Aduncum Essential Oil Research Articles

Effects of Piper aduncum (Piperales: Piperaceae) Essential Oil and Its Main Component Dillapiole on Detoxifying Enzymes and Acetylcholinesterase Activity of Amblyomma sculptum (Acari: Ixodidae).

Amblyomma sculptum is a species of tick in the family Ixodidae, with equids and capybaras among its preferred hosts. In this study, the acaricidal activity of the essential oil (EO) from Piper aduncum and its main component, Dillapiole, were evaluated against larvae of A. sculptum to establish lethal concentration values and assess the effects of these compounds on tick enzymes. Dillapiole exhibited slightly greater activity (LC50 = 3.38 mg/mL; 95% CI = 3.24 to 3.54) than P. aduncum EO (LC50 = 3.49 mg/mL; 95% CI = 3.36 to 3.62) against ticks. The activities of α-esterase (α-EST), β-esterase (β-EST), and glutathione-S-transferase (GST) enzymes in A. sculptum larvae treated with Dillapiole showed a significant increase compared to the control at all concentrations (LC5, LC25, LC50 and LC75), similar results were obtained with P. aduncum EO, except for α-EST, which did not differ from the control at the highest concentration (LC75). The results of the acetylcholinesterase (AChE) activity show an increase in enzyme activity at the two lower concentrations (LC5 and LC25) and a reduction in activity at the two higher, lethal concentrations (LC50 and LC75) compared to the control. These results suggest potential mechanisms of action for these natural acaricides and can provide guidance for the future development of potential plant-derived formulations.

The activity of spiked pepper fruit essential oil against fall armyworm larvae

Spiked pepper (Piper aduncum) essential oil has the potency to develop as a botanical insecticide in controlling fall armyworm (Spodoptera frugiperda). This study aimed to determine the activity of spiked pepper fruit essential oils against fall armyworm larvae. This study was held from November 2020 to March 2021 at the Insect Bioecology Laboratory, Faculty of Agriculture, Andalas University, West Sumatera, Indonesia. The experiment used a Completely Randomized Design (CRD), including preliminary and advanced tests. The preliminary test was conducted using three concentration levels (0%, 0.25%, and 0.5%) and consisted of 4 replications. The advanced test was conducted using 5 concentration levels and control (0%, 0.05%, 0.07%, 0.11%, 0.17% and 0.25%) and consisted of 5 replications. The test ran with the leaf-dipped method, with parameters observed were larval mortality, feeding inhibition activity (antifeedant), and larval development time. The observation data were analyzed using analysis of variance, and if there were any significant differences, it continued with a further test using Least Significant Difference (LSD) at a 5% level. LC50 and LC95 values were analyzed using the POLO PC software. The result showed that spiked pepper fruit essential oil could cause larval mortality, inhibit feeding activity, and inhibit Fall armyworm larval growth. The treatment with a concentration of 0.17% showed the best result, which could lead to 98.67% larvae mortality, inhibit feeding activity by 91.23% and inhibit larvae growth from reaching the sixth instar around 3.26 days compared to the control. The LC50 and LC95 value of spiked pepper fruit essential oil solution was 0.068% and 0.151%, respectively. Overall, spiked pepper essential oil has insecticidal activity against fall armyworm larvae.

Development, validation and application of a gas chromatography method for the determination of dillapiole from Piper aduncum essential oil in skin permeation samples.

