Identification and Quantitation of Allelochemicals from the Lichen Lethariella canariensis: Phytotoxicity and Antioxidative Activity

Phytotoxicity-based extraction and fractionation were employed to separate allelochemicals contained in an extract of Lethariella canariensis. Twelve phenolic substances were isolated from the phytotoxic fraction Letharal of the thalli. These were identified by spectroscopic methods, physicochemical constants, and HPLC chemical correlation, and determined to be atranol (2), chloroatranol (3), hematommic acid (4), chlorohematommic acid (5), methyl hematommate (6), methyl chlorohematommate (7) (new compound), ethyl hematommate (8), ethyl chlorohematommate (9), methyl -orsellinate (10), atranorin (11), chloroatranorin (12), and (+)-usnic acid (13). Further identification and quantification of these allelochemicals in the environment were conducted by HPLC. Several phenolic compounds showed moderate antimicrobial activity. The cytostatic activity of the polyphenols was investigated on U937 and HL-60 cells. All compounds were assayed, with the exception of 10. The Letharal mixture decreased cell viability in both cell lines. Protection against lipid peroxidation was investigated using brain homogenates. Compounds 2, 3, 6, 8, 11, and Letharal decreased H₂O₂/Fe⁺² induced lipid peroxidation in a concentration-dependent manner, while 10 and 13 were unable to protect tissue against oxidative stress.     

Responses of the Aphids Phorodon humuli and Rhopalosiphum padi to Sex Pheromone Stereochemistry in the Field

Gynoparous female and male damson-hop aphids, Phorodon humuli (Schrank), were caught in the field by water traps that were releasing the sex pheromone of this species, (1RS,4aR,7S,7aS)-nepetalactol. No behavioral activity was elicited by (4aS,7S,7aR)-nepetalactone, the major sex pheromone component of other aphid species such as Megoura viciae Buckton, even though olfactory cells were found in the secondary rhinaria on the third antennal segment of P. humuli that responded strongly to this compound. Gynoparous female P. humuli in the field responded less strongly to (1R,4aS,7S,7aR)-nepetalactol, the sex pheromone of the bird cherry-oat aphid, Rhopalosiphum padi (L.), than they did to the (4aR,7S,7aS)-nepetalactols, but males responded only to the latter. The (4aR,7S,7aS)-nepetalactone showed no electrophysiological activity so was not used in field trials. Releasing either the (4aS,7S,7aR)-nepetalactone or the (1R,4aS,7S,7aR)-nepetalactol with the (4aR,7S,7aS)-nepetalactols did not inhibit the response of P. humuli gynoparous females and males to the latter. Males of R. padi responded as strongly to the (4aR,7S,7aS)-nepetalactols as they did to (1R,4aS,7S,7aR)-nepetalactol. Males of P. humuli and R. padi responded positively to an increased concentration of the (4aR,7S,7aS)-nepetalactols released from two vials compared with that from a single vial, as did P. humuli (in one of two experiments) and R. padi to the (1RS,4aR,7S,7aS)- and (1R,4aS,7S,7aR)-nepetalactols when released together.     

Stability of carotenoid pigments in foods

Carotenoids are responsible for the colour of a wide variety of both vegetable and animal foods. Several studies published recently have shown that these compounds have a beneficial effect in human health, thus, from a nutritional point of view, it is important to know the factors related to their degradation, because carotenoid losses, not only produce changes in food colour, but also decrease their nutritional value. The instability of carotenoids is due to the fact that they are highly unsaturated compounds, thus degradation is due mainly to oxidation. Other factors, such as temperature, light or pH can produce important qualitative changes in these compounds by means of isomerization reactions.     

林甸县地下水动态研究分析

通过对地下水动态变化的研究分析,可以更好地掌握地下水资源数量和质量的变化规律及其时空分布规律,为研究地下水资源、合理开发利用水资源提供技术支撑。此次地下水动态分析以2008年为现状年,2008年林甸县共布设地下水观测井19眼,通过对19眼长观井地下水位埋深资料的整理分析,选择了县城东部、南部、西部、北部和县城中心5个区域的5眼观测井做为代表井,完成了林甸县地下水的动态分析研究工作。     

Homogeneous iron-catalyzed photochemical degradation of muconic acid in water

Iron photochemical oxidation has been used to remove muconic acid from water. Two different light systems were used: black lamps and solar irradiation. The effect of iron concentration, intensity of incident radiation, pH and presence of oxalic acid was investigated. The first two variables yield positive effects on the removal rate of muconic acid while higher efficiency was achieved at pH 3. Oxalic acid enhances the oxidation rate because of the formation of photoactive ferrioxalate ion. Stoichiometric results indicated formation of two hydroxyl radicals to degrade 1 mol of muconic acid. At similar experimental conditions, initial oxidation rates of muconic acid were higher when solar light was used to irradiate the aqueous solutions, although in this case, the oxidation process is stopped because of the consumption of photoactive species.