New Bioactive Peptides from the Mediterranean Seagrass Posidonia oceanica (L.) Delile and Their Impact on Antimicrobial Activity and Apoptosis of Human Cancer Cells

The demand for new molecules to counter bacterial resistance to antibiotics and tumor cell resistance is increasingly pressing. The Mediterranean seagrass Posidonia oceanica is considered a promising source of new bioactive molecules. Polypeptide-enriched fractions of rhizomes and green leaves of the seagrass were tested against Gram-positive (e.g., Staphylococcus aureus, Enterococcus faecalis) and Gram-negative bacteria (e.g., Pseudomonas aeruginosa, Escherichia coli), as well as towards the yeast Candida albicans. The aforementioned extracts showed indicative MIC values, ranging from 1.61 mu g/mL to 7.5 mu g/mL, against the selected pathogens. Peptide fractions were further analyzed through a high-resolution mass spectrometry and database search, which identified nine novel peptides. Some discovered peptides and their derivatives were chemically synthesized and tested in vitro. The assays identified two synthetic peptides, derived from green leaves and rhizomes of P. oceanica, which revealed interesting antibiofilm activity towards S. aureus, E. coli, and P. aeruginosa (BIC50 equal to 17.7 mu g/mL and 70.7 mu g/mL). In addition, the natural and derivative peptides were also tested for potential cytotoxic and apoptosis-promoting effects on HepG2 cells, derived from human hepatocellular carcinomas. One natural and two synthetic peptides were proven to be effective against the in vitro liver cancer cell model. These novel peptides could be considered a good chemical platform for developing potential therapeutics.

Automated summary

There is a growing demand for new bioactive molecules to combat antibiotic and tumor cell resistance. The Mediterranean seagrass Posidonia oceanica is being investigated as a potential source of these molecules. Polypeptide-enriched fractions of the seagrass have shown promising antibacterial and antifungal activity, with nine novel peptides being identified. Two of these peptides exhibited antibiofilm activity and showed efficacy against liver cancer cells in vitro.