pH-induced difference spectrophotometric assay of acetazolamide, hydrochlorothiazide, and furosemide.

On the basis of pH-induced spectral changes for acetazolamide, hydrochlorothiazide, and furosemide, 3 different spectrophotometric methods are described. The methods were successfully applied to the assay of these drugs in different pharmaceutical formulations (tablets and ampoules). The accuracy of the analysis is increased by using the suggested methods as compared with conventional spectrophotometry.     

Sensitive spectrophotometric assay for 3-hydroxy-substituted flavonoids, based on their binding with molybdenum, antimony, or bismuth

A sensitive spectrophotometric assay has been developed for flavonoids based on their binding with molybdenum, antimony, or bismuth. Acetylation of the hydroxyl group of flavonoids abolished metal binding, thus suggesting a direct role of the hydroxyl groups. From a comparison of several related flavonoids differing in the position of hydroxyl substitutions, the hydroxyl group at position 3 was found to be an important requirement for the formation of a yellow complex. This flavonoid metal complex showed that a specific and significant bathochromic shift in the visible spectrum of the native flavonoid and the corresponding lambda(max) value was used for the colorimetric assays with different metal salts. The molybdenum complex was found to yield higher absorbance compared to antimony and bismuth complexes of various flavonoids. The present method offers a sensitive assay in the 5-25 nM range for these flavonoids and gave comparable results with HPLC quantitative determination.     

The origin and nature of organic nitrogen in soil as assessed by acidic and alkaline hydrolysis

The origin and nature of much of the organic nitrogen in soil is unknown or speculative. Alkaline hydrolysis was used to fractionate soils into alkali‐soluble and insoluble fractions. Alkali‐insoluble residues from a wide variety of soils contained largely fixed ammonium or chitin or both. Acid hydrolysis of alkali‐insoluble residues from soils, microbes, insects and well‐rotted plant litter confirmed the presence of hexosamine‐N. The hexosamine‐N derived from estimates of soil biomass accounted for less than 10% of the chemically determined hexosamine‐N values. It is suggested that most of the hexosamines are held in complexes formed between chitin complexed with other materials, e.g. pigments, that occur predominantly in the cell walls of microbes and insects. These complexes show resistance to enzymes during the life of soil organisms that persists after their death.     

酶解法和碱解法海藻提取物对梨树苗生长和养分吸收的影响

以盆栽梨树苗为试材,研究了酶解法和碱解法海藻提取物对梨树苗生长、生理特性和养分吸收的影响。结果表明,浇施海藻提取物提高了梨树苗的叶面积、百叶鲜重、根体积和净光合速率,其中酶解法海藻提取物处理在高浓度条件下叶面积最大,较对照显著提高27.76%,碱解法海藻提取物处理叶面积均显著高于对照,海藻提取物浓度处理间差异不显著;与对照相比,浇施海藻提取物均增加叶片丙二醛、磷和钾含量,显著降低脯氨酸含量,其中,酶解法海藻提取物分别在低和中浓度处理的叶片磷和钾含量最高,较对照分别显著提高30.17%和7.00%。主成分分析综合得分显示,酶解法海藻提取物低浓度处理得分最高（1.21）,其次为碱解法海藻提取物低浓度处理（0.81）。初步得出结论,酶解法和碱解法海藻提取物均能促进梨树苗生长和增加叶片磷、钾含量,其中,以低浓度（5 mg/L）酶解法海藻提取物的效果最优。     

Mineralization of benzyl glucosinolate and its hydrolysis product the biofumigant benzyl isothiocyanate in soil

Plants produce many secondary metabolites that are used as a defense against herbivores, pests and pathogens. Among them are the glucosinolates (GSLs) that are produced by plants of the Brassicales order. Upon enzymatic hydrolysis, GSLs are transformed to primarily isothiocyanates (ITCs) and nitriles. ITCs are toxic compounds with the potential to be used as biofumigants for the control of soil-borne pests. In this study, mineralization kinetics of benzyl GSL and benzyl ITC in a sandy and a clayey soil at 8–9 °C were investigated. Mineralization of ¹⁴C-benzyl GSL, which was de novo synthesized and purified from transgenic Arabidopsis thaliana after administering l-[U-¹⁴C]phenylalanine, showed that 40–50% was mineralized after 60 days. Mineralization of ¹⁴C-benzyl ITC produced by enzymatic hydrolysis of the ¹⁴C-benzyl GSL resulted in mineralization of 35–50% after 45 days. The ITC or a metabolite of ITC was rate limiting for mineralization of ITC during the first 10–15 days in incubations with subsoils. This effect may be attributed to toxicity of the ITC or an ITC metabolite, or that a lag phase was required for the relevant degraders to grow. Although the compounds are of natural origin and thus “known” to microbial degraders the extent of mineralization was not higher than for synthetic compounds like pesticides. After termination of the mineralization experiments, the soils were extracted with water, ethyl acetate and 4 M NaOH, respectively. These extractions indicated that a large amount of the applied ¹⁴C-labeled benzyl GSL and benzyl ITC was incorporated in organic fractions with low bioavailability.     

