Simultaneous optimisation of extraction of xanthone and benzophenone a-glucosidase inhibitors from Cyclopia genistoides and identification of superior genotypes for propagation Stephanie C. Bosman a , Dalene de Beer a,b , Theresa Beelders a , Elize L. Willenburg b , Christiaan J. Malherbe b , Beata Walczak c , Elizabeth Joubert a,b,⇑ a Department of Food Science, Stellenbosch University, Private Bag X1, Matieland 7602, South Africa b Plant Bioactives Group, Post-Harvest and Wine Technology Division, Agricultural Research Council (ARC), Infruitec-Nietvoorbij, Private Bag X5026, Stellenbosch 7599, South Africa c Institute of Chemistry, The University of Silesia, 9 Szkolna Street, 40-006 Katowice, Poland article info Article history: Received 22 December 2016 Received in revised form 1 March 2017 Accepted 3 March 2017 Chemical compounds studied in this article: 3-b-D-glucopyranosyliriflophenone (PubChem CID: 53396784) Isomangiferin (PubChem CID: 5318597) Mangiferin (PubChem CID: 5281647) Keywords: Mammalian a-glucosidase inhibition Nutraceutical extract Phenolic content Plant selection Response surface methodology abstract Extraction of xanthones and benzophenones from Cyclopia genistoides was optimised in terms of solvent composition (ethanol concentration) and extraction temperature, using a central composite design, response surface methodology and multi-response desirability profiling. Compounds of interest were the xanthones, mangiferin and isomangiferin, and the benzophenones, 3-b-D-glucopyranosyl-4-b-D- glucopyranosyloxyiriflophenone and 3-b-D-glucopyranosyliriflophenone, present in high levels in C. genistoides. Optimum extraction conditions (40% ethanol; 70 °C; 10:1 solvent:solid ratio; 30 min) applied to different batches of plant material (n = 10), delivered mean extract, xanthone and benzophe- none yields of 37.8, 4.12 and 1.99 g/100 g plant material, respectively, with a mean a-glucosidase inhibitory activity of 39.5% at 100 lg/mL. Similar a-glucosidase inhibitory activity was demonstrated for mangiferin and isomangiferin, indicating that the position of the sugar moiety on the dibenzo-c- pirone structure did not affect activity. Superior C. genistoides genotypes in terms of xanthone and benzophenone content were identified. Ó 2017 Elsevier Ltd. All rights reserved. 1. Introduction Food and beverage manufacturers continually seek novel food sources or ingredients to meet a growing consumer demand for natural, additive-free, health-promoting products. The high inci- dence of type 2 diabetes created market opportunities with nutraceutical manufacturers turning their focus to plant-based extracts to aid management of blood sugar levels (Moloughney, 2016). Diminished release of glucose from complex carbohydrates to control postprandial spiking of blood glucose levels is targeted as a means to manage blood sugar levels. Plant extracts able to inhibit a-glucosidase and thus delay carbohydrate digestion, there- fore, have commercial potential (Rengasamy, Aderogba, Amoo, Stirk, & Van Staden, 2013). Screening of plant extracts and their compounds for a-glucosidase inhibitory potential usually entails in vitro testing, using yeast (Tan et al., 2013; Yang, Zhao, Liu, Song, & Liu, 2014) or mammalian intestinal a-glucosidase (Azuma et al., 2011; Shibano, Kakutani, Taniguchi, Yasuda, & Baba, 2008). The reported differences in primary structure of a-glucosidases from yeasts to those from mammalian origins (Kimura, Lee, Lee, Lee, & Park, 2004; Oki, Matsui, & Osajima, 1999), however, could lead to misleading results as inhibitors http://dx.doi.org/10.1016/j.jff.2017.03.011 1756-4646/Ó 2017 Elsevier Ltd. All rights reserved. Abbreviations: ANOVA, analysis of variance; CCD, central composite design; EHD, eriodictyol-O-hexose-O-deoxyhexoside; EtOH, ethanol; HPCCC, high perfor- mance counter-current chromatography; HPLC, high-performance liquid chro- matography; IDG, 3-b-D-glucopyranosyl-4-b-D-glucopyranosyloxyiriflophenone; IMG, 3-b-D-glucopyranosyliriflophenone; LOF, lack of fit; LSD, least significant difference; MMG, 3-b-D-glucopyranosylmaclurin; MUG, 7-O-a-D-glucopyranosyl-4- methylumbelliferone; NHD, naringenin-O-hexose-O-deoxyhexoside; PCA, principal component analysis; PM, plant material; rMANOVA, regularised multivariate analysis of variance; RSM, response surface methodology. ⇑ Corresponding author at: Plant Bioactives Group, Post-Harvest and Wine Technology Division, Agricultural Research Council (ARC), Infruitec-Nietvoorbij, Private Bag X5026, Stellenbosch 7599, South Africa. E-mail addresses: stephbosman@yahoo.com (S.C. Bosman), DBeerD@arc.agric.za (D. de Beer), BeeldersT@gmail.com (T. Beelders), elizel@gmail.com (E.L. Willenburg), MalherbeCh@arc.agric.za (C.J. Malherbe), beata.walczak@us.edu.pl (B. Walczak), JoubertL@arc.agric.za (E. Joubert). Journal of Functional Foods 33 (2017) 21–31 Contents lists available at ScienceDirect Journal of Functional Foods journal homepage: www.elsevier.com/locate/jff