In vitro a-glucosidase inhibition by honeybush (Cyclopia genistoides) food ingredient extract-potential for dose reduction of acarbose through 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/d0fo01306dThe original publication is available at http://pubs.rsc.org/en/Journals/Journal/FOExtracts 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 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.https://pubs.rsc.org/en/content/articlelanding/2020/fo/d0fo01306dPublishers versio

Development of On-Line High Performance Liquid Chromatography (HPLC)-Biochemical Detection Methods as Tools in the Identification of Bioactives

Biochemical detection (BCD) methods are commonly used to screen plant extracts for specific biological activities in batch assays. Traditionally, bioactives in the most active extracts were identified through time-consuming bio-assay guided fractionation until single active compounds could be isolated. Not only are isolation procedures often tedious, but they could also lead to artifact formation. On-line coupling of BCD assays to high performance liquid chromatography (HPLC) is gaining ground as a high resolution screening technique to overcome problems associated with pre-isolation by measuring the effects of compounds post-column directly after separation. To date, several on-line HPLC-BCD assays, applied to whole plant extracts and mixtures, have been published. In this review the focus will fall on enzyme-based, receptor-based and antioxidant assays

Rooibos (Aspalathus linearis), honeybush (Cyclopia intermedia) and cancer bush (Sutherlandia frutescens subsp. microphylla) protect against tobacco-specific mutagenesis in vitro

ArticleAntimutagenesis studies against the tobacco-specific mutagens 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) and N-oxide, 4 (methyl-nitrosamino)-1-(3-pyridyl)-1-butanol (NNAL), were conducted using hot water aqueous extracts of rooibos (Aspalathus linearis), honeybush (Cyclopia intermedia), and cancer bush (Sutherlandia frutescens). Aqueous extracts of both “fermented” and “unfermented” (green) rooibos and honeybush were included, while extracts of green and black teas (Camellia sinensis) served as benchmarks. A polyphenol-enriched methanol extract of unfermented rooibos (RgM) was included to further elucidate the possible role of rooibos polyphenols. Studies were performed in the presence of the metabolic activation against Salmonella typhimurium tester strain TA1535, using the standard plate incorporation and micro-suspension, pre-incubation assays. The mutagenic effects of NNK against the strain TA1535 was best demonstrated using the standard plate incorporation assay, while a higher mutagenicity was demonstrated for NNAL using the micro-suspension, pre-incubation method. Black tea and RgM exhibited the highest protection against NNK-induced mutagenesis followed by the aqueous extracts of rooibos ≥ green tea ≥ honeybush ≥ cancer bush. Black tea, green tea, RgM and unfermented rooibos were the most effective against NNAL-induced mutagenesis, followed by fermented rooibos. The two honeybush extracts exhibited similar, but the weakest protective response. When considering the amount of total polyphenols (TPP) incorporated in the plate incorporation assay, cancer bush exhibited similar protection to that of fermented and unfermented honeybush against NNK mutagenesis. The involvement of specific polyphenol-cytochrome P450 (CYP450) interactions is likely to be involved in the protection against tobacco-related mutagenesis. Polyphenol constituents of rooibos, honeybush and cancer bush could play an important role in the protection against mutagenesis induced by the major tobacco-specific carcinogens

Adipose tissue as a possible therapeutic target for polyphenols : a case for Cyclopia extracts as anti-obesity nutraceuticals