Stereoselectivity of the generation of 3-mercaptohexanal and 3-mercaptohexanol by lipase-catalyzed hydrolysis of 3-acetylthioesters

The enantioselectivity of the generation of 3-mercaptohexanal and 3-mercaptohexanol, two potent sulfur-containing aroma compounds, by lipase-catalyzed hydrolysis of the corresponding 3-acetylthioesters was investigated. The stereochemical course of the kinetic resolutions was followed by capillary gas chromatography using modified cyclodextrins as chiral stationary phases. The enzyme preparations tested varied significantly in terms of activity and enantioselectivity (E). The highest E value (E = 36) was observed for the hydrolysis of 3-acetylthiohexanal catalyzed by lipase B from Candida antarctica resulting in (S)-configured thiol products. Immobilization of the enzyme (E = 85) and the use of tert-butyl alcohol as cosolvent (E = 49) improved the enantioselectivity. Modification of the acyl moiety of the substrate (3-benzoylthiohexanal) had no significant impact. The sulfur-containing compounds investigated possess attractive odor properties, and only one of the enantiomers exhibits the pleasant citrus type note.     

Pathways for the hydrolysis of phorate: product studies by (31)P NMR and GC-MS

A new intramolecular mechanism is proposed for the hydrolysis of phorate. (31)P NMR was used to study the formation of P-containing products of phorate hydrolysis in situ. When hydrolysis was followed by (31)P NMR, a dominant P-containing product was found and was identified to be diethyl dithiophosphate using methylation and GC-MS. Combining the data from phorate hydrolysis at three different temperatures, thermodynamic parameters were calculated. The contributions of various possible pathways to phorate hydrolysis are discussed.     

Biotransformation of 3-methyl-4-nitrophenol, a main product of the insecticide fenitrothion, by Aspergillus niger

Biotransformation of the environmental pollutant 3-methyl-4-nitrophenol (MNP), a newly characterized estrogenic chemical, and the primary breakdown product of the heavily used insecticide fenitrothion was investigated using a common soil fungus. In 96 h, daily culture sacrifice, extraction, and analysis showed that the filamentous fungus, Aspergillus niger VKM F-1119, removed more than 85% of the MNP present in solution (original concentration = 25 mg/L), mostly through biodegradation. Additionally, in 16-day time-course studies, A. niger was capable of biotransformation of MNP at concentrations as high as 70 mg/L. Gas chromatography mass spectroscopy (MS) analyses of culture fluid extracts indicated the formation of four metabolites: 2-methyl-1,4-benzenediol, 4-amino-3-methylphenol, and two singly hydroxylated derivatives of MNP. Culture scale up and metabolite analysis by liquid chromatography MS resulted in the confirmation of the original metabolites plus the detection of an azo derivative metabolite that has not been previously reported before during MNP biodegradation by any micro-organisms.     

The hydrolysis of kaolinitic soils as affected by the type of the exchangeable cation

The hydrolysis of four kaolinitic soils from the Transvaal (RSA), and the effects of exchangeable Na, Ca and Mg were studied by monitoring the changes in the electrical conductivity of the soil suspension with time. The rate of the hydrolysis was found to be linearly related to the square root of time. The rates of the hydrolysis of the Half-Way House and Krugersdorp soils were appreciably lower than those of the Potchefstroom and Amsterdam soils, and rates reported in the literature for smectite soils. This was probably because of the low content of hydrolysable bases in the Half-Way House and Krugersdorp soils, resulting from the low cation exchange capacity of their clay fraction. The extensive hydrolysis observed in the Potchefstroom and Amsterdam soils could be ascribed to the presence of significant amounts of smectite in the former and high silt content in the latter; both factors are known to enhance the rate of weathering and hydrolysis. With the exception of the Potchefstroom soil, the rate of hydrolysis was not affected by the cationic composition of the adsorbed phase. Contrary to expectations, exchangeable Mg did not inhibit hydrolysis in the soils studied, probably because of the limited isomorphic substitutions in kaolinite which lead to very small amounts of octahedral Mg in the crystal. The hydrolysis of the Potchefstroom soil was enhanced in the presence of exchangeable Mg compared to exchangeable Ca; the reason for this is not fully understood.     

