Effects of Root Exudates of Cucumber (Cucumis sativus) and Allelochemicals on Ion Uptake by Cucumber Seedlings

The effects of root exudates of cucumber, aromatic carboxylic acids in root exudates, and their analogs upon the uptake of NO₃, $H_2 PO_4^ - $ $SO_4^{2 - } $ K⁺, Ca²⁺, Mg²⁺, and Fe²⁺ by intact cucumber seedlings were examined. Root exudates inhibited the uptake of all the ions analyzed except for $H_2 PO_4^ - $ . Inhibition of ion uptake by cinnamic acid, a main component of root exudates, was both concentration- and pH-dependent. With decreasing pH, the inhibitory effect on the ion uptake increased. With benzoic and cinnamic acids, the substitution of hydrophilic group(s) on the benzene ring alleviated the inhibition of ion uptake. Aromatic acids enhanced ion leakage. The potency was in proportion, but not equal, to the extent of uptake inhibition. The lipophilicity was a valuable index for evaluating the allelopathic potential of aromatic acids.     

Phytotoxic substances in root exudates of cucumber (Cucumis sativus L.)

The addition of activated charcoal to a nutrient solution for the hydroponic culture of cucumber resulted in significant increases in the dry weight of the plant and fruit yield. Hydrophobic root exudates were collected at different growth stages with Amberlite XAD-4 resin and bioassayed with lettuce seedlings. The exudates at the reproductive stage were more phytotoxic than those at the vegetative stage. The exudates contained organic acids such as benzoic,p-hydroxybenzoic, 2,5-dihydroxybenzoic, 3-phenylpropionic, cinnamic,p-hydroxycinnamic, myristic, palmitic, and stearic acids, as well asp-thiocyanatophenol and 2-hydroxybenzothiazole, all of which, except 2-hydroxybenzothiazole, were toxic to the growth of lettuce.     

Effects of Microbial Utilization of Phenolic Acids and their Phenolic Acid Breakdown Products on Allelopathic Interactions

Reversible sorption of phenolic acids by soils may provide some protection to phenolic acids from microbial degradation. In the absence of microbes, reversible sorption 35 days after addition of 0.5–3 mol/g of ferulic acid or p-coumaric acid was 8–14% in Cecil A_p horizon and 31–38% in Cecil B_t, horizon soil materials. The reversibly sorbed/solution ratios (r/s) for ferulic acid or p-coumaric acid ranged from 0.12 to 0.25 in A_p and 0.65 to 0.85 in B_t horizon soil materials. When microbes were introduced, the r/s ratio for both the A_p and B_t horizon soil materials increased over time up to 5 and 2, respectively, thereby indicating a more rapid utilization of solution phenolic acids over reversibly sorbed phenolic acids. The increase in r/s ratio and the overall microbial utilization of ferulic acid and/or p-coumaric acid were much more rapid in A_p than in B_t horizon soil materials. Reversible sorption, however, provided protection of phenolic acids from microbial utilization for only very short periods of time. Differential soil fixation, microbial production of benzoic acids (e.g., vanillic acid and p-hydroxybenzoic acid) from cinnamic acids (e.g., ferulic acid and p-coumaric acid, respectively), and the subsequent differential utilization of cinnamic and benzoic acids by soil microbes indicated that these processes can substantially influence the magnitude and duration of the phytoxicity of individual phenolic acids.     

Effects of Temperature and Photoperiod on Phytotoxic Root Exudates of Cucumber (Cucumis sativus) in Hydroponic Culture

