Analysis of Physiological Activity and Cytotoxicity of Fermented and Hot Water Extracts Using Residues after Onion Harvest

Abstract

The purpose of this study was to investigate the value of residue discarded after harvesting sweet potatoes (Ipomoea batatas L.). The study analyzed the physiological activity and cytotoxicity of the fermented extract and the hot water extract gathered from the residue. The pH level of the extracts indicated that all were acidic. The organic content was similar in the fermented extract and the hot water extract, at 0.98% and 0.97%, respectively. The macroelements phosphoric acid, potassium, calcium, and magnesium were all higher in the hot water extract than in the fermented extract. Nitrogen was the only macroelement that was the same in both extracts. The microelements were higher in the hot water extract than the fermented extract, except for zinc. The total polyphenol content was 60.5±2.7 mg/g in the hot water extract. This result was 37.8 mg/g higher than the 22.7±4.2 mg/g of the total polyphenol content of the fermented extract (p<0.05). The total flavonoid content was 50.7±2.7 mg/g in the hot water extract. This result was 36.7 mg/g higher than the fermented extract content of 14.0±2.1 mg/g. This showed that the hot water extract had a higher total level of polyphenol content than the fermented extract (p<0.05). DPPH and ABTS radical scavenging ability showed higher antioxidant activity in the hot water extract than in the fermented extract (p<0.05). A cytotoxicity test was conducted on the extracts using the MTT assay. The cytotoxicity was found to be weak at all concentrations for both extracts. Therefore, the results of the study suggest that the extract of the residue discarded after harvesting sweet potatoes would be suitable for functional feed or agricultural materials.