Aliphatic Chemicals Research Articles

Silver Nanoparticles Loaded with Bark Extract of Sterculia foetida: Their Green Synthesis, Characterization, and Anti-bacterial Activity Evaluation

Sterculia foetida is a subject of interest in many scientific fields as researchers look for novel treatments because of its varied medicinal qualities and chemical richness. Terpenoids are aromatic and aliphatic chemicals with anti-bacterial properties and can prevent free radical damage. They are present in S. foetida extract. Moreover, it possesses immunomodulatory, hepatoprotective, antiviral, antioxidant, anti-inflammatory, and antifungal properties. This work aims to green synthesize, characterize, and evaluate the anti-bacterial activity of Sterculia foetida bark extract-loaded silver nanoparticles. Chemicals like Methanol, Petroleum Ether, and water have been used to extract the phytoconstituents from the plant bark. AgNO3 and Silver have been used to synthesize the nanoparticles. Instruments like ATR-IR Spectrophotometer, UV- spectrophotometer, DLS, and SEM instruments have been used to characterize the nanoparticles. Bacterial strains like Staphylococcus aureus (ATCC-6538), Escherichia coli (ATCC 25922), saline water, AMX30, swab stick, inoculation loop, susceptibility scale have been used for studying the anti-bacterial activity. DLS and zeta potential analysis demonstrated the creation of stable nanoparticles with a particle size of 79 nm. The anti-bacterial activity of AgNPs with the methanolic bark extract showed significant anti-bacterial activity compared to the standard marketed drug AMX30. The highest zone of inhibition was observed against gram-positive bacteria S.aureus (1.68 cm) and gram-negative bacteria E.coli (1.74 cm), respectively, at 500 μg/ml concentration. The study concludes that greenly synthesized S. foetida bark extract containing nanoparticles is a potential anti-bacterial agent, especially against gram-negative bacteria. Further, in vivo studies are needed to establish its potential. Keywords: Sterculia foetida, Green synthesis, Silver Nanoparticles (AgNPs), ATR-IR, DLS, SEM, Zeta-potential, Anti-bacterial.

Breaking down lignin in gamma-valerolactone: advances into a bioelectrorefinery

ABSTRACT This study builds upon our experience with electrocatalyzed dearomatization of lignin in aqueous systems, which has shown to produce sodium levulinate, sodium 4-hydroxyvalerate, sodium acetate, and sodium formate as major products. Here, we extend this investigation by exploring a water/γ-valerolactone (GVL) solvent system for electrochemical depolymerization and dearomatization of lignin, using Na2CO3 as electrolyte. GVL, derived from biomass, has frequently been employed for biomass treatment, notably in the Organosolv process. Consequently, various biorefinery strategies have emerged utilizing GVL as a green platform, primarily for its potential in delignifying lignocellulosic biomass when combined with water and dilute acid. This study proposes electrochemical depolymerization of lignin in GVL as a step toward the concept of a bioelectrorefinery, aiming to convert lignin into aliphatic organic chemicals. Consistent with our prior work in aqueous systems, applying a current of −100 mA over 8 h yielded sodium levulinate, sodium 4-hydroxyvalerate, sodium acetate, and sodium formate. Confirmation was provided by liquid chromatography electrospray ionization high-resolution mass spectrometry, nuclear magnetic resonance, and infrared spectroscopy. These findings advance our understanding of GVL as a biomass-based platform, highlighting its potential not only for biomass treatment but also as a medium for converting lignin into valuable aliphatic chemicals.

Phytochemical Mapping to Comprehend the Bioactivity of Bixa orellana L.

Abstract: The "lipstick tree" is another name for the ornamental plant Bixa orellana L., which is indigenous to South and Central America, the Caribbean Islands, and other regions of Asia. The plant, also known as "Sinduri" or "Latkan," is utilized in India's food, dye, cosmetics, and traditional medicine sectors. Commercially, the plant seeds are significant because they yield bixin, a carotenoid that colours dairy products and is used to manufacture "sindur" and "lipstick." The primary substances present in various portions of this plant include carotenoids, apo carotenoids, terpenes, terpenoids, sterols, and aliphatic chemicals. The various plant parts exhibit a variety of possible health advantages, including antibacterial, anti-hyperglycemic, anti-histaminic, anti-diarrheal, anti-cancer, anti-inflammatory, and antioxidant qualities. The current study provides an overview of Bixa orellana L.