In order to elucidate the effects of temperature and photoperiod on the quality and quantity of plant root exudates, a Japanese cucumber (Cucumis sativus, cv. Shougoin-Aonaga-Fushinari) was grown hydroponically in growth chambers under controlled temperature and photoperiod conditions with or without the addition of activated charcoal (AC) to the nutrient solutions. Fresh AC was used to trap the organic compounds exuded from cucumber roots every two weeks. Cucumber plants without AC were severely retarded in root growth and in the accumulation of dry matter, especially at high temperature and long photoperiod, compared to those with AC. The growth inhibitors, adsorbed on the AC or accumulated in the nutrient solution without AC, were extracted by organic solvents and analyzed by GC-MS. Benzoic acid and its derivatives, cinnamic acid derivatives, and fatty acids were identified. The rate of root exudation in vegetative and reproductive stages for some of these organic acids increased with the elevation of temperature and the elongation of photoperiod, and the mean rate was two or more times higher than the minimum exudation at low temperature with short photoperiod. Some of the identified compounds significantly inhibited the germination and/or root growth of lettuce and cucumber.     

Antioxidant and Biological Activities of Novel Structured Monoacylglycerol Derivatives with Phenolic Acids

Novel structured monoacylglycerol (MAG)-based phenolic lipids are synthesized from11-bromoundecanoic acid, phenolic acids, and solketal. Selected phenolic acids namely 4-hydroxy benzoic, vanillic, syringic, cinnamic, p-coumaric, sinapic, 4-fluorocinnamic, 4-hydroxyphenyl acetic acid, 3-(4-hydroxyphenyl) propanoic and dihydrocaffeic acids are employed for the synthesis of ten novel MAG-based phenolic lipids. The synthesized phenolic lipids are characterized by FT-IR, NMR, and mass spectra analysis. All the compounds are evaluated for antioxidant, antimicrobial, and cytotoxic activities. MAG derivative 8g of sinapic acid exhibits excellent antioxidant activity in both DPPH assay and inhibition of lipid oxidation assay. MAG derivative 8f bearing p-coumaric acid shows good antimicrobial activity against both Gram-positive and Gram-negative bacterial strains with a minimum inhibitory concentration (MIC) value of 6.25 µm mL⁻¹. All the synthesized compounds are found to exhibit cytotoxicity against B16, DU145, and CHO cell lines, while sinapic and p-coumaric acid derivatives exhibit better activities compared to other derivatives.     

Use of water and EDTA extractions to estimate available (free and reversibly bound) phenolic acids in Cecil soils

Sterile and microbe reinfested Cecil A_p and B_t soil materials amended with 0 to 5 µmol/g of ferulic acid,p-coumaric acid,p-hydroxybenzoic acid, or vanillic acid were extracted after varying time intervals with water, EDTA, or NaOH to characterize sorption of cinnamic and benzoic acid derivatives and to determine the effectiveness of water and EDTA extractions in estimating concentrations of free and reversibly bound phenolic acids in soils. Basic EDTA (0.5 M, pH 8) extractions and water extractions provided good estimates of both free and reversibly bound cinnamic acid derivatives, but not of benzoic acid derivatives. Neutral EDTA (0.25 M, pH 7) and water extractions, however, were effective for both cinnamic and benzoic acid derivatives Rapid initial sorption of both cinnamic and benzoic acid derivatives was followed by slow long-term sorption of the cinnamic acid derivatives. Slow long-term sorption was not observed for the benzoic acid derivatives. The amount of sorption of phenolic acids in soil materials was directly related to the concentration of phenolic acids added to soil materials. The addition of a second phenolic acid to the soil materials did not substantially affect the sorption of each individual phenolic acid. Sodium hydroxide extractions, which were made only after phenolic acids in phenolic acid-amended and non-amended soil material were depleted by microbes, confirmed that neutral EDTA and water extractions of soils can be used to make accurate estimates of baseline (residual) levels of free and reversibly bound phenolic acids available to soil microbes and, thus, potentially to seeds and roots.The use of trade names in this publication does not imply endorsement by the North Carolina Agricultural Research Service of products named, nor criticism of similar ones not mentioned.     

