Fat-soluble carotenoids have been reported to have a singlet-oxygen scavenging activity. The Singlet Oxygen Absorption Capacity (SOAC) method is used to measure singlet oxygen scavenging activity. Since watermelon contains carotenoid lycopene and β-carotene, the singlet-oxygen scavenging activity of watermelon concentrate was examined using SOAC. Watermelon sugar concentration, which has long been used as a traditional folk remedy, was used as a guide. Since there is no designation of the extraction solvent from the sample in the SOAC method, the erasing activity may depend on the extraction solvent, whose notation is thus necessary. Consequently, chloroform, which is generally used for extracting fat-soluble components,hexane/ethanol/acetone/toluene (10/7/6/7, v/v/v/v, HEAT), and ethanol/chloroform/heavy water (50/50/1, v/v/v, ECD), which are used in the measurement of SOAC method, were investigated. The extraction solvent of SOAC showed the highest value. The amount of carotenoid content was also positively correlated with the SOAC value. We suggest that the extraction solvent of SOAC is most suitable for watermelon concentrate extraction. Also, since the antioxidant ability was improved by concentration, a new value of watermelon processing could be expected.
