Visualization of Aspalathin in Rooibos (Aspalathus linearis) Plant and Herbal Tea Extracts Using Thin-Layer Chromatography

Abstract

Aspalathin, the main polyphenol of rooibos (Aspalathus linearis), is associated with diverse health promoting properties of the tea. During fermentation, aspalathin is oxidized and concentrations are significantly reduced. Standardized methods for quality control of rooibos products do not investigate aspalathin, since current techniques of aspalathin detection require expensive equipment and expertise. Here, we describe a simple and fast thin-layer chromatography (TLC) method that can reproducibly visualize aspalathin in rooibos herbal tea and plant extracts at a limit of detection (LOD) equal to 178.7 ng and a limit of quantification (LOQ) equal to 541.6 ng. Aspalathin is a rare compound, so far only found in A. linearis and its (rare) sister species A. pendula. Therefore, aspalathin could serve as a marker compound for authentication and quality control of rooibos products, and the described TLC method represents a cost-effective approach for high-throughput screening of plant and herbal tea extracts.

Transcriptomics of the Rooibos (Aspalathus linearis) Species Complex

“…Biochemical screening of plant samples for specific compounds of interest can represent a cost-limiting factor, since many of these compounds can only be detected using expensive technologies such as HPLC, Near Infrared Spectroscopy (NIS) or Raman Spectroscopy (RS). In this study, high-throughput biochemical screening was completed using thin layer chromatography (TLC) analyses that permitted detection of aspalathin and identification of plant-specific fingerprints [ 50 ]. TLC is a simple and easily scalable method for detection of diverse compounds in plant extracts, herbal products, and foods [ 66 ].…”

“…Thin-layer chromatography was performed on all collected plant samples as described in [ 50 ]. Four plants that differed in their morphological characteristics and in their thin-layer chromatography (TLC) profiles were selected for further biochemical characterization.…”

“…Then, 50 mg of plant material was extracted with 5 mL methanol. All samples were mixed at 40 rpm on a Benchmark rotating mixer (Benchmark Scientific, Edison, NJ, USA) at 4 • C for 24 h. Thin-layer chromatography was performed on all collected plant samples as described in [50]. Four plants that differed in their morphological characteristics and in their thin-layer chromatography (TLC) profiles were selected for further biochemical characterization.…”

“…The IDBA-Trans assembly had the highest proportion of duplicated BUSCOs (indicating redundancy), as well as the lowest number of fragmented BUSCOs and the highest proportion of transcripts that matched a BUSCO (indicating assembly accuracy). SOAPdenovo-Trans produced the lowest total number of transcripts (50,503), approximately half of which were longer than 1 kb. It was the only assembler that produced transcripts longer than 10 kb.…”

Rooibos (Aspalathus linearis) Genome Size Estimation Using Flow Cytometry and K-Mer Analyses

“…Typically, fresh leaf material is the material of choice for flow cytometry analyses. For rooibos, once harvested, leaves turn red-brown in a very short period of time, which is mostly due to the degradation of aspalathin [39]. Preliminary flow cytometry tests showed that these tissues do not yield peaks in the histograms.…”