Biodegradation of hexachlorocyclohexane (HCH) by microorganisms

The organochlorine pesticide Lindane is the -isomer of hexachlorocyclohexane (HCH). Technical grade Lindane contains a mixture of HCH isomers which include not only -HCH, but also large amounts of predominantly -, - and -HCH. The physical properties and persistence of each isomer differ because of the different chlorine atom orientations on each molecule (axial or equatorial). However, all four isomers are considered toxic and recalcitrant worldwide pollutants. Biodegradation of HCH has been studied in soil, slurry and culture media but very little information exists on in situ bioremediation of the different isomers including Lindane itself, at full scale. Several soil microorganisms capable of degrading, and utilizing HCH as a carbon source, have been reported. In selected bacterial strains, the genes encoding the enzymes involved in the initial degradation of Lindane have been cloned, sequenced, expressed and the gene products characterized. HCH is biodegradable under both oxic and anoxic conditions, although mineralization is generally observed only in oxic systems. As is found for most organic compounds, HCH degradation in soil occurs at moderate temperatures and at near neutral pH. HCH biodegradation in soil has been reported at both low and high (saturated) moisture contents. Soil texture and organic matter appear to influence degradation presumably by sorption mechanisms and impact on moisture retention, bacterial growth and pH. Most studies report on the biodegradation of relatively low ( 500 mg/kg) concentrations of HCH in soil. Information on the effects of inorganic nutrients, organic carbon sources or other soil amendments is scattered and inconclusive. More in-depth assessments of amendment effects and evaluation of bioremediation protocols, on a large scale, using soil with high HCH concentrations, are needed.     

Toxicity and bioremediation of pesticides in agricultural soil

Pesticides are one of the persistent organic pollutants which are of concern due to their occurrence in various ecosystems. In nature, the pesticide residues are subjected to physical, chemical and biochemical degradation process, but because of its high stability and water solubility, the pesticide residues persist in the environment. Moreover, the prevailing environmental conditions like the soil characteristics also contribute for their persistence. Bioremediation is one of the options for the removal of pesticides from environment. One important uncertainty associated with the implementation of bioremediation is the low bioavailability of some of the pesticides in the heterogeneous subsurface environment. Bioavailability of a compound depends on numerous factors within the cells of microorganism like the transportation of susbstrate across cell membrane, enzymatic reactions, biosurfactant production etc. as well as environment conditions such as pH, temperature, availability of electron acceptor etc. Pesticides like dichlorodiphenyltrichloroethane (DDT), hexachlorocyclohexane (HCH), Endosulfan, benzene hexa chloride (BHC), Atrazine etc. are such ubiquitous compounds which persist in soil and sediments due to less bioavailability. The half life of such less bioavailable pesticides ranges from 100 to 200 days. Most of these residues get adsorbed to soil particles and thereby becomes unavailable to microbes. In this review, an attempt has been made to present a brief idea on ‘major limitations in pesticide biodegradation in soil’ highlighting a few studies.     

Quantitative analysis of polychlorinated biphenyls, organochlorine insecticides, polycyclic aromatic hydrocarbons, polychlorinated hydrocarbons and polynitrohydrocarbons in spiked samples of soil, water and plasma by selected-ion monitoring gas chromatography–mass spectrometry