Enzymatic hydrolysis as a means of expanding the cold gelation conditions of soy proteins

Acid-induced cold gelation of soy protein hydrolysates was studied. Hydrolysates with degrees of hydrolysis (DH) of up to 10% were prepared by using subtilisin Carlsberg. The enzyme was inhibited to uncouple the hydrolysis from the subsequent gelation; the latter was induced by the addition of glucono-delta-lactone. Visual observations, confocal scanning laser microscopy images, and the elasticity modulus showed that hydrolysates gelled at higher pH values with increasing DH. The nonhydrolyzed soy protein isolate gelled at pH approximately 6.0, whereas a DH = 5% hydrolysate gelled at pH approximately 7.6. Gels made from hydrolysates had a softer texture when manually disrupted and showed syneresis below a pH of 5-5.5. Monitoring of gelation by measuring the development of the storage modulus could be replaced by measuring the pH onset of aggregate formation (pH(Aggr-onset)) using turbidity measurements. The rate of acidification was observed to also influence this pH(Aggr-onset). Changes in ionic strength (0.03, 0.2, and 0.5 M) had only a minor influence on the pH(Aggr-onset), indicating that the aggregation is not simply a balance between repulsive electrostatic and attractive hydrophobic interactions, but is much more complex.     

Yield of sugar beet,soybean, corn,field bean,and wheat as affected by lime application on alkaline soils

Abstract

Environmental regulations and limited storage space compel processors to remove spent limestone and not stockpile it on site. This material is often used as a liming material to control pH on acid soils, but in some cases may have to be applied to alkaline soils. This study was undertaken to evaluate the effect of applying sugar beet processing lime on soils with an alkaline solum. Studies were conducted at seven sites representing four soil series. Lime was applied at rates of 0,1.4, 2.8, and 5.6 magnesium (Mg) ha^‐1. Sugar beet (Beta vulgaris L.), soybean (Glycine max L.), cora (Zea mays L.), field bean (Phaseolus vulgaris L.), and wheat (Triticum aestivum L.) were used as test crops. Yield of sucrose and roots of sugar beet as well as yield of soybean, corn, field bean, and wheat were not affected by lime application. Manganese (Mn) and zinc (Zn) concentration in leaves of sugar beet and soybean, and whole field bean plants decreased with increasing lime rates. These results show this lime may be applied at rates up to 5 Mg ha^‐1 once every three years on these alkaline soils without negatively affecting the yield of sugar beet, soybean, corn, field bean, and wheat. Nutritional status of these crops should be carefully monitored after lime application.     

Rapid automated turbidimetric assay for chlortetracycline hydrochloride, using Leuconostoc mesenteroides as the test organism.

A rapid turbidimetric assay has been developed for chlortetracycline hydrochloride (CTC-HCl) in finished animal feeds and feed supplements, using Leuconostoc mesenteroides as the test organism. Two modifications are presented: The incubation period of modification 1 is 2.5 hr and the sensitivity of the assay is 0.03 microgram CTC-HCl/assay tube. Modification 2 has a sensitivty of 0.01 microgram CTC-HCl/assay tube and requires an incubation period of 3.5 hr. For 21 feed formulations, the turbidimetric method recovered 95.7% of label claim. Recoveries of CTC-HCl standards from the same feeds ranged from 93.4 to 134% with a mean of 103%. The relative standard deviation among day-to-day duplicates is 3.50% for the faster modification and 1.63% for the more sensitive modification.     

Stability of black tea polyphenol, theaflavin, and identification of theanaphthoquinone as its major radical reaction product

In the current study, we have focused on isolation and detection of major radical oxidation products from theaflavin in order to better understand antioxidation mechanisms of this compound. Theanaphthoquinone was identified as a major oxidation product of theaflavin from two different oxidant model systems: DPPH and peroxidase/hydrogen peroxide. This result indicated that the benzotropolone moiety in theaflavin may play an important role in its antioxidant properties. The stability of theaflavin was studied in varying pH solutions: simulated gastric juice and buffer solutions of pH 5.5, pH 7.4, and pH 8.5. The results indicated that theaflavin is unstable in alkaline conditions, while it was stable in acidic conditions. Theanaphthoquinone was identified as an autoxidation product of theaflavin during its stability study in alkaline conditions.     

