Copaiba Research Articles

Physical-Chemical and Sensorial Quality of Eggs Coated With Copaiba Oil Biofilm and Stored At Room Temperature for Different Periods

ABSTRACT The present study aimed at evaluating the effects of a coating based on copaiba oil on the quality of eggs stored for different periods. Eggs were coated with copaiba oil solutions (4, 8, 12, 16, or 20% copaiba oil) or not (control) and stored for 1, 7, 14, 21, 28 or 35 days at room temperature. The following parameters were evaluated: egg weight loss, egg components (albumen, yolk, and eggshell) relative weights, egg specific gravity, Haugh units, eggshell quality, and sensorial attributes. Eggs stored for 35 days presented the highest weight losses. Coating (20% copaiba oil solution) reduced egg weight loss up to 41.02%. Coated eggs presented better internal quality (yolk and albumen heights, specific gravity, and eggshell strength). Sensorial attributes were negatively affected by storage time (aroma and flavor), and copaiba oil solution (aroma, appearance, and flavor), with the natural odor of copaiba described by the tasters. Egg internal, external, and sensorial quality worsened with storage time. Solutions containing 16 and 20% copaiba oil can be used as a biofilm to coat eggs, preserving its internal and external quality, and may affect their sensory characteristics, and therefore, may be a viable alternative for maintaining the internal quality of eggs stored at room temperature for long periods.

Physicochemical Characterizations and Antioxidant Property of Copaiba Oil Loaded into SNEDDS Systems

Self-nanoemulsion drug delivery systems (SNEDDS) represent a potential carrier to improve solubility and bioavailability of health care products. In this sense, copaiba oil (CO) loaded on cosurfactant-free SNEDDS formulations (CO-SNEDDS) were obtained by using phase diagram performed on different concentrations of constituents (oil, surfactant and water). The CO-SNEDDS are composed of 1% (m/m) of oil phase, 20% (m/m) of Tween 80, and 79% (m/m) of double-distilled water. Specifically, varying the oil phase to 1% of CO affords the so-called SNECO system, and 1% of CO blended on a 1:1 ratio with coconut oil or sunflower oil affords, respectively, the SNECO-COO and SNECO-SO derivative systems. CO sample was authenticated by gas chromatography equipped with a flame ionization detector and the CO-SNEDDS samples were characterized by droplet particle size, zeta potential, polarized light microscopy, pH, conductivity, refractive index, rheological and surface tension analyses. According to the antioxidant tests reducing power and hydroxyl inhibiting formation, the findings displayed 47.89 and 72.92% for SNECO, 46.48 and 84.11% for SNECO-COO, and 52.46 and 74.48% for SNECO-SO, respectively. From now on CO-SNEDDS based systems become available as promising targets for novel medicinal investigations and also could be undertaken for the oral administration of poorly water soluble drugs.

In vitro evaluation of PVA gels loaded with Copaiba Oil and Duotrill®

Abstract Enrofloxacin can be slowly delivered through polymeric systems and the addition of oil could increase the polymeric gels hydrophobicity and help the continuous release. The present work intended to develop and characterize microstructurally (XRD and FTIR) and in vitro (swelling and antimicrobial tests) the PVA hydrogels loaded with copaiba oil and Duotrill (enrofloxacin) to treat bacterial infections, as pyelonephritis, in the veterinary field. Duotrill® and oil combined diminished the gels degree of crystallinity and it was observed interaction between phases due to a new band found only in PVA hydrogels loaded with copaiba oil and Duotrill (PVA-D-O) FTIR spectrum. The samples with oil swelled less than samples without it, where copaiba oil altered the samples’ hydrophilicity. PVA-D-O presented lower weight loss and higher gel fraction than PVA, indicating the loaded material increased the gels stability. All samples containing oil and Duotrill® inhibited S. aureus.

EFFECT OF COPAIBA OIL IN INTESTINAL MUCOSA OF RATS SUBMITTED TO HYPOVOLEMIC SHOCK.