OLFACTORY RESPONSES OF AULACOPHORA FOVEICOLLIS LUCAS – AN ECOLOGICALLY IMPORTANT PEST - FROM WEST BENGAL, INDIA

Pumpkin, Cucurbita maxima, is severely harmed by Aulacophora foveicollis Lucas (Coleoptera: Chrysomelidae), as a major insect pest of the plant. Based on Scanning electron microscopic analysis, compared to mechanosensilla, prevalence of antennal olfactory sensilla, was observed. The number of olfactory sensilla in the circumferential band of IXth antennal segment was higher in female species. Stimulation of the sensilla present on the antennae of A. foveicollis was analyzed by electroantennogram (EAG) at four different concentrations viz. 10.0, 5.0, 1.0, and 0.1 mg/ml in both sexes. The male species displayed greatest peak amplitude at 5mg/mL for heneicosane, whereas the female species displayed maximum peak amplitude at 10.0 mg/mL for 2-methyl phenol followed by 5.0 mg/mL for 1,4-dimethoxybenzene. However, pooled EAG data revealed that GLV elicited the strongest reactions, followed by aliphatic chemicals, oxygenated monoterpenes, hydrocarbon monoterpenes, and sesqueterpenes. These findings univocally shows that the pest's antennal responses clearly displayed sexual dimorphism.

DEVELOPMENT AND EVALUATION OF TOPICAL LIPOSOMAL GEL OF LEMON OIL AND ORANGE OIL FOR SYNERGISTIC EFFECT TO ENHANCE SKIN BEAUTY

Background: In the development of cosmeceuticals for skin care, nanotechnology is critical. Essential oils are complex mixtures of numerous derivatives, including terpenoids, aliphatic chemicals, and phenol derived compounds. Due to their numerous qualities such as virucidal, bactericidal, fungicidal, local anaesthetic, anti inflammatory, analgesic, and so on, they have been widely utilized for a long time. Essential oils are chosen over synthetically manufactured medications because they are safer for the skin. To improve the penetration of essential oils via the skin, novel nanosystems such as liposomes, niosomes, nanoemulsions, solid lipid nanoparticles, dendrimers, and nanospheres are used. These nanocarriers allow for controlled release of natural components while also improving their stability. Furthermore, nanotechnology-based skin care products have a pleasing appearance.

Addressing Short-Chain PFAS Contamination in Water with Nanofibrous Adsorbent/Filter Material from Electrospinning.

ConspectusPer- and polyfluoroalkyl substances (PFAS) stand for thousands of fully/highly fluorinated aliphatic chemicals, which have been widely manufactured and used in consumer products. Due to easy deprotonation of headgroups and high strength of C-F bonds in their molecules, PFAS are water-soluble and extremely stable in our environment. Significant accumulation of PFAS in water bodies started as early as the beginning of their production in the late 1940s. Recent studies confirmed the occurrence and accumulation of PFAS in all human tissues as well as their harmful health effects. Upon environmental regulations and health advisories, the PFAS industry quickly shifted to short-chain PFAS, e.g., hexafluoropropylene oxide dimer acid and its ammonium salt (GenX), to replace traditional long-chain PFAS. According to the recent fact sheet by the U.S. Environmental Protection Agency (EPA) in October 2021, however, GenX turned out to be more toxic than people originally thought and has shown health effects on liver, kidney, immune system, and so forth upon animal tests. On June 15, 2022, the EPA released the final health advisory for GenX, which is just 10 ppt. Thus, there is an urgent need of novel adsorbents for highly effective GenX remediation from water.Until now, there have been just a few reports on the remediation of GenX from water despite its popular use. In this Account, we reviewed current technology on PFAS remediation and illustrated our research on how to use polyacrylonitrile (PAN), a common and economic polymer for water filtration, in the form of nanofibrous membrane with handy chemical surface modification to develop innovative adsorbent/filter material for effective and scalable GenX remediation from water at the largest HBCU in the nation together with opportunities and challenges that are associated with this research. For the first time, we compared the GenX removal capability of electrospun PAN (ESPAN) nanofibrous membrane and amidoxime surface-functionalized ESPAN (ASFPAN) nanofibrous membrane. By modifying the surface of ESPAN nanofibrous membrane and introducing amidoxime functional group, the maximum GenX removal capacity (weight-normalized GenX removal) was almost doubled and reached ∼0.6 mmol/g at pH 4, which is higher than or comparable to that of most reported adsorbents for GenX removal. Hydrophobic interaction and dipole-dipole interaction could be the GenX adsorption mechanism on the ESPAN nanofibrous membrane while surface hydrophilicity and electrostatic interaction play major roles in GenX adsorption on the ASFPAN nanofibrous membrane. Our research shed light on understanding the GenX adsorption mechanism and developing new adsorbent/filter materials for practical short-chain PFAS remediation from water.