Urea hydrolysis in soils: Factors influencing the effectiveness of phenylphosphorodiamidate as a retardant

Studies to determine the factors influencing the effectiveness of phenylphosphorodiamidate (PPD) to retard urea hydrolysis in soils showed that the inhibitory effect of PPD on hydrolysis of urea by soil urease increased markedly with the amount of PPD added and decreased markedly with time and with increase in temperature from 10 to 40°C. They also showed that the ability of PPD to retard urea hydrolysis in 15 surface soils selected to obtain a wide range in properties was significantly correlated with organic C content (r = ?0.68⁷), total N content (r = ?0.74⁷), cation-exchange capacity (r = ?0.65⁷), sand content (r=0.66⁷), clay content (r = ?0.64⁷) and surface area (r = ?0.60¹), but was not significantly correlated with pH, silt content, urease activity or CaCO₃ equivalent. Multiple-regression analyses indicated that the effectiveness of PPD to retard urea hydrolysis in soils tends to increase with decrease in soil organic-matter content.     

Use of lignin extracted from different plant sources as standards in the spectrophotometric acetyl bromide lignin method

A nongravimetric acetyl bromide lignin (ABL) method was evaluated to quantify lignin concentration in a variety of plant materials. The traditional approach to lignin quantification required extraction of lignin with acidic dioxane and its isolation from each plant sample to construct a standard curve via spectrophotometric analysis. Lignin concentration was then measured in pre-extracted plant cell walls. However, this presented a methodological complexity because extraction and isolation procedures are lengthy and tedious, particularly if there are many samples involved. This work was targeted to simplify lignin quantification. Our hypothesis was that any lignin, regardless of its botanical origin, could be used to construct a standard curve for the purpose of determining lignin concentration in a variety of plants. To test our hypothesis, lignins were isolated from a range of diverse plants and, along with three commercial lignins, standard curves were built and compared among them. Slopes and intercepts derived from these standard curves were close enough to allow utilization of a mean extinction coefficient in the regression equation to estimate lignin concentration in any plant, independent of its botanical origin. Lignin quantification by use of a common regression equation obviates the steps of lignin extraction, isolation, and standard curve construction, which substantially expedites the ABL method. Acetyl bromide lignin method is a fast, convenient analytical procedure that may routinely be used to quantify lignin.     

A spectrophotometric procedure, using carboxypeptidase A, for the quantitative measurement of ochratoxin A.

In the method described, ochratoxin A is eleaved into ochratoxin alpha (free isocoumarin chromophore) and phenylaline, using carboxypeptidase. Detection is based on the difference in fluorescence excitation spectra of ochratoxin A (380 NM, maximum) and ochratoxin alpha (340 nm, maximum). The quantitation of ochratoxin A is based on the loss of fluorescence intensity at 380 nm. The method has been used for the quantitative determination of as little as 4 mug ochratoxin A/kg barley and barley meal but it could be extended to other products.     

Luciferase preparation,assay conditions and calculated extraction efficiency as factors in the estimation of soil ATP content

Summary Several factors affecting the measurement of soil adenosine 5-triphosphate (ATP) using a crude (macerated firefly tail) preparation of luciferase and a luminometer were investigated. These factors were luciferase preparation purity (crude or purified), use of Tris(hydroxymethyl)methylamine (Tris) or sodium arsenate (arsenate) buffer for the luciferase preparation and the bioluminescent reaction, storage temperature of luciferase throughout the assay (20°C or 1°C), modes of measuring bioluminescence (peak height or integration of bioluminescence decay) and efficiency of extraction (recovery) of ATP from soil.Crude luciferase produced a linear relationship between bioluminescence and ATP concentration very similar to that produced by purified luciferase and could be stored at 20°C for 3 h without deterioration. Arsenate was, overall, the preferred buffer for the assay. Integrating light output within 15 s of mixing luciferase-luciferin and ATP avoided interference from other reactions in the crude extracts. The procedure used to calculate the ATP concentration and the amount of exogenous ATP added to soil both affected the calculated efficiency of ATP recovery. Thus an assay for soil ATP content using crude preparations has been developed which is as sensitive as those using purified preparations.