Elsevier

Fitoterapia

Volume 109, March 2016, Pages 206-211
Fitoterapia

Ericoside, a new antibacterial biflavonoid from Erica mannii (Ericaceae)

https://doi.org/10.1016/j.fitote.2015.12.022Get rights and content

Abstract

A new dihydroflavonol–flavonol biflavonoid derivative, named ericoside was isolated from the ethanol extract of the whole plant of Erica mannii along with the known flavonoid, taxifolin 3-O-α-l-rhamnopyranoside; and two readily available sterols (sitosterol, sitosterol 3-O-β-d-glucopyranoside). The isolation was performed using chromatographic methods and the structure of purified molecules were elucidated using spectroscopic techniques (e.g. MS, NMR) and by comparison with literature data. The crude ethanol extract, ericoside, and taxifolin 3-O-α-l-rhamnopyranoside were tested against ten Gram-negative bacteria including multidrug resistant clinical isolates using a broth microdilution method. The crude ethanol extract showed no noteworthy activity. Of the purified compounds, ericoside displayed moderate activity against the resistant Escherichia coli AG100 with a MIC of 64 μg/mL.

Introduction

Erica mannii is one of the 700 species of the genus Erica (Ericaceae family), many of which are distributed throughout Europe, the Middle East and Africa. Traditionally uses such as hypotensive, anti-inflammatory, urinary antiseptic, diuretic [1], and wounds healing [2] have been reported for members of this genus. Erica species are chemotaxonomically characterized based on their flavonoids [3] although, they are also known to possess 1,9-diarylnonanoids [4], phenylpropanoids [5], triterpenoids [6], and tannins [7], [8]. In the course of our ongoing research on new bioactive compounds from Cameroonian medicinal plants, we have undertaken the isolation of the chemical constituents of E. mannii. We herein report, the isolation, the characterization and antibacterial activity of a new dihydroflavonol–flavonol biflavonoid derivative. Moreover, this is the first report of a biflavonoid from the genus Erica.

Section snippets

General experimental procedures

High resolution ESI mass spectra and the corresponding higher collision dissociation (HCD) measurements (normalized collision energy 50%) were obtained on an Orbitrap Elite™ mass spectrometer (ThermoFisher Scientific, Bremen, Germany) equipped with an HESI ion source (spray voltage 4 kV; capillary temperature 275 °C, source heater temperature 40 °C; FTMS resolution 30.000). Nitrogen was used as the sheath gas. Sample solutions were introduced continuously via a 500 μL Hamilton syringe pump at 5 

Isolation and determination of structures

Four compounds including a new biflavonoid (Fig. 1) were isolated from the ethanol extract of the whole plant of E. mannii through silica gel and Sephadex LH-20 column chromatography. Their structures were determined by interpretation of their spectroscopic data and by comparison with values previously reported in the literature for similar or related molecules.

Ericoside (1) was obtained as a yellow powder in CH2Cl2, [α]D24 — 96.8, (c. 0.64, MeOH). The molecular formula C42H40O19 was deduced

Conclusions

This study presents the characterization of a new antibacterial biflavonoid from the whole plant of E. mannii. To the best of our knowledge, this is the first report on the antibacterial activity of the crude extract and compounds from this plant species. The overall results of this study can be considered promising in view of the development of new phytodrugs to fight against MDR bacterial infections of public health importance since the tested microorganisms are highly resistant to

Authors' contributions

GTMB and SBT were field investigators and drafted the manuscript. AHLK collected the plant material. JDSM contributed to the interpretation of NMR data and correction of the manuscript. VK provided the bacterial strains and chemicals for antibacterial assays. AT, SAFT, ATT, and LAW participated in spectroscopic and physical data analysis and with VK revised and finalized the manuscript. PT designed and supervised the work.

Competing interests

The authors declare that they have no competing interests.

Acknowledgments

We are grateful to the University of Dschang for financing some consumables used in this work. We thank Dr. Jürgen Schmidt (IPB, Halle) for HR-MS measurements. SAFT is grateful to the German Academic Exchange Service (DAAD) for the financial support.

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