Relationships between Phenolic Acid Concentrations,Transpiration, Water Utilization,Leaf Area Expansion,and Uptake of Phenolic Acids: Nutrient Culture Studies

Phenolic acid treatments of cucumber seedlings (Cucumis sativus cv “Early Green Cluster”) inhibited transpiration, water utilization, leaf area, and absolute and relative rates of leaf expansion. The cinnamic acids, ferulic and p-coumaric acids, were two to five times more inhibitory than the benzoic acids, p-hydroxybenzoic acid and vanillic acid. When phenolic acid concentrations were maintained at inhibitory concentrations through multiple successive treatments, percent inhibition of water utilization remained relatively constant for a given concentration and phenolic acid, percent inhibition of leaf area initially increased and then leveled off to a constant percent, and percent inhibition of transpiration and rates of leaf area expansion declined over time. Subsequently, p-coumaric acid was chosen as the model compound for further study. When p-coumaric acid was inhibitory, percent inhibition of transpiration, water utilization, and rates of leaf area expansion of actively growing leaves rapidly declined (i.e., was lost) as p-coumaric acid concentrations surrounding roots decreased. Absolute and relative rates of leaf expansion, for example, declined approximately 12 and 14%, respectively, for every 0.1 mM decline in p-coumaric acid concentration. Uptake of p-coumaric acid by cucumber seedling roots was continuous over the 24- or 36-hr periods monitored, but was not consistently related to the initial p-coumaric acid treatment concentrations. However, declining p-coumaric acid concentrations monitored at 6- or 12-hr intervals over the 24- or 36-hr periods continued to be highly correlated to the initial p-coumaric acid treatment concentrations. A 25% depletion by 13-d-old cucumber seedlings took 8.5, 12, 19.5, 25, and 29.5 hr for 0.125-, 0.25-, 0.5-, 0.75-, and 1-mM treatments, respectively. Uptake during periods when phenolic acid concentrations and root uptake (depletion from solution) were related appeared to represent periods dominated by apoplastic movement into the intercellular spaces of roots. Uptake during periods without this relationship likely represented periods dominated by symplastic movement. The ability of cucumber seedlings to modify active phenolic acid concentrations surrounding their roots suggests that cucumber seedling can directly influence the magnitude of primary and secondary effects of phenolic acids through feedback regulation.     

Conversion of benzoic acid during TiO2-mediated photocatalytic degradation in water

The photocatalytic degradation of benzoic acid in water over Degussa P-25 TiO₂ suspensions was studied. UVA irradiation at 365 nm was supplied by a medium pressure mercury lamp providing 25 mW cm⁻² light intensity. Experiments were conducted at benzoic acid initial concentrations between 25 and 150 mg L⁻¹, catalyst loadings between 0.2 and 1 g L⁻¹ and initial solution pH values between 2 and 10.6. Conversion increased with increasing catalyst loading up to about 0.6 g L⁻¹ and it was favored at alkaline or neutral conditions but impeded at extremely acidic conditions. Increasing initial substrate concentration led to decreased benzoic acid conversion, which was found to follow a Langmuir–Hinshelwood kinetic expression. High performance liquid chromatography (HPLC) was employed to follow benzoic acid concentration profiles as well as to identify reaction by-products, while chemical oxygen demand (COD) and total organic carbon (TOC) analyses were carried out to assess the extent of mineralization. Benzoic acid hydroxylation by-products, namely 2-, 3- and 4-hydroxybenzoic acids as well as phenol were identified as reaction intermediates, although these contributed only a small fraction of the residual organic content. Although benzoic acid at 50 mg L⁻¹ was not ecotoxic to marine photobacteria Vibrio fischeri, its photodegraded solution exhibited substantial toxicity, which, however, proved not to be due to the identified intermediates.     

