Biochemistry and Microbiology

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Browsing Biochemistry and Microbiology by Author "Bowles, S.L"

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    Evaluation of excipients for enhanced intestinal absorption of Rooibos flavonoids
    (University of Zululand, 2017) Hlengwa, Nokulunga; Muller, C.J,F; Basson, A.K; Bowles, S.L; Joubert, E.
    Aspalathin, a dihydrochalcone C-glucoside, and a major flavonoid unique to Rooibos, has been shown to ameliorate insulin resistance, improve glucose uptake in vitro and improve glycaemia in animal models. However, the poor bioavailability of aspalathin limits its potential as a nutraceutical. This study investigated the intestinal absorption of aspalathin, its flavone derivatives, orientin and isoorientin, and nothofagin, its 3-deoxy-derivative, from different green Rooibos extracts in an in vitro intestinal epithelial model, the Caco-2 cell model. Addition of excipients and a nanosome preparation of green Rooibos extract to improve absorption of these flavonoid C-glucosides was also investigated. Methods : Seven green Rooibos extracts, prepared using different solvents (60% ethanol, 80% ethanol and an aqueous extracts), were assessed for the intestinal absorption of their major flavonoids, i.e. aspalathin and its flavone derivatives, orientin and isoorientin, as well as nothofagin, the 3-deoxy-derivative of aspalathin. For testing, two samples per extract type were selected from a large set, based on their bioactivity and chemical dissimilarity. These samples were prepared from different batches of plant material. Caco-2 cells were used as an in vitro intestinal epithelial model to assess absorption of the compounds. Intestinal permeability of the compounds was quantified by analysis of the apical and basolateral samples by HPLC-DAD. The relative transport rate (Papp values) was calculated from the detected concentrations of the compounds crossing the Caco-2 monolayer from the apical to the basolateral compartment. The effect of different extract types, addition of excipients (β-cyclodextrin and inulin) and encapsulation of green Rooibos extract in a nanosome formulation on the absorption of the flavonoids was also explored. Results: At the highest soluble and non-toxic concentration of 1 mg/mL, the transport of aspalathin, nothofagin, orientin and isoorientin across the Caco-2 cell monolayer was confirmed, as these compounds were detected in the basolateral compartment by HPLC-DAD analysis. Standardization of the different extracts (n = 7) to their aspalathin equivalent concentration of 150 μM demonstrated that the transport rate of aspalathin (±1.72 x 10-06 cm/s) was not markedly altered by extract composition as determined by the extraction solvent and plant material. The rate transport was not increased by the addition of β-cyclodextrin (6.99 x 10-07 cm/s) and inulin (1.21977 x 10-06 cm/s), nor by using a nanosome (3.020 X 10-07 cm/s), implying that the strategies used in this study did not enhance intestinal absorption of aspalathin. Conclusion: This study has provided novel information about the intestinal absorption of aspalathin which was not significantly altered by extract composition as determined by extract type and plant material variation. Neither the addition of excipients nor nanosome formulation of the extract could enhance the absorption of aspalathin.
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    Intestinal absorption and metabolism of bush tea major phenolic compounds exhibiting anti-diabetic activity.
    (University of Zululand, 2017) Ntamo, Yonela; Bowles, S.L; Kappo, A.P; Muller, C.J,F; Malherbe, C.J.
    Athrixia phylicoides (A. phylicoides), popularly known as ‘bush tea’, is an indigenous aromatic shrub found in mountainous and grassland areas of the northern and eastern parts of Southern Africa. The plant is traditionally used for the treatment of several ailments, including coughing, treating infected wounds, boils, sore throat, hypertension and heart disease. An aqueous extract of A. phylicoides, has been shown to improve glucose uptake in vitro when tested in muscle, liver and fat cells. While an aqueous extract of A. phylicoides has been shown to have bioactivity, there is limited knowledge regarding absorption and bioavailability of phenolic compounds present in A. phylicoides. Aim of the study: The present study aims to identify major phenolic compounds in an aqueous extract of A. phylicoides, and describe their transport characteristics across the Caco-2 monolayer. Methods and materials: HPLC-DAD and LC/MS was used to identify major phenolic compounds within the extract as well as monitor the transport of these compounds across the intestinal barrier. Differentiated Caco-2 cells were used as a model to predict bioavailability and identify metabolite formation, respectively. Specific inhibitors were used to assess efflux characteristics of these compounds. Results: Nine major phenolic compounds of the aqueous extract of A. phylicoides were identified with para-coumaric acid identified for the first time. Three other major phenolic compounds; protocatechuic acid (PCA), caffeic acid (CA) and para-coumaric acid (p-CA), were demonstrated to cross the Caco-2 cell monolayer in significant amounts, with Papp values 4.52, 4.35 and 23.80 (x 106) cm/s, respectively. Conclusion: The present study reports, for the first time, the transport of phenolic compounds from an aqueous extract of A. phylicoides with PCA, CA and p-CA being the major transported compounds having relatively low bioavailability.
University of Zululand