Tinospora Cordifolia (Gurjo) and Its Potential Role to Combat with COVID-19: A Review

Plant-based medicines have been used to maintain health and treat disease since the dawn of civilization. The present review focuses on studies that have been done on the characteristics of T. cordifolia to see if they may be used to combat COVID-19 Pandemic. During the review, various methodological activities were involved from developing the review concept, reviewing the articles, analyzing them, and finally writing the paper. The result shows that herbal medicine is used by 80% of the world’s population for some aspect of basic health care. T. cordifolia is a medicinal plant which is a useful home remedy for chronic fever, as it calms burning sensations and boosts energy and hunger. Glycosides, alkaloids, steroids, diterpenoid lactones, sesquiterpenoid, and aliphatic chemicals are the most common substances found in this herb. Scientific research on this medicine could lead to a novel method as well as knowledge into COVID-19 prevention, management, and the development of a new therapeutic component.

EPA's detection methods, the drinking water treatability database, and innovative technologies for PFAS remediation

AbstractPer‐ and polyfluoroalkyl substances (PFAS) are a large group of highly fluorinated, aliphatic chemicals detected throughout the environment, including in human serum. Several regulatory milestones have been achieved in the United States for these environmentally toxic chemicals linked to health problems in humans, the latest one being the US Environmental Protection Agency's (EPA's) PFAS Strategic Roadmap necessitating detection and remediation of PFAS. This article, in addition to briefly discussing these regulatory milestones, evaluates the EPA's detection methods for PFAS including EPA Methods 533, 537.1, and 8327 and other methods currently under development such as the total organic fluorine (TOF) and total organic precursor (TOP) methods. The article also mentions the methods used by other federal agencies for PFAS quantitation. The EPA's drinking water treatability database (TDB) is also described along with the advantages and challenges of the effective treatment methods for PFAS. Most of these treatment methods in the EPA's drinking water TDB face the challenge of disposing wastes containing PFAS, an issue not faced by innovative technologies, and some of these innovative technologies are also discussed. This article will help to understand the current status on the detection and remediation technologies for PFAS treatment in soil and water. It is imperative to have these technologies ready to assist with the remediation objectives in the PFAS Strategic Roadmap.

Investigation the impact of using the recess air bio-filter (TBAB) with integrated system of a cyclic 2-recess adsorption/desorption unit for treatment of squander gas streams