A broad range of pollutants such as polycyclic aromatic hydrocarbons (PAHs), polychlorinated hydrocarbons (PCHs), polynitrohydrocarbons (PNHs), polychlorinated biphenyls (PCBs) and organochlorine (OCs) insecticides were simultaneously analyzed in spiked soil, water or plasma samples by using gas chromatography–mass spectrometry (GC–MS). Water and plasma samples containing the pollutants were extracted by a solid-phase extraction (SPE) method using florisil columns. The soil samples, fortified with the toxicants, were extracted with water, methanol or dichloromethane (DCM). The water extract was processed by the SPE method. The methanol and DCM samples were dried, dissolved in acetonitrile and subjected to the SPE extraction. The extracted samples were analyzed by GC–MS programmed to monitor selected ions. The deuterium labelled compounds were used as the internal standards. The chromatographic profile of total ions indicated complete separation of some compounds such as isophorone, naphthalene, all PCBs, most OC insecticides and PNHs; high M_r PAHs and some PCHs were partially or incompletely separated. The chromatographic profile of individual ion indicated good separation of each ion. The minimum detection limit ranged from 1 to 4 pg injected when 1 or 2 ions were monitored or from 20 to 200 pg injected when 20 ions were monitored. The SPE method that provided 60–105% recovery of pollutants from water samples, provided only 2–60% recovery from plasma samples. This may be due to the binding of pollutants to plasma proteins. Water recovered 1–30%, while methanol or DCM recovered 65–100% of the pollutants added to the soil samples. The use of internal standards corrected for the loss of pollutants from plasma or soil.     

Analysis of glucosinolates, isothiocyanates, and amine degradation products in vegetable extracts and blood plasma by LC-MS/MS

Dietary glucosinolates are under intensive investigation as precursors of cancer-preventive isothiocyanates. Quantitation of the dose and bioavailability of glucosinolates and isothiocyanates requires a comprehensive analysis of the major dietary glucosinolates, isothiocyanates, and related metabolites. We report a liquid chromatography with tandem mass spectrometric detection (LC-MS/MS) analytical method for the comprehensive analysis of the seven major dietary glucosinolates, related isothiocyanates, and putative amine degradation products. The parent glucosinolates were sinigrin, gluconapin, progoitrin, glucoiberin, glucoraphanin, glucoalyssin, and gluconasturtiin. The LC-MS/MS analysis method for these compounds was developed and validated; a standard addition analysis protocol was used generally to avoid the requirement for stable isotopic standards. Where stable isotopic standards were available, internal standardization with these gave estimates in agreement with those obtained by the standard addition analysis protocol. For glucosinolates, negative ion electrospray LC-MS/MS analysis was performed. Isothiocyanates and amines were prederivatized to the corresponding thiourea and N-acetamides, respectively, and were quantified by positive ion electrospray LC-MS/MS. The limits of detection were 0.5-2 pmol; the recoveries for glucosinolates, isothiocyanates, and amines were 85-90%, 50-85%, and 60-70%, respectively; and the intra- and interbatch coefficients of variation were 1-4% and 3-10%, respectively. These methods provide facile access to comprehensive analytical data on the major dietary glucosinolates and related metabolites to quantify inputs and metabolic formation of these compounds in cancer prevention and related studies.     

Studies of Enantiomeric Degradation of the Triazole Fungicide Hexaconazole in Tomato,Cucumber, and Field Soil by Chiral Liquid Chromatography–Tandem Mass Spectrometry

Chiral pesticide enantiomers often show different bioactivity and toxicity; however, this property is usually ignored when evaluating their environmental and public health risks. Hexaconazole is a chiral fungicide used on a variety of crops for the control of many fungal diseases. This use provides opportunities for the pollution of food and soil. In this study, a sensitive and convenient chiral liquid chromatography coupled with tandem mass spectrometry (LC‐MS/MS) method was developed and validated for measuring hexaconazole enantiomers in tomato, cucumber, and soil. Separation was by a reversed‐phase Chiralcel OD‐RH column, under isocratic conditions using a mixture of acetonitrile‐2 mM ammonium acetate in water (60/40, v/v) as the mobile phase at a flow rate of 0.4 mL/min. Parameters including the matrix effect, linearity, precision, accuracy and stability were undertaken. Then the proposed method was successfully applied to investigate the possible enantioselective degradation of rac‐hexaconazole in plants (tomato and cucumber) and soil under field conditions. The degradation of the two enantiomers of hexaconazole proved to be enantioselective and dependent on the media: The (+)‐enantiomer showed a faster degradation in plants, while the (?)‐enantiomer dissipated faster than the (+)‐form in field soil, resulting in relative enrichment of the opposite enantiomer. The results of this work demonstrate that both the environmental media and environmental conditions influenced the direction and rate of enantioselective degradation of hexaconazole. Chirality 25:160–169, 2013. © 2013 Wiley Periodicals, Inc.     

