Kyoung-Ja Kim

Antitumor and antioxidant activity of protocatechualdehyde produced from Streptomyces lincolnensis M-20

We characterized the biological functions of protocatechualdehyde (PA) isolated from the butanol extract of culture supernatant from Streptomyces lincolnensis M-20. Following butanol extraction, it was purified by silica gel and Sephadex LH-20 column chromatography. PA was analyzed by Furier Transform Infrared Spectroscopy (FT-IR), Gas chromatograph-Mass Spectrometer (GC-MS), and Nuclear Magnetic Resonance (NMR). PA had potent antioxidant activity, as measured by 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity. Antitumor activity against MCF-7 human breast cancer cells was evaluated by the 3-(4,5-dimethylthazol-2-yl)-2,5-diphenyl tetrazolium-bromide (MTT) assay. PA treatment (0∼150 μM) dose-dependently blocked apoptosis, as shown by improved cell viability and inter-nucleosomal DNA fragmentation. Our findings suggest that Streptomyces lincolnensis M-20, a lincomycin producer, also produces protocatechualdehyde.

Identification of actinomycins by high performance liquid chromatography and fast atom bombardment mass spectrometry

An actinomycin complex isolated from culture broth of a soil microorganism, SNUS 9305-011 has been examined by High performance liquid chromatography (HPLC). From the analysis of the fractions obtained by column chromatography of the ethyl acetate extract, three actinomycin components are confirmed. The HPLC analysis is carried out with a CN-bonded nucleosil column. Comparison of the retention times of the components with those of actinomycin D, C complex, Xoβ, and V suggests that they are different actinomycins. FAB mass spectra of the components also shows different molecular ions from those of standards and other reported actinomycins. The present work has demonstrated that actinomycin components can be separated by a CN-bonded HPLC column, and that comparison of their HPLC chromatograms with authentic samples and information on their molecular ions can be successfully employed for identification of actinomycins.

Production of protocatechualdehyde using tyrosinase purified from potato

Tyrosinase is responsible for the enzymatic browning of fruits and vegetables and usually catalyze the conversion of monophenols to o-diphenols and oxidation of diphenols to corresponding quinines. However, when 3,4-dihydroxymandelic acid is provided as the substrate, it catalyzes the oxidative decarboxylation reaction to generate 3,4-dihydroxybenzaldehyde (protocatechualdehyde, PA. In the present study, tyrosinase was purified from potato with 27.9 purification fold by salting out with ammonium sulfate, DEAE-Sepharose and Sephadex G-150 column chromatography. The purified tyrosinase was confirmed by tyrosinase active staining following SDS-PAGE. Tyrosinase activity was visualized in the gel as a dark band. The molecular weight of tyrosinase from potato was 38kDa as determined by SDS-PAGE. Purified tyrosinase mediated oxidative decarboxylation of 3,4-dihydroxymandelate. The identity of the reaction product, PA was confirmed by high-performance liquid chromatography (HPLC) as well as ultraviolet spectral studies. Phenol oxidase inhibitors such as potassium cyanide, sodium azide, and phenylthiourea inhibited the participation of the active site copper of the enzyme in the catalysis.

Tyrosinase inhibitory activity and antimicrobial activity by mixtures of ultrasonicated chitosan and Maillard reaction products

The aim of this study was to investigate the tyrosinase inhibitory activity and antimicrobial activity by mixtures of ultrasonicated chitosan and Maillard reaction products. Analysis of tyrosinase was purified from potato and confirmed by active staining after SDS-PAGE. Maillard reaction products (MRPs) were formed from various sugars (glucose, fructose, galactose, xylose, arabinose or ribose) and cystein. MRPs inhibited the tyrosinase purified from potato. The highest tyrosinase inhibitory activity was shown by MRP from glucose and cystein. Ultrasonicated chitosan (over 1 hr) showed antimicrobial activity at the concentration of 1% against E. coli and S. aureus. For the development of antibrowning agent with antimicrobial activity, tyrosinase inhibitory and antimicrobial activity by the mixtures of ultrasonicated chitosan and MRP were tested. 1:1 mixture of ultrasonicated chitosan and MRP from glucose and cystein was the best antibrowning agent having antimicrobial activity.