Marine algae have been used as food since ancient times and today are consumed as a regular part of the diet. In this study, we hypothesized that H. grandifolius phlorotannins-enriched extract exerts cytotoxic selective effects against tumor cell lines promoting cell death trough apoptosis mechanisms. The aim of the present study is to characterize chemically and investigate the selective cytotoxic effect of the H. grandifolius extract on epithelial tumour cell lines (A375, A549, Hep-2, HeLa) compared to non-malignant cell line (Hek-293), and evaluate possible molecular mechanisms involved in the programmed cell death pathway. High-resolution directly-infusion mass spectrometry (HR-DIMS) analysis with electrospray ionization (ESI) was performed in positive and negative mode. Cytotoxicity was evaluated through colorimetric assay and morphological altera-* Corresponding author.
G. Gambato et al.
99tions were observed in giemsa stained cells after extract treatment. Apoptosis was further evaluated by annexin V staining. Spectra showed peaks m/z between 370 and 430 and molecular formula was defined upon isotopic ratio. Extract showed selectivity to the non-tumor line with enhanced cytotoxicity in tumor cells according to the concentration and exposure time. After 72 h treatment, the HeLa strain was more susceptible to the extract, followed by lines Hep2, A375 and A549. Morphological changes by giemsa were observed after increased doses of extracts and staining for annexin V showed majority of tumor cells at early stages of the apoptotic process. Here, selective anti-tumor activity of extract taken from the alga H. grandifolius was able to suppress proliferation and promote apoptosis-mediated cell death with induction of initial stages of apoptosis in different cell lines.
Microalgae have the ability to assimilate atmospheric carbon dioxide and organic and inorganic pollutants while simultaneously producing a range of useful intracellular metabolites. Harvesting and concentrating microalgal suspensions, which is commonly performed via coagulation, flocculation, or filtration, is complex, owing to the dynamic character of the cells. The availability of nitrogen to the cells plays a crucial role in the synthesis of intracellular products and in the release of extracellular organic matter. These are expected to have an extensive impact on the harvesting/dewatering behavior. In this study, the role of nitrogen availability in the production and release of extracellular matter was investigated by characterizing the extracellular organic matter composition and association with the cells for three commercially relevant microalgae: Nannochloropsis salina, a marine Chlorella sp., and Haematococcus pluvialis. The results showed that nitrogen limitation reduced the amount of extracellular matter on a per cell basis, despite the bulk concentration increasing due to the increase in the total biomass surface area. In particular, the protein content of the extracellular material was found to decrease across all three species upon nitrogen deprivation. However, there was significant variation in the amount and composition of the extracellular organic matter between the microalgae. This study provides new knowledge of the variations of extracellular substances in relation to microalgae species and cultivation conditions. This has important implications for species selection and optimization of microalgae production, harvesting, and dewatering processes.
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