In this study, we evaluated the phytochemical compositions of the fruits of the pear cactus, mulberry, and Korean black raspberry to determine how they related to antioxidant capacity. Specifically, the total soluble polyphenol, flavonoid and anthocyanin contents were determined, and the phenolic compounds were evaluated by HPLC. In addition, the antioxidant capacity was evaluated by electron paramagnetic resonance (EPR), SOD-like activity and nitrate scavenging activity. Korean black raspberry was found to have the highest level of phytochemicals, followed by mulberry and pear cactus (p<0.05). Furthermore, EPR revealed that Korean black raspberry extract (100 ${mu}g$/mL) removed 78.6% of the superoxide radicals in a xanthin-xanthin oxidase. Additionally, when the removal of hydroxyl radicals was evaluated, the extract of pear cactus showed 50% scavenging activity at 1000 ${mu}g$/mL. Korean black raspberry extract showed the highest SOD-like activity, which was 44% (p<0.05). Finally, the nitrate scavenging activity of both extracts of mulberry and Korean black raspberry were found to be 93%, while that of the pear cactus was 63% at pH 1.2 (p<0.05).