An undescribed biflavone from coastal halophyte Suaeda maritima subsp. salsa (L.) Soó

The halophyte Suaeda maritima subsp. salsa (L.) Soó has been utilised as a traditional medicinal herb in China. Its phytochemical profile remains inadequately elucidated to date. In this study, twelve compounds, including one previously undescribed biflavonoid, 3′-methoxy-4′,4′″,5,5″-tetrahydroxy-[C₇-O-C_7″]-biflavone (1), and eleven known compounds (2∼12), were isolated from the whole plant of S. salsa. Their structures were fully determined via NMR, MS data analysis and literature comparison. The anti-microbial assay revealed that compounds 1, 9, and 12 exhibited an inhibitory effect against P. aeruginosa with an MIC of 25 μg/mL. Additionally, compounds 3, 5, 7, 9 and 12 displayed potent inhibitory activity against the growth of E. coli, with their MIC values ranging from 12.5 to 25 μg/mL. Furthermore, compound 1 showed the cytotoxic activity against human SGC-7901 cells with an IC₅₀ of 89.04 ± 0.26 μm. Biflavonoid 1 represents the first reported occurrence of this class of compounds within the genus Suaeda.