Effect of Surfactant Tween 80 on the Anaerobic Degradation and Desorption of HCHs and DDX in Aged Soil under Saturated Condition with Low Liquid/Solid Ratio

The application of surfactant Tween 80 was investigated to accelerate the anaerobic degradation of HCHs (α-, β-, γ- and δ-hexachlorocyclohexane) and DDX (p,p′-DDT, o,p′-DDT, p,p′-DDE and p,p′-DDD) in aged soil from a former organochlorine pesticide manufacturing plant under saturated condition with low liquid/solid ratio (liquid/solid ratio = 0.50). The surfactant Tween 80 did not facilitate the degradation of HCHs and DDX in the soil used in this experiment. Subsequent desorption experiment results also showed that the surfactant Tween 80 did not increase the pollutant desorption from the soil. The results in this study are not in accordance with the results reported in previous literature. This difference might be due to the fact that the soils used in this experiment were polluted by HCHs and DDX for more than 20 years, and soil aging reduced the desorption of HCHs and DDX in soil. Furthermore, the surfactants might be adsorbed by soils in low liquid/solid ratio condition.     

Optimization of microwave-assisted extraction followed by solid phase micro extraction and gas chromatography-mass spectrometry detection for the assay of some semi volatile organic pollutants in sebum

Methodology using MAE/SPME/GC-MS is being pursued for the analysis of organic pollutants in sebum. The microwave-assisted extraction (MAE) of standards of semi volatile organic pollutants from sebum was optimized. All compounds were extracted from sebum with recoveries analyzed by GC/MS ranging from 94% to 100% under the optimum MAE conditions: 10mL acetone-hexane (2:1), 60 degrees C, and 10 min microwave heating. To improve the detection limits a SPME procedure was optimized. Linearity ranged from 0.70 ppb to 25 ppb. R.S.D. were in the range of 1-23% for the SPME step. Preliminary real samples were analyzed and a range of compounds was detected. The optimized MAE/SPME/GC-MS methodology promises to be useful for different applications.     

杀虫剂类POPs对土壤中微生物群落多样性的影响

农药类持久性有机污染物(POPs)如DDT和HCH在我国2 0世纪5 0年代到80年代曾广泛使用,在停止使用2 0 a后,在土壤中仍然可以检测到DDT和HCH的残留。利用BIOL OG微平板研究土壤微生物群落功能多样性,意在反映有机氯杀虫剂类POPs对土壤微生物群落多样性的影响。结果表明,加了HCH后土壤微生物群落的颜色平均变化值(AWCD)的变化速度和最终能达到的AWCD值要高于空白土壤,并且随着农药浓度的加大,AWCD值的变化速率也越来越快,最终能达到的最大值也呈比例增大。加了DDT后的土壤与空白土壤的AWCD变化速度和程度相差不大。方差分析结果表明:空白土壤、HCH0 .5mg/kg、HCH1.5 mg/kg各处理间土壤的AWCD值有显著性差异(p<0 .0 1) ,空白土壤、DDT0 .5 m g/kg、DDT1.5 m g/kg各处理间土壤的AWCD值达不到显著性差异的水平(p>0 .0 5 ) ,表层土壤的AWCD值要高于第2层土壤(p<0 .0 1)。从多样性指数的变化来看,当加入到土壤中的DDT和HCH含量稍低时,微生物会利用农药为碳源进行分解作用,从而刺激了微生物的生长,这时表现出丰富度、均匀性和多样性都呈增长趋势。但当农药的浓度进一步加大时,反而会抑制某些种的微生物生长,另外一些种则对加入到土壤中的农药有一定的耐受性,从而表现出群落的均匀性下降,而丰富度升高。在相同施用浓     

