acylated flavonol glycoside and hydrolysable tannins from Callistemon lanceolatus flowers and leaves

• Published in: Phytochemical analysis Vol. 19; no. 6; pp. 541 - 549
• Main Author: Marzouk, Mohamed S.A
• Format: Journal Article
• Language: English
• Published: Chichester, UK John Wiley & Sons, Ltd 01.11.2008
• Subjects: 2D NMR; acylation; butylflavonol glycoside; Callistemon citrinus; Callistemon lanceolatus; Chromatography, High Pressure Liquid - economics; Chromatography, High Pressure Liquid - methods; flavonols; Gallic Acid - analogs & derivatives; Gallic Acid - analysis; gallotannin; Glucosides - analysis; glycosides; high performance liquid chromatography; HPLC-ESI/MS; hydrolysis; Hydrolyzable Tannins - analysis; Magnetic Resonance Spectroscopy; mass spectrometry; medicinal plants; Methanol - chemistry; Myrtaceae; Myrtaceae - chemistry; Plant Components, Aerial - chemistry; Plant Extracts - chemistry; Plants, Medicinal - chemistry; quercetin; Quercetin - analogs & derivatives; Quercetin - analysis; spectral analysis; Spectrometry, Mass, Electrospray Ionization - economics; Spectrometry, Mass, Electrospray Ionization - methods; Spectrophotometry, Ultraviolet; tannins
• ISSN: 0958-0344; 1099-1565
• DOI: 10.1002/pca.1082

Introduction - Callistemon lanceolatus DC. (Myrtaceae) is a plant rich in polyphenols, and is used as anticough, antibronchitis and insecticide in folk medicine. Because of the biological importance of plant polyphenols, particularly tannins, a phytochemical study was of interest to investigate the constitutive poyphenols in the extracts of flowers and leaves.Objective - To avoid time-consuming methodology for isolation of a complex mixture of known metabolites, HPLC-ESI/MS was employed for fast picking up of the new compounds followed by identification of the structures with UV and one- and two-dimensional NMR.Methodology - Flowers and leaves were separately extracted with hot aqueous methanol under reflux (70°C). Pre-isolation of the total extracts was achieved through column chromatographic fractionation on polyamide with water-methanol for gradient elution. The main fractions were purified using repeated column chromatography on cellulose and/or Sephadex LH-20 with suitable eluents. HPLC-ESI/MS analyses were carried out in the single ion monitoring (SIM) and negative ion modes. The pure compounds in methanol-water (1:1) were analysed by direct infusion ESI/MS. Final structure elucidation was obtained by one- and two-dimensional NMR.Results - Two new metabolites namely quercetin 3-O-β-D-glucuronopyranoside n-butyl ester (1) and n-butylgallate 4-O-(2',6'-di-O-galloyl)-β-d-glucopyranoside (4) along with nine known ones were identified from the aqueous methanol extracts of flowers and leaves.Conclusion - The study has shown that Callistemon lanceolatus is rich in polyphenols. HPLC-ESI/MS may be used, in negative ion mode, as an efficient and rapid analytical tool for investigating complex plant extracts. Copyright © 2008 John Wiley & Sons, Ltd.