Enzymatic Synthesis of Enantiopure α‐ and β‐Amino Acids by Phenylalanine Aminomutase‐Catalysed Amination of Cinnamic Acid Derivatives

The phenylalanine aminomutase (PAM) from Taxus chinensis catalyses the conversion of α‐phenylalanine to β‐phenylalanine, an important step in the biosynthesis of the N‐benzoyl phenylisoserinoyl side‐chain of the anticancer drug taxol. Mechanistic studies on PAM have suggested that (E)‐cinnamic acid is an intermediate in the mutase reaction and that it can be released from the enzyme's active site. Here we describe a novel synthetic strategy that is based on the finding that ring‐substituted (E)‐cinnamic acids can serve as a substrate in PAM‐catalysed ammonia addition reactions for the biocatalytic production of several important β‐amino acids. The enzyme has a broad substrate range and a high enantioselectivity with cinnamic acid derivatives; this allows the synthesis of several non‐natural aromatic α‐ and β‐amino acids in excellent enantiomeric excess (ee >99 %). The internal 5‐methylene‐3,5‐dihydroimidazol‐4‐one (MIO) cofactor is essential for the PAM‐catalysed amination reactions. The regioselectivity of amination reactions was influenced by the nature of the ring substituent.     

Studies on the enzymatic synthesis of lipophilic derivatives of natural antioxidants

The esterification of some natural antioxidants such as cinnamic acid derivatives and ascorbic acid in non-aqueous media, catalyzed by immobilized lipases from Candida antarctica and Rhizomucor miehei, was investigated. The alcohol chain length affected the rate of esterification of cinnamic acids by both lipases. Higher reaction rates were observed when the esterification was carried out with medium- or long-chain alcohols. The rate also depended on aromatic acid structure. The reactivity of the carboxylic function of the cinnamic acids was affected by electron-donating substituents in the aromatic ring. Higher yields were observed for the esterification of p-hydroxyphenylacetic acid (97%) catalyzed by C. antarctica lipase and for the esterification of cinnamic acid (59%) catalyzed by R. miehei lipase. Candida antarctica lipase was more suitable for producing ascorbic acid fatty esters, catalyzing with a relatively high yield (up to 65% within 24 h) the regioselective esterification of ascorbic acid with various fatty acids in 2-methyl-2-propanol. The reaction rate and yield depended on the fatty acid chain length and on the molar ratio of reactants. All ascorbic acid fatty esters produced by this procedure exhibited a significant antioxidant activity in a micellar substrate composed of linoleic acid.     

Inhibition of growth ofPhytophthora parasitica var.nicotianae by aromatic acids and coumarins in a laboratory bioassay

Hydroxy-, dihydroxy-, trihydroxy-, methoxy-, dimethoxy-, hydroxy-+methoxy-, amino-, chloro-, and nitro-substituted benzoic, phenylacetic, phenylpropanoic, and phenylpropenoic (cinnamic) acids were evaluated for activity against the growth ofPhytophthora parasitica var.Nicotianae, Races 0 and 1, in a laboratory bioassay. Several substituted coumarins were also tested. In general, for Race 0, the phenylpropenoic acids were more active (on a millimolar basis), than the corresponding benzoic, phenylacetic, or phenylpropionic acids (9 of 14 series). Among the most active acids wereo-hydroxycinnamic and the chloro- and methoxycinnamic acids. The activities of unsubstituted benzoic and phenylpropionic acids were comparable to the most active compounds tested. Monohydroxyaromatic acids were more active than most dihydroxy acids of the same chain length. Dihydro-3,4-dihydroxycinnamic acid was slightly more active than the corresponding cinnamic acid, while the reverse was true for the mono-p-hydroxycinnamic acid versusp-hydroxyphenylpropionic acid. Coumarin was more active than its hydroxy, methyl, hydroxymethyl, or methoxy derivatives. In general, Race 1 was even more significantly affected by the aromatic acids. Glycosylated coumarins were inactive in the bioassay, compared to their aglycones.     