Changes in the bacterial community and lin genes diversity during biostimulation of indigenous bacterial community of hexachlorocyclohexane (HCH) dumpsite soil

In this study hexachlorocyclohexane (HCH) contaminated soil (with HCH level 84 g/kg of soil) from HCH dumpsite (Ummari village, Lucknow, India) was used to demonstrate biostimulation approach for HCH bioremediation. Different nutrients (molasses and ammonium phosphate) were used in different pits having contaminated soil to stimulate the indigenous microbial community. There was a substantial reduction in the total HCH content of the soil in 12 months long experiment. Maximum reduction was seen in the pit that received a combination of molasses and ammonium phosphate. A change in the microbial community concomitant with degradation of HCH was observed. Sphingomonads, which are known degraders of HCH, were found to dominate the experimental pits. Moreover changes in linA and linB gene (primary genes involved in HCH degradation) diversity and number were also seen as revealed by T-RFLP and RT-PCR respectively. The study suggests the prospects of biostimulation in decontaminating soils heavily contaminated with HCH.     

Prenatal diagnosis for organic acid disorders using two mass spectrometric methods, gas chromatography mass spectrometry and tandem mass spectrometry

We performed prenatal diagnosis of organic acid disorders using two mass spectrometric methods; gas chromatography mass spectrometry (GC/MS) and tandem mass spectrometry (ESI/MS/MS). Of 28 cases whose amniotic fluid was tested, 11 cases were diagnosed as "affected". All cases whose samples were diagnosed as "unaffected" were confirmed to have no symptoms or abnormalities in urinary organic acid analysis after birth. Of the 11 "affected" cases, two cases were missed by ESI/MS/MS but not by GC/MS. When the stability of metabolites in amniotic fluid was checked, it was found that acylcarnitines degraded in one week at room temperature, whereas organic acids such as methylmalonate or methylcitrate were stable for at least 14 days. Prenatal diagnosis by analysis using simultaneous two or more methods may be more reliable, though attention should be paid to sample transportation conditions.     

Compound-Specific Stable Isotope Analysis: Implications in Hexachlorocyclohexane in-vitro and Field Assessment

Assessment of biotic and abiotic degradation reactions by studying the variation in stable isotopic compositions of organic contaminants in contaminated soil and aquifers is being increasingly considered during the last two decades with development of Compound specific stable isotope analysis (CSIA) technique. CSIA has been recognized as a potential tool for evaluating both qualitative and quantitative degradation with measurement of shifts in isotope ratios of contaminants and their degradation products as its basis. Amongst a wide variety of environmental pollutants including monoaromatics, chlorinated ethenes and benzenes etc., it is only recently that its efficacy is being tested for assessing biodegradation of a noxious pollutant namely hexachlorocyclohexane (HCH), by pure microbial cultures as well as directly at the field site. Anticipating the increase in demand of this technique for monitoring the microbial degradation along with natural attenuation, this review highlights the basic problems associated with HCH contamination emphasizing the applicability of emerging CSIA technique to absolve the major bottlenecks in assessment of HCH. To this end, the review also provides a brief overview of this technique with summarizing the recent revelations put forward by both in vitro and in situ studies by CSIA in monitoring HCH biodegradation.     

Isolation of hexachlorocyclohexane-degrading Sphingomonas sp. by dehalogenase assay and characterization of genes involved in gamma-HCH degradation

