In vitro antioxidant properties of 3 different extracts of black mulberry (Morus nigra L.) were investigated. Acidified methanol, acidified water, and non-acidified methanol/water solutions were used to prepare extracts. Different solvents caused different protonation on black mulberry anthocyanin structures, which were predicted according to their UV-VIS spectrum. Extracts indicated 2 main peaks at about similar to 280 and similar to 520 nm with different peak areas in their UV-VIS spectrum. The rank of extracts' total phenolic content and reducing power values were both found to be in correlation with their absorbance at similar to 280 nm. Meanwhile the same relationship was observed between DPPH scavenging activity and absorbance values at similar to 520 nm. Acidified extract of black mulberry was higher in beta-carotene prevention and DPPH radical scavenging activity than non-acidified extract. However, non-acidified extract represented a higher reducing power and metal chelating activity, and a higher content of total phenolics.