Acylphloroglucinol derivatives from the aerial parts of Syzygium borneense and their cytotoxic activities

Four new acylphloroglucinol derivatives, borneensinones A-D (1–4) along with five known compounds (5-9) were isolated from the aerial parts of Syzygium borneense. Their structures were elucidated based on the interpretation of spectrometric and spectroscopic data (HRESI-MS, 1D- and 2D-NMR) and by comparison with literature data for known compounds. All acylphloroglucinol derivatives (1–6) were tested for their cytotoxic activities against four human cancer cell lines (KB, MCF-7, HepG-2, and A549). Among the six tested compounds, compound 6 exhibited the strongest inhibitory activity against four tested cancer cell lines, with IC₅₀ values ranging from 6.21 to 26.96 μM. Compound 1 was more active against KB and HepG2 comparing to the A549 and MCF7 cells. Compound 5 had a moderate cytotoxicity with IC₅₀ values ranging from 27.71 to 97.32 μM.