Discovery of Horsfieldia macrothyrsa Bioactives with Cytotoxic Effects on Breast Cancer Cells Through In Vitro and Docking Analyses

This study investigated the phytochemical constituents and biological activities of Horsfieldia macrothyrsa leaves to identify their bioactive compounds. Methanol extracts were fractionated using n-hexane and ethyl acetate, followed by silica gel column chromatography with a stepwise polarity gradient. From 100 g of powdered leaves, three major compounds were successfully isolated from the ethyl acetate fraction: 1-(2,4,6-trihydroxyphenyl)dodecan-1-one (1), sesamin (2), and β-sitosterol (3). Their chemical structures were confirmed using UV, IR, LC–MS/MS, and NMR spectroscopy. Biological activities of the fractions and isolates were evaluated through DPPH antioxidant assays, α-glucosidase inhibition for antidiabetic activity, MTT assays on MCF-7 and T47D breast cancer cell lines for cytotoxicity, and antibacterial tests (MIC and MBC) against Escherichia coli, Bacillus subtilis, Staphylococcus aureus, and Pseudomonas aeruginosa. The ethyl acetate fraction showed the strongest DPPH and α-glucosidase inhibitory activities, with IC₅₀ values of 12.72 ± 0.12 and 6.69 ± 0.44 μg/mL, respectively. Isolate 1 exhibited the highest antioxidant potential and mild antibacterial effects against B. subtilis, P. aeruginosa, and E. coli. β-sitosterol (3) demonstrated significant cytotoxicity toward MCF-7 (IC₅₀ = 20.71 μg/mL) and T47D (IC₅₀ = 18.19 μg/mL), while sesamin (2) showed moderate cytotoxicity on MCF-7 cells. Molecular docking against EGFR (PDB ID: 4HJO) indicated strong binding affinities for all three isolate: -7.41 kcal/mol (1), -9.99 kcal/mol (2), and -9.15 kcal/mol (3). These results suggest that sesamin and β-sitosterol form stable interactions with EGFR. Overall, the methanol and ethyl acetate fractions of H. macrothyrsa represent promising natural sources of antioxidants, while isolate 1-3 exhibit potential antibacterial and anticancer activities.