Wu TW, Lee CC, Hsu WH, Hengel M and Shibamoto T
The antioxidant activity of organic solvent extracts from green mate leaves (Ilex paraguariensis), lotus plumule (Nelumbo nucifera Gaertn.) and fresh rhubarb (Rheum rhabarbarum L.) stalks was investigated using four antioxidant assays. An extract obtained with 60% methanol solution from mate leaves exhibited antioxidant activity of 99.96 ± 1.20% at the level of 2000 g/mL (TBA assay) and of 81.80 ± 0.54% at the level of 125 g/mL (DPPH assay), respectively. In this fraction, five polyphenols, including chlorogenic acids, were identified by HPLC/MS analysis. Methanol extracts from lotus and rhubarb showed potent antioxidant activity of 98.45 ± 0.78% and 83. 93 ± 2.39%, respectively, at the level of 100 L/mL in a malonaldehyde/gas chromatography assay. Analysis of a hexane fraction of lotus and rhubarb identified several volatile antioxidants, such as 1-octen-3-ol and benzaldehyde. The results of the present study demonstrate that mate, lotus and rhubarb are excellent natural sources of antioxidants.
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