Acute, sublethal, antifeedant, and synergistic effects of monoterpenoid essential oil compounds on the tobacco cutworm, Spodoptera litura (Lep., Noctuidae)

Monoterpenoids (terpenes and biogenically related phenols) commonly found in plant essential oils were tested for acute toxicity via topical application to tobacco cutworms (Spodoptera litura Fab.). The most toxic among 10 such compounds was thymol (LD(50) = 25.4 microg/larva) from garden thyme, Thymus vulgaris. The compounds were then tested for sublethal effects, specifically inhibition of larval growth after topical application of low doses. Among 6 compounds tested, an LD(10) dose reduced growth by 20% on average 3 days after administration. Feeding deterrence was determined using a cabbage leaf disk choice test. The most deterrent compound was thymol, with a DC(50) of 85.6 microg/cm(2) leaf disk area. Because minor constituents in complex essential oils have been suggested to act as synergists, binary mixtures of the compounds were tested for synergy vis à vis acute toxicity and feeding deterrence. trans-Anethole acted synergistically with thymol, citronellal, and alpha-terpineol, in terms of both acute toxicity and feeding deterrence. On the basis of these findings, several complex mixtures were developed and tested as leads for effective control agents. Candidate mixtures demonstrated good synergistic effects. The observed LD(50) of mixture 3 was 40.6 microg/larvae compared to an expected value of 74.6 microg/larvae. The result of this research is a proprietary product suitable for commercial production.

Elevated interleukin 6 is induced by prostaglandin E2 in a murine model of inflammation: possible role of cyclooxygenase-2

Injection of mineral oils such as pristane into the peritoneal cavities of BALB/c mice results in a chronic peritonitis associated with high tissue levels of interleukin 6 (IL-6). Here we show that increased prostaglandin E2 (PGE2) synthesis causes induction of IL-6 and that expression of an inducible cyclooxygenase, Cox-2, may mediate this process. Levels of both PGE2 and IL-6 are elevated in inflammatory exudates from pristane-treated mice compared with lavage samples from untreated mice. The Cox-2 gene is induced in the peritoneal macrophage fraction isolated from the mice. A cause and effect relationship between increased macrophage PGE2 and IL-6 production is shown in vitro. When peritoneal macrophages are activated with an inflammatory stimulus (polymerized albumin), the Cox-2 gene is induced and secretion of PGE2 and IL-6 increases, with elevated PGE2 appearing before IL-6. Cotreatment with 1 microM indomethacin inhibits PGE2 production by the cells and reduces the induction of IL-6 mRNA but has no effect on Cox-2 mRNA, consistent with the fact that the drug inhibits catalytic activity of the cyclooxygenase but does not affect expression of the gene. Addition of exogenous PGE2 to macrophages induces IL-6 protein and mRNA synthesis, indicating that the eicosanoid stimulates IL-6 production at the level of gene expression. PGE2-stimulated IL-6 production is unaffected by addition of indomethacin. Taken together with the earlier finding that indomethacin diminishes the elevation of IL-6 in pristane-treated mice, the results show that PGE2 can induce IL-6 production in vivo and implicate expression of the Cox-2 gene in the regulation of this cytokine.

Activation of octopaminergic receptors by essential oil constituents isolated from aromatic plants: possible mode of action against insect pests

As a result of screening a large number of essential oils from Israeli aromatic plants and their biologically active constituents, we isolated two oils with high activity against several stored-product insects. In this study the effect of these compounds on the acetylcholinesterase and the octopamine systems in insects was studied in order to elucidate their mode of action. Inhibition of acetylcholinesterase activity in vitro was evident only at high concentrations (10(-3) M) and could not account effectively for the low-dose mortality for some stored-product insects observed in vivo. However, the essential oil constituents were found to cause a significant increase in the levels of the intracellular messenger, cyclic AMP of abdominal epidermal tissue in the model insect, Helicoverpa armigera Hübn. The effect was significant even at low, physiological concentrations (10(-8) M) when tested directly on abdominal epidermal tissue preparations in vitro. This intracellular response was found to resemble closely the significant increases in the levels of the cyclic AMP of abdominal epidermal tissue due to treatment with the neurotransmitter/neuromodulator, octopamine. Subsequent treatment with the octopaminergic antagonist, phentolamine, effectively inhibited the cyclic AMP levels induced by essential oil treatment, indicating possible competitive activation of octopaminergic receptors by essential oil constituents.

Aromatherapy: evidence for sedative effects of the essential oil of lavender after inhalation

The sedative properties of the essential oil of Lavender (Lavandula angustifolia Miller) and of its main constituents--linalool and linalyl acetate--were investigated in mice followed up in a series of experimental procedures. The significant decrease in the motility of female and male laboratory animals under standardized experimental conditions is found to be closely dependent on the exposure time to the drugs. Nevertheless after an injection of caffeine into mice a hyperactivity was observed which was reduced to nearly a normal motility only by inhalation of these fragrance drugs. In particular the correlation of the motility of the animals to linalool in serum is experimentally proven, thus furnishing evidence of the aromatherapeutical use of herbal pillows employed in folk medicine since ancient times in order to facilitate falling asleep or to minimize stressful situations of man.

Interleukin 6 is essential for in vivo development of B lineage neoplasms

Interleukin (IL) 6 has been suggested to be the major cytokine responsible for proliferation of neoplastic plasma cells in both human myeloma and mouse plasmacytoma. Much of the evidence supporting this suggestion is derived from in vitro studies in which the survival or proliferation of some plasma cell tumors has been found to be IL-6 dependent. However, it remains unclear whether this dependency is the consequence of in vivo or in vitro selective pressures that preferentially expand IL-6-responsive tumor cells, or whether it reflects a critical in vivo role for IL-6 in plasma cell neoplasia. To address this question, we have attempted to induce plasma cell tumors in normal mice and in IL-6-deficient mice generated by introduction of a germline-encoded null mutation in the IL-6 gene. The results demonstrate that mice homozygous (+/+) or heterozygous (+/-) for the wild-type IL-6 allele yield the expected incidences of plasma cell tumors. In contrast, mice homozygous for the IL-6-null allele (-/-) are completely resistant to plasma cell tumor development. These studies define the essential role of IL-6 in the development of B lineage tumors in vivo and provide experimental support for continued efforts to modulate this cytokine in the treatment of appropriate human B cell malignancies.

Toxicity of selected plant volatiles in microbial and mammalian short-term assays

In this study, several short-term microbial and mammalian in vitro assays were used to evaluate cytotoxicity and genotoxicity of four plant volatiles showing antifungal activity: cinnamaldehyde, carvacrol, thymol and S(+)-carvone. All inhibited viability and proliferation of Hep-2 cells in a dose-dependent manner. IC50 ranged from 0.3 mM (cinnamaldehyde) to 0.7 mM (thymol) in viability tests and from 0.2 mM (carvacrol) to 0.9 mM (carvone) in the proliferation test. The morphological analysis suggested an involvement of apoptosis in the cases of carvone, carvacrol and cinnamaldehyde. At nontoxic doses, carvacrol and thymol increased the number of revertants in the Ames test by 1.5-1.7 times, regardless of metabolic activation. In the SOS-chromotest, none of the four plant volatiles caused DNA damage at non-toxic doses. In the DNA repair test, a marked dose-dependent differential toxicity was observed with carvone and, to a lesser extent, with cinnamaldehyde, while with thymol and carvacrol, this effect was less pronounced. In conclusion, the considered in vitro cytotoxicity assays have shown to be sensitive enough to highlight a variety of toxic effects at the cellular level, which can be rather different between chemically closely related compounds, such as isomers.

Induction of apoptosis by garcinol and curcumin through cytochrome c release and activation of caspases in human leukemia HL-60 cells

Garcinol, a polyisoprenylated benzophenone, was purified from Garcinia indica fruit rind. The effects of garcinol and curcumin on cell viability in human leukemia HL-60 cells were investigated. Garcinol and curcumin displayed strong growth inhibitory effects against human leukemia HL-60 cells, with estimated IC(50) values of 9.42 and 19.5 microM, respectively. Garcinol was able to induce apoptosis in a concentration- and time-dependent manner; however, curcumin was less effective. Treatment with garcinol caused induction of caspase-3/CPP32 activity in a dose- and time-dependent manner, but not caspase-1 activity, and induced the degradation of poly(ADP-ribose) polymerase (PARP). Pretreatment with caspase-3 inhibitor inhibited garcinol-induced DNA fragmentation. Treatment with garcinol (20 microM) caused a rapid loss of mitochondrial transmembrane potential, release of mitochondrial cytochrome c into cytosol, and subsequent induction of procaspase-9 processing. The cleavage of D4-GDI, an abundant hematopoietic cell GDP dissociation inhibitor for the Ras-related Rho family GTPases, occurred simultaneously with the activation of caspase-3 but preceded DNA fragmentation and the morphological changes associated with apoptotic cell death. Of these, Bcl-2, Bad, and Bax were studied. The level of expression of Bcl-2 slightly decreased, while the levels of Bad and Bax were dramatically increased in cells treated with garcinol. These results indicate that garcinol allows caspase-activated deoxyribonuclease to enter the nucleus and degrade chromosomal DNA and induces DFF-45 (DNA fragmentation factor) degradation. It is suggested that garcinol-induced apoptosis is triggered by the release of cytochrome c into the cytosol, procaspase-9 processing, activation of caspase-3 and caspase-2, degradation of PARP, and DNA fragmentation caused by the caspase-activated deoxyribonuclease through the digestion of DFF-45. The induction of apoptosis by garcinol may provide a pivotal mechanism for its cancer chemopreventive action.

Interleukin 6 dependence of anti-DNA antibody production: evidence for two pathways of autoantibody formation in pristane-induced lupus

Pristane induces a lupus-like syndrome in nonautoimmune mice characterized by the development of glomerulonephritis and lupus-associated autoantibodies. This is accompanied by overproduction of interleukin (IL)-6, a cytokine linked with autoimmune phenomena. The goal of this study was to evaluate the role of IL-6 in autoantibody production in pristane-induced lupus. BALB/cAn IL-6-deficient (-/-) and -intact (+/+) mice were treated with pristane or phosphate-buffered saline, and autoantibody production was evaluated. Pristane induced high levels of immunoglobulin (Ig)G anti-single-stranded DNA, -double-stranded (ds)DNA, and -chromatin antibodies in IL-6(+/+), but not IL-6(-/-) mice by enzyme-linked immunosorbent assay. High titer IgG anti-dsDNA antibodies also were detected in sera from +/+, but not -/-, mice by Crithidia luciliae kinetoplast staining. The onset of IgG anti-dsDNA antibody production in +/+ mice occurred >5 mo after pristane treatment, well after the onset of nephritis, suggesting that these antibodies are not directly responsible for inducing renal disease. In contrast to anti-DNA, the frequencies of anti-nRNP/Sm and anti-Su antibodies were similar in pristane-treated IL-6(-/-) and IL-6(+/+) mice. However, levels were higher in the +/+ group. These results suggest that IgG anti-DNA and chromatin antibodies in pristane-treated mice are strictly IL-6 dependent, whereas induction of anti-nRNP/Sm and Su autoantibodies is IL-6 independent. The IL-6 dependence of anti-DNA, but not anti-nRNP/Sm, may have implications for understanding the patterns of autoantibody production in lupus. Anti-DNA antibodies are produced transiently, mainly during periods of disease activity, whereas anti-nRNP/Sm antibody levels are relatively insensitive to disease activity. This may reflect the differential IL-6 dependence of the two responses.

Insecticidal activity of essential oils: octopaminergic sites of action

A study was conducted to determine the insecticidal activity and mechanism of action of three essential oils (eugenol, alpha-terpineol and cinnamic alcohol) and an equal part mixture (3-blend) against American cockroaches (Periplaneta americana). To address species differences in response to treatment with the test oils, Carpenter ants (Camponotus pennsylvanicus De Geer), and German cockroaches (Blattella germanica) were included in this study. Exposed American cockroaches demonstrated hyperactivity followed by hyperextension of the legs and abdomen, then fast knockdown or quick immobilization followed by death. Ants and German cockroaches showed fast immobilization/knockdown followed by mortality. The 1:1:1 mixture (3-blend) was substantially effective against all test insects. One of the most remarkable observations was the increased frequency of heartbeats of American cockroaches in response to topical application of test oils. The changes in the pattern of cAMP level was biphasic. A significant increase in the cAMP level was found in response to 1 nmol/ml of eugenol, or 3-blend or 10 nmol/ml of alpha-terpineol. At higher concentrations a significant decrease in cAMP level was found. Blockage of octopamine receptors binding sites was also illustrated at lower concentrations of the test chemicals as judged by the decreased binding activity of [3H]octopamine to its receptors.

IN CONCLUSION

(1) test oils are neuro-insecticides and their insecticidal activity is species-dependent; (2) a synergistic effect of the three oils was found when they were equally mixed (3-blend); and (3) the octpaminergic system mediates the insecticidal activity of eugenol, alpha-terpienol and the 3-blend.

Retinoic acid-mediated gene expression in transgenic reporter zebrafish

Retinoic acid-mediated gene activation is important for normal vertebrate development. The size and nature of retinoic acid make it difficult to identify the precise cellular location of this signaling molecule throughout an embryo. Additionally, retinoic acid (RA) signaling is regulated by a complex combination of receptors, coactivators, and antagonizing proteins. Thus, in order to integrate these signals and identify regions within a whole developing embryo where cells can respond transcriptionally to retinoic acid, we have used a reporter transgenic approach. We have generated several stable lines of transgenic zebrafish which use retinoic acid response elements to drive fluorescent protein expression. In these zebrafish lines, transgene expression is localized to regions of the neural tube, retina, notochord, somites, heart, pronephric ducts, branchial arches, and jaw muscles in embryos and larvae. Transgene expression can be induced in additional regions of the neural tube and retina as well as the immature notochord, hatching gland, enveloping cell layer, and fin by exposing embryos to retinoic acid. Treatment with retinoic acid synthase inhibitors, citral and diethylaminobenzaldehyde (DEAB), during neurulation, greatly reduces transgene expression. DEAB treatment of embryos at gastrulation phenocopies the embryonic effects of vitamin A deprivation or targeted disruption of the RA synthase retinaldehyde dehydrogenase-2 in other vertebrates. Together these data suggest that the reporter expression we see in zebrafish is dependent upon conserved vertebrate pathways of RA synthesis.

Mechanisms of the formation and disposition of reactive metabolites that can cause acute liver injury

Acetaminophen and pulegone are just two examples for many agents that can form reactive metabolites that can cause acute liver injury. Two other classic organic compounds that have been extensively studied are carbon tetrachloride (for a recent review see Ref. 159, and for other discussions see Refs. 8 and 9) and bromobenzene (for review see Ref. 160). Different kinds of protein adducts of reactive metabolites of bromobenzene have been partially characterized [161], and specific antibodies to these adducts are now being used to isolate and identify the proteins that are modified (162). In contrast, carbon tetrachloride and other agents, such as the herbicide diquat, may form radicals that bind to and/or oxidize lipids and proteins in causing liver injury (163, 164). Therefore, the recent development [165] of antibodies to detect oxidative damage to proteins will be important in the identification and characterization of macromolecules that do not form adducts with reactive metabolites but are damaged oxidatively. Thus, some major challenges in the coming years are to identify hepatocellular macromolecules that are modified by reactive metabolites, and then approach the more difficult task of integrating this information into a time course and sequence of events leading to lethal hepatocellular injury.

Mutagenicity testing (+/-)-camphor, 1,8-cineole, citral, citronellal, (-)-menthol and terpineol with the Salmonella/microsome assay

The essential oils and their monoterpenoid constituents have been widely used as fragrances in cosmetics, as flavouring food additives, as scenting agents in a variety of household products, as active ingredients in some old drugs, and as intermediates in the synthesis of perfume chemicals. The present study was undertaken to investigate the mutagenic potential of six monoterpenoid compounds: two aldehydes (citral and citronellal), a ketone ((+/-)-camphor), an oxide (1,8-cineole, also known as eucalyptol), and two alcohols (terpineol and (-)-menthol). It is part of a more comprehensive toxicological screening of monoterpenes under way at our laboratory. Mutagenicity was evaluated by the Salmonella/microsome assay (TA97a, TA98, TA100 and TA102 tester strains), without and with addition of an extrinsic metabolic activation system (lyophilized rat liver S9 fraction induced by Aroclor 1254). In all cases, the upper limit of the dose interval tested was either the highest non-toxic dose or the lowest dose of the monoterpene toxic to TA100 strain in the preliminary toxicity test. No mutagenic effect was found with (+/-) camphor, citral, citronellal, 1,8-cineole, and (-) menthol. Terpineol caused a slight but dose-related increase in the number of his+ revertants with TA102 tester strain both without and with addition of S9 mixture. The results from this study therefore suggest that, with the exception of terpineol, the monoterpenoid compounds tested are not mutagenic in the Ames test.

Corn silk (Stigma maydis) in healthcare: a phytochemical and pharmacological review

Corn silk (Stigma maydis) is an important herb used traditionally by the Chinese, and Native Americans to treat many diseases. It is also used as traditional medicine in many parts of the world such as Turkey, United States and France. Its potential antioxidant and healthcare applications as diuretic agent, in hyperglycemia reduction, as anti-depressant and anti-fatigue use have been claimed in several reports. Other uses of corn silk include teas and supplements to treat urinary related problems. The potential use is very much related to its properties and mechanism of action of its plant's bioactive constituents such as flavonoids and terpenoids. As such, this review will cover the research findings on the potential applications of corn silk in healthcare which include its phytochemical and pharmacological activities. In addition, the botanical description and its toxicological studies are also included.

Protective and pathogenic roles for B cells during systemic autoimmunity in NZB/W F1 mice

Delineating the relative contributions of B lymphocytes during the course of autoimmune disease has been difficult. Therefore, the effects of depleting all mature B cells using a potent CD20 mAb, or of depleting circulating and marginal zone B cells using a ligand-blocking CD22 mAb, were compared in NZB/W F(1) mice, a model for human systemic lupus erythematosus. Single low-dose mAb treatments depleted B cells efficiently in both NZB/W F(1) and C57BL/6 mice. Prophylactic B cell depletion by repeated CD20 mAb treatments prolonged survival during pristane-accelerated lupus in NZB/W F(1) mice, whereas CD22 mAb had little effect. Despite effective B cell depletion, neither mAb treatment prevented autoantibody generation. In addition, CD20, CD22, and control mAb-treated NZB/W F(1) mice developed anti-mouse IgG autoantibodies in contrast to parental NZB and NZW strains, which may have reduced the effectiveness of B cell depletion. Despite this, low-dose CD20 mAb treatment initiated in 12-28-wk-old mice, and administered every 4 wk thereafter, significantly delayed spontaneous disease in NZB/W F(1) mice. By contrast, B cell depletion initiated in 4-wk-old mice hastened disease onset, which paralleled depletion of the IL-10-producing regulatory B cell subset called B10 cells. B10 cells were phenotypically similar in NZB/W F(1) and C57BL/6 mice, but were expanded significantly in young NZB/W F(1) mice. Thus, B cell depletion had significant effects on NZB/W F(1) mouse survival that were dependent on the timing of treatment initiation. Therefore, distinct B cell populations can have opposing protective and pathogenic roles during lupus progression.

Quorum sensing antagonism from marine organisms

With the global emergence of multiresistant bacteria there is an increasing demand for development of new treatments to combat pathogens. Bacterial cell-cell communication [quorum sensing (QS)] regulates expression of virulence factors in a number of bacterial pathogens and is a new promising target for the control of infectious bacteria. We present the results of screening of 284 extracts of marine organisms from the Great Barrier Reef, Australia, for their inhibition of QS. Of the 284 extracts, 64 (23%) were active in a general, LuxR-derived QS screen, and of these 36 (56%) were also active in a specific Pseudomonas aeruginosa QS screen. Extracts of the marine sponge Luffariella variabilis proved active in both systems. The secondary metabolites manoalide, manoalide monoacetate, and secomanoalide isolated from the sponge showed strong QS inhibition of a lasB::gfp(ASV) fusion, demonstrating the potential for further identification of specific QS antagonists from marine organisms.

Insecticidal properties of essential plant oils against the mosquito Culex pipiens molestus (Diptera: Culicidae)

The insecticidal activities of essential oil extracts from leaves and flowers of aromatic plants against fourth-instar larvae of the mosquito Culex pipiens molestus Forskal were determined. Extracts of Myrtus communis L were found to be the most toxic, followed by those of Origanum syriacum L, Mentha microcorphylla Koch, Pistacia lentiscus L and Lavandula stoechas L with LC50 values of 16, 36, 39, 70 and 89 mg litre-1, respectively. Over 20 major components were identified in extracts from each plant species. Eight pure components (1,8-cineole, menthone, linalool, terpineol, carvacrol, thymol, (1S)-(-)-alpha-pinene and (1R)-(+)-alpha-pinene) were tested against the larvae. Thymol, carvacrol, (1R)-(+)-alpha-pinene and (1S)-(-)-alpha-pinene were the most toxic (LC50 = 36-49 mg litre-1), while menthone, 1,8-cineole, linalool and terpineol (LC50 = 156-194 mg litre-1) were less toxic.

Responses of L929 mouse fibroblasts, primary and immortalized bovine dental papilla-derived cell lines to dental resin components

OBJECTIVE

The use of adequate target cells for cytotoxicity testing of dental restorative materials has often been experimentally assessed with respect to the clinical relevance of the test results. In the present study, the responses in primary bovine dental papilla-derived cells (pulp cells) were compared with those in transformed dental papilla-derived cell lines and L929 mouse fibroblasts after exposure to various dental resin compounds.

METHODS

Primary bovine dental papilla-derived cells (CPC), tCPC B (CPC cells transformed with SV40 T-antigen), tCPC E (CPC cells transformed with E6/E7 oncogen), and L929 mouse fibroblast cells were exposed to various compounds of dental resin materials for 24 h, and cytotoxicity was determined using the MTT assay. Bis-GMA, UDMA, 1,6 hexane diol dimethacrylate (HDDM), TEGDMA, HEMA, MMA, camphorquinone (CQ), bisphenol A (BPA), and glycidyl methacrylate (GMA) were tested. Concentrations leading to 50% cell survival (TC50 values) were calculated from fitted dose-response curves.

RESULTS

The simple ranking of the cytotoxic effects of the dental resin compounds in the four cell types was identical, and TC50 values determined in L929 cells here were consistent with findings by other authors using continuous cell lines. However, the concentrations of the resin compounds necessary for eliciting cytotoxic responses in the various cells were clearly different. The analyses of TC50 values of the resin compounds revealed a linear correlation between cell lines, and the overall sensitivities increased as follows: CPC=tCPC B<tCPC E<L929.

SIGNIFICANCE

The low sensitivities of primary cells and transformed tCPC B cells compared with the continuous L929 cell line and the transformed tCPC E cells indicates the presence of specific structural and functional properties relevant in vivo. The differences between the transformed tCPC B and tCPC E cells may indicate modifications of cellular functions caused by the different transformation processes.

The biology of ophiobolins

This review article aims at summarizing the research findings on the biological aspects of ophiobolins, phytotoxins produced by the pathogenic fungi Bipolaris species, which usually infect rice, maize and sorghum. The topics covered include the organisms that produce the various ophiobolins, the structural variations of ophiobolins, the biological actions of ophiobolins in plants, animals and microorganisms, and the mode of action and the possible use of ophiobolin A as a calmodulin antagonist.

Safety evaluation and risk assessment of d-Limonene

d-Limonene, a major constituent of citrus oils, is a monoterpene widely used as a flavor/fragrance additive in cosmetics, foods, and industrial solvents as it possesses a pleasant lemon-like odor. d-Limonene has been designated as a chemical with low toxicity based upon lethal dose (LD50) and repeated-dose toxicity studies when administered orally to animals. However, skin irritation or sensitizing potential was reported following widespread use of this agent in various consumer products. In experimental animals and humans, oxidation products or metabolites of d-limonene were shown to act as skin irritants. Carcinogenic effects have also been observed in male rats, but the mode of action (MOA) is considered irrelevant for humans as the protein α(2u)-globulin responsible for this effect in rodents is absent in humans. Thus, the liver was identified as a critical target organ following oral administration of d-limonene. Other than the adverse dermal effects noted in humans, other notable toxic effects of d-limonene have not been reported. The reference dose (RfD), the no-observed-adverse-effect level (NOAEL), and the systemic exposure dose (SED) were determined and found to be 2.5 mg/kg/d, 250 mg/kg//d, and 1.48 mg/kg/d, respectively. Consequently, the margin of exposure (MOE = NOAEL/SED) of 169 was derived based upon the data, and the hazard index (HI = SED/RfD) for d-limonene is 0.592. Taking into consideration conservative estimation, d-limonene appears to exert no serious risk for human exposure. Based on adverse effects and risk assessments, d-limonene may be regarded as a safe ingredient. However, the potential occurrence of skin irritation necessitates regulation of this chemical as an ingredient in cosmetics. In conclusion, the use of d-limonene in cosmetics is safe under the current regulatory guidelines for cosmetics.

Fragrance compound geraniol forms contact allergens on air exposure. Identification and quantification of oxidation products and effect on skin sensitization

Fragrances are common causes of contact allergy. Geraniol (trans-3,7-dimethyl-2,6-octadiene-1-ol) is an important fragrance terpene. It is considered a weak contact allergen and is used for fragrance allergy screening among consecutive dermatitis patients. Analogous to other monoterpenes studied, such as limonene and linalool, geraniol has the potential to autoxidize on air exposure and form highly allergenic compounds. The aim of the present study was to investigate and propose a mechanism for the autoxidation of geraniol at room temperature. To investigate whether allergenic compounds are formed, the sensitizing potency of geraniol itself, air-exposed geraniol, and its oxidation products was determined using the local lymph node assay in mice. The results obtained show that the allylic alcohol geraniol follows an oxidation pattern different from those of linalool and limonene, which autoxidize forming hydroperoxides as the only primary oxidation products. The autoxidation of geraniol follows two paths, originating from allylic hydrogen abstraction near the two double bonds. From geraniol, hydrogen peroxide is primarily formed together with aldehydes geranial and neral from a hydroxyhydroperoxide. In addition, small amounts of a hydroperoxide are formed, analogous to the formation of the major linalool hydroperoxide. The autoxidation of geraniol greatly influenced the sensitizing effect of geraniol. The oxidized samples had moderate sensitizing capacity, quite different from that of pure geraniol. The hydroperoxide formed is believed to be the major contributor to allergenic activity, together with the aldehydes geranial and neral. On the basis of the present study and previous experience, we recommend that the possibility of autoxidation and the subsequent formation of contact allergenic oxidation products are considered in risk assessments performed on fragrance terpenes.

Antimalarial activity of plant metabolites

This review covers the structures of compounds with antiplasmodial activity isolated from plants and is organized according to plant family. A total of 170 structures has been reviewed from 186 references found in the literature up to December 2000.

Plant compounds that induce polychlorinated biphenyl biodegradation by Arthrobacter sp. strain B1B

Plant compounds that induced Arthrobacter sp. strain B1B to cometabolize polychlorinated biphenyls (PCBs) were identified by a screening assay based on the formation of a 4,4'-dichlorobiphenyl ring fission product. A chemical component of spearmint (Mentha spicata), l-carvone, induced Arthrobacter sp. strain B1B to cometabolize Aroclor 1242, resulting in significant degradation of 26 peaks in the mixture, including selected tetra- and pentachlorobiphenyls. Evidence for PCB biodegradation included peak disappearance, formation of a phenylhexdienoate ring fission product, and chlorobenzoate accumulation in the culture supernatant. Carvone was not utilized as a growth substrate and was toxic at concentrations of greater than 500 mg liter-1. Several compounds structurally related to l-carvone, including limonene, p-cymene, and isoprene, also induced cometabolism of PCBs by Arthrobacter sp. strain B1B. A structure-activity analysis showed that chemicals with an unsaturated p-menthane structural motif promoted the strongest cometabolism activity. These data suggest that certain plant-derived terpenoids may be useful for promoting enhanced rates of PCB biodegradation by soil bacteria.

Widespread susceptibility among inbred mouse strains to the induction of lupus autoantibodies by pristane

Unlike other agents associated with drug-induced lupus, the isoprenoid alkane pristane induces autoantibodies pathognomonic of lupus, including anti-Sm, anti-dsDNA, and anti-ribosomal P in BALB/c and SJL/J mice. The susceptibility of other strains of mice to pristane-induced lupus is unknown and is the focus of the present study. Anti-nRNP/Sm, anti-Su, and anti-ribosomal P autoantibodies were produced by most strains of mice surveyed within several months of pristane treatment, although there was marked interstrain variability in their frequencies, levels, and times of onset. In sharp contrast, the production of autoantibodies against the double-stranded RNA binding proteins NF45/NF90/p110 was restricted to B6 and B10.S mice. We conclude that pristane selectively induces lupus-specific autoantibodies in virtually any strain of mouse regardless of its genetic background. However, H-2-linked as well as non-H2 genes influenced the expression of individual autoantibody markers. The widespread susceptibility of pristane-treated mice to lupus autoantibody production and the relatively small effect of MHC are unique features of this chemically induced lupus syndrome, with potential implications for understanding the pathogenesis of autoantibodies in idiopathic human systemic lupus erythematosus.

d-Limonene-induced male rat-specific nephrotoxicity: evaluation of the association between d-limonene and alpha 2u-globulin

d-Limonene is a naturally occurring monoterpene, which when dosed orally, causes a male rat-specific nephrotoxicity manifested acutely as the exacerbation of protein droplets in proximal tubule cells. Experiments were conducted to examine the retention of [14C]d-limonene in male and female rat kidney, to determine whether d-limonene or one or more of its metabolites associates with the male rat-specific protein, alpha 2u-globulin, and if so, to identify the bound material. The results indicated that, 24 hr after oral administration of 3 mmol d-limonene/kg, the renal concentration of d-limonene equivalents was approximately 2.5 times higher in male rats than in female rats. Equilibrium dialysis in the presence or absence of sodium dodecyl sulfate indicated that approximately 40% of the d-limonene equivalents in male rat kidney associated with proteins in a reversible manner, whereas no significant association was observed between d-limonene equivalents and female rat kidney proteins. Association between d-limonene and male rat kidney proteins was characterized by high-performance gel filtration and reverse-phase chromatography. Gel filtration HPLC indicated that d-limonene in male rat kidney is associated with a protein fraction having a molecular weight of approximately 20,000. Separation of alpha 2u-globulin from other kidney proteins by reverse-phase HPLC indicated that d-limonene associated with a protein present only in male rat kidney which was definitively identified as alpha 2u-globulin by amino acid sequencing. The major metabolite associated with alpha 2u-globulin was d-limonene-1,2-oxide. Parent d-limonene was also identified as a minor component in the alpha 2u-globulin fraction. Thus, d-limonene, and more specifically d-limonene-1,2-oxide, associates with alpha 2u-globulin in a reversible manner in male rat kidney. This interaction may be responsible for excessive accumulation of alpha 2u-globulin in kidneys of male rats exposed to d-limonene.