Flavonoid concentrations in the inner leaves of head lettuce genotypes

Typical HPLC profiles of phenolics from head lettuce (butter lettuce) genotypes showed quercetin (Qu) compounds Qu 3-O-glucuronide, Qu 3-O-(6-malonylglucoside), an acidic luteolin (Lu) glycoside, chlorogenic acid and chicoric acid as the main compounds in outer and - except the Lu conjugate - inner leaves.The outer leaves of some genotypes additionally contained cyanidin 3-O-(6-malonylglucoside). The generally marginal flavonoid concentrations of the cores of lettuce heads increased between 10-fold and 20-fold during the illumination of opened inner leaves. This indicated the competence of inner leaves of lettuce heads to perform the light-dependent flavonoid biosynthesis. After hydrolysis of flavonoid extracts from 15 head lettuce varieties, Qu concentrations were detected between 19.4 and 152.1 µg/g dry plant material (DW) in inner leaves and from 417.3 to 2482.7 µg/g DW in outer leaves. While the Qu concentrations of the inner leaves of most genotypes, including the commercial varieties, amounted to about 3% of those found in outer leaves, these proportions were 15% and 19% in two genotypes. Two other varieties showed relatively high Qu values of cores in connection with maximum flavonoid levels of outer leaves. It is indicated that such genotypes may be useful in increasing the flavonoid concentrations in the inner leaves of commercial head lettuce varieties by conventional breeding methods.     

Improved HPLC method for the evaluation of the major steviol glycosides in leaves of Stevia rebaudiana

A simple reversed-phase high-performance liquid chromatographic method has been developed for the determination of the major steviol glycosides, the diterpene sweeteners derived from Stevia rebaudiana. The method is based on a water extraction step and a solid-phase extraction (SPE) clean-up. Different SPE cartridges and two HPLC columns were tested in the separation of the main steviol glycosides stevioside and rebaudioside A. A good separation was performed on a Luna HILIC analytical column with a mobile phase consisting of acetonitrile/water (85:15 v/v). The calibration curves were linear from 10 to 800 μg/mL and the recoveries for stevioside and rebaudioside A were 99 ± 4.4 and 100 ± 5.0%, respectively. The applicability of this method was demonstrated in the analysis of stevioside and rebaudioside A from Stevia plants grown in two different areas in Germany. Stevioside and rebaudioside A contents showed statistically significant differences (F- and t-test) between the two harvests. Nevertheless, the total concentrations (>12%) and the ratio of stevioside to rebaudioside A (6:4) were similar to those found in the countries in which Stevia rebaudiana originates. Based on a comparison of yields from different harvests, we discussed whether Stevia rebaudiana can be economically grown in the temperate zones of the northern European hemisphere.     

Photoirradiation of dissolved humic acid induces arsenic(III) oxidation

The fate of arsenic in aquatic systems is influenced by dissolved natural organic matter (DOM). Using UV-A and visible light from a medium-pressure mercury lamp, the photosensitized oxidation of As(III) to As(V) in the presence of Suwannee River humic acid was investigated. Pseudo-first-order kinetics was observed. For 5 mg L(-1) of dissolved organic carbon (DOC) and 1.85 mEinstein m(-2) s(-1) UV-A fluence rate, the rate coefficient k degrees exp was 21.2 +/- 3.2 10(-5) s(-1), corresponding to a half-life <1 h. Rates increased linearly with DOC and they increased by a factor of 10 from pH 4 to 8. Based on experiments with radical scavengers, heavy water, and surrogates for DOM, excited triplet states and/or phenoxyl radicals seem to be important photooxidants in this system (rather than singlet oxygen, hydrogen peroxide, hydroxyl radicals, and superoxide). Photoirradiation of natural samples from freshwater lakes, rivers, and rice field water (Bangladesh) showed similar photoinduced oxidation rates based on DOC. Fe(III) (as polynuclear Fe(III)-(hydr)oxo complexes or Fe(III)-DOC complexes) accelerates the rate of photoinduced As(III) oxidation in the presence of DOC by a factor of 1.5-2.     

Occurrence of Fusarium species and trichothecenes in Nigerian maize

A total of 180 maize samples meant for human consumption from four maize-producing states of southwestern Nigeria were screened for twelve major Fusarium mycotoxins (trichothecenes). Mycological examination of the samples showed that Fusarium verticillioides was the most commonly isolated fungi (71%), followed by F. sporotrichioides (64%), F. graminearum (32%), F. pallidoroseum (15%), F. compactum (12%), F. equiseti (9%), F. acuminatum (8%), F. subglutinans (4%) and F. oxysporum (1%). The trichothecenes include deoxynivalenol (DON), 3, mono-acetyldeoxynivalenol (3-AcDON), 15, mono-acetyldeoxynivalenol (15-AcDON), nivalenol (NIV), HT-2 toxin (HT-2), neosolaniol (NEO), T-2 toxin (T-2), T-2 tetraol and T-2 triol, diacetoxyscirpenol (DAS), MAS-monoacetoxyscirpenol (MAS) and fusarenone-X. Quantification was by high performance liquid chromatography coupled with mass spectroscopy (HPLC/MS); the detection limits for each of the mycotoxins varied between 20 and 200 microg kg(-1). Sixty six samples (36.3%) were contaminated with trichothecenes, DON (mean: 226.2 microg kg(-1); range: 9.6-745.1 microg kg(-1)), 3-AcDON (mean: 17.3 microg kg(-1); range: 0.7-72.4 microg kg(-1)) and DAS (mean: 16.0 microg kg(-1); range: 1.0-51.0 microg kg(-1)) were detected in 22%, 17% and 9% of total samples respectively. There were no 15-AcDON, NIV, HT-2, NEO, T-2, T-2 tetraol, T-2 triol, MAS and fusarenone-X detected. This is the first comprehensive report about the natural occurrence of DON, AcDON and DAS in maize for direct human consumption in Nigeria.     

