Isolation, identification and stability of acylated derivatives of apigenin 7-O-glucoside from chamomile (Chamomilla recutita [L.] Rauschert)

The major flavonoids in the white florets of chamomile (Chamomilla recutita [L.] Rauschert) were rapidly purified using a combination of polyamide solid-phase extraction and preparative HPLC. From the combined LC/MS, LC/MS/MS, and NMR data the apigenin glucosides were identified as apigenin 7-O-glucoside (Ap-7-Glc), Ap-7-(6″-malonyl-Glc), Ap-7-(6″-acetyl-Glc), Ap-7-(6″-caffeoyl-Glc), Ap-7-(4″-acetyl-Glc), Ap-7-(4″-acetyl,6″-malonyl-Glc), and a partially characterised apigenin-7-(mono-acetyl/mono-malonylglucoside) isomer. Malonyl and caffeoyl derivatives of Ap-7-Glc have not previously been identified in chamomile. The two mono-acetyl/mono-malonyl flavonoids have not previously been reported in any plant species. These acylated glucosides are unstable and degrade to form acetylated compounds or Ap-7-Glc. The degradation products formed are dependent on the extraction and storage conditions, i.e. temperature, pH and solvent.