Identification and Characterisation of Phenolics from Ixora coccinea L. (Rubiaceae) by Liquid Chromatography Multi-stage Mass Spectrometry

IntroductionIxora 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. ObjectivesTo develop a LC-MSn method for the identification and characterisation of phenolic compounds of I. coccinea L. leaves and stem. MethodsAqueous methanolic (70% methanol) extracts of I. coccinea leaves and stem were used for LC-MSn 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. ResultsThe phenolics were identified by their typical UV absorptions at 254, 280 and 320nm. 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. ConclusionIt 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. Copyright (c) 2014 John Wiley & Sons, Ltd. The phenolics of the leaves and stem of Ixora coccinea L., a traditional Sudanese and Indian medicinal plant, were investigated qualitatively by LC-MSn. Fifty-one phenolics were detected comprising six chlorogenic acids, two methyl caffeoylquinates, two caffeoylshikimates, four B-type dimeric proanthocyanidins, five A-type dimeric proanthocyanidins, B-type trimeric proanthocyanidin, nine A-type trimeric proanthocyanidins, seven quercetin glycosides and ten kaempferol glycosides. Forty-two of them have not previously been reported from this source, and two of them are not reported in nature.