Honeybush (Cyclopia spp.) as nutraceutical – Integrated strategy aimed at increasing bioactive content of extracts

Abstract

Commercial interest in the genus, Cyclopia (family Fabaceae), endemic to South Africa has led to concerted efforts to develop an industry [1]. Key issues included cultivation to lessen dependence on natural populations and primary processing for herbal tea production. Investigation of the phenolic composition and biological activities indicated potential for production of pharmaceutical and/or nutraceutical extracts [2, 3]. The aim of the present paper is to describe the integrated strategy followed by the Agricultural Research Council of South Africa to enable production of high-value products, in particular extracts high in the anti-diabetic xanthones, mangiferin and isomangiferin. Several Cyclopia species were evaluated with highest xanthone levels demonstrated in C. genistoides Vent and C. longifolia Vogel. As C. longifolia was thought to be extinct and cultivation is still in an experimental stage, further focus fell on C. genistoides. Promising individual plants (16 genotypes), based on biomass yield, were selected from natural populations and three seedling plantations, one situated in the Southern Cape and two in the Overberg, and cuttings planted at one location for further selection. Apart from primary criteria such as growth habit, growth vigour, leaf-shoot ratio, etc., advanced selection criteria include phytochemical content. PCA showed clear separation between genotypes with high hesperidin content and those with high content of other major compounds. Whilst hesperidin levels of the leaves were not affected by harvesting date, highest xanthone levels accumulated during summer (high solar radiation, high temperature, and water deficit), while lowest levels were observed during winter [4]. Mangiferin levels in the leaves were 5 to 10 times higher than that of isomangiferin. Post-harvest product improvement entailed development of “green” honeybush, as well as optimisation of xanthone extraction using a food-grade solvent and membrane-enrichment.