Mechanism of hepatoprotective activity of methanolic extract of Melastoma malabathricum L. leaves

The objective of this study was to determine the hepatoprotective activity of methanolic extracts of Melastoma malabathricum leaves (MEMM) and its partitions using rats’ model, by evaluating the prophylactic effect of the plants extracts administered prior to the induction of liver toxicity using a hepatotoxic agent. The study were design as hepatoprotective potential of MEMM has never been reported. In an attempt to establish the pharmacological properties, the hepatoprotective potential of MEMM was investigated using carbon tetrachloride (CCl4)- and paracetamol (PCM)- induced hepatotoxicity in rats. Throughout this study, the animals were divided into 22 groups containing 6 rats each group. In the first stage of in vivo study, rats were divided into groups and administered orally once daily with 10 % dimethyl sulfoxide (DMSO) as negative control, 200 mg/kg silymarin as positive control, or MEMM (50, 250, 500 mg/kg) for 7 days, followed by hepatotoxicity induction using CCl4 or PCM. In the second stage, MEMM was partitioned into 3 fractions: petroleum ether extract (PEMM), ethyl acetate extract (EAMM), aqueous extract (AQMM). PEMM, EAMM and AQMM were then tested on PCM-induced hepatotoxicity in rats. Blood sample underwent biochemical analysis to evaluate alanine transferase (ALT), aspartate aminotransferase (AST) and alkaline phosphatase (ALP) levels; the livers were subjected to microscopic analysis. All extracts (MEMM, PEMM, EAMM AQMM) underwent antioxidant study using oxygen radical absorbance capacity (ORAC) test, Total phenolic compound (TPC), 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity and superoxide scavenging assay, and anti-inflammatory evaluation via lipoxygenase (LOX) and xanthine oxidase (XO) assays. Total phenolic content (TPC), phytochemical screening and high-performance liquid chromatography (HPLC) evaluation were also performed. From the histological observation, lymphocyte infiltration and marked necrosis were observed in the DMSO-treated groups (negative control). MEMM showed encouraging activity for reducing the toxic effect of CCl4 or PCM on the liver by reducing the weight of the liver in a dose independent manner; histological observation demonstrated normalization of the histopathological changes, preserving hepatocyte structure, causing a significant decline in AST and ALT levels (p<0.05). PEMM, EAMM and AQMM which contains non-polar compounds, intermediate compounds and polar compounds, respectively, attenuated the liver enzyme levels in a dose-independent manner. Overall, EAMM had the best activity for attenuating the liver enzymes. MEMM had the highest TPC value, followed by AQMM, EAMM, and PEMM. All the extracts (MEMM, PEMM, EAMM, and AQMM) demonstrated potential free radical scavenging activity in SOD and DPPH assays. However, the different trend was showed by ORAC assay from that DPPH and SOD. EAMM and AQMM had high ORAC value, which determine the capacity of an extract to act as an antioxidant. In the anti-inflammatory assays, MEMM and EAMM showed the moderate inhibition in LOX activity, but weak anti-inflammatory activity in XO. Phytochemical screening showed that the extracts showed that MEMM, PEMM and EAMM contained flavonoids, triterpenes, tannins, saponins, polyphenolic compounds and steroids, but not alkaloids. In contrast, the AQMM extract contained fewer compounds. HPLC analysis demonstrated that four to eight peaks detected at different wavelengths of the chromatogram of MEMM, PEMM, EAMM and AQMM, which were suggested to be flavonoid-based compounds. In conclusions, MEMM exerted potential hepatoprotective activity that can be partly attributed to its antioxidant activity, and EAMM was considered to have the best activity among the fractions, which warrants further investigation.

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