In vitro antioxidant activity of Lippia adoensis Var. Koseret, Thymus schimperi Ronniger and Rosmarinus officinalis Leaf extracts and their effects on oxidative stability of ground raw beef meat during refrigeration storage

Abstract

Rosmarinus officinalis,Thymus schimperi Ronniger, and Lippia adoensis var. koseret, locally known as Rosemary, Tosign, and Koseret respectively are widely used dietary herbs in Ethiopia. In this study, the antioxidant activity and effect of Rosemary, Tosign, and Koseretethanol (80% v/v) extract on lipid oxidation of ground beef during storage were studied. Folin-Ciocalteu and aluminium chloride were used to determine total phenolic content (TPC) and total flavonoid content (TFC), respectively. Antioxidant activities of herbs were evaluated using 2, 2-diphenyl-1-picrylhydrazyl (DPPH) scavenging, ferric reducing power and iron chelating activities. The peroxide and thiobarbituric acid reactive substances assays were used to evaluate the ability of the extracts to prevent lipid peroxidation in ground beef stored at 4°C. Tosign extract had highest TPC (70.93±1.53 mg GAE/g) and TFC (16.94±0.12 mg CE/g). Also, Tosign had the strongest effect of DPPH scavenging (IC50 = 33.35±1.56µg/mL) and ferric reducing power (IC50 = 175.71±1.03 µg/mL). But the strongest iron-chelating activity was observed in Rosemary extract (IC50 = 160.24±2.55 µg/mL). Minimum peroxide value (0.185±0.09 milli equivalent peroxide/kg of beef) and the highest thiobarbituric acid reactive substances (80.20±20%) were recorded for ground beef treated with Rosemary at the end of storage days. In conclusion, these herbs are very effective antioxidants comparable to butylated hydroxytoluene. Thus, they could be a good substitution to synthetic antioxidants used in food preservation.