Primary Metabolites and Polyphenols in Rapeseed (Brassica napus L.) Cultivars in China

Defatted meals of 10 rapeseed (Brassica napus L.) varieties were investigated for their total phenolic, phenolic acid (free, esterified, and insoluble-bound forms), and tannin contents. The antioxidant capacities (AC) of methanol extracts from samples were assessed using the 2,2′-diphenyl-1-picrylhydrazyl radical (DPPH•), Folin–Ciocalteu method and ferric reducing antioxidant power (FRAP), and β-carotene–linoleic acid tests. In the fraction of free phenolic acids, sinapic, caffeic, ferulic, syringic, gallic, and p-coumaric acids were identified. In the fraction of esterified phenolic acids, sinapine, sinapoyl glucoside, and disinapoyl gentiobiose were identified. After basic hydrolysis, sinapic, ferulic, cinnamic, and 4-hydroxybenzoic acids were identified, and sinapic acid (SA) constituted 98.3% to 99.6% of the total esterified phenolic acids. Eleven components (sinapic, protocatechuic, p-coumaric, syringic, vanillic, gallic, caffeic, ferulic, salicylic, cinnamic, and 4-hydroxybenzoic acids) in the fraction of insoluble-bound phenolic acids were identified. The AC of the samples correlated with the total phenolic content. Overall, the total phenolics showed a better correlation with AC than the individual phenolic compounds. Moreover, SA, sinapoyl glucoside, and disinapoyl gentiobiose showed a highly significant and strong positive correlation with the AC of rapeseed meals, and the derivatives of cinnamic acid showed a higher correlation with AC than the derivatives of benzoic acid. The change in the canolol content in rapeseeds under microwave irradiation is discussed. The correlation of the canolol formed with SA and its derivatives is discussed.     

The Acrylation of Glycerol: A Precursor to Functionalized Lipids

With the objective of expanding the number of functionalized lipids available, the reactive vinyl group of acrylic acid was introduced to triacylglycerol by esterification of glycerol. Didecanoylacryloylglycerol was synthesized from decanoic and acrylic acids and glycerol using K₂O as catalyst. 2 g (21.7 mmol) glycerol, 11.3 g (65.4 mmol) decanoic acid, 6.2 g (86.1 mmol) acrylic acid, 60 ml hexane, and 400 mg K₂O were added to 300-ml closed stainless steel reactor and maintained at 200 °C for 5 h. The resulting product, designated DDA, was isolated at about 40% yield based on the acylglycerol products. The other products included tridecanoylglycerol, diacryloyldecanoylglycerol, and the diacylglycerols of these acids. DDA was then converted to functionalized lipids by the Michael addition and Heck reaction. The Michael addition of thiophenol and 4-bromothiophenol yielded the corresponding linear thioethers whereas and Heck reaction products from bromobenzene and bromoanisole yielded triacylglycerols containing trans-cinnamic acid and trans-(4-methoxy)cinnamic acid, respectively.     

Effects of a Coumarin Derivative, 4-Methylumbelliferone,on Seed Germination and Seedling Establishment in <Emphasis Type="Italic">Arabidopsis</Emphasis>

The root system is central for plant adaptation to soil heterogeneity and is organized primarily by root branching. To search for compounds that regulate root branching, a forward chemical genetics screen was employed, and 4-methylumbelliferone (4-MU), a coumarin derivative, was found to be a potent regulator of lateral root formation. Exogenous application of 4-MU to Arabidopsis thaliana seeds affected germination and led to reduced primary root growth, the formation of bulbous root hairs, and irregular detached root caps accompanied by reorganization of the actin cytoskeleton in root tips before seedling establishment. Abundant lateral roots formed after exposure to 125 μM 4-MU for 22 days. Molecular, biochemical, and phytochemical approaches were used to determine the effect of 4-MU on root growth and root branching. Arabidopsis seedlings grown in the presence of 4-MU accumulated this compound only in roots, where it was partially transformed by UDP-glycosyltransferases (UGTs) into 4-methylumbelliferyl-β-D-glucoside (4-MU-Glc). The presence of 4-MU-Glc in seedling roots was consistent with the upregulation of several genes that encode UGTs in the roots. This shows that UGTs play an integral role in the detoxification of 4-MU in plants. The increased expression of two auxin efflux facilitator genes (PIN2 and PIN3) in response to 4-MU and the lack of response of the auxin receptor TIR1 and the key auxin biosynthetic gene YUCCA1 suggest that auxin redistribution, rather than auxin biosynthesis, may directly or indirectly mediate 4-MU-induced root branching.     