The essential oil extracted from the leaves of Piper aduncum has antifungal, insecticidal and antibacterial activity. Studies with its main compound, dillapiole (DIL) revealed antibacterial and anti-inflammatory potential. Despite all this bioactivity, there is no updated report on the development and validation of analytical and bioanalytical methodology to quantify DIL in skin samples. A selective, precise, accurate and adequate method for the determination of DIL in solutions, porcine ear skin samples and receptor fluid was developed and validated by headspace extraction-gas chromatography with flame ionization detection (HS-GC-FID). HS-GC-FID was applied to determine DIL in Franz cell permeation and retention studies using porcine ear skin samples. In the HS-GC-FID method, matrix-related interferences were not observed at the peak of the DIL retention time. The results showed a high recovery (>97%) after the extraction procedure, allowing the quantification of DIL in complex matrices. In vitro permeation/retention for DIL showed cumulative amounts permeated in the order: receptor fluid (21.98 ± 1.19 μg/cm2 ) > epidermis (15.40 ± 1.20 μg/cm2 ) > dermis (9.52 ± 1.13 μg/cm2 ). HS-GC-FID was successfully validated and the results point to DIL transdermal permeation and to the potential to develop pharmaceutical formulations for skin delivery to treat inflammation or infections.

Piper aduncum Essential Oil Rich in Dillapiole: Development of Hydrogel-Thickened Nanoemulsion and Nanostructured Lipid Carrier Intended for Skin Delivery.

The essential oil extracted from the leaves of Piper aduncum, an aromatic plant from the Amazon region, is rich in dillapiole and presents anti-inflammatory activity. In this study, nanoemulsions (NE) and nanostructured lipid carriers (NLC), which are biocompatible nanostructured systems of a lipid nature, were prepared by high-pressure homogenization for the yet unexplored skin delivery of dillapiole. The addition of hydroxyethylcellulose produced hydrogel-thickened NE or NLC in view to improving the viscosity and skin adherence of the nanoformulations. Formulations were characterized with respect to dillapiole content, droplet size, polydispersity index, zeta potential, morphology, rheological behavior, bioadhesion, skin permeation profile, and in vitro irritancy (HET-CAM). The formulations developed presented spherical, homogeneous nanometric particle size (around 130 nm), narrow polydispersity index (<0.3), and negative zeta potential (around -40 mV). Dillapiole content was slightly lower in NLC compared to NE since the production process involves heating. The hydrogels containing nanocarriers showed pseudoplastic behavior with bioadhesive characteristics. The developed formulations exhibited a controlled release profile, dillapiole delivery up to the dermis, the layer of interest for anti-inflammatory potential, and low irritant potential in the chorioallantoic membrane (HET-CAM). Both hydrogels-thickened NE and NLC seemed to be promising formulations for skin delivery of Piper aduncum essential oil.

The effect of various essential oil and solvent additives on the botanical pesticide of Piper Aduncum essential oil on formulation antifungal activity

This study aims to obtain a formulation of the botanical pesticide P aduncum with additives and the right type of solvent. The research was arranged in a completely randomized design in factorial, the first factor being essential oil additives; citronellagrass oils (Andropogon nardus), lemongrass oils (Cimbopogon flexiosus), Ceylon cinnamon leaf oils (Cinnamomum zeylanicum), Padang cinnamon leaf oils (Cinnamomum burmanii), clove leaf oils (Eugenia aromatica) and wild ginger leaf oils (Elettariopsis slahmong), both types of solvent (ethanol, methanol and turpentine). The experiment was carried out at the Laing Solok IPPTP parasitology laboratory. The results showed that all additive materials had a positive effect in increasing the antifungal activity of the botanical pesticide P aduncum essential oil with different effectiveness against the test fungi. Citronella oil showed the highest antifungal effectiveness compared to other additives, especially against S. rolfsii and Pestalotia sp, with diameter and biomass inhibition of fungal colonies tested S rolfsii 92.15% and 92.70%, Pestalotia sp 84.82% and 86,34% and F. oxysporum 43.87 and 47.17%. All solvents can be used for the formulation of the botanical pesticide P aduncum, ethanol solvent is better than methanol and turpentine with the highest inhibition capacity of the diameter and biomass of the fungus colonies tested S rolfsii 91.28% and 92.05%, Pestalotia sp 83.56% and 86.02% and for F. oxysporum 40.31 and 48.36%, respectively.

