The Polyphenol Content and Antimicrobial Activity of Selected Propolis’ Extracts

Propolis is a resinous natural product,produced by bees(Apis mellifera),from vegetable parts and plant secretions.Propolis’samples A,B,C and D were extracted with phosphate buffer saline(PBS)or with 70%EtOH at pH values 8.0,7.2 and 6.4 followed by:(1)reverse-phase high-performance liquid chromatography(RP-HPLC)on Purospher®Star RP-18 column,the quantity of caffeic acid,chrysin,pinocembrin and galangin was determined;(2)determination of total flavonoids in both extracts;(3)antimicrobial tests of both extracts against(a)Gram-positive bacteria:methicillin-resistant Staphylococcus aureus(MRSA),St.aureus,Streptococcus pyogenes,Str.agalactiae,(b)Gram-negative bacteria:Escherichia coli,Pseudomonas aeruginosa,Proteus mirabilis,Acinetobacter baumanii and(c)yeast:Candida albicans.The antimicrobial activity of propolis’PBS extracts against Gram-positive bacteria shows the lowest minimal inhibitory concentration(MIC,mg/mL)at pH 8.0 in sample C,followed by A,B and D.In sample C,MICs at pH 8.0 were 0.007(Str.agalactiae),0.015(MRSA),0.015(Str.pyogenes)and 0.007(St.aureus).The polyphenol content of sample C is:flavonoid content 5.47±0.62 mg/mL,caffeic acid 1.33±0.92 mg/mL,chrysin 41.02±4.22μg/mL,pinocembrin 2.93±0.33 mg/mL and galangin 41.87±4.23 mg/mL.PBS extracts against Gram-negative bacteria show the lowest MIC(mg/mL)at pH 8.0 in sample D,followed by B,C and A.In sample D,MICs at pH 8.0 were 0.003(Acin.baumanii,Pr.mirabilis,Ps.aeruginosa)and 0.007(E.coli).Polyphenol content of sample D is:flavonoids 8.28±0.92 mg/mL,caffeic acid 3.56±0.32 mg/mL,chrysin 677.42±68.42μg/mL,pinocembrin 146.49±13.89 mg/mL and galangin 59.81±5.86 mg/mL.The strongest anti C.albicans activity,with the lowest MIC(mg/mL),at pH 8.0 was in the sample C,followed by samples D,A and B.In sample C,the MIC at pH 8.0 is 0.001(PBS extract).The antimicrobial activities of selected propolis samples correlate with their polyphenol content,more precisely,flavonoid,caffeic acid,chrysin,pinocembrin and galangin content.

Leaching Phenomena of Antifouling Agents from Ships＇ Hull Paints

The effects ofpH, dissolved ion content and relative water velocity on the release rate of an antifouling agent, cuprous oxide, from ships＇ hull paint have been investigated by rotating cylinder tests. Additionally, test paint panels were attached to a vessel and recovered after a certain period of voyage for the validation of the laboratory tests. In the initial period, the release rates are influenced by pH, dissolved ion content and water velocity, but once after a certain period of test, those effects become less significant. These phenomena can be explained when the paint film is fresh, the rate is controlled by chemical reaction, the surface and/or diffusion layer in the water phase governs the rate. After the antifouling substance in the paint film leached out from the near-surface region, a diffused layer （leached layer）, that has little antifouling agent remained, is formed at the surface of the coating, and the diffusion in that layer can be a rate-determining process. The development of the leached layer is affected by a balance between the leaching rate of the antifouling ingredient and paint resin determined by the chemical properties and speed of the water. Thus, the leaching rates of antifouling agents are affected by the history of the paint in the water.

Integration of Chemical Methods and Biomarkers for Assessment of Chlorimuron-Ethyl Bioavailability in Soil

Bioavailability is a critical factor for assessing the environmental risk of organic pollutants in soil. In this study, extractions with 3 different solvents, including 2 aqueous solutions, calcium chloride(CaCl_2) and a phosphate buffer solution(PBS), and a mixture of aqueous solution and organic solvent, a PBS-methanol(8:2,volume/volume) mixture(PBS-M), were performed to assess the bioavailability of chlorimuron-ethyl in soil in comparison to a battery of toxicity tests in wheat seedlings. The results indicated that the peroxidase(POD) activity in wheat leaves after 7 d of exposure was one of the sensitive biomarkers of chlorimuron-ethyl in soil.The extractability of chlorimuron-ethyl by all the 3 solvents decreased with exposure time, and the rate of decrease of the PBS-M extraction between 1 and 7 d of exposure was substantially higher than those of the aqueous solution extractions. Chlorimuron-ethyl gradually changed from a water-soluble form into a soil organic matter(SOM)-bound form in the soil. The PBS extraction correlated best with the POD activity in the leaves after 7 d of exposure.