Isolation and structure determination of a sesquiterpene lactone (vernodalinol) from Vernonia amygdalina extracts

Abstract

Context: Vernonia amygdalina Del. (VA; Asteraceae or Compositae) is a small tree growing throughout tropical Africa. It is widely used for food and medicinal purposes by local people. It was reported that it had several qualities, including anticancer activity.

Objective: A sesquiterpene lactone, vernodalinol, was isolated from VA leaves. The first reported source of vernodalinol was in 2009 from a different plant, only ¹H NMR spectrum and no detailed structural analysis were carried out. No whole spectroscopic data were provided.

Materials and methods: VA dried leaves were extracted with 85% ethanol followed by further separation into four fractions by liquid–liquid extraction technique using various solvents: hexane, chloroform, and n-butanol. Vernodalinol was separated from the n-butanol fraction by column chromatography. The biological activity of vernodalinol was evaluated in estrogen receptor-positive (ER⁺) human breast carcinoma cells (MCF-7) in vitro.

Results: Results indicated that vernodalinol (25 and 50 μg/mL) inhibited breast cancerous cell growth (DNA synthesis) by 34% (P < 0.025) and 40% (P < 0.025), respectively. It is reasonable to expect an LC₅₀ of 70–75 μg/mL for vernodalinol in MCF-7 cells.

Discussion and conclusion: Vernodalinol structure was confirmed using a battery of spectroscopic methods, 1D and 2D NMR, high-resolution mass spectrometry (HR-MS), UV, IR, and X-ray. These results suggest that vernodalinol, although it has some biological activity, is likely to work in concert with other ingredients responsible for the anticancer activity exhibited of VA.

Keywords::

• Vernonia amygdalina
• vernodalinol
• sesquiterpene lactone
• breast cancer

Acknowledgement

We thank Dr. Gregorio B. Begonia, Department of Biology, Jackson State University, USA, for his help to verify the VA from Nigeria, and Dr. Azeem Hasan, Mass Spectrometry Facility of Department Chemistry, Louisiana State University, USA, for collecting HR ESI-MS data. This work was supported by National Center for Research Resources (NCRR) (G12RR013459) and National Science Foundation (NSF CHE-0821357) for the 500 MHz NMR. The purchase of the diffractometer was made possible by grant LEQSF (1999–2000)-ENH-TR-13, administered by the Louisiana Board of Regents.

Declaration of interest

The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.