In the chemical industry, fluctuations in influent concentrations and shifts in the composition of waste air make biofiltration a challenging technique. As a possible solution to the constraints of biofiltration technology, this research designs and implements an integrated system that includes a cyclic 2-bed adsorption/desorption unit and a trickling bed air biofilter (TBAB). The study's major goal was to keep the TBAB volatile organic compound (VOC) degradation performance stable and consistent over time. The studies were conducted on different TBABs with a single VOC exchange and a biomass control of periodic backwashing. Solvents that are routinely used in paint booths were examined as VOCs. Two aromatic chemicals (styrene and toluene) were investigated, as well as two aliphatic chemicals (methyl ethyl ketone (MEK) and methyl isobutyl ketone) (MIBK). While the production process rotated, our study duplicated VOC emission rotation in certain chemical sectors. When VOCs were switched to aromatics, the biofilter required an apparent re-acclimation period, according to the results. The second phase looked at two different combinations of these VOCs in two separate TBAB trains with a step change in influent concentration. In the third phase, the buffering performance of a cyclic 2-bed adsorption unit was tested for a feeding composition based on an EPA industrial emission report under a square wave of fluctuating conditions. The VOC mixture was treated in the fourth step with an integrated system that includes two cyclic adsorption/desorption beds as well as TBAB. When compared to the control unit, the integrated system was able to achieve high steady performance, according to the studies' findings. Lastly, researchers looked at the microbial communities of the biofilters employed in the VOC interchange and VOC mixing studies. The interchange of VOCs demonstrated a steady transition in microbial diversity. The community structure of VOC mixes demonstrated a significant degree of independence from the component content.

Superhydrophobic surface of glass powder derived from wet milling with aliphatic chemicals modification

Glass frit has emerged recently as a promising material for incorporation in adhesive of electronic components owing to its high sealing density, environmental stability and easy processing. This requires the glass surface to be hydrophobic to ensure high dispersity, grinding uniformity, and high-temperature sintering performance of the glass frit. However, the glass surface is usually hydrophilic. In this work, we developed a wet milling method to effectively produce hydrophobic glass powder by using aliphatic chemicals modification. We employed a series of aliphatic chemicals containing nucleophilic functional groups to prepare ultrafine lead aluminosilicate electronic glass powders. The nucleophilic substitution reaction of amino groups, carboxylic acid groups, hydroxyl groups and phosphoric acid groups reduces the hydroxyl content on the surface of the glass powder to 0.10 mg/m2, and generates steric hindrance and hydrophobicity (contact angle: 153.0°) through the long carbon chain. The obtained powder therefore shows a uniform particle size distribution, anti-agglomerated property, and maximum 25 °C lower hemispheric point temperature compared to powder prepared by conventional hydrophilic milling method. This work provides a versatile method to simultaneously control the structural and surface properties of glass powders at their formation stage.

Facile and Efficient Synthesis of Primary Amines via Reductive Amination over a Ni/Al2O3 Catalyst

The production of primary amines with high efficiency and selectivity employing appropriate catalysts is of central importance yet challenging. Here, we reported Ni nanoparticles supported on γ-Al2O3 as a highly active heterogeneous catalyst for the synthesis of primary amines through reductive amination in the presence of ammonia and hydrogen. The resulting Ni/Al2O3 catalyst exhibited outstanding performance for the selective reductive amination of carbonyl compounds (aldehydes and ketones) involving aromatic, branched, and purely aliphatic chemicals converted into their corresponding primary amines with excellent yields (87∼99%) under mild reaction conditions (100 °C and 2 MPa), which was attributed to the synergistic effect of strong metal–support interaction combined with medium acidic sites. In particular, the yield of primary amines for earth-abundant Ni catalysts was superior to that for precious metal catalysts (Ru, Rh, and Pd), suggesting that the Ni/Al2O3 catalyst could be a promising candidate for the industrial production of amines.

Exploring 3D structural influences of aliphatic and aromatic chemicals on α-cyclodextrin binding

Binding of solutes to macromolecules is often influenced by steric effects caused by the 3D structures of both binding partners. In this study, the 1:1 α-cyclodextrin (αCD) binding constants (Ka1) for 70 organic chemicals were determined to explore the solute-structural effects on the αCD binding. Ka1 was measured using a three-part partitioning system with either a headspace or a passive sampler serving as the reference phase. The Ka1 values ranged from 1.08 to 4.97 log units. The results show that longer linear aliphatic chemicals form more stable complexes than shorter ones, and that the position of the functional group has a strong influence on Ka1, even stronger than the type of the functional group. Comparison of linear and variously branched aliphatic chemicals indicates that having a sterically unhindered alkyl chain is favorable for binding. These results suggest that only one alkyl chain can enter the binding cavity. Relatively small aromatic chemicals such as 1,3-dichlorobenzene bind to αCD well, while larger ones like tetrachlorobenzene and 3-ring aromatic chemicals show only a weak interaction with αCD, which can be explained by cavity exclusion. The findings of this study help interpret cyclodextrin binding data and facilitate the understanding of binding processes to macromolecules.

