In vitro a-glucosidase inhibition by honeybush (Cyclopia genistoides) food ingredient extract-potential for dose reduction of acarbose through synergism
Date
2020-06-29
Journal Title
Journal ISSN
Volume Title
Publisher
Royal Society of Chemistry
Abstract
Extracts of Cyclopia species are used as food ingredients. In vitro α-glucosidase (AG) inhibition by ultrafiltered C. genistoides extract, fractions enriched in xanthones (XEF) and benzophenones (BEF), as well as mangiferin, isomangiferin, 3-β-D-glucopyranosyliriflophenone (I3G) and 3-β-D-glucopyranosyl-4-O-β-D-glucopyranosyliriflophenone (IDG) was determined with acarbose as positive control. XEF was more potent than the extract and BEF (IC50 = 43.3, 95.5 and 205.7 μg mL−1, respectively). Compounds demonstrated potency in the descending order: acarbose (IC50 = 44.3 μM) > mangiferin (102.2 μM) > isomangiferin (119.8 μM) > I3G (237.5 μM) > IDG (299.4 μM). The combination index (CI) was used to determine synergism (CI < 0.7) as demonstrated for combinations of acarbose with XEF, BEF or the respective compounds at 50% and 75% effect levels. The greatest potential acarbose dose reductions (>six-fold) across all effect levels were calculated for combinations of acarbose with mangiferin or isomangiferin, explaining the greater acarbose dose reduction potential of XEF vs. BEF. The effect of batch-to-batch variation (n = 10) of raw plant material on AG inhibition was quantified at a fixed concentration (160 μg mL−1). XEFs (xanthone content = 223–481 g kg−1) achieved AG inhibition of 63–72%, whereas BEFs (benzophenone content = 114–251 g kg−1) achieved AG inhibition of 26–34%, with weak linear correlation (R2 < 0.43) between target compound content of the fractions and their achieved AG inhibition. Thus, extract fractions of C. genistoides, enriched in xanthones and benzophenones, show potential in reducing the effective dose of acarbose required to prevent postprandial hyperglycaemia.
Description
CITATION: Miller, N.; Malherbe, C. J. & Joubert, E. 2020. In vitro α-glucosidase inhibition by honeybush (Cyclopia genistoides) food ingredient extract—potential for dose reduction of acarbose through synergism. Food and Function, 11:6476–6486. doi:10.1039/d0fo01306d
The original publication is available at http://pubs.rsc.org/en/Journals/Journal/FO
The original publication is available at http://pubs.rsc.org/en/Journals/Journal/FO
Keywords
In vitro α-glucosidase, Cyclopia genistoides extract, Honeybush (Cyclopia genistoides), Dose reduction of acarbose, Drug synergism
Citation
Miller, N.; Malherbe, C. J. & Joubert, E. 2020. In vitro α-glucosidase inhibition by honeybush (Cyclopia genistoides) food ingredient extract—potential for dose reduction of acarbose through synergism. Food and Function, 11:6476–6486. doi:10.1039/d0fo01306d