Evaluation of capillary electrophoresis for the analysis of rooibos and honeybush tea phenolics

Abstract

Rooibos and honeybush are popular herbal teas produced from the shrubs of Aspalathus linearis and Cyclopia spp., respectively, which are indigenous to South Africa. Both herbal teas are rich in polyphenols and their consumption is associated with several health benefits, partly ascribed to their phenolic constituents. Quantification of phenolics in extracts and teas for quality control and research purposes is generally performed using HPLC, although dedicated and often species-specific methods are required. CE offers an attractive alternative to HPLC for the analysis of phenolics, with potential benefits in terms of efficiency, speed and operating costs. In this contribution, we report quantitative CZE methods for the analysis of the principal honeybush and rooibos phenolics. Optimal separation for honeybush and rooibos phenolics was achieved in 21 and 32 min, respectively, with good linearity and repeatability. Quantitative data for extracts of "unfermented" and "fermented" rooibos and two honeybush species were statistically comparable with those obtained by HPLC for the majority of compounds. The developed methods demonstrated their utility for the comparison of phenolic contents between different species and as a function of manufacturing processes, thus offering cost effective, although less sensitive and robust, alternatives to HPLC analysis.

Aspalathin from Rooibos (Aspalathus linearis): A Bioactive C-glucosyl Dihydrochalcone with Potential to Target the Metabolic Syndrome

“…The use of mass spectrometric detection increases the sensitivity and specificity of the method. The suitability of capillary zone electrophoresis for quantification of aspalathin and other phenolic compounds in rooibos was investigated by Arries et al [39]. It was deemed less sensitive and a smaller number of compounds could be quantified with suitable reproducibility, but has potential as a rapid, inexpensive alternative method, especially for quantification of the major compounds.…”

Qualitative and Quantitative Analysis of Polyphenols in Lamiaceae Plants—A Review

“…Separation and analysis of polyphenols in herbs and spices by CE involves separation based on the electrophoretic mobilities of a solution that consists of electrically charged species, in small-diameter capillaries [ 92 ] it is recognized as being effective in phenolic characterization, offering practical operation, rapid analysis, low consumption of solvent, and low cost. This method represents a valuable alternative to HPLC in the separation of closely associated phenolics, but its major drawbacks are its lower reproducibility and sensitivity as compared to HPLC [ 93 ]. Maher et al [ 47 ] used an optimized CE with DAD to identify luteolin and apigenin in Thymus vulgaris and an additional herb extract ( Table 2 ).…”

Analytical Methods for Exploring Nutraceuticals Based on Phenolic Acids and Polyphenols

“…Capillary electrophoresis (CE) can also be used owing to the ionizable nature of polyphenols. For instance, the phenolic content of herbal, fruit, or vegetable extracts has been determined using different CE modes such as capillary zone electrophoresis (CZE), micellar electrokinetic chromatography (MEKC), capillary isotachophoresis (CITP), and capillary electrochromatography (CEC) [61][62][63][64][65].…”