Identification and Characterisation of Phenolics fromIxora coccineaL. (Rubiaceae) by Liquid Chromatography Multi-stage Mass Spectrometry

Abstract

Ixora coccinea L. leaves and stem are used in traditional Sudanese and Ayurvedic medicinal systems for the treatment of diarrhoea, fever, headache, skin diseases, eye trouble, wounds, sores and ulcers. Recent studies show that I. coccinea has anti-oxidant, anti-bacterial, anti-cancer, anti-inflammatory, analgaesic, anti-diarrhoeal, hepatoprotective, cardioprotective, anti-mutagenic, wound healing and anti-tumour activities. Ixora coccinea is a rich source of polyphenols such as proanthocyanidins, flavonoids, flavonoids glycosides and tannins. To develop a LC-MS(n) method for the identification and characterisation of phenolic compounds of I. coccinea L. leaves and stem. Aqueous methanolic (70% methanol) extracts of I. coccinea leaves and stem were used for LC-MS(n) to ensure efficient extraction of phenolics. A C18 amide reverse-phase HPLC column allowed separation of the phenolic compounds, including different isomers. For the LC-MS measurements, negative ion mode was used in order to obtain better tandem mass spectra and high-resolution mass spectra. The phenolics were identified by their typical UV absorptions at 254, 280 and 320 nm. All the flavonol glycosides showed a neutral loss of the glycan part; hydroxycinnamates showed loss of the cinnamoyl/cinnamic acid part; while proanthocyanidins showed a Diels-Alder fragment in negative ion mode mass spectra. It was possible to identify C-3 and C-7 flavonol glycosides by their order of elution and it was also possible to predict the glycosylation position in flavonol diglycosides from their tandem mass spectra.