ABSTRACT Background: Hypovolemic shock is a common disease in polytrauma patients and may develop ischemia in various organs, increasing morbidity and mortality. The bowel is usually most affected by this condition. Aim: To evaluate the effects of copaiba oil on the intestinal mucosa’s injury of rats submitted to hypovolemic shock. Method: Fifteen rats were divided into three groups: sham - simulated surgery; ischemia - animals submitted to hypovolemic shock; and copaiba - animals submitted to hypovolemic shock previously treated with copaiba oil. Mean blood pressure, arterial blood gas after shock induction, degree of intestinal lesion and villus length were evaluated. Results: The sham presented the lowest values of lactate and PaCO2 and the highest values of mean arterial pressure, pH and bicarbonate in relation to the other groups. The degree of mesenteric lesion was zero in the sham group; 3.00±1.00 in the ischemia group; and 3.00±0.71 in the copaiba group. The villus length was 173.60±8.42 in the sham, 142.77±8.33 in the ischemia and 143.01±9.57 in the copaiba group. There was a significant difference between the sham and the other groups (p<0.05); however, there not significant difference between groups Ischemia and copaiba. Conclusion: Administration of copaiba oil did not reduce the intestinal mucosa lesion of rats after hypovolemic shock.

CROHN'S DISEASE: EXPERIMENTAL MODELS AND THERAPEUTIC ALTERNATIVES

Crohn's disease (CD) is a chronic disease of idiopathic cause that triggers an severe inflammatory condition . This inflammation has a transmural characteristic that can affect all the intestinal (mucosa, submucosa, muscular and serous) . To understand the pathogenesis therapeutic measures are used through experimental models that ar e used in animals that resemble humans due to the inflammation process stimulating new therapeutic strategies . The aim of this study is to evaluate the experimental therapeutic strategies for Crohn's disease, including the advantages and disadvantages of t he experimental models.The study methodology is an exploratory bibliographic review, using secondary sources from the LILACS, MEDLINE, PUBMED, SCIELO database and, using scientific articles fr om the last 10 years , in Portuguese and English. Development incl udes experimental models to induce intestinal inflammatory diseases in rodents, and trinitrobenzenesulfonic (TNBS), dinitrobenzene sulfonic (DNBS), sodium dextran sulfate (DSS) and acetic acid are among the methods used.The most widely used therapeutic alt ernatives for the treatment of DC as natural methods are propolis, Trichiliacatigua , Zatariamultiflora , methyl jasmonate, resver atrol, copaiba oil and curcumina . Among the different methods used to simulate DC, we highlight the frequent use of TNBS in rode nts. The therapeutic alternatives used experimentally have properties to minimize inflammatory tissue characteristics. &nbsp

Efficiency of Vegetable Oils in Wood Resistance to Cryptotermes brevis Termites

ABSTRACT Natural products have been studied in order to ensure environmental sustainability, human health, and diminish the use of traditional products. The objective of this study was to evaluate the efficiency of pure andiroba (Carapa guianensis), copaiba (Copaifera langsdorffii) and jatropha (Jatropha curcas) oils and enriched with iodine (I2) on the biological resistance of Pinus elliottii wood to dry-wood termites (Cryptotermes brevis). The oils were enriched with 1%, 3%, and 5% of I2 and impregnated into the wood by cold immersion. The treated samples were subjected to volatilization and leaching. Volatilization and leaching did not affect the loss of mass caused by termites, except for treatments with pure and enriched with 1% iodine copaiba oil. Leached samples were more damaged. The addition of iodine to the oils resulted in a greater efficiency against termites. Andiroba (3% and 5% I2) and jatropha oils (5%) were the most efficient, providing total termite mortality.

Diethyldithiocarbamate loaded in beeswax-copaiba oil nanoparticles obtained by solventless double emulsion technique promote promastigote death in vitro.

Leishmaniasis is considered a neglected tropical disease that represents a Public Health problem due to its high incidence. In the search of new alternatives for Leishmaniasis treatment diethyldithiocarbamate (DETC) has shown an excellent leishmanicidal activity and the incorporation into drug carrier systems, such as solid lipid nanoparticles (SLNs), is very promising. In the present work DETC loaded in beeswax nanoparticles containing copaiba oil were obtained by the double emulsion/melt technique. The nanoparticles were characterized and leishmanicidal activity against L. amazonensis promastigotes forms and cytotoxicity in murine macrophages were evaluated. SLNs presented size below 200 nm, spherical morphology, negative charge surface, high encapsulation efficiency, above 80%, and excellent stability. Moreover, Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC) analyses were performed to evaluate the chemical structure and possible interactions between DETC and SLNs. SLNs provided a protection for DETC, decreasing its cytotoxic effects in macrophages, which led to an improvement in the selectivity against the parasites, which almost doubled from free DETC (11.4) to DETC incorporated in SLNs (18.2). These results demonstrated that SLNs had a direct effect on L. amazonensis promastigotes without affect the viability of macrophage cell, can be a promising alternative therapy for the cutaneous treatment of L. amazonensis.

