Flavonoids from the capitula of Eriocaulon australe

A flavan, eriocaulin A (1), and three flavone acyl glucosides, eriocaulosides A–C (2–4) were isolated from the capitula of Eriocaulon australe R. Br. (Eriocaulaceae), a Chinese medicine and an herb for health care beverages, together with seven known flavones and three isoflavones (5–14). The new flavonoids were elucidated as (2S)-3′,4′-methylenedioxy-5-methoxy-7-hydroxyflavan (1), hispidulin 7-O-β-d-(6-O-cinnamoyl)glucopyranoside (2), jaceosidin 7-O-β-d-(6-O-p-coumaroyl)glucopyranoside (3), jaceosidin 7-O-β-d-(6-O-p-hydroxybenzoyl)glucopyranoside (4) based on their spectroscopic data. All the 14 flavonoids were obtained from this species for the first time. The in vitro cytotoxicity of compounds 1–14 against human lung adenocarcinoma A549, human breast adenocarcinoma MCF-7, and human cervical carcinoma HeLa cell lines was evaluated using the MTT colourimetric assay. Compounds 1, 7, and 9 were cytotoxic to A549, compounds 1, 2, 7, 9, 12, and 14 to MCF-7, and compounds 7, 9, and 14 to HeLa cells, with IC50 values ranging from 7.17 to 29.57 μg/ml, while the others were inactive (IC50 > 50 μg/ml).