Assessment of antioxidant activity of ethanolic extracts of marjoram (Origanum majorana L.) evaluated by different in vitro methods
Natural antioxidants can protect the human body from damage of free radicals and could retard the progress of many chronic diseases. There is a growing interest in the addition of natural antioxidants, especially herbs and spices, in food technology. Due to its possible carcinogenicity, the synthetic antioxidants have been rejected by the consumers. Therefore, the aim of this study was to evaluate the antioxidant activity of marjoram (Origanum majorana L.) ethanolic extract (OMEE) using four in vitro methods: 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2-azinobis (3-ethylbenzthiazoline-6-sulphonic acid) (ABTS), ferric reducing antioxidant potential (FRAP) and the β-carotene/linoleic acid system. The commercial antioxidants, butylated hydroxytoluene (BHT), butylated hydroxyanisole (BHA) and alpha-tocopherol were used as positive controls. The total phenolic and flavonoids content were quantified by spectrophotometry analysis using the Folin-Ciocalteu reagent and Al(Cl)3, respectively. The profile of phenolic compounds was analyzed by High Performance Liquid Chromatography NDASH Photodiode Diode Array detector (HPLC/PDA). The OMEE showed phenolic content of 41,89±0,46 mg GAE g-1 (gallic acid equivalent) and 11.28±0.02 mg quercetin g-1, respectively. Five phenolic acids and 3 flavonoids in the extracts were found. The IC50 value of OMEE was 395.91 µg mL-1 while for the commercial antioxidants BHT, BHA and alpha-tocopherol, the values were 114.66, 72.25 and 61.22 µg mL-1, respectively. The ABTS analysis, showed antioxidant activity in the OMEE of 227.03±2.12 µmol TEAC g-1. In analysis of ferric reducing antioxidant power, OMEE showed activity of 217.27±0.84 µmol Fe2+ g-1 of plant. The level of inhibition of free radicals generated during linoleic acid peroxidation by the OMEE was 82.60±0.27% (5 mg mL-1). This value was higher than those presented by commercial antioxidants. Finally, the results obtained showed the potential of the ethanolic extract of marjoram and indicate the possibility of use of this herb as a source of natural antioxidants.
Serafini, L.F., Schmidt, C.A.P., Oldoni, T.L.C., Carpes, S.T., Haminiuk, C.W.I. and Ribeiro, I.S. (2018). Assessment of antioxidant activity of ethanolic extracts of marjoram (Origanum majorana L.) evaluated by different in vitro methods. Acta Hortic. 1198, 85-92
phenolic compounds, scavenging, DPPH, ABTS, FRAP