The antidiarrhoeal evaluation of Psidium guajava L. against enteropathogenic Escherichia coli induced infectious diarrhoea

Abstract

Ethnopharmacological relevance: The plant Psidium guajava L. (Myrtaceae), commonly used as an edible fruit is traditionally used worldwide in treatment of various gastrointestinal problems including diarrhoea. The leaves of the plant have also been evaluated for antidiarrhoeal activity in various chemical induced diarrhoea models.

Objective: The main objective of the present study was to evaluate the potency of P. guajava leaves and its major biomarker quercetin against enteropathogenic Escherichia coli (EPEC) induced infectious diarrhoea using preclinical and computational model.

Material and methods: P. guajava alcoholic leaf extract (PGE) was initially standardized using HPLC taking quercetin as a biomarker and was then subjected to antidiarrhoeal evaluation on rats in an EPEC induced diarrhoea rat model. The study included assessment of various behavioral parameters, initially for 6 h and then for up to 24 h of induction which was followed by estimation of stool water content, density of EPEC in stools and blood parameters evaluation. The colonic and small intestinal tissues of the treated animals were subjected to various biochemical estimations, in vivo antioxidant evaluation, estimation of ion concentration, Na⁺/K⁺-ATPase activity, assessment of pro-inflammatory cytokines and histopathological studies. Further, the major biomarker off PGE, quercetin was subjected to molecular docking studies with Na⁺/K⁺-ATPase and EPEC.

Results: The results demonstrated a significant antidiarrhoeal activity of quercetin (50 mg/kg), PGE at 200 and 400 mg/kg, p.o., where quercetin and PFGE at 200 mg/kg, p.o. were found to be more prominent, as confirmed through higher % protection, water content of stools and density of EPEC in stools. PGE and its biomarker quercetin also significantly recovered the WBC, Hb, platelets loss and also revealed a significant restoration of altered antioxidants level, pro-inflammatory cytokines (IL-1β and TNF-α) expression and had positive influence on Na⁺/K⁺-ATPase activity. The docking studies of quercetin with Na⁺/K⁺-ATPase showed favourable interactions and residues Glu 327, Ser 775, Asn 776, Glu 779 and Asp 804 of Na⁺/K⁺-ATPase were adequately similar to quercetin for donating ligands for binding, while quercetin was also found to terminate the linkage between mammalian cells and EPEC thus, preventing further infection from EPEC.

Conclusion: Inhibition in intestinal secretion, reduced nitric oxide production and inflammatory expression along with reactivation of Na⁺/K-ATPase activity could be attributed to the observed antidiarrhoeal potential of PGE against infectious diarrhoea, where quercetin was confirmed to be the main contributing factor.

Keywords: Antidiarrhoeal activity; Diarrhoea score; Enteropathogenic Escherichia coli; Na(+)/K(+)–ATPase; Psidium guajava; Quercetin.