Selective 1D-TOCSY and chemometrics to evaluate authenticity of Turnera diffusa and related botanical extracts

Abstract

Nuclear magnetic resonance (NMR) spectroscopy has emerged as a powerful tool for the development of new analytical methods in metabolomics and metabolic profiling of a plethora of biological samples, including natural products. NMR-based metabolomics enables characterisation of metabolites and biomarkers in plant extracts. Selective 1D- Total Correlation Spectroscopy TOCSY (1D-TOCSY) has been used in metabolomic research as a direct method for spectroscopic separation and identification of chemical compounds in complex mixtures. In this work, a method for the specific identification of the biomarker compound hepatodamianol in Turnera diffusa plants and related botanical extracts, based on NMR and multivariate analysis, was developed. For this purpose, methanolic extracts from T. diffusa samples were prepared and analysed using 1H-NMR. Hepatodamianol selective 1D-TOCSY spectra were recorded to obtain the spectroscopic fingerprint of carbohydrate moieties, and then compared against authenticated T. diffusa extracts and commercial samples. 1H-NMR data were collected to generate a PCA statistical model to explore the chemical variability between samples of T. diffusa extracts. The selective 1D-TOCSY experiment was successfully applied for unambiguous identification of hepatodamianol in T. diffusa extracts and commercial botanical remedies to verify authenticity of botanical material. This combined methodology based on NMR metabolomics is a useful analytical tool to establish if T. diffuse is present in herbal preparations claiming to be prepared from this plant. Prospectively, this method could be extended to analyse traditional remedies and herbal medicines, as a quality control proof to assess the presence of bioactive compounds.