Physicochemical Properties,Chemical Composition and Antioxidant Activity of <Emphasis Type="Italic">Dalbergia odorifera</Emphasis> T. Chen Seed Oil

The heartwood or root of Dalbergia odorifera T. Chen is an important traditional medicine in Asia. The aim of the present study was to evaluate the physicochemical properties, chemical composition and antioxidant activity of Dalbergia odorifera T. Chen seed oil. Oil, protein, carbohydrate, moisture, ash and total phenolic contents were found to be 12.96, 26.86, 42.58, 13.70, 3.90 and 5.55%, respectively. Free fatty acids, iodine number, peroxide value, saponification number and unsaponifiable matter were 1.66%, 106.53 g/100 g, 5.07 meq O₂/Kg, 196.78 mg KOH/g and 1.70%, respectively. The oil showed high absorbance in the UV-B and UV-C ranges with potential for use as a broad spectrum UV protectant. The major fatty acids were linoleic acid (60.03%), oleic acid (17.48%) and palmitic acid (16.72%). The total tocopherol, total phenolics and β-carotene were 511.9, 351.1 and 62.2 mg/kg oil, respectively. In addition, the methanol extract of seed oil showed significant in vitro antioxidant activity in four assays including DPPH radical scavenging activity, reducing power, linoleic acid peroxidation inhibition and chelating activity. This study suggests that Dalbergia odorifera T. Chen seed oil has the potential to be used in new products in the functional food, cosmetic or pharmaceutical industries.     

<Emphasis Type="Italic">trans</Emphasis>-Fatty Acid Isomers in Adipose Tissue Have Divergent Associations with Adiposity in Humans

The aim of this study was to evaluate the association between adipose tissue trans-fatty acid isomers and adiposity. This cross-sectional study included 1,785 subjects from Costa Rica. Fatty acid concentrations (as a percentage of the total fatty acids) in subcutaneous adipose tissue were assessed by gas–liquid chromatography. Dietary intakes were assessed with a food frequency questionnaire. Multivariate linear regression models were used to relate adipose tissue trans-fatty acid content to BMI, waist circumference, and skinfold thickness while adjusting for age, sex, and area of residence. To account for variations in lifestyle, we adjusted for smoking, physical activity, income, self-reported history of diabetes and hypertension, and for adipose tissue alpha-linolenic acid and energy intake in a third model. After adjustments, positive associations were found between 18:2t-fatty acids (primarily from partially hydrogenated oils) and BMI, waist circumference, and skinfold thickness (P for each association <0.01). Rumenic acid was positively associated with skinfold thickness (P < 0.0001), but not with BMI or waist circumference (P > 0.05). Inverse associations were found between 16:1n-7t-fatty acids and skinfold thickness and between 18:1t-fatty acids and BMI and waist circumference (P < 0.0001). This study suggests that individual trans-fatty acid isomers may have divergent effects on adiposity. 18:2t-fatty acids show consistent positive associations with measures of adiposity. These isomer-specific associations are an interesting new finding. Other prospective and intervention studies are necessary to examine these relationships further.     

Characterization of Turkish <Emphasis Type="Italic">Quercus</Emphasis> L. Taxa Based on Fatty Acid Compositions of the Acorns

