Development of surrogate standards approach for the determination of polyphenols in Vernonia amygdalina Del.

This paper describes an analytical approach for polyphenol components determination in Vernonia amygdalina Del. (VA) using surrogate standards, extracts of green coffee and Achillea asplenifolia 9602, and rutin as an internal standard. HPLC–PDA fingerprint profiles of the polyphenol complex of VA and surrogate standards were developed. By comparison between the chromatographic and spectral characteristics of VA and the surrogate standards using the relative retention times towards rutin, it was possible to identify the polyphenol components in VA. Additionally, peak identity was confirmed by HRMS spectra, to verify the truthfulness of the procedures. Recoveries of rutin, LOD, LOQ, and RSD% were determined, to validate the method as highly accurate and applicable. The polyphenol complex of VA contained dicaffeoylquinic acids and luteolin glycosides as main components. A method using Nucleosil C18 provided the best separation of 1,5- and 3,5-dicaffeoylquinic acids in VA. Their amount reached up to 1.49 ± 0.21 mg g−1. The content of 4,5-dicaffeoylquinic acid was 0.35 ± 0.04 mg g−1. Luteolin glycosides and luteolin were found at 0.40 ± 0.04 mg g−1 and 0.14 ± 0.01 mg g−1, respectively. The presence of luteolin 4′-O-glucoside, apigenin 7-O-rutinoside, apigenin 7-O-glucoside and apigenin as minor constituents in VA is reported for the first time. Results suggest the implementation of the surrogate standard approach in food analytical practice as highly advisable.