Controle da antracnose em frutos de Persea Americana Miller com óleos essenciais

A antracnose é uma doença causada pelo patógeno Colletotrichum gloeosporioides afeta frutos de abacateiro (Persea americana Miller), tornando-os impróprios para a comercialização. Buscando-se o manejo alternativo de doenças, objetivou-se determinar o efeito de óleos essenciais no controle da antracnose em frutos de abacateiro e sua influência sobre a qualidade físico-química. O trabalho foi conduzido no Laboratório de Fitopatologia de Universidade Federal da Paraíba, campus II. Os frutos de abacateiro foram tratados com óleos essenciais de capim-limão, canela, eucalipto, rícino, copaíba, andiroba, alecrim, canola, cravo e linhaça, que foram adicionados ao meio de cultura BDA, na concentração de 0,75 μLmL-1 e adicionado a estes duas gotas de Tween 80. Além do fungicida Tiabendazol 400 ml/100L acrescido no meio BDA e a testemunha (meio de cultura puro). Foram avaliados: índice da velocidade de crescimento micelial, produção de conídios e severidade do patógeno. As avaliações físico-químicas dos frutos foram: perda de massa fresca; firmeza da casca; pH; relação SS/AT. Os óleos essenciais de canela, capim limão, eucalipto, cravo, erva-doce, copaíba e alecrim reduzem o crescimento micelial. Os óleos utilizados mostram potencial como tratamento alternativo reduzindo o uso de fungicidas. O óleo de canela na concentração 0,75 μLmL-1 reduz significativamente o crescimento e esporulação do patógeno. Os óleos essenciais não interferem na qualidade pós-colheita de frutos de abacate P. americana Miller.

Hydrophobin-stabilized nanoemulsion produced by a low-energy emulsification process: A promising carrier for nutraceuticals

Hydrophobin II (HFBII) is an amphiphilic biopolymer that could be explored to stabilize oil-in-water nanoemulsions as nutraceutical delivery systems. This study reports the production of HFBII-stabilized nanoemulsions by a spontaneous emulsification process using copaiba oil as a bioactive lipid. HFBII was isolated from a wild-type Trichoderma reesei and characterized. A 23 full factorial design with three central points was used to obtain an optimal nanoemulsion system, whose physical-chemical properties were studied under different ionic strength and pH. The peptide similarity search allowed the identification of a series of 6 ion fragments from the isolated fraction, which can be attributed to the amino acid sequences of the HFBII database. The optimal nanoemulsion system presented a nanoscale droplet size (<200 nm), a narrow size distribution (PDI <0.2) and a negative zeta potential of ≈ −30 mV, which was stable at low salt content and pH values close to the neutrality. These results demonstrated the feasibility of using HFBII as a biopolymer to stabilize nanoemulsion systems. Furthermore, the HFBII-stabilized nanoemulsion is a promising carrier for nutraceuticals in food technology applications.

Chitosan/Copaiba oleoresin films for would dressing application

Biopolymeric films can be used as dressings for the treatment of skin burns and other chronic wounds. The healing properties of these films may be enhanced by the addition of Copaiba oil (Copaifera L.) which properties have already been well-described. The aim of this study was to evaluate the addition of Copaiba oil in chitosan films prepared by casting solvent evaporation technique using chitosan solution (2% or 1% wt/wt) and Copaiba oil (0.1 or 1.0% wt/wt) at different concentrations. Films were characterized by color analysis, scanning electron microscopy, mechanical properties, thermal analysis, and fluid handling capacity. The developed films demonstrated potential for wound dressing, translated by the fluid handling capacity similar to that of commercial dressings. While no surfactant was present in the formulation, the droplets of Copaiba oil were well-dispersed and homogeneously distributed in the chitosan matrix even after drying. The thermal analysis translated the occurrence of interactions between the oil and chitosan.

