Liver is the largest organ in the human body and is a key organ of metabolism [1, 2]. Despite its considerable regenerative capacity, continuous and various exposures to xenobiotics, environmental pollutants, and chemotherapeutic agents could suppress and possibly overcome the natural protective mechanisms of the liver, leading to liver malfunction and later if it is not treated properly leads to injury. Despite the remarkable progresses in conventional medical therapies in the last 20 years, drugs available for the treatment of liver diseases were often limited in efficacy and could have triggered various unwanted side effects when compared to other medical therapies for liver diseases which were often difficult to handle . Moreover, some of these modern hepatoprotective drugs did not offer protection against injury to the vital organ despite their direct or indirect action to improve the liver function. In response to these factors that limit the use of conventional drugs, attempts were continuously made by scientists all over the world working in the area of hepatoprotective drug discovery to identify new sources of agents with potential liver protective activity [4, 5].
Interestingly, in line with increase in patients attempt to use complementary and alternative medicines, particularly herbal/plant-based therapies, to cure various diseases, efforts are increasingly being carried out by scientists to investigate the hepatoprotective potential of various medicinal plants. One of the medicinal plants that have been widely used in the Malay traditional medicine is Melastoma malabathricum L., which is locally known as “Senduduk”. This small shrub belongs to the family Melastomaceae and is native to tropical and temperate Asia, including Malaysia, and the Pacific Islands. Despite being a well-known herb in Malaysia wherein its leaves, shoots and roots are prepared in various ways to treat various types of diseases (i.e. to treat cuts or wounds, puerperal infections, high blood pressure, diabetes, dysentery, diarrhea, piles, leucorrhea, epilepsy, ulcers, gastric ulcers, scar, skin diseases, pimple and black spot at skin, hemorrhoidal bleeding, rheumatism, arthritis, prolonged fever, cancer and tenderness in the legs, to stop bleeding, to prevent scarring from smallpox, and to relieve a toothache), attempts to scientifically investigate and confirm those claims are however lacking . Scientifically, various types of extracts from different parts of M. malabathricum have been prepared and tested using a variety of in vitro and in vivo test models. The plant has been reported to possess various types of pharmacological activities (i.e. antibacterial, antiviral, antiparasitic, cytotoxicity, anticoagulant, platelet-activating factor inhibitory, wound healing, antiulcer, antidiarrheal, antivenom, anti-inflammatory, antinociceptive and antipyretic) at different doses or concentrations .
Various phytochemical constituents have been isolated and identified from various parts and extracts of M. malabathricum. Focusing, particularly, on the leaves, several bioactive compounds have been identified from different types of extracts, namely: i) 70% acetone extract – isoquercitrin 6″-O-gallate, malabathrin-A, -B, -C, -D, -E and -F, 1,4,6-tri-O-galloyl-β-D-glucoside, 1,2,4,6-tetra-O-galloyl-β-D-glucoside, strictinin, casuarictin, pedunculagin, nobotanin-B, -D, -G, -H and -J, pterocarinin C, new complex tannins in which an ellagitannin and a flavan-3-ol are bound by a C-glycosidic linkage belonging to type II + tannins, casuarinin, (−)-epicatechin gallate, (−)-epicatechin, stachyurin, procyanidin-B2 and -B5, stenophyllanins A and B, alienanin B, and brevifolincarboxylic acid; ii) methanol extract – ursolic acid, 2-hydroxyursolic acid and asiatic acid, as well as glycerol-1,2-dilinolenyl-3-O-β-Dgalactopyranoside and glycerol 1,2-dilinolenyl-3-O- (4,6-di-O-isopropylidene)-β-D-galactopyranoside, 2,5,6-trihydroxynaphtoic carbonic acid, methyl-2,5,6-trihydroxynaphtalene carbonate, flavonol glycoside derivative, quercitrin and kaempferol-3-O-(2′,6′-di-O-p-trans-coumaroyl)-β-glucoside; iii) hexane fraction of methanol extract – β-sitosterol, α-amyrin, uvaol, quercetin, quercitrin, rutin, and sitosterol-3-O-β-D-glucopyranoside; iv) 90% aqueous methanolic extract – ursolic acid, 2α-hydroxyursolic acid and asiatic acid, β-sitosterol 3- O-β-Dglucopyranoside, glycerol 1,2-dilinolenyl-3-O-β-D-galactopyranoside and glycerol 1,2-dilinolenyl-3-O-(4,6-O-isopropylidene)-β-D-galactopyranoside; v) ethyl acetate extract – 2,5,6-trihydroxynaphtoic carbonic acid, methyl-2,5,6-trihydroxynaphtalene carbonate, and flavonol glycoside derivative, quercetin and quercitrin; and vi) hexane extract – 2,5,6-trihydroxynaphtoic carbonic acid, methyl-2,5,6-trihydroxynaphtalene carbonate, and flavonol glycoside derivative, α-amyrin, patriscabatrine and auranamide.
Based on the previously demonstrated anti-inflammatory activity of M. malabathricum and the reports relating, at least, the anti-inflammatory and antioxidant activities to the hepatoprotective mechanism [9–11], the present study was carried out with an attempt to explore the antioxidant and hepatoprotective activities of M. malabathricum. It is postulated that M. malabathricum leaves extract, which possesses the anti-inflammatory activities, will also exert antioxidant and hepatoprotective activities. Therefore, the aim of the present study was to determine the hepatoprotective activity of methanol extract of M. malabathricum (MEMM) using the paracetamol-induced liver damage in rats as the animal model. In addition, the antioxidant activity, phytochemical content and HPLC profile of MEMM were also verified to support the hepatoprotective potential of the extract.