Aim: To screen and identify bacteria from contaminated soil samples which can degrade hexachlorocyclohexane (HCH)‐isomers based on dechlorinase enzyme activity and characterize genes and metabolites. Methods and Results: Dechlorinase activity assays were used to screen bacteria from contaminated soil samples for HCH‐degrading activity. A bacterium able to grow on α‐, β‐, γ‐ and δ‐HCH as the sole carbon and energy source was identified. This bacterium was a novel species belonging to the Sphingomonas and harbour linABCDE genes similar to those found in other HCH degraders. γ‐Pentachlorocyclohexene 1,2,4‐trichlorobenzene and chlorohydroquinone were identified as metabolites. Conclusions: The study demonstrates that HCH‐degrading bacteria can be identified from large environmental sample‐based dehalogenase enzyme assay. This kind of screening is more advantageous compared to selective enrichment as it is specific and rapid and can be performed in a high‐throughput manner to screen bacteria for chlorinated compounds. Significance and Impact of the Study: The chlorinated pesticide HCH is a persistent and toxic environmental pollutant which needs to be remediated. Isolation of diverse bacterial species capable of degrading all the isomers of HCH will help in large‐scale bioremediation in various parts of the world.     

Protocol for determining bioavailability and biokinetics of organic pollutants in dispersed, compacted and intact soil systems to enhance in situ bioremediation

The development of effective in situ and on-site bioremediation technologies can facilitate the cleanup of chemically-contaminated soil sites. Knowledge of biodegradation kinetics and the bioavailability of organic pollutants can facilitate decisions on the efficacy of in situ and on-site bioremediation of contaminated soils and determine the attainable treatment end-points. Two kinds of compounds have been studied: (1) phenol and alkyl phenols, which represent hydrophilic compounds, exhibiting high water solubility and moderate to low soil partitioning; and (2) polycyclic aromatic hydrocarbons which are hydrophobic compounds with low water solubility and exhibit significant partitioning in soil organic carbon. Representative data are given for phenol and naphthalene. The results provide support for a systematic multi-level protocol using soil slurry, wafer and porous tube or column reactors to determine the biokinetic parameters for toxic organic pollutants. Insights into bioremediation rates of soil contaminants in compact soil systems can be attained using the protocol. Received 04 December 1995/ Accepted in revised form 31 January 1997     

Study on the maltooligosaccharide composition of mucilage samples collected along the northern Adriatic coast

The mucilage phenomenon, a sporadic but massive accumulation of gelatinous material, can cause serious damage to the tourism and fishing industries along the Adriatic coast. Mucilage is presently thought to be the result of the aggregation of dissolved organic matter (DOM) into particulate organic matter (POM). Three principal classes of compounds have been identified in organic matter by spectrometric determination: carbohydrates, proteins and lipids. Carbohydrates are suspected to play a role in the first steps of DOM aggregation. Despite its importance in understanding the processes leading to mucilage formation, our present knowledge of the composition of the mucilage carbohydrate fraction is incomplete. Due to its high sensitivity and specificity, liquid chromatography coupled with electrospray-ionization tandem mass spectrometry (LC-ESIMS/MS) is gaining an increasing importance as a powerful technique for carbohydrate purification and characterization in complex samples. In this work, LC-ESIMS/MS is proposed as a useful method for the investigation of the oligosaccharide content in mucilage samples. The approach was applied using 3-7 unit maltooligosaccharides as reference compounds. The composition of the investigated mucilage sample was further investigated combining LC-ESIMS/MS with classic approaches, such as spectroscopic techniques and liquid chromatography coupled with the refractory index LC-RI.     

Mineralization of hexachlorocyclohexane in soil during solid-phase bioremediation

Soil containing hexachlorocyclohexane (HCH) was spiked with ¹⁴C--HCH and then subjected to bioremediation in bench-scale microcosms to determine the rate and extent of mineralization of the ¹⁴C-labeled HCH to ¹⁴CO₂. The soil was treated using two different DARAMEND amendments, D6386 and D6390. The amendments were previously found to enhance natural HCH bioremediation as determined by measuring the disappearance of parent compounds under either strictly oxic conditions (D6386), or cycled anoxic/oxic conditions (D6390). Within 80 days of the initiation of treatment, mineralization was observed in all of the strictly oxic microcosms. However, mineralization was negligible in the cycled anoxic/oxic microcosms throughout the 275-day study, even after cycling was ceased at 84 days and although significant removal (up to 51%) of indigenous -HCH (146 mg/kg) was detected by GC with electron capture detector. Of the amended, strictly oxic treatments, only one, in which 47% of the spiked ¹⁴C-HCH was recovered as ¹⁴CO₂, enhanced mineralization compared with an unamended treatment (in which 34% recovery was measured). Other oxic treatments involving higher amendment application rates or auxiliary carbon sources were inhibitory to mineralization. Thus, although HCH degradation occurs during the application of either oxic or cycled anoxic/oxic DARAMEND treatments, mineralization of -HCH may be inhibited depending on the amendment and treatment protocol.     

