High performance thin layer chromatography fingerprinting of rooibos (Aspalathus linearis) and honeybush (Cyclopia genistoides, Cyclopia intermedia and Cyclopia subternata) teas

Abstract

High performance thin layer chromatography (HPTLC) has been widely implemented for the rapid chemical fingerprinting of medicinal plant extracts for identification and authentication purposes. Despite herbal teas of rooibos (Aspalathus linearis) and honeybush (Cyclopia spp.) being important local and export products of South Africa, characteristic and well-defined HPTLC chemical profiles for the species that could assist in identification and authentication, have not been established and reported. ‘Fermentation’, an oxidation processing step for flavour and colour development, is known to alter the chemical composition of these plant materials, with consequences for their therapeutic properties. In this study, HPTLC fingerprints were established that characterise these herbal teas in terms of phenolic constituents linked to their health benefits. Selected flavonoids present in rooibos were clearly distinguished from the extract matrix, and the marked depletion of aspalathin in the fermented samples was demonstrated. The analytical method developed for honeybush achieved partial separation of the major xanthone constituents, mangiferin and isomangiferin. Lower relative concentrations of the regio-isomers were evident in the fermented samples of C. genistoides compared to their unfermented counterparts. The chemical profile of fermented C. subternata was markedly different to those of C. genistoides and C. intermedia in that mangiferin/isomangiferin was detected in only one of the five samples of C. subternata. Cost-effective HPTLC methods are herein described that can be used for the rapid analysis of multiple samples in industrial environments, as a tool for quality control, in particular for the identification of these herbal teas of South African origin.