CITATION: Jack, B. U., et al. 2019. Adipose tissue as a possible therapeutic target for polyphenols : a case for Cyclopia extracts as anti-obesity nutraceuticals. Biomedicine and Pharmacotherapy, 120:109439, doi:1016/j.biopha.2019.109439.The original publication is available at https://www.sciencedirect.comENGLISH ABSTRACT: Obesity is a significant contributor to increased morbidity and premature mortality due to increasing the risk of many chronic metabolic diseases such as type 2 diabetes, cardiovascular disease and certain types of cancer. Lifestyle modifications such as energy restriction and increased physical activity are highly effective first-line treatment strategies used in the management of obesity. However, adherence to these behavioral changes is poor, with an increased reliance on synthetic drugs, which unfortunately are plagued by adverse effects. The identification of new and safer anti-obesity agents is thus of significant interest. In recent years, plants and their phenolic constituents have attracted increased attention due to their health-promoting properties. Amongst these, Cyclopia, an endemic South African plant commonly consumed as a herbal tea (honeybush), has been shown to possess modulating properties against oxidative stress, hyperglycemia, and obesity. Likewise, several studies have reported that some of the major phenolic compounds present in Cyclopia spp. exhibit anti-obesity effects, particularly by targeting adipose tissue. These phenolic compounds belong to the xanthone, flavonoid and benzophenone classes. The aim of this review is to assess the potential of Cyclopia extracts as an anti-obesity nutraceutical as underpinned by in vitro and in vivo studies and the underlying cellular mechanisms and biological pathways regulated by their phenolic compounds.https://www.sciencedirect.com/science/article/pii/S0753332219330562Publisher's versio

Food ingredient extracts of Cyclopia subternata (Honeybush) : variation in phenolic composition and antioxidant capacity

CITATION: De Beer, D., et al. 2012. Food Ingredient Extracts of Cyclopia subternata (Honeybush) : Variation in Phenolic Composition and Antioxidant Capacity. Molecules, 17(12):14602-14624, doi:10.3390/molecules171214602.The original publication is available at http://www.mdpi.comCyclopia subternata plants are traditionally used for the production of the South African herbal tea, honeybush, and recently as aqueous extracts for the food industry. A C. subternata aqueous extract and mangiferin (a major constituent) are known to have anti-diabetic properties. Variation in phenolic composition and antioxidant capacity is expected due to cultivation largely from seedlings, having implications for extract standardization and quality control. Aqueous extracts from 64 seedlings of the same age, cultivated under the same environmental conditions, were analyzed for individual compound content, total polyphenol (TP) content and total antioxidant capacity (TAC) in a number of assays. An HPLC method was developed and validated to allow quantification of xanthones (mangiferin, isomangiferin), flavanones (hesperidin, eriocitrin), a flavone (scolymoside), a benzophenone (iriflophenone-3-C-β-glucoside) and dihydrochalcones (phloretin-3',5'-di-C-β-glucoside, 3-hydroxyphloretin-3',5'-di-C-hexoside). Additional compounds were tentatively identified using mass spectrometric detection, with the presence of the 3-hydroxyphloretin-glycoside, an iriflophenone-di-O,C-hexoside, an eriodictyol-di-C-hexoside and vicenin-2 being demonstrated for the first time. Variability of the individual phenolic compound contents was generally higher than that of the TP content and TAC values. Among the phenolic compounds, scolymoside, hesperidin and iriflophenone-3-C-β-glucoside contents were the most variable. A combination of the measured parameters could be useful in product standardization by providing a basis for specifying minimum levels.http://www.mdpi.com/1420-3049/17/12/14602Publisher's versio

Benzophenone <i>C</i>- and <i>O</i>‑Glucosides from <i>Cyclopia genistoides</i> (Honeybush) Inhibit Mammalian α‑Glucosidase

An enriched fraction of an aqueous extract prepared from the aerial parts of <i>Cyclopia genistoides</i> Vent. yielded a new benzophenone di-<i>C,O</i>-glucoside, 3-<i>C</i>-β-d-glucopyranosyl-4-<i>O</i>-β-d-glucopyranosyl­iriflophenone (<b>1</b>), together with small quantities of a known benzophenone <i>C</i>-glucoside, 3-<i>C</i>-β-d-glucopyranosylmaclurin (<b>2</b>). The isolated compounds showed α-glucosidase inhibitory activity against an enzyme mixture extracted from rat intestinal acetone powder. Compound <b>2</b> exhibited significantly (<i>p</i> < 0.05) higher inhibitory activity (54%) than <b>1</b> (43%) at 200 μM. In vitro tests in several cell models showed that <b>1</b> and its 3-<i>C</i>-monoglucosylated derivative (3-<i>C</i>-β-d-glucopyranosyl­iriflophenone) were marginally effective (<i>p</i> ≥ 0.05) in increasing glucose uptake