Bioremediation of hexachlorocyclohexane (HCH) in soil using spent mushroom compost of Pleurotus ostreatus

Abstract

Hexachlorocyclohexane (HCH), a highly chlorinated pesticide, was used worldwide in the 1950s and 1960s. HCH toxic residues are still detected in environmental compartments. Thus, effective, viable and eco-friendly strategy is required for its remediation. In this study, degradation of four HCH isomers was evaluated by amending contaminated soil using four treatments of spent mushroom compost (SMC) of Pleurotus ostraetus. The soil was incubated for 5 weeks and was sampled every seven days. Quantitative attenuation in HCH was calculated using gas chromatography–electron capture detector (GC-ECD) and metabolite was identified using gas chromatography–mass selective detector (GC-MSD). Maximum reduction 58%, 26%, 45%, and 64% for α-, β-, γ- and δ-HCH isomers, respectively, using SMC and soil (both unsterilized) showed that this treatment was the best for bioremediation of HCH in soil. However, when one of the factors, either soil or SMC, was sterilized, a significant reduction in HCH degradation was noticed. The second most reduction of isomers was seen during treatment where unsterilized SMC was added in sterilized soil followed by treatment where SMC was sterilized but soil was not. Abiotic control did not remove any significant quantities of HCH. Simple first-order (SFO) kinetic confirmed that SMC reduced the half-live manifolds as compared to biotic control. Only one metabolite δ-PCCH was identified during the course of study.     

Evaluation of a protocol for metabolic profiling studies on human blood plasma by combined ultra-performance liquid chromatography/mass spectrometry: From extraction to data analysis

The investigation presented here describes a protocol designed to perform high-throughput metabolic profiling analysis on human blood plasma by ultra-performance liquid chromatography/mass spectrometry (UPLC/MS). To address whether a previous extraction protocol for gas chromatography (GC)/MS-based metabolic profiling of plasma could be used for UPLC/MS-based analysis, the original protocol was compared with similar methods for extraction of low-molecular-weight compounds from plasma via protein precipitation. Differences between extraction methods could be observed, but the previously published extraction method was considered the best. UPLC columns with three different stationary phases (C8, C18, and phenyl) were used in identical experimental runs consisting of a total of 60 injections of extracted male and female plasma samples. The C8 column was determined to be the best for metabolic profiling analysis on plasma. The acquired UPLC/MS data of extracted male and female plasma samples was subjected to principal component analysis (PCA) and orthogonal projections to latent structures discriminant analysis (OPLS-DA). Furthermore, a strategy for compound identification was applied here, demonstrating the strength of high-mass-accuracy time-of-flight (TOF)/MS analysis in metabolic profiling.     

Specific method for determination of gefitinib in human plasma, mouse plasma and tissues using high performance liquid chromatography coupled to tandem mass spectrometry

