Antioxidant activity and hepatoprotective potential of leaf extracts from Morella serrata (Lam.) Killick (Myricaceae).
Morella serrata L. Killick (Myricaceae) - is a South African plant finding therapeutic applications in oxidative stress related disorders including asthma, diabetes and male sexual dysfunction. The plant has not been scientifically investigated for its antioxidant and hepatoprotective activity. Thus the present study was aimed at determining the chemical constituents, antioxidant activity of M. serrata leaf extracts (ethanol, hydroalcohol and water) and hepatoprotective potential of aqueous-ethanol extract against carbon tetrachloride-induced liver injury in Wistar rats. Phytochemical screening coupled with quantification of phenolic compounds was performed in extracts using standard methods. The preliminary screening of M. serrata leaf extracts revealed the presence of flavonoids, tannins, phenols, saponins, steroids, terpenoids and resins whilst alkaloids, phlabotannins as well as cardiac glycosides were not detected. The total phenolic, flavonoid and flavonol content of the extracts ranged from 0.06± 0.01 to 0.24±0.02 mg GAE/g; 1.25± 0.01 to 2.04± 0.03 mg QE/g; and 0.35± 0.01 to 0.50± 0.01 mg QE/g respectively. The antioxidant activity of the extracts was assessed using DPPH, ABTS, nitric oxide, hydroxyl radical, reducing power, hydrogen peroxide and metal chelating assays using ascorbic acid as reference. Of all the tested extracts, the ethanol extract showed maximum free radical scavenging activity in the DPPH and nitric oxide scavenging activity assays while water extract showed maximum free radical scavenging activity in the ABTS, hydroxyl radical, hydrogen peroxide and metal chelating assay. Hydroalcohol extract showed maximum scavenging activity in the reducing power assay as compared to other extracts. A 21-day daily double dose protective effect of the graded doses (100, 200, 400 mg/kg body weight) of M. serrata hydro-alcohol extract was tested against CCl4-induced hepatotoxicity in Wistar rats using silymarin as a positive control. The effect of CCl4 was investigated on liver and body weight, feed and water intake, haematological parameters, serum biochemical functions, liver marker enzymes and liver histology. Findings revealed a significant increase in liver weight in CCl4-alone intoxicated rats compared to normal control. All groups intoxicated with CCl4 displayed a loss in appetite after CCl4 administration as compared to normal control. A decrease in body weight was observed in rats treated with CCl4-alone which was reversed following treatment with extract and silymarin. CCl4 intoxicated rats showed severe liver damage which was indicated by altered haematological parameters and elevated serum activity of ALP, ALT and AST. This was accompanied by a reduction in activity of marker enzyme CAT and a significant rise in TBARS concentration. This was however ameliorated in MSLAEE and silymarin treatments groups. Histopathological micrographs of hepatotoxic group revealed extensive liver damage characterised by severe necrosis, however, such damage was prevented in MSLAEE and silymarin pre-treated groups. The degree of damage in liver tissues was in the order CCl4- alone treated rats > 200 mg/kg b.w MSLAEE treated rats > 400 mg/kg b.w treated rats > 100 mg/kg b.w treated rats > Silyamrin treated rats > Normal control. Our findings from the research work provide support and evidence on the folkloric use Morella serrata as a potential natural antioxidant in treating oxidative stress induced ailments. The study also diverts from the perception that only the roots can be used to treat such ailments as the leaf extracts also showed effective antioxidant activity, thus contributing to the conservation of the plant. Data emanating from the further indicate that M. serrata was able to protect the liver against CCl4-induced oxidative damage in rats which may be attributed to its antioxidant and free radical scavenging activities.