Development of HPLC method for quantification of phenolic compounds in Cyclopia intermedia (honeybush) herbal tea infusions
2021
de Beer, D. | du Preez, B.V.P. | Joubert, E.
Cyclopia intermedia is the major source material for the production of honeybush tea, specifically the ‘fermented’ (oxidised) product. The phenolic composition of ‘cup-of-tea’ infusions from other Cyclopia species has been reported, but such information is lacking for C. intermedia. The HPLC method previously developed for extracts of green, unoxidised C. intermedia is not suitable due to the co-elution of unidentified compounds with mangiferin and isomangiferin. A method was developed and validated to quantify the major phenolic compounds in infusions of fermented C. intermedia at ‘cup-of-tea’ strength. Eighteen compounds were identified or tentatively identified and 14 compounds could be quantified with suitable intra- and inter-day repeatability (relative standard deviation < 8%). In a large sample set (n = 96) of fermented C. intermedia, hesperidin, 3-β-D-glucopyranosyl-4-O-β-D-glucopyranosyliriflophenone and mangiferin were present at the highest concentrations (mean > 5 mg/L) in the infusions, followed by isomangiferin, vicenin-2, 3-β-D-glucopyranosyliriflophenone, neoponcirin, hesperetin and protocatechuic acid (mean > 1 mg/L). Agglomerative hierarchical clustering analysis and principal component analysis showed the separation of samples into two groups mainly based on the presence (n = 32) or absence (n = 64) of neoponcirin. Based on information about the origin of the samples, the presence of chemotypes in different geographical areas is postulated.
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