To utilize Smilax china L. leaves as a natural preservatives, solvent fractions from crude methanol extract were prepared and investigated their antioxidant and antimicrobial activities against Staphylococcus aureus. Antioxidant activities were examined by 1,1-diphenyl-1-picrylhydrazyl radical scavenging and ferric ion reducing antioxidant power assays. Ethyl acetate fraction from Smilax china L. leaves exhibited the strongest antioxidant and antimicrobial activities among the fractions (P<0.05), as well as the highest total phenolic and total flavonoid contents. Caffeic acid, ferulic acid, quercetin, and kaempferol contents in the ethyl acetate fraction from Smilax china L. leaves were determined by TLC and HPLC. In aqueous phase, as well as the n-butanol and n-hexane fractions, quercetin, ferulic acid, and kaempferol were detected in small amounts. Ferulic acid, which showed the highest content, is the major active compound from Smilax china L. leaves.

Grape juice is consumed worldwide and studied due to the high antioxidant activities and contents. The color of grape juice is due to the presence of phenolic compounds such as anthocyanins. Therefore, color values can be an indicator of antioxidant capacities of grape juice. However, the correlation between color values and antioxidant activities in grape juice has not been well studied. In this study, the physicochemical characteristics and correlation between color values and antioxidant capacities of Korean red grape juices (five commercial juices from market and two juices prepared in the laboratory) were investigated to estimate antioxidant capacities. Antioxidant capacities were determined by 1,1-diphenlyl-2-picrylhydrazyl radical scavenging assay, ferric ion reducing antioxidant power assay, and oxygen radical absorbance capacity assay. Total phenolic contents, total flavonoid contents, and total anthocyanin contents, including five kinds of polyphenolic compounds, were examined by high performance liquid chromatography (HPLC). The results for physicochemical properties showed similar values, except titratable acidity. The color hue values of the prepared juices were higher than those of commercial juices, which was in contrast to the lower color intensity values (P<0.05). The Hunter L, a, and b values showed almost no difference between commercial and prepared juices. The antioxidant activities and total phenolic contents of commercial juices were higher than those of prepared ones. Gallic acid, catechin, and quercetin were confirmed by HPLC in all samples. The total phenolic and total flavonoid contents showed positive correlation with antioxidant activities. In addition, antioxidant activities and contents correlated with color values. Thus, estimation of antioxidant capacity could be feasible through the spectrophotometric measurement of color values.

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