Evaluation of MCF-7 Breast Cancer Cell Cytotoxic and Antioxidant Activities of Peptide Fractions from Symbiotic Bacteria of Jellyfish Catostylus sp.

Marine-derived symbiotic microorganisms are recognized as a promising source of bioactive compounds with potential therapeutic applications, yet research on jellyfish-associated bacteria remains limited. This study examines the bioactivity of peptide fractions derived from symbiotic bacteria isolated from the jellyfish Catostylus sp., collected from the coastal waters of South Sulawesi, Indonesia, with a focus on their anticancer and antioxidant properties. Following sample collection, the symbiont bacteria were isolated, enzymatically hydrolyzed, and purified before their biological activity was evaluated. Preliminary cytotoxicity screening using the brine shrimp lethality assay revealed that the extracellular peptide fraction (5–10 kDa) and intracellular peptide fraction (3–5 kDa) exhibited the highest cytotoxic effects. Subsequent testing against MCF-7 breast cancer cells demonstrated potent anticancer activity, with IC₅₀ values of 19.83 µg/mL (5–10 kDa) and 6.43 µg/mL (3–5 kDa). Antioxidant assays using the DPPH and ABTS methods showed that the 5–10 kDa fraction achieved IC₅₀ values of 254.25 µg/mL (DPPH) and 41.30 µg/mL (ABTS), whereas the 3–5 kDa fraction recorded IC₅₀ values of 218.02 µg/mL (DPPH) and 37.89 µg/mL (ABTS). These findings suggest that peptide fractions from jellyfish-associated symbiotic bacteria exhibit significant in vitro anticancer and antioxidant properties. Although the present study is limited to in vitro analysis, it provides novel evidence supporting the potential of Catostylus sp.-derived bacterial peptides as candidates for the development of antioxidant-based therapies for cancer prevention and treatment, particularly breast cancer