Influence of drying on the chemical composition and bioactivity of Piper aduncum (Piperaceae) essential oil against Aedes aegypti (Diptera: Culicidae)

Piper species are producers of essential oils with high yield and promising chemical composition for both perfumery and the pharmaceutical industry. They present bioactivity against pathogens and against insect pests, whether agricultural or medical, such as Aedes aegypti, for example, a vector of arboviruses with a high incidence in tropical and subtropical regions. In this study, an investigation was carried out to elucidate the chemical composition of essential oils from the leaves and inflorescences of Piper aduncum collected in the state of Goiás, Brazil. Evaluating the interference of the drying process on yield, chemical composition and larvicide potential against Ae. aegypti. Leaves and inflorescences of P. aduncum were collected in the rural area of the municipality of Iporá-GO. Fresh and dried samples were processed separately and subjected to hydrodistillation for two hours. The oil obtained was qualitatively evaluated by gas-coupled chromatography and mass spectrometry. Greater yield was observed in samples submitted to the drying process. Oils obtained from fresh samples had a higher percentage of monoterpene hydrocarbons. Variation was observed between the major components of samples of fresh leaves and inflorescences, with eupatoriochrome being the major component in dried samples. Larvicidal activity against Ae. aegypti was considered promising (LC50<100µg/mL) in all samples. The results obtained showed a chemical composition different from that generally presented by P. aduncum. This reinforces the idea of intraspecific variability of essential oils and the need for chemical evaluation between samples even if they belong to the same species.

Genotoxic and mutagenic effects of methyl ether dillapiole on the development of Aedes aegypti (Diptera: Culicidae)

Dillapiole, extracted from Piper aduncum essential oil and its derivatives, has been shown to be a potential alternative to the control of Aedes aegypti, which has become resistant to synthetic insecticides. Methyl ether dillapiole (MED) and temephos (TM) were compared to complement the data on the genotoxicity and developmental changes of Ae. aegypti. Over four generations (G1 -G4 ), third stage larvae were treated with MED at 60, 80 and 100 μg/mL and TM at 0.002, 0.005 and 0.007 μg/mL for 4 h. Adult females were separated to estimate oviposition and hatching rates, and total egg length. Over the four generations, a significant reduction was recorded in oviposition and hatching rates, and in mean egg length (Tukey, P< 0.05), compared with the negative control (NC). Cytological slide preparations were done from adult oocytes and larval neuroblasts. The cumulative effects of genotoxic (bridges, budding and nuclear fragmentation) and mutagenic (micronucleus and chromosomal breakage) damage was observed in the neuroblasts and oocytes of exposed mosquitoes. Developmental changes and damage to the genome of MED-treated Ae. aegypti were greater than those caused by TM. Further studies should focus on understanding the effects of the MED molecule on Ae. aegypti.

Ecological risk assessment of Piper aduncum essential oil in non-target organisms

ABSTRACT One possible alternative to chemotherapeutic agents in the treatment and prevention of diseases in fish farms is the use of Piper aduncum essential oil. However, ecotoxicological data are required to ensure its proper use and to prevent adverse effects on non-target organisms. These data are relevant since this essential oil is described as having insecticidal, molluscicidal and cytotoxic activitiy that may be associated with its chemical composition. Thus, the aim of this study was to evaluate the ecotoxicity of P. aduncum essential oil to five test organisms using the species sensitivity distribution (SSD) statistical approach. The chemical composition of the essential oil was characterized by means of gas chromatography coupled to mass spectrometry (GC-MS) and gas chromatography-flame ionization detection (GC-FID) for identification and quantitation purposes, respectively. The main component (75.5%) of the essential oil was dillapiole. The hazardous concentration for 5% of biological species (HC5) was calculated to determine the 95% protection level, resulting in a value of 0.47 mg L-1 (with a confidence interval of 0.028 - 1.19 mg L-1. ). A concentration range related to the level of protection for aquatic communities (the predicted no-effect concentration, PNEC) was determined through the application of safety factors to the HC5 value. The ecotoxicity parameters showed that P. aduncum essential oil can be used safely in water bodies at a concentration equal to or below 0.09 mg L-1.

