Planta Med 2019; 85(11/12): 987-996
DOI: 10.1055/a-0948-9072
Biological and Pharmacological Activities
Original Papers
Georg Thieme Verlag KG Stuttgart · New York

In Vitro Modulation of Glibenclamide Transport by P-glycoprotein Inhibitory Antidiabetic African Plant Extracts[ 1 ]

Udoamaka F. Ezuruike
1   Department of Pharmaceutical and Biological Chemistry, University College London School of Pharmacy, London, United Kingdom.
,
Elisabetta Chieli
2   Department of Translational Research on New Technologies in Medicine and Surgery, School of Medicine, University of Pisa, Pisa, Italy.
,
Jose M. Prieto
1   Department of Pharmaceutical and Biological Chemistry, University College London School of Pharmacy, London, United Kingdom.
› Author Affiliations
Further Information

Publication History

received 31 January 2019
revised 04 June 2019

accepted 05 June 2019

Publication Date:
26 July 2019 (online)

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Abstract

The rise of diabetes incidence in Nigeria enhances the use of popular remedies that may interact with conventional therapies. The aqueous extracts of 27 popular Nigerian “antidiabetic” plants were tested for their in vitro effects on glutathione levels within HepG2 cells, P-glycoprotein (P-gp)-mediated Rh-123 efflux activity in Caco-2 vincristine-resistant cells, and modulation of glibenclamide transport in Caco-2 monolayers. The extract from Ximenia americana significantly depleted intracellular glutathione at 100 µg/mL similarly to the reference buthionine sulphoximine (p < 0.05). Other 10 extracts raised glutathione levels. Eight extracts inhibiting P-gp efflux in a concentration-dependent manner (p < 0.01) were selected for further evaluation in a bi-directional transport model across Caco-2 monolayers: Annona senegalensis, Bridellia ferruginea, Cassytha filiformis, Daniellia ogea, Khaya ivorensis, Syzygium guineense, Terminalia avicennioides, and X. americana. When interferences in paracellular transport were discarded, only 3 of them may be modulating the efflux ratio of glibenclamide (efflux ratio: 2.65 ± 0.13) in the same manner the reference drug verapamil (efflux ratio: 1.14 ± 0.25, p < 0.01) does: Syzygium guineense (efflux ratio: 1.70 ± 0.23, p < 0.01), Terminalia avicennioides (efflux ratio: 1.80 ± 0.25, p < 0.05), and X. americana (efflux ratio: 1.66 ± 0.10, p < 0.01). HPLC-UV analyses for P-gp inhibitors in these extracts revealed several phenolic compounds such as rutin, gallic acid, and ellagic acid reported to decrease P-gp expression and/or directly modify its function. In conclusion, some popular herbal medicines used by Nigerian diabetic patients are here shown to potentially affect glibenclamide absorption at concentrations that could be reached in the intestinal tract.

1 Dedicated to Professor Dr. Cosimo Pizza 70th birthday in recognition of his outstanding contribution to natural product research.


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