

Marine microorganisms such as phytoplanktons are a rich resource of bioactive components with antioxidant and anti-proliferative activities that can act as novel functional food ingredients. In this study, the pigment profiles, total mycosporine-like amino acids (MAAs) and total phenolic contents (TPCs) in solvent extracts including 90% acetone and methanol from five marine phytoplanktons including Nitzschia closterium (Bacillariophyta), Isochrysis zhangjiangensis (Haptophyta), Platymonas subcordiformis (Chlorophyta), Porphyridium cruentum (Rhodophyta) and Synechocystis pevalekii (Cyanobacteria) were analyzed. Each phytoplankton from different phyla had its unique compositions of carotenoids and chlorophylls. The 90% acetone extract from I. zhangjiangensis had the highest MAA content (508.30 µg per g DW) while the methanol extract from N. closterium had the highest level of TPCs (6.15 mg GAE per g DW) among all the phytoplanktons investigated. The amounts of total carotenoids in all the 90% acetone extracts from the five phytoplanktons as well as total MAAs in those from within the four microalgae except S. pevalekii were found to be strongly correlated with their antioxidant activities evaluated by the DPPH, TEAC and FRAP assays. Only the level of total carotenoids in the phytoplanktons was correlated with their anti-proliferative activities assessed by the MTT assays using MCF-7 cells. Therefore, individual carotenoid pigments seemed to be mainly responsible for the antioxidant and anti-proliferative (or anticancer) activities found in the solvent extracts of the five phytoplanktons. Hence these phytoplanktons have the potential as novel sources of natural food antioxidants and anticancer agents to be used as active ingredients in functional food products.

Photodynamic inactivation of methylene blue and tungsten-halogen lamp light against food pathogen Listeria monocytogenes.

The aim of this study was to verify the bactericidal effect and the damage of photodynamic inactivation (PDI) using methylene blue (MB) and tungsten-halogen lamp over Listeria monocytogenes via atomic force microscopy, absorption spectrophotometry, agarose gel electrophoresis, real-time PCR and SDS-PAGE. The obtained data indicated that the viability of L. monocytogenes was ca 7-log reduced by illumination with 10 min tungsten-halogen lamp light under the presence of 0.5 µg mL(-1) MB, and this bactericidal activity against L. monocytogenes of PDI increased proportionally to the concentration of MB and the duration of irradiation. Moreover, after irradiation with MB and visible light, the leakage of intracellular contents was estimated by spectrophotometer at OD(260) and OD(280), which correlated with morphological alterations. Furthermore, genomic DNA cleavage and protein degradation were also detected after PDI treatment. Consequently, breakage of the membrane, damage of the genomic DNA and degradation of bacterial proteins may play an important role in the mechanisms involved in PDI-MB bactericidal activity on L. monocytogenes.