Piper aduncum essential oil: a promising insecticide, acaricide and antiparasitic. A review.

Several studies have assessed the potential of essential oils as substitutes for synthetic pesticides, in order to counter insect resistance to commercial pesticides. Piper aduncum L. is a very common shrub in the Amazon Rainforest and in other subtropical areas. The objective of this review was to analyse the existing information on P. aduncum essential oil as a raw material for new bioproducts for sustainable pest disease management. With this review, we collected and critically analysed 59 papers, representing all the studies that aimed to evaluate the essential oil properties of this species as an insecticide, acaricide and antiparasitic. The chemical composition differs depending on the origin, although phenylpropanoid dillapiole is the most cited component, followed by myristicin, 1,8-cineole and β-ocimene. Between the acaricidal, antiparasitic and synergistic activities, the insecticidal effects are highly promising, with optimal results against the malaria vector Aedes aegypti, with an LC50 that ranges between 57 and 200μg/mL. Acaricidal activity has mainly been reported against Tetranychus urticae, showing an LC50 that ranges between 5.83 and 7.17μg/mL. Antiparasitic activity has predominately been found on Leishmania amazonensis, and antipromastigote activity has been found to be between 23.8 and 25.9μg/mL. Concerning the synergistic effect between dillapiole and synthetic insecticides, four studies on Spodoptera frugiperda found promising results with cypermethrin. In this review, we highlighted the potential of P. aduncum essential oil as a biopesticide, also focusing on the lack of information about applied research. We also provide suggestions for future investigations.

Microwave-assisted extraction: an alternative to extract Piper aduncum essential oil

Microwave-assisted extraction: an alternative to extract Piper aduncum essential oil

Genotoxic Effects of Semi-Synthetic Isodillapiole on Oviposition in Aedes aegypti (Linnaeus, 1762) (Diptera: Culicidae).

INTRODUCTION: Semi-synthetic dillapiole compounds derived from Piper aduncum essential oil are used as alternative insecticides to control insecticide-resistant Aedes aegypti. Thus, we aimed to evaluate the genotoxic effects of semi-synthetic isodillapiole on the nuclei of neuroblasts (larvae) and oocytes (females) and the mean oviposition rates of the females over four generations (G1, G2, G3, and G4) of Ae. aegypti.METHODS: Larvae were captured in the city of Manaus, Amazonas state, Brazil, and exposed to isodillapiole in bioassays (20, 40, and 60 µg/mL) and a negative control (0.05% DMSO in tap water) for 4 h. The cerebral ganglia were extracted from the larvae and oocytes from the adult females to prepare slides for cytogenetic analysis. Breeding pairs were established and eggs counts were quantified taken after the bioassays. RESULTS: The analysis of 20,000 interphase nuclei of neuroblasts and oocytes indicated significant genotoxicity (micronuclei, budding, polynucleated cells, and other malformations) compared to that of the control. Metaphasic and anaphasic nuclei presented chromosomal breaks; however, no significant variation and damage was observed in the negative control. A significant reduction in mean oviposition rates was also recorded following exposure to isodillapiole over the four generations (G1, G2, G3, and G4). CONCLUSIONS: The toxic and genotoxic effects of isodillapiole on Ae. aegypti were caused by reduced oviposition in the females and nuclear abnormalities over the four generations of the trials. Further studies are required, rather than our in vitro assays, to verify the efficacy of exposure to this compound for controlling Ae. aegypti.

