VARIATION IN MAJOR POLYPHENOLS OF ROOIBOS (ASPALATHUS LINEARIS) AND HONEYBUSH (CYCLOPIA SUBTERNATA)

Abstract

Aspalathus linearis and Cyclopia subternata, fynbos plants endemic to South Africa, are commonly known as the respective herbal teas, rooibos and honeybush. Powdered extracts of both plants are also produced for the food and nutraceutical markets. Cyclopia subternata is one of the Cyclopia species currently of interest, and only one of two under commercial cultivation. The objective of the study was to investigate variation in some of the major polyphenols, and bioactive compounds, i.e. aspalathin and rutin in rooibos and mangiferin and hesperidin in honeybush in randomly selected seedling plants. Water-acetonitrile extracts of the leaves of rooibos and the shoots (leaves and stems) of honeybush samples were analysed by DAD-HPLC. Authentic standards were used for quantification. Large variation in the dry matter content was obtained for the respective compounds. For both species a high concentration of a compound in a specific sample was not necessarily accompanied by a high concentration of the other compound (eg. aspalathin and rutin). The aspalathin to rutin ratio varied from 6 to 32 with 38% of the samples giving a ratio of 11 to 12 (average values - ratio 13; 8.25% aspalathin; 0.66% rutin). The mangiferin to hesperidin ratio varied from 0.3 to 4.5 with 46% of the samples giving a ratio of 0.6 to 1.0 (average values - ratio 1.4; 0.50% mangiferin; 0.44% hesperidin). The variation in content and ratio of compounds in extracts from seedlings will result in extracts differing in bioactivity. To overcome variation in composition and support standardization of nutraceutical extracts, plant improvement through breeding and selection will be required.