Total oil content and the composition of fatty acids were analyzed in the acorns of 16 Quercus taxa from Turkey. The range of total fat varied between 0.7 and 7.4%. Oleic (10.2–54.4%), linoleic (24.2–49.1%), palmitic (13.4–30.4%), alpha linolenic (1.5–8.6%) and stearic acid (1.5–4.5%) were major fatty acids for all taxa. Significantly differences at section level were found (p < 0.05) for palmitic, stearic and oleic acid concentration. Saturated (17.0–38.6%), mono unsaturated (11.0–55.5%) and unsaturated fatty acids (57.4–81.6%) in total oil were also significantly different between section Quercus, Cerris and Ilex (p < 0.05). In addition, sectional differences were significant (p < 0.02) for the relative concentrations of saturated fatty acids compared to mono, poly and total unsaturated fatty acids. Considerable variation of individual fatty acid levels were observed in related species and varieties. The species from section Ilex Loudon exhibited the highest levels of saturated fatty acid while the lowest levels were found in Q. brantii, Q. libani and Q. trojana from section Cerris Loudon. These species also had the highest levels of unsaturated fatty acids. Whereas the lowest values were detected in the species of section Ilex. Both varieties of Q. cerris showed significant differences (p < 0.05) from the other species in section Cerris for all parameters, except for stearic acid and exhibited little variations among their individual populations. Different concentrations of fatty acids may be useful biochemical markers for the characterization of Quercus at the infrageneric level. Interesting ratios of linoleic:α-linolenic acid especially in Q. robur ssp. robur, Q. hartwissiana, Q. vulcanica, Q. ithaburensis ssp. macrolepis and Q. libani also were detected with respect to dietary reference for fatty acid intake.     

Synthesis and characterization of conducting homopolymers and copolymers of o‐anisidine and o‐toluidine in inorganic and organic supporting electrolytes

The influence of inorganic and organic supporting electrolytes on the electrochemical, optical, and conducting properties of poly(o‐anisidine), poly(o‐toluidine), and poly(o‐anisidine‐co‐o‐toluidine) thin films was investigated. Homopolymer and copolymer thin films were synthesized electrochemically, under cyclic voltammetry conditions, in aqueous solutions of inorganic acids (H₂SO₄, HCl, HNO₃, H₃PO₄, and HClO₄) and organic acids (benzoic acid, cinnamic acid, oxalic acid, malonic acid, succinic acid, and adipic acid) at room temperature. The films were characterized by cyclic voltammetry, ultraviolet–visible spectroscopy, and conductivity measurements with a four‐probe technique. The ultraviolet–visible spectra were obtained ex situ in dimethyl sulfoxide. The optical absorption spectra indicated that the formation of the conducting emeraldine salt (ES) phase took place in all the inorganic electrolytes used, whereas in organic acid supporting electrolytes, ES formed only with oxalic acid. Moreover, the current density and conductivity of the thin films was greatly affected by the nature and size of the anion present in the electrolyte. For the copolymer, the conductivity lay between the conductivity of the homopolymers, regardless of the supporting electrolyte used. The formation of the copolymer was also confirmed with differential scanning colorimetry. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2634–2642, 2003     

Corrosion Behavior of Bitter Almond Oil During Processing

This study aims to explore the corrosion behavior of bitter almond oil (BAO) during processing. Hydrocyanic acid (HCN) and benzoic acid in oil are speculated as the main components that corrode the screw oil expeller. Immersion and simulation corrosion tests are carried out to verify this hypothesis. Immersion test results show that crude BAO (CBAO) containing 5.07 ± 0.06 mg kg^?1 benzoic acid and 4.25 ± 0.04 mg kg^?1 HCN exhibits corrosive effects on steel. Simulation corrosion test results indicate that the addition of CN^? or benzoic acid has significant effect on the corrosion of steel. Specifically, at ≥1 × 10⁴ mg kg^?1 benzoic acid concentration or ≥5 mg kg^?1 CN^? concentration, the mass of steel blocks in oil decreases and the contents of Fe, Zn, Al, and Mg ions in oil increase significantly. Therefore, HCN in CBAO is the main cause of screw oil expeller corrosion in BAO processing and benzoic acid is the secondary cause. Practical Applications: The corrosion behavior of CBAO not only damages the integrity of the screw oil expeller but also increases the dissolution of toxic metals from the components into oil. The study of corrosion has practical value in taking effective measures, such as detoxification before pressing and addition of natural inhibitors, to reduce corrosion and ensure the quality of CBAO. Corrosion study provides the basis for the selection of steel materials of screw oil expeller.