Physiological and sanitary quality of seeds of Dimorphandra gardneriana Tul. treated with essential oils

Dimorphandra gardneriana, popularly known as fava d’anta, is a medicinal species whose fruits and seeds are used in the manufacture of medicines. The objective of this study was to evaluate the efficiency of clove (Syzygium aromaticum (L.) Merr. &amp; L.M. Perry) and copaíba (Copaifera sp.) essential oils in antifungal treatment of seeds of D. gardneriana and their influence on physiological quality of the seeds. Two experiments were carried out in a completely randomized design using seeds treated with different concentrations of copaiba and clove oils (0.5, 1.0, 1.5, and 2.0 mL) and two controls—seeds were treated with distilled water or fungicide. The variables analyzed were: incidence of fungi in seeds in the first experiment and seed germination and vigor (first germination, length and dry mass of root and shoot of the seedlings) in the second one. The incidence of fungi of the genera Aspergillus sp., Penicillium sp., and Rhizopus sp. in the seeds was elevated. The copaiba oil at the concentrations used did not satisfactorily reduce the incidence of fungi in the seeds of D. gardneriana, while the treatment of the seeds with clove oil at concentrations of 2.0 and 0.5 mL reduced the incidence of Penicillium sp. and Rhizopus sp., respectively. Seed germination and vigor increased at concentrations of 2 mL of clove oil and 1.25 mL of copaiba oil.

Copaiba Oil Attenuates Right Ventricular Remodeling by Decreasing Myocardial Apoptotic Signaling in Monocrotaline-Induced Rats.

There is an increase in oxidative stress and apoptosis signaling during the transition from hypertrophy to right ventricular (RV) failure caused by pulmonary arterial hypertension (PAH) induced by monocrotaline (MCT). In this study, it was evaluated the action of copaiba oil on the modulation of proteins involved in RV apoptosis signaling in rats with PAH. Male Wistar rats (±170 g, n = 7/group) were divided into 4 groups: control, MCT, copaiba oil, and MCT + copaiba oil. PAH was induced by MCT (60 mg/kg intraperitoneally) and, 7 days later, treatment with copaiba oil (400 mg/kg by gavage) was given for 14 days. Echocardiographic and hemodynamic measurements were performed, and the RV was collected for morphometric evaluations, oxidative stress, apoptosis, and cell survival signaling, and eNOS protein expression. Copaiba oil reduced RV hypertrophy (24%), improved RV systolic function, and reduced RV end-diastolic pressure, increased total sulfhydryl levels and eNOS protein expression, reduced lipid and protein oxidation, and the expression of proteins involved in apoptosis signaling in the RV of MCT + copaiba oil as compared to MCT group. In conclusion, copaiba oil reduced oxidative stress, and apoptosis signaling in RV of rats with PAH, which may be associated with an improvement in cardiac function caused by this compound.

Zero-spiked regression models generated by gamma random variables with application in the resin oil production

ABSTRACTZero-inflated data are more frequent when the data represent counts. However, there are practical situations in which continuous data contain an excess of zeros. In these cases, the zero-inflated Poisson, binomial or negative binomial models are not suitable. In order to reduce this gap, we propose the zero-spiked gamma-Weibull (ZSGW) model by mixing a distribution which is degenerate at zero with the gamma-Weibull distribution, which has positive support. The model attempts to estimate simultaneously the effects of explanatory variables on the response variable and the zero-spiked. We consider a frequentist analysis and a non-parametric bootstrap for estimating the parameters of the ZSGW regression model. We derive the appropriate matrices for assessing local influence on the model parameters. We illustrate the performance of the proposed regression model by means of a real data set (copaiba oil resin production) from a study carried out at the Department of Forest Science of the Luiz de Queiroz School of Agriculture, University of São Paulo. Based on the ZSGW regression model, we determine the explanatory variables that can influence the excess of zeros of the resin oil production and identify influential observations. We also prove empirically that the proposed regression model can be superior to the zero-adjusted inverse Gaussian regression model to fit zero-inflated positive continuous data.