Effectiveness of products from four locally grown plants for the management of Acanthoscelides obtectus (Say) and Zabrotes subfasciatus (Boheman) (both Coleoptera: Bruchidae) in stored beans under laboratory and farm conditions in Northern Tanzania

The effectiveness of whole or powdered leaves (botanicals) from four locally grown plant species applied at a rate of 1.5 kg per 100 kg beans (Phaseolus vulgaris) against Acanthoscelides obtectus and Zabrotes subfasciatus was compared under laboratory and farm conditions. In the laboratory, Chenopodium ambrosioides, applied as powder or as whole leaves, was the most effective, with 100% mortality of adult insects in less than three days and no progeny. Less C. ambrosioides (about 200 g per 100 kg beans) still resulted in 100% mortality within 24 h. Tagetes minuta applied as powder also increased mortality and reduced oviposition and progeny production significantly. The other treatments - T. minuta applied as leaves, and Azadirachta indica or Cupressus lusitanica applied as powder or as whole leaves - had no significant effects upon mortalities, oviposition rate, or progeny production compared with control treatments. When the rate of application was increased to about 8.3 kg per 100 kg beans, there was a slight increase in mortality using T. minuta and A. indica, but not with C. lusitanica. An additional trial with C. ambrosioides from different collections and with plants at different stages of development revealed considerable variations in the efficacy of the treatment.In the on-farm trials, A. indica-seed powder was the most effective treatment, followed respectively by leaf powders of C. ambrosioides, C. lusitanica and T. minuta. All treatments were significantly more effective than the control in reducing the numbers of live insects; they also reduced numbers of damaged beans and maintained germination rates after 5 months of storage. The results of evaluations of the treatments made by farmers just after the trials and five years later are reported.     

Platelet activating factor-induced pulmonary accumulation of111indium-oxine labelled neutrophils in anesthetized guinea pigs

The thoracic accumulation of neutrophils labelled with¹¹¹Indium-oxine in response to infusion of platelet activating factor (PAF, 18 ng/kg/min × 5 min, i.v.) was studied using an automated isotope monitoring system (AIMSplus) in anesthetized guinea-pigs. Loss of cell associated radioactivityin vitro was less than 1% over 4 hr. Labelled neutrophils maintained their functional capacity (oxidative response to the cell stimulants N-formyl-L-methionine-L-leucine-L-phenylalanine and phorbol myristate acetate) and >95% viability (ethidium bromide/acridine orange stain)in vitro. Total thoracic radioactivity increased significantly from baseline in response to PAF with a slight tachyphylaxia in the neutrophil-accumulation after a repeat PAF infusion. The highest ratios of radiolabel (tissue/blood) were found in the spleen >>liver>lung. Based in part on a paper presented at the Third Internatioinal Conference on Platelet-Activating-Factor and Structurally Related Alkyl Ether Lipids, Tokyo, Japan, May 1989.     

New Results of Free Radical Additions to Unsaturated Fatty Compounds

Unsaturated fatty acids such as oleic acid are 1,2-dialkyl substituted alkenes, which can be functionalized by free radical addition to the C, C double bond. We have been able to add enolizable compounds, e.g. acetone, acetic acid and malonic acid to methyl oleate mediated by manganese(III)acetate. Azide radicals, generated by manganese(III)acetate-oxidation of sodium azide, have also been added to methyl oleate. Perfluoralkyl iodides have been added via perfluoroalkyl radicals to methyl 10-undecenoate and methyl oleate to form the corresponding addition products. Reduction of the iodides by tributyltin hydride and saponification leads to interesting partially fluorinated fatty acids.     

Fließinjektionssysteme und Enzym-Elektroden zur On-line-Analytik von Bioreaktoren

Flow injection analysis and enzyme electrodes for bioprocess monitoring. This review outlines the role played by enzyme electrodes and flow injection analysis (FIA) in bioprocess monitoring. The review is limited to a survey of the application of these systems to the monitoring of physiologically active parameters, such as substrate, product and biomass concentration. Priority is placed on a comparison of the presently available in situ and online techniques including the disadvantages associated with and the advantages offered by each system. An overview of the available sampling systems is given plus their suitability when coupled with FIA for bioprocess monitoring. The survey will be restricted to those techniques which have already been applied to bioprocess monitoring. The review will be illustrated by recent examples of the application of enzyme electrodes and FIA to microbial fermentation and cultivation and animal cell culture.