Antioxidant properties of onion (Allium cepa L.) and potato (Solanum Tuberosum L.) dried skin / Mohamed Zikrihakim Mohamed Nazari

Allium cepa L. and Solanum Tuberosum L. are very good vegetables as source of vitamins and other health benefits content most likely came from the antioxidant substances in them. However, most of the people did not realize the importance of these vegetables dried skin which has leaded them to removes the skin as a waste especially the onions. Also, the use of synthetic antioxidants can be harmful to human body compared to natural antioxidants as they contain substances which may cause adverse effect to human organs and have no nutritional qualities. Natural antioxidants involved higher production costs but provide multiple health benefits and readily accepted by human body. In this research, the antioxidant properties of onion and potato skins are to be determined. The antioxidants were extracted using solvent extraction method using methanol as the medium at the extraction temperatures and concentrations ranging from 50°C to 80°C and 30% to 60%. The antioxidant activities were obtained using the DPPH radical solution in which 80% methanol is used as the blank for determining its absorbance at a wavelength of 517 nm. The total phenolic content of the potato and onion skins were determined using the Folin-Ciocalteu method and the absorbance values were determined at 765 nm using the same blank. From the results obtained, the optimum conditions of the onion skin herb for the determination of total phenolic content and antioxidant activity were at the extraction temperature of 80.00°C with 35.52% methanol concentration. The amount of total phenolic content and antioxidant activity yielded at this condition for the onion skin were 89.85 mg/g and 65.39% in which, achieved the targeted amounts of 88.08 mg/g for total phenolic content and 65.39% for antioxidant activity. For the potato skin, the optimum condition for was at the extraction temperature of 60.38°C with 30.00% methanol concentration. The amount of total phenolic content and antioxidant activity yielded at this condition were 69.05 mg/g and 66.89%, in which, achieved the targeted amount of 65.39% for antioxidant activity. In conclusion, both onion and potato dried skin contain several kind of antioxidants such as gallic acid and quercetin which gave a significant impact to this study and the research was successful.