Effects of a massage-like essential oil application procedure using Copaiba and Deep Blue oils in individuals with hand arthritis

Background and PurposeExisting research suggests that both massage and essential oils may have analgesic and anti-inflammatory benefits. We investigate the benefits of the AromaTouch Hand Technique® (ATHT), a procedure that combines a moderate pressure touch with the application of essential oils to the hand, in individuals with hand arthritis. Methods and materialsThirty-six participants with rheumatoid arthritis, osteoarthritis, and/or chronic inflammation received ATHTs with either a 50/50 preparation of Deep Blue® and Copaiba oil or a coconut oil placebo twice daily for 5 consecutive days. Changes in maximum flexion in finger and thumb joints, items from the Arthritis Hand Function Test, and hand pain scores were evaluated. ResultsParticipants treated with the essential oil preparation required significantly less time to complete dexterity tasks and showed about 50% decrease in pain scores, increased finger strength, and significantly increased angle of maximum flexion compared to subjects treated with coconut oil. ConclusionThe ATHT with Copaiba and Deep Blue may have ameliorative effects on hand arthritis.

Meta-analysis on Copaiba Oil: Its Functions in Metabolism and Its Properties as an Anti-inflammatory Agent

AbstractMany medicinal plants are sought as alternative therapies for various conditions, as opposed to synthetic alternatives. The Brazilian Amazon provides a plethora of plants with various therapeutic and medicinal properties. One of them is copaiba oil, a natural product of the biodiversity of the Amazon. The anti-inflammatory and antimicrobial properties of copaiba oil have been drawing the attention of the scientific community as a great alternative in the treatment of illnesses associated with inflammatory and infectious processes. The purpose of the present study is to evaluate and analyze the latest publications on the use of copaiba oil in the PubMed/Medline database from 2014 to 2017. Forty-two articles were collected, verifying anti-inflammatory activity, antimicrobial activity, healing, and antitumor activity. The results found on researches with copaiba oil according to publication dates were 11.9% in 2014, 38.1% in 2015, 16.7% in 2016, and 33.3% in 2017. In the analyzed studies, the proposed administration of copaiba oil was 50% topical, 28.6% oral, 9.5% enteral, 4.8% subcutaneous, and 7.1% others. In the objectives of the presente study in relation to the administration of copaiba oil, the result was 31% antimicrobial, 28.6% anti-inflammatory, 9.5% antitumor, 9.5% healing, and 21% others. Regarding the types of research, we have found 50% in vitro, 40.4% in vivo animals, 2.4% in vivo human, 2.4% review and 4.8% others. Regarding the significance factor evaluation, the result was 100% positive in antitumor activity, 84% positive in infection and inflammation pathology, 62% positive in others, like dental processes, food technology application support and as a drug absorption vehicle, and 50% in healing. The results presented in the current meta-analysis show that copaiba oil is an effective alternative to treatments of illnesses such as chronic inflammation, infectious diseases, various types of cancer, autoimmune diseases, and as a vehicle for the absorption of other drugs. Thus, more studies regarding the benefits of copaiba oil could provide a great contribution to the medical community in the treatment of the aforementioned illnesses.

Why analyze germination experiments using Generalized Linear Models?

Abstract: We compared the goodness of fit and efficiency of models for germination. Generalized Linear Models (GLMs) were performed with a randomized component corresponding to the percentage of germination for a normal distribution or to the number of germinated seeds for a binomial distribution. Lower levels of Akaikes’s Information Criterion (AIC) and Bayesian Information Criterion (BIC) combined, data adherence to simulated envelopes of normal plots and corrected confidence intervals for the means guaranteed the binomial model a better fit, justifying the importance of GLMs with binomial distribution. Some authors criticize the inappropriate use of analysis of variance (ANOVA) for discrete data such as copaiba oil, but we noted that all model assumptions were met, even though the species had dormant seeds with irregular germination.

β-Caryophyllene, the major constituent of copaiba oil, reduces systemic inflammation and oxidative stress in arthritic rats.