Fixatives Increase the Efficacy of Gel Formulations Containing Piper aduncum Linnaeus (Piperales: Piperaceae) Essential Oil as Repellenty

Piper aduncum essential oil exhibit repellency activity and has a potential to be use as an alternative for synthetic repellent such as N,N-diethyl-3- methylbenzamide, (DEET). However, the volatility properties of the essential oil decrease their persistence as a topical repellent. Study has shown that formulation of the essential oil with some fixatives may increase their effectiveness. Therefore, this study was conduct to evaluate the effectiveness of gel formulation containing P. aduncum essential oil with two fixative; vanillin and paraffin oil. Gel formulations containing P. aduncum essential oil with 5% and 10% vanillin and 6% paraffin oil was prepared and tested against Aedes aegypti in laboratory using Standards and Industrial Research Institute of Malaysia (SIRIM) bioassay method. After 240 minute post-application, formulation containing 5% and 10% vanillin was able to provide >70% repellency percentage against mosquito while formulation containing 6% paraffin oil gives <30% repellency percentage. As conclusion, P. aduncum based repellent gel containing 5% and 10% vanillin was able to prolong the effect of P. aduncum essential oil as repellent against dengue vector in laboratory. DOI : http://dx.doi.org./10.17576/JSKM-2019-1701-02

Phytochemical of Piper essential oil and acute toxicity against Helicoverpa armigera (Lepidoptera: Noctuidae)

Plant essential oils have been recognized as important natural resources for bioprospection of new insecticides. Here, we provided a chemical analysis and assessing the toxicity of the essential oil of Piper aduncum L. (Piperaceae) against Helicoverpa armigera Hubner (Lepidoptera: Noctuidae) a cosmopolite and key pest in agricultural systems. The essential oil was obtained from the leaves of P. aduncum via hydrodistillation. Subsequently, acute mortality bioassays with two modes of exposure (ingestion and topical methods) were conducted to assess the lethal effects. The chromatograph analysis of P. aduncum essential oil indicated myristicin, isomyristicin, asaricim, dillapiole and isocroweacin the compounds more abundant. The acute toxicity bioassays exhibited concentration-dependent to mortality of larvae of first and third instar of H. armigera, when exposure by ingestion or topical application to Piper essential oil, with highlight to reduction in survival in 1st instar larvae. The median lethal time (LT50) when larvae were treated by ingestion was of LT50 < 14.20 days (first instar) and LT50 = 16.89 days (third instar). Whereas to larvae treated by topical method the median lethal time was of LT50 < 14.68 days (first instar) and LT50 < 10.73 days (third instar), which demonstrate a drastic reduction in survival of insect, when contrasted to control. In summary, our results highlight toxicity of P. aduncum essential oil against H. armigera and provide more information on plant-compounds that can be use in bioprospection of new insecticide molecules to pest management.

Essential Oil from Piper aduncum: Chemical Analysis, Antimicrobial Assessment, and Literature Review.

Background: The challenge in antimicrobial chemotherapy is to find safe and selective agents with potency that will not be compromised by previously developed resistance. Terrestrial plants could provide new leads to antibacterial, antifungal, or antiprotozoal activity. Methods: The essential oil (EO) of Piper aduncum L. (Piperaceae) from Cuba was analyzed by gas chromatography—mass spectrometry (GC-MS). A cluster analysis of P. aduncum EO compositions reported in the literature was carried out. The EO was screened against a panel of microorganisms (bacteria, fungi, parasitic protozoa) as well as for cytotoxicity against human cells. In addition, a review of scientific literature and a bibliometric study was also conducted. Results: A total of 90 compounds were identified in the EO, of which camphor (17.1%), viridiflorol (14.5%), and piperitone (23.7%) were the main components. The cluster analysis revealed at least nine different chemotypes. The EO did not show notable activity against bacteria or fungi, but was active against parasitic protozoa. Conclusions: The results from this study indicate P. aduncum from Cuba is a unique chemotype, support the importance of P. aduncum EOs as medicines, and demonstrate the promise of Cuban P. aduncum EO as a chemotherapeutic agent against parasitic protozoal infections.

Nerolidol, the main constituent of Piper aduncum essential oil, has anti-Leishmania braziliensis activity.

Leishmania (Viannia) braziliensis is a protozoan that causes mucocutaneous leishmaniasis, which is an infectious disease that affects more than 12 million people worldwide. The available treatment is limited, has side-effects or is inefficient. In a search for alternative compounds of natural origin, we tested the microbicidal activity of Piper aduncum essential oil (PaEO) on this parasite. Our data showed that PaEO had an inhibitory effect on the growth of L. braziliensis promastigotes with an IC50/24 h=77·9 µg mL-1. The main constituent (nerolidol: 25·22%) presented a similar inhibitory effect (IC50/24 h = 74·3 µg mL-1). Ultrastructural observation of nerolidol-treated parasites by scanning and transmission electron microscopies revealed cell shrinkage and morphological alterations in the mitochondrion, nuclear chromatin and flagellar pocket. Flow cytometry analysis showed a reduction in the cell size, loss of mitochondrial membrane potential, phosphatidylserine exposure and DNA degradation, which when associated with the morphological changes indicated that nerolidol induced incidental cell death in the L. braziliensis promastigotes. The results presented here indicate that nerolidol derivatives are promising compounds for further evaluation against Leishmania parasites.

Essential oil of spiked pepper, Piper aduncum L. (Piperaceae), for the control of caterpillar soybean looper, Chrysodeixis includens Walker (Lepidoptera: Noctuidae)

The resistance of pests to insecticides and the high costs of pest control have prompted a search for less harmful alternatives to the environment. Phytoinsecticides can be a promising option in the control of pests. The insecticidal properties of the essential oil of Piper aduncum L. (Piperaceae) have been demonstrated by several authors. This study was aimed at evaluating the insecticidal activity of P. aduncum essential oil on caterpillars of the soybean looper, Chrysodeixis includens Walker. Two bioassays were conducted: The first was based on the ingestion of treated leaves, while the second, on direct contact. Chromatography was performed, and the resulting oil was used to treat larvae fed cotton leaves at the concentrations of 0.5, 1.0, 2.0, 4.0, and 8.0%. The controls consisted of water and acetone. The first assessment was carried out 24 h after the application. The main compounds identified by chromatography were dillapiole, myristicin, and Z-carpacin. In the ingestion bioassay, mortality reached 90% for the highest concentration in the first 24 h after application. For the topical application of P. aduncum essential oil, no significant differences were observed until the end of the life cycle of C. includens. This study demonstrates the insecticidal activity essential oil of P. aduncum on C. includens and its potential in the control of this insect by ingestion.

Dermal Toxicity of a Repellent Formulation Containing &lt;i&gt;Piper Aduncum&lt;/i&gt; Linnaeus (Piperales: Piperaceae) Essential Oil

It has been shown in previous research that Piper aduncum Linnaeus essential oil has the potential to be developed as an alternative mosquito repellent. When the essential oil was formulated into cream, it was able to provide >2h of protection against Aedes aegypti in the laboratory; thus, it can be commercialized as an alternative to synthetic repellent especially N, N-diethyl-3-methylbenzamide (DEET). In this study, the irritation and sensitization potential of a cream formulation containing P. aduncum essential oil was investigated to verify its safety for application purposes. The P. aduncum essential oil was formulated into a cream containing 10% of the essential oil for irritation and skin sensitization assays on New Zealand white rabbits and guinea pigs (Hartley strain), respectively, following the ISO10993-10:2010 (E) guidelines. The macroscopic and histological observations from both assays revealed that the cream formulation containing P. aduncum essential oil caused slight irritation on rabbit skin, with a Primary Irritation Index (PII) of 1.54; however, no positive response was detected in the skin sensitization assay. In conclusion, the cream formulation containing 10% P. aduncum essential oil was slightly irritating to rabbit skin but did not cause sensitization in the animals tested.

