Studying On Antimicrobial, Antioxidant And Dna-binding Activities Of Natural Products

Antimicrobial, antioxidant and DNA-binding activities of 47 natural products from 4 plants were investigated. Antimicrobial activities of 14 lignans were checked by paper disc diffusion method. At 200μg/disc syringaresinol (9) had the highest activity and showed 13 and 16 mm diameter of the inhibition zone against S.aureus and B.subtilis, followed by de-4'-O-methylyangambin (7). The other compounds showed no activities against the two bacteria strains at the same concentration. Antimicrobial activities of twenty-seven xanthones and two flavonoids were checked by broth microdilution method. 12b-Hydroxy-des-D-garcigerrin A (24) was found to be the most active compound against three gram-positive bacteria strains. The MIC value was 25.03μM (S. aereus), 25.03μM (B. subtilis) and 12.52μM (B. mucilaginosus), respectively. Bigarcinenone A (43) was the most active compound against C. albicans and C. tropicalis. Its MIC value was 16.59μM. The photoactivated antimicrobial activity of four alkaloids was determined by TLC bioautography technology. In this case, glycoborinine (44) showed the highest photoactivated antimicrobial activity. Contrast to the dark, the activities of inhibition against S.aureus and B.subtilis increased 8 times and 2 times after UVA irradiated, respectively.A chemiluminescence and flow-Injection system quenching superoxide anion radical (O-·2) and hydroxyl radical (·OH) was established and optimized.·OH scavenging activity was determined by Co(II)/EDTA-H2O2-luminol system. Compound 27, 1,2,5-trihydroxy-6-methoxyxanthone was found to be the most active compound with IC50 value of 0.09μM. Compound 18, 19, 22, 14-28, 30, 35-39 also showed stronger activities than that of ascorbic acid. Structure-activity relationship was discussed. The result showed, xanthones isolated from Garcinia xanthochymus was a potential antioxidant and it provided us an evidence to research it further.A 1.8kb DNA fragment was synthesized by the polymerase chain reaction (PCR) using plasmid pET-28a as a template, and DNA-binding activity of four alkaloids was studied by gel electrophoresis method. Glycoborinine (44) showed a DNA-binding activity after UVA irradiated that can insert a DNA sequence which had 5′-TpA and 5′-ApT. Inhibition was found for Nde I, Nco I, Xba I, and Bcl I at their restriction sites. Although glybomine B (45), carbalexin A (46) and N-p-coumaroyltyramine (47) had a photoactivated antimicrobial activity, they did not show photoactivated DNA-binding activity, so DNA may not be its target. Carbazole alkaloids were a new natural photosensitizer from plants.