Antiadhesive activity of hydroethanolic extract from bean pods of Phaseolus vulgaris (common bean) against uropathogenic E. coli and permeability of its constituents through Caco-2 cells monolayer

Abstract

Ethnopharmacological relevance: Phaseaoli pericarpium (bean pods) is a pharmacopeial plant material traditionally used as a diuretic and antidiabetic agents. Diuretic activity of pod extracts was reported first in 1608. Since then Phaseoli pericarpium tea figures in many textbooks as medicinal plant material used by patients.

Aim of the study: Despite the traditional use of extracts from Phaseolium vulgaris pericarp, limited information is available on bioactivity, chemical composition, and bioavailability of such preparations. The following study aimed to investigate the phytochemical composition, the in vitro permeability of selected extract's constituents over the Caco-2 permeation system, and potential antivirulence activity against uropathogenic Escherichia coli of a hydroalcoholic Phaseoli pericarpium extract (PPX) in vitro to support its traditional use as a remedy used in urinary tract infections.

Material and methods: The chemical composition of the extract PPX [ethanol:water 7:3 (v/v)] investigated by using UHPLC-DAD-MSⁿ and subsequent dereplication. The permeability of compounds present in PPX was evaluated using the Caco-2 monolayer permeation system. The influence of PPX on uropathogenic E. coli (UPEC) strain NU14 proliferation and against the bacterial adhesion to T24 epithelial cells was determined by turbidimetric assay and flow cytometry, respectively. The influence of the extract on the mitochondrial activity of T24 host cells was monitored by MTT assay.

Results: LC-MSⁿ investigation and dereplication, indicated PPX extract to be dominated by a variety of flavonoids, with rutin as a major compound, and soyasaponin derivatives. Rutin, selected soyasaponins and fatty acids were shown to permeate the Caco-2 monolayer system, indicating potential bioavailability following oral intake. The extract did not influence the viability of T24 cells after 1.5h incubation at 2 mg/mL and UPEC. PPX significantly reduced the bacterial adhesion of UPEC to human bladder cells in a concentration-dependent manner (0.5-2 mg/mL). Detailed investigations by different incubation protocols indicated that PPX seems to interact with T24 cells, which subsequently leads to reduced recognition and adhesion of UPEC to the host cell membrane.

Conclusions: PPX is characterised by the presence of flavonoids (e.g. rutin) and saponins, from which selected compounds might be bioavailable after oral application, as indicated by the Caco-2 permeation experiments. Rutin and some saponins can be considered as potentially bioavailable after the oral intake. The concentration-dependent inhibition of bacterial adhesion of UPEC to T24 cells justifies the traditional use of Phaseoli pericarpium in the prevention and treatment of urinary tract infections.

Keywords: Adhesion; Caco-2; Phaseolus vulgaris; Saponins; UPEC; Urinary tract infections.