Orange by-products e.g. orange peel and the extract of orange juice are used as sources for biological antioxidants such as ascorbic acid, flavonoids, phenolic compounds and pectins. In this study these antioxidants were successfully used to prepare nanosized materials of α-MnO2 by cost effective and eco-friendly green chemistry method. The prepared oxides of MnO2 which have unique properties as a storage cathode material were tested as a pseudocapacitor electrode materials in this study. X-ray powder diffraction (XRD) confirmed the structure of α-MnO2 for the prepared samples. Thermal behavior of prepared oxides was tested using thermogravimetric analysis (TGA). Transmission electron microscopy (TEM) showed the nanosized nature of the prepared oxides. N2- adsorption–desorption isotherms and pore-size distributions of prepared oxides showed that the surface areas are 5.63 and 8.40 m2. g−1 for sample prepared from the extract of orange juice (OJ-MnO2) and that prepared from the extract of orange peel (OP-MnO2), respectively. Better electrochemical properties are obtained for OP-MnO2, the capacitance of OP-MnO2 (139 F/g) is more than two times and half that obtained for OJ-MnO2 (50 F/g) at the current density 0.5 A/g.