Green seaweed Caulerpa racemosa - Chemical constituents, cytotoxicity in breast cancer cells and molecular docking simulation

Marine and terrestrial organisms are rich in chemical compounds with medicinal and pharmacological properties, including antitumor agents for chemoprevention. Caulerpa racemosa, a marine species, is a potential source of novel compounds with therapeutic agents for human cancer. This study aimed to determine the anticancer activity of C. racemosa extracts in breast cancer cells, identify compounds, and determine the mechanism using computational models. Seaweed (C. racemosa) was taken from North Sulawesi, Indonesia; Followed by authentication and identification according to the previously published protocol and extracted with three different solvent: hexane, ethyl acetate, and ethanol. C. racemosa were evaluated for cytotoxicity against breast cancer MCF-7 cells using MTT (3-(4,5-dimethylthiazol-2-yl)-2-5-diphenyltetrazolium bromide) assay. Antioxidant activities were assessed based on free radical scavenging (2,2-diphenyl-1-picrylhydrazyl (DPPH)) and ferric-reducing antioxidant power (FRAP) assays. The phytochemical constituents were identified with a liquid chromatography-electrospray ionization quadrupole time-of-flight mass spectrometry (LC-ESI-QTOF-MS) system. The interaction of the identified compounds with human epidermal growth factor 2 (HER2) protein was achieved by molecular docking with PyRx-vina application and protein-ligand complex visualization. The hexane extract exhibited the highest cytotoxicity against breast cancer cells, followed by the ethyl acetate and the ethanol extract (IC₅₀ 23.7 ± 2.0; 66.7 ± 5.8 and 182.7 ± 14.3 μg/mL). The best antioxidant sample for DPPH was the ethyl acetate extract (IC₅₀ 21.5 ± 2.0 μg/mL) while the hexane extract was the most active in the FRAP value (14.5 ± 1.3 μg gallic acid equivalent/g). Data from LC-ESI-QTOF-MS allowed the identification of 21 compounds. The molecular docking study showed that 12 of the compounds could prevent tumors in breast cancer by acting as inhibitors of the anti-apoptotic HER2 protein. C. racemosa has potential in the chemoprevention of breast cancer through its radical scavenging capacity and inhibition of the HER2 protein. More studies are needed to investigate the efficacy of extracts in different models.