A rapid, sensitive and specific method was developed and validated using liquid chromatography-tandem mass spectrometry (LC/MS/MS) for determination of gefitinib in human plasma and mouse plasma and tissue. Sample preparation involved a single protein precipitation step by the addition of 0.1 mL of plasma or a 200 mg/mL tissue homogenate diluted 1/10 in human plasma with 0.3 mL acetonitrile. Separation of the compounds of interest, including the internal standard (d8)-gefitinib, was achieved on a Waters X-Terra C18 (50 mm x 2.1 mm i.d., 3.5 microm) analytical column using a mobile phase consisting of acetonitrile-water (70:30, v/v) containing 0.1% formic acid and isocratic flow at 0.15 mL/min for 3 min. The analytes were monitored by tandem mass spectrometry with electrospray positive ionization. Linear calibration curves were generated over the range of 1-1000 ng/mL for the human plasma samples and 5-1000 ng/mL for mouse plasma and tissue samples with values for the coefficient of determination of > 0.99. The values for both within- and between-day precision and accuracy were well within the generally accepted criteria for analytical methods (< 15%). This method was subsequently used to measure concentrations of gefitinib in mice following administration of a single dose of 150 mg/kg intraperitoneally and in cancer patients receiving an oral daily dose of 250 mg.     

Polynuclear Aromatic Hydrocarbons (PAHs) in fish from the Red Sea Coast of Yemen

A detailed analytical study using combined normal phase high pressure liquid chromatography (HPLC), gas chromatography (GC) and gas chromatography/mass spectrometry (GC/MS) of Polynuclear Aromatic Hydrocarbons (PAHs) in fish from the Red Sea was undertaken. This investigation involves a preliminary assessment of the sixteen parent compounds issued by the U.S. Environmental Protection Agency(EPA). The study revealed measurable levels of Σ PAHs (the sum of three to five or six ring parent compounds) (49.2 ng g⁻¹ dry weight) and total PAHs (all PAH detected) (422.1 ng g⁻¹ dry weight) in edible muscle of fishes collected from the Red Sea. These concentrations are within the range of values reported for other comparable regions of the world. Mean concentrations for individual parent PAH in fish muscles were; naphthalene 19.5, biphenyl 4.6, acenaphthylene 1.0, acenaphthene 1.2, fluorene 5.5, phenanthrene 14.0, anthracene 0.8, fluoranthene 1.5, pyrene 1.8, benz(a)anthracene 0.4, chrysene 1.9, benzo(b)fluoranthene 0.5, benzo(k)fluoranthene 0.5, benzo(e)pyrene 0.9, benzo(a)pyrene 0.5, perylene 0.2, and indeno(1,2,3-cd)pyrene 0.1 ng g⁻¹ dry weight respectively. The Red Sea fish extracts exhibit the low molecular weight aromatics as well as the discernible alkyl-substituted species of naphthalene, fluorene, phenanthrene and dibenzothiophene. Thus, it was suggested that the most probable source of PAHs is oil contamination originating from spillages and/or heavy ship traffic. It was concluded that the presence of PAHs in the fish muscles is not responsible for the reported fish kill phenomenon. However, the high concentrations of carcinogenic chrysene encountered in these fishes should be considered seriously as it is hazardous to human health. Based on fish consumption by Yemeni‘s population it was calculated that the daily intake of total carcinogens were 0.15 μg/person/day. This revised version was published online in August 2006 with corrections to the Cover Date.     

Phytochemical Content,Antidiabetic, Anticholinergic,and Antioxidant Activities of Endemic Lecokia cretica Extracts

The aim of this work was to investigate the enzyme inhibition, antioxidant activity, and phenolic compounds of Lecokia cretica (Lam .) DC. Acetylcholinesterase (AChE), butyrylcholinesterase (BChE), and α‐glycosidase enzymes were strongly inhibited by the L. cretica extracts. IC₅₀ values for the three enzymes were found as 3.21 mg/mL, 2.1 mg/mL, and 2.07 mg/mL, respectively. Antioxidant activities were examined in both aqueous and ethanol (EtOH) extracts using CUPRAC, FRAP, and DPPH method. Also, the phenolic compounds of the endemic plant were identified and quantified by using HPLC/MS/MS. According to the results, the extracts have remarkable antioxidant activities. The most abundant phenolic acids of L. cretica in EtOH extract were determined as quinic acid (12.76 mg/kg of crude extract), chlorogenic acid (3.39 mg/kg), and malic acid (2.38 mg/kg).