Screening and prioritization of chemicals for REACH: The cumulative PBT Index model in QSARINS

The aim of this paper was to investigate baseline toxicity to rats and effect of exposure routes on toxicity in rats and fish. In this paper, 1588 industrial chemicals were selected to investigate baseline toxicity to rats. The results showed that rat toxicity varies around a constant for classified compounds or homologues. The toxic contributions of substituted functional groups have been calculated and alkanes were used as baseline toxicity. The toxic contributions, equal to toxic ratios (TR), show that small changes in chemical structure can result in different toxic effect in rat toxicity. However, this situation has not been observed in fish toxicity because the threshold of excess toxicity (e.g. log TR = 1) was too high to distinguish differences in toxicity. Very close critical body residues (CBRs) calculated from percentage of absorption and bioconcentration factors indicate that most of aliphatic chemicals may share the same modes of toxic action between rat and fish species. The high estimation error of bioconcentration factor calculated from computer programs for some compounds suggests that classification of excess toxicity should be based on the CBRs, rather than the TR because the TR is closely related to the exposure routes.

Investigation on baseline toxicity to rats based on aliphatic compounds and comparison with toxicity to fish: Effect of exposure routes on toxicity

The aim of this paper was to investigate baseline toxicity to rats and effect of exposure routes on toxicity in rats and fish. In this paper, 1588 industrial chemicals were selected to investigate baseline toxicity to rats. The results showed that rat toxicity varies around a constant for classified compounds or homologues. The toxic contributions of substituted functional groups have been calculated and alkanes were used as baseline toxicity. The toxic contributions, equal to toxic ratios (TR), show that small changes in chemical structure can result in different toxic effect in rat toxicity. However, this situation has not been observed in fish toxicity because the threshold of excess toxicity (e.g. log TR=1) was too high to distinguish differences in toxicity. Very close critical body residues (CBRs) calculated from percentage of absorption and bioconcentration factors indicate that most of aliphatic chemicals may share the same modes of toxic action between rat and fish species. The high estimation error of bioconcentration factor calculated from computer programs for some compounds suggests that classification of excess toxicity should be based on the CBRs, rather than the TR because the TR is closely related to the exposure routes.

FLUORESCENCE EVOLUTION OF LEACHATES DURING TREATMENT PROCESSES FROM TWO CONTRASTING LANDFILLS

Landfill leachates are composed of a complex mixture of organic matter, including a wide range of potentially fluorescent organic compounds. The fluorescence excitation–emission matrix (FEEM) of leachates during treatment processes is investigated. Particular attention is paid to the fluorescence evolution of leachates during treatment processes. Two typical types of landfill, landfill A (a direct municipal solid waste (MSW) landfill) and landfill B (disposal of bottom ashes from MSW incinerators), in a city in Southern China were selected. The results show that two characteristic and intense excitation–emission peaks located at Ex/Em = 310–330 nm/395–410 nm (peak α) and Ex/Em = 250–260 nm/450–460 nm (peak α′) are observed. As the aromatic chemicals, capable of emitting fluorescence, are more recalcitrant to biodegradation than aliphatic chemicals, enhancement of the dissolved organic carbon normalized fluorescence intensities is demonstrated during treatment processes of leachate A and leachate B. This is confirmed by the variation of ultraviolet absorptivity of leachates at 254 nm. Peak α′ and peak α are attributed to a mixture of xenobiotic organic compounds with low molecular weight and relatively stable aromatic fulvic‐like matters with high molecular weight, respectively. Humic substances are more resistant to biodegradation than xenobiotic organic compounds, so a significant reduction in the Iα′ /Iα values (fluorescence intensity ratios of peak α′ and peak α) of leachate A was observed during treatment processes. However, no evident variation for the Iα′ /Iα values of leachate B was found during treatment processes owing to the low concentrations of xenobiotic organic compounds in leachate B after incineration.

