Hepatoprotective activity of Alstonia boonei (De Wild) stem bark in isoniazid-induced Wistar rats: Antioxidant, anti-inflammatory and in silico evaluations

Abstract

Introduction

Liver damage is mainly caused by exposure to toxic chemicals and is a global health challenge. A variety of Alstonia species including Alstonia boonei has been used in Traditional Chinese Medicines (TCM) for the treatment of fever, asthma and as analgesics. In this research, the potential of A. boonei stem bark ethanol extract and ethyl acetate fraction in restoring isoniazid-induced hepatic damage in rats was studied using antioxidative and anti-inflammatory mechanisms.

Methods

A. boonei stem bark was extracted with ethanol and fractionated with n-hexane, ethyl acetate, and butanol. In vitro phytochemical screening and quantification, DPPH, ferrous ion chelating and ferric reducing antioxidant activity of the extracts were carried out. Determination of erythrocyte membrane stabilizing and inhibition of protein denaturation activity of the extracts and fractions were used to evaluate anti-inflammatory activity. Gas chromatography- mass spectrometry (GCMS) of the most active fraction was analyzed. A total of 18 and 35 (7 groups of 5) rats were used for both acute and sub-chronic toxicity studies respectively for a period of 60 days. The control group received normal saline, while 15 mg/kg isoniazid (INH) was used to induce liver toxicity. 25, 50 and 100 mg/kg ethyl acetate fractions (EAF), 50 mg/kg of ethanolic extract and 50 mg/kg vitamin C were used as treatment against INH-induced toxicity. The rats were sacrificed and plasma and liver tissues were obtained for biochemical and histological analyses. Plasma markers of hepatic function including alanine aminotransferase (ALT), aspartate amino transferase (AST), lactate dehydrogenase (LDH), gamma-glutamyl transferase (GGT), albumin and bilirubin levels were determined. Activity of Liver enzyme antioxidants including superoxide dismutase (SOD) and catalase were also analyzed. Liver tissues were further subjected to histological analyses. In silico molecular docking and ADMET studies were used to analyze the binding interactions with arginase 1 and thioredoxin reductase and physicochemical properties of the GC–MS identified compounds.

Results

Phytochemicals including alkaloids, flavonoids and phenols were present in the plant's extract and fractions, while they also demonstrated antioxidant activity against DPPH radicals, and ferrous ion, with the ethyl acetate fraction possessing the highest antioxidant and anti-inflammatory activity. The ethanolic extract and ethyl acetate fraction of A. boonei stem bark demonstrated significant reductions in the elevated levels of plasma liver function enzymes and were also able to significantly restore the activities of enzyme antioxidants (SOD and catalase). Furthermore, restorations in liver histoarchitecture were observed in groups treated with the extract and fractions. In silico analysis revealed high negative binding interactions between compounds identified in the extract and arginase 1and thioredoxin reductase. While ADMET analysis shows good pharmacodynamic and physicochemical properties of the identified compounds

Discussion

The study shows that A. boonei stem bark extracts were able to ameliorate liver damage caused by isoniazid. This might be explained by the antioxidant and anti-inflammatory properties of the extract and fractions. This was further corroborated by the mechanistic molecular docking studies in which there were interactions between the identified compounds and specific enzyme targets.