The current study investigated the action of β-caryophyllene, the major constituent of copaiba oil, on the systemic inflammation, oxidative status, and liver cell metabolism of rats with adjuvant-induced arthritis, a model for rheumatoid arthritis. This study also compared the actions of β-caryophyllene with those previously reported for copaiba oil on arthritic rats. For this purpose, Holtzman healthy and arthritic rats received215 and 430 mg·kg-1 β-caryophyllene orally once a day during 18 days. Both doses of β-caryophyllene reduced the adjuvant-induced paw edema, swollen of lymph nodes, and number of circulating and articular leukocytes. β-Caryophyllene, at the dose of 430 mg·kg -1 , abolished the increases of protein carbonyl groups and myeloperoxidase activity in the liver and plasma of arthritic rats and, at both doses, it restored the increased levels of reactive oxygen species and reduced glutathione in the arthritic liver. These beneficial actions were of the same extension as those of copaiba oil ( Copaifera reticulata) and, therefore, β-caryophyllene is possibly responsible for the anti-inflammatory and antioxidant actions of the oil. Hepatic gluconeogenesis was 40% lower in arthritic rats, which also presented a reduced number of hepatocytes per liver area (-23%) associated with increased hepatocyte area (+18%) and liver weight (+50%). None of these hepatic alterations were improved by β-caryophyllene, but not even by ibuprofen. However, unlike copaiba oil, β-caryophyllene did not modify the hepatic morphology and metabolism of healthy rats. These results reveal that β-caryophyllene improves the systemic inflammation and oxidative status of arthritic rats and, in addition, it was not associated with hepatotoxicity.

A synergistic nanoformulation of babassu and copaiba oils as natural alternative for prevention of benign prostatic hyperplasia

Benign Prostatic Hyperplasia (BPH) is a common progressive condition that affects the quality of life of older men. Since current pharmacological interventions can cause severe side effects, this study aimed to develop, characterize and evaluate a natural alternative based on the use of babassu oil (BBS) and copaiba oil-resin (COP) incorporated into self-emulsifying drug delivery systems (SEDDS). Initially, the major components of each of the natural oils were analyzed by gas chromatography/mass spectrometry to provide a means to track their incorporation into nanoformulations. An effective analytical methodology was developed to detect lauric acid and β-caryophyllene as chemical tracers for BBS and COP, respectively. The physical characteristics of the resulting nanoemulsions were next analyzed to identify preparations suitable for in vitro toxicity and in vivo tests. The two most promising SEDDS formulations, containing BBS with and without COP, were thermodynamically stable with a zeta potential less than −20 mv and droplet size around 30 nm. In addition, both were non-cytotoxic and genotoxic. These formulations, in rat model of BPH, showed promising potential to reduce the onset of this pathological process. In conclusion, SEDDS containing BBS and COP were successfully developed that could serve as natural alternatives for the prevention of BPH.

The use of copaiba oil in broiler chicks feed to replace antibiotic caused an anti-inflammatory effect and promoted weight gain

The objective of this study was to assess the effect of copaiba oils (Copaifera reticulata and Copaifera duckei) on the health and performance of broiler chicks along with their anti-inflammatory activity. The experiment was performed in duplicate, using 60 chicks at a time. Groups were formed by broiler chicks fed with basal diet (control); basal diet and antibiotic (zinc bacitracin, 25 mg/kg of feed); basal diet and copaiba oil (0.15 mL/kg of feed); and basal diet and copaiba oil (0.30 mL/kg of feed) for 15 days. Sampling was performed on days 7 and 15 of life. Animals treated with 0.15 mL/kg of copaiba showed higher body weight (p 0.05); however, glucose and triglyceride levels were reduced on days 7 and 15 in animals that received copaiba oil, respectively (p < 0.05). No histopathological lesions were observed in the jejunum of all groups. Crypt and villus sizes were lower in animals treated with 0.15 mL/kg of copaiba oil. It is possible to conclude that copaiba vegetable oil at a dose of 0.15 mL/kg improved body weight gain and have anti-inflammatory effect.

Trypanocidal activity of copaiba oil and kaurenoic acid does not depend on macrophage killing machinery

Activity, mechanisms of action, and toxicity of natural compounds have been investigated in a context in which knowledge on which pathway is activated remains crucial to understand the action mechanism of these bioactive substances when treating an infected host. Herein, we showed an ability of copaiba oil and kaurenoic acid to eliminate Trypanosoma cruzi forms by infected macrophages through other mechanisms in addition to nitric oxide, reactive oxygen species, iron metabolism, and antioxidant defense. Both compounds induced an anti-inflammatory response with an increase in IL-10 and TGF-β as well as a decrease in IL-12 production. Despite being able to modulate the immune response in host cells, the antimicrobial activity of copaiba oil and kaurenoic acid seems to be a direct action of the compounds on the parasites, causing their death.