Utilization of Coal as a Source of Chemicals

Coal consists carbon-based substances can be used as a source of specialty aromatic chemicals and aliphatic chemicals. Four widespread processes allow for making chemicals from coals: gasification, liquefaction, direct conversion, and co-production of chemicals and fuels along with electricity. Coal is gasified to produce synthesis gas (syngas) with a gasifier which is then converted to parafinic liquid fuels and chemicals by Fischer-Trops synthesis. Liquid product from coal gasification mainly contains benzene, toluene, xylene (BTX), phenols, alkylphenols, and cresol. Methanol is made using coal or syngas with hydrogen and carbon monoxide in a 2 to 1 ratio. Coal-derived methanol has many preferable properties as it is free of sulfur and other impurities. Syngas from coal can be reformed to hydrogen. Ammonium sulfate from coal tar by pyrolysis can be converted to ammonia. The humus substances can be recovered from brown coal by alkali extraction.

Structure−Toxicity Relationships for the Effects to Tetrahymena pyriformis of Aliphatic, Carbonyl-Containing, α,β-Unsaturated Chemicals

Toxicity data for 82 aliphatic chemicals with an alpha,beta-unsaturated substructure were compiled. Toxicity was assessed in the 2-day Tetrahymena pyriformis population growth impairment assay. Toxic potency [log(IGC50(-1))] for most of these chemicals was in excess of baseline narcosis as quantified by the 1-octanol/water partition coefficient (log K(ow)). The toxicity of the alpha,beta-unsaturated aldehydes was modeled well by log K(ow) in conjunction with the sum of partial charges on the vinylene carbon atoms (Q(C4) + Q(C3)) and the energy of the lowest unoccupied molecular orbital (E(lumo)). These electronic descriptors were also successful at modeling the toxicity of alpha,beta-unsaturated ketones. The toxicity of a range of acrylates was constant within about 0.2 of a log unit. Conversely, the toxicity of methacrylates and esters containing the vinylene group varied considerably and was explained by their hydrophobicity. The comparison of the quantitative structure-activity relationship (QSAR) for the methacrylates and esters with that for non-polar narcosis showed little significant difference and hence suggested that substitution on the carbon-carbon double bond in the methacrylates and vinylene unsaturated esters does not enhance toxicity over that of baseline. Substitution on the carbon-carbon double bond in the alpha,beta-unsaturated aldehydes resulted in toxicity that was similar to that for saturated derivatives. Although an excellent hydrophobicity-dependent QSAR was developed for the esters containing ethynylene group, these compounds are considered to act as Michael-type acceptors. Attempts to combine different groups of Michael-type acceptors into a single QSAR, based on mechanistically derived descriptors, were unsuccessful. Thus, the modeling of the toxicity of the alpha,beta-unsaturated carbonyl domain is currently limited to models for narrow subdomains.

Percutaneous absorption and skin irritation upon low-level prolonged dermal exposure to nonane, dodecane and tetradecane in hairless rats

Even though the dermal toxicity of hydrocarbon fuels has been well established in the literature, there is little information available on the dermal penetration kinetics and irritation potential of the individual hydrocarbons. The penetration and skin retention of nonane, dodecane and tetradecane was assessed in vitro using hairless rats' skin. The effects of unocclusive dermal exposures of these chemicals (15 microL every 2 h for 8 h a day for four days) on the transepidermal water loss (TEWL) and erythema were measured in CD hairless rats. The expression of interleukin 1alpha (IL- 1alpha) and TNF-alpha in the skin and blood were measured at the end of dermal exposures. The flux of dodecane was 3- and 77-fold higher than nonane and tetradecane. The retention of chemicals in stratum corneum (SC) was in the order of tetradecane > dodecane > nonane, and directly correlated to the log Kp (r2 = 0.9900) and molecular weight of the chemicals (r2 = 0.8782). The TEWL and erythema data indicate that irritation was in the following order: tetradecane > dodecane > nonane. Likewise, the expression of IL-lalpha in the blood and TNF-alpha in the skin after dermal exposures was higher for tetradecane followed by dodecane and nonane compared to control. In conclusion, the aliphatic hydrocarbon chemicals of the present study induced cumulative irritation upon low-level repeat exposures for a four-day period. The affinity of the chemicals to SC and their gradual accumulation in the skin in the present study is the probable cause for the differences in the skin irritation profiles of different aliphatic chemicals. The findings of the present study will be helpful in understanding the skin irritation response of the chemicals in humans; indeed the reality check arises from dermal exposures in humans and human experience in occupational handling of these chemicals.

Partial Least Squares Modelling of the Acute Toxicity of Aliphatic Compounds to Tetrahymena pyriformis

The aim of this study was to evaluate a multivariate statistical model, utilising Partial Least Squares (PLS) analysis, for the prediction of the acute toxicity of aliphatic chemicals to the ciliate Tetrahymena pyriformis. A model was developed that was capable of making a prediction regardless the mechanism of toxic action. The toxicity of 476 compounds, possessing different mechanisms of toxic action was considered. A set of 74 descriptors, including the octanol–water partition coefficient, molecular-orbital descriptors, geometrical, topological and connectivity indices, was generated. A three-component, eight-descriptor PLS model was developed. It was validated by a Y-permutation test and by simulation of external prediction for complementary subsets. A comparison with existing class or mechanism-based models, derived on the same data set, was made.

Structure-toxicity relationships for aliphatic chemicals evaluated with Tetrahymena pyriformis.

Quantitative structure-activity relationships were developed for the toxicity data of 500 aliphatic chemicals tested in the two-day Tetrahymena pyriformis population growth impairment assay. These chemicals represented a number of structural classes spanning a variety of mechanisms of toxic action including narcoses and electrophilic mechanisms. A series of quantitative structure-toxicity models correlating toxic potency [log(IGC(50)(-1))] with a limited number of mechanistically interpretable descriptors were developed for toxicological domains within the data set. The descriptors included the 1-octanol/water partition coefficient (log K(ow)) (for hydrophobicity) and the energy of the lowest unoccupied molecular orbital (E(lumo)) to quantify electrophilic reactivity. Neutral (nonpolar) narcosis was well modeled by the equation [log(IGC(50)(-1)) = 0.723(0.140) (log K(ow)) - 1.79(0.031); n = 215, r(2) (adj.) = 0.926, s = 0.274, r(2) (pred.) = 0.925]. Chemical classes fitting this domain included saturated alcohols, ketones, nitriles, esters, and sulfur-containing compounds. When the neutral narcotic chemicals were combined with diester narcotics, carboxylic sodium salts, Schiff-based forming aldehydes, electrophilic compounds capable of acting by a S(N)2 mechanism, and proelectrophiles, the model [log(IGC(50)(-1)) = 0.45(0.014) (log K(ow)) - 0.342 (0.035) (E(lumo)) - 1.11(0.05); n = 353, r(2) (adj.) = 0.859, s = 0.353, r(2) (pred.) = 0.857] provided a good fit to the data. The model [log(IGC(50)(-1)) = 0.273(0.018) (log K(ow)) - 0.116(0.056) (E(lumo)) - 0.558(0.054); n = 35, r(2) (adj.) = 0.873, s = 0.141, r(2) (pred.) = 0.838] provided an excellent fit of the data for compounds containing a carboxyl [RC(=O)O] group. The toxicity of aliphatic amines [RCN] was modeled by the equation [log(IGC(50)(-1)) = 0.676(0.048) (log K(ow)) - 1.23(0.08) n = 30, r(2) (adj.) = 0.873, s = 0. 336, r(2) (pred.) = 0.848]. The potency of saturated aliphatic isothiocyanates was a constant (0.0202 mM). Aliphatic chemicals that did not model well by equations involving log K(ow) and E(lumo) included amino alcohols and alpha-haloactivated compounds.