A spectrophotometric study of the copigmentation of malvin with caffeic and ferulic acids

The process of copigmentation of the anthocyanin molecule malvidin 3, 5-diglucoside with two organic monocarboxylic phenolic acids, caffeic and ferulic acids, was studied via their absorption electronic spectra. The dependence of the copigmentation process on the pH of the medium, molecular concentration, and temperature was established. The process of copigmentation was observed at two pH values: 2.50 and 3.65. The stoichiometric ratio was 1:1 at both pH values. The copigmentation was characterized by approximately equal values of the equilibrium constant, K, within each of the pH values. The temperature was found to be a significant factor that determines the thermodynamic conditions of the copigmentation process, because the process is spontaneous (DeltaG degrees < 0), and results in entropy loss (DeltaS degrees < 0) at both pH values.     

Workshop summary statement: Terrestrial bioshperic carbon fluxesquantification of sinks and sources of CO2

Understanding the role of terrestrial ecosystems in the global carbon (C) cycle has become increasingly important as policymakers consider options to address the issues associated with global change, particularly climate change. Sound scientific theories are critical in predicting how these systems may respond in the future, both to climate change and human actions. In March 1993, 60 scientists from 13 nations gathered in Bad Harzburg, Germany, to develop a state-of-the-science assessment of the present and likely future C fluxes associated with the major components of the earth's terrestrial biosphere. In the process, particular emphasis was placed on the potential for improving C sinks and managing long-term C sequestration. The majority of the week's work was conducted in eight working groups which independently considered a particular biome or subject area. The working groups considered: the Global Carbon Cycle; Boreal Forests and Tundra; Temperate Forests; Tropical Forests; Grasslands, Savannas and Deserts; Land and Water Interface Zones; Agroecosystems; and Biomass Management. This paper presents a brief overview of their major conclusions and findings. In addition, Table 1 brings together the best estimates from each group as to the current magnitude and estimated future direction of changes in the terrestrial C fluxes.     

Kinetics and mechanism of the nucleophilic displacement reactions of chloroacetanilide herbicides: investigation of alpha-substituent effects

The ease with which alpha-chloroacetanilide herbicides undergo displacement reactions with strong nucleophiles, and their recalcitrance toward weak ones, is intimately related to their herbicidal properties and environmental chemistry. In this study, we investigate the kinetics and mechanisms of nucleophilic substitution reactions of propachlor and alachlor in aqueous solution. The role played by the alpha-amide group was examined by including several structurally related analogs of propachlor possessing modified alpha substituents. The overall second-order nature of the reaction, the negative DeltaS(double dagger) values, the weak influence of ionic strength on reactivity, and structure-reactivity trends together support an intermolecular S(N)2 mechanism rather than an intramolecular reaction for alpha-chloroacetanilides as well as the alpha-chlorothioacetanilide analog of propachlor. In contrast, the alpha-methylene analog exhibits kinetics and a salt effect consistent with anchimeric assistance by the aniline nitrogen. Electronic interactions with the alpha-anilide substituent, rather than neighboring group participation, can be inferred to govern the reactivity of alpha-chloroacetanilides toward nucleophiles.     

The effect of thermal history on the maillard reaction in a glassy matrix

To test whether the extent of physical aging affected the reaction rate, Maillard reaction kinetics were studied in glassy model preservation systems subjected to two different thermal histories. The glass transition temperature and physical aging of the matrix were determined using differential scanning calorimetry, and the normalized heat capacities were modeled using the Tool-Narayanaswamy-Moynihan approach. Samples prepared using the different thermal histories initially had different degrees of aging, but these were practically indistinguishable after 10 h under the reaction conditions (65 degrees C); the samples underwent rapid structural relaxation at that temperature. The reaction of glucose and lysine in an amorphous trehalose/sucrose matrix was followed using spectrophotometric and chromatographic analysis. A difference in reaction rate could only be distinguished in the rate of consumption of glucose, which was approximately 20% faster in the minimally aged matrix; no significant differences were seen in any other indicator of reaction.     

Fatty acid content and juice characteristics in black currant (Ribes nigrum L.) genotypes

The fatty acid compositions of seeds from 29 black currant genotypes were determined using a rapid small-scale procedure. There was interest in alpha-linolenic, stearidonic, and, especially, gamma-linolenic acid (GLA) contents, and most samples showed values between 11.1 and 18.7%, between 2.5 and 4.5%, and between 11.6 and 17.4%, respectively. However, six genotypes exhibited gamma-linolenic contents >18%, and values >20% were recorded in four of these genotypes. The fatty acid contents of the six genotypes were also analyzed by using a conventional procedure, and only slight differences in fatty acid composition were found between the two methods. Although GLA content was not strongly correlated with juice parameters, some genotypes had both high GLA contents and desirable juice characteristics. The results obtained provide evidence that it is possible to select for GLA contents without negatively affecting juice quality, and both aspects can be combined in a single cultivar, thereby increasing the added value of the whole fruit.     

The use of reflectometric test kits for estimating nitrification and soil invertase activity in the field

The objective of this study was to test the applicability of different reflectometric test kits for the determination of potential nitrification and the activity of invertase in soil directly in the field. For the investigation of nitrification in the field, the incubation time was reduced because a linear correlation between incubation time and nitrification rates was found. Likewise, a linear correlation between invertase activity and the incubation temperature was observed which allowed for the calculation of temperature‐dependent factors. Activity measurements in the field at lower temperatures in comparison to the standard procedure were corrected by these factors. Ten different soils were investigated for potential nitrification and invertase activity with standard methods in comparison to field tests with reflectometric detection of the reaction products. The results showed that the reflectometric test kits are suitable for the estimation of potential nitrification and invertase activity directly in the field.     

Variation for cadmium uptake among Nicotiana species

Fifty nine species of Nicotiana were tested for the potential to take up cadmium from soil either with a natural cadmium content of 0.15 ppm or enriched with 8 mg Cd per 1 kg soil added as Cd(NO₃)₂. When grown on the soil with natural cadmium content the highest leaf absorbers of cadmium were N. raimondii (6.15 ppm), N. bigelovii (5.47 ppm) and the botanical varieties of N. tabacum (3.92 – 5.75 ppm); the highest root absorber was N. rosulata (3.17 ppm). On the soil with an addition of 8 mg cadmium/kg the highest leaf cadmium contents were in N. langsdorfii (116.28 ppm), N. plumbaginifolia (99.49 ppm), N. setchellii (94.16 ppm) N. debneyi (69.12 ppm), N. velutina (62.15 ppm) and the highest root cadmium contents in N. miersii (32.2 ppm), N. clevelandii (30.45 ppm) and N. nudicaulis (30.45 ppm). Significant differences between sections were most frequently shown for the cadmium enriched soil and rarely for the control treatments. No significant differences were found between the botanical varieties of the same species when grown on the cadmium enriched vs. natural cadmium soil.     

Cytotoxicity of withanolides isolated from Acnistus arborescens

A new withanolide identified by spectroscopic analysis as 12β-acetoxy-4-deoxy-5,6-deoxy-Δ⁵–withanolide D and Withanolide D, were isolated from the leaves of Acnistus arborescens. Cytotoxic activity of these two compounds against human tumor cell lines HT-29, MCF-7, MKN-45, HEp-2, HeLa, U-937 and two human normal fibroblast cultures, Fib04 and Fib05, were assessed. Withanolide D presented in vitro cytotoxic activity against tumor cell lines at the low micromolar range (LC₅₀:1.0 to 1.69 µM) and showed a slightly lower activity against Fib04, suggesting moderated selectivity among tumoral and normal cells. No cytotoxic effect was observed for 12β-acetoxy-4-deoxy-5,6-deoxy-Δ⁵–withanolide D.     

Analysis of fatty acids in Longissimus muscle of steers of different genetic breeds finished in pasture systems

The chemical composition, the fatty acids profile, and conjugated linoleic acids content in Longissimus muscle (LM) of steers have been determined. For such, 18 steers (6, Nellore, NEL) and their Simmental (6, NSI), and Santa Gertrudes (6, NSG) crossbreds finished in pasture system with Brachiaria brizantha cv. marandu for about 3 months with approximate weight at slaughter of 480 kg at average age approximate of 25 months. The lipid content increased in the following order influenced by genetic groups: Nellore, F1 Nellore × Simmental and F1 Nellore × Santa Gertrudes crossbreds. The lipid content increased while moisture, ash and protein contents decreased. The content of saturated fatty acids (SFA) was affected by genetic groups. The conjugated linoleic acids contents (CLA) in fat were similar in the genetic groups, but the quantity of CLA concentrations in muscle lipids of steers with larger total lipid was higher. The predominant CLA was CLA cis-9, trans-11.