Abstract
Athrixia phylicoides, known as “bush tea”, grows abundantly in South Africa. An infusion of the leaves
is used as a beverage and to treat a multitude of health conditions. The aim of this
study was to investigate the chemical variation within A. phylicoides and to identify characteristic compounds for quality control. Samples from 12 locations
in South Africa were analysed using ultra-performance liquid chromatography. Hierarchical
cluster analysis of the aligned ultra-performance liquid chromatography-time-of-flight
mass spectrometry data indicated two groups on the resulting dendrogram, representing
48 samples. Five marker compounds, identified through visual inspection and the construction
of a discriminant analysis model, were evident on the ultra-performance liquid chromatography-MS
profiles. Four of these compounds were isolated and identified, three as hydroxy methoxyflavones
and the fourth as a coumarate, using nuclear magnetic resonance spectroscopy. An ultra-performance
liquid chromatography-photodiode array method was developed and validated for the
determination of the marker compounds using the isolates as standards. The limits
of detection for the four compounds ranged from 0.92 – 2.50 µg/mL. Their recoveries
at three concentration levels (1.00, 10.0, and 100 µg/mL) were between 97.0 and 101%,
while acceptable intra- and inter-day precision was obtained as reflected by percentage
relative standard deviation values below 2.24%. The concentrations of all the marker
compounds were found to be higher in samples corresponding to Group 1 of the dendrogram
than in those from Group 2. This may be attributable to differences in altitude, climate,
and some edaphic factors. Identification of these marker compounds will make a valuable
contribution towards the quality control and sustainable commercialisation of bush
tea.
Key words
Athrixia phylicoides
- Asteraceae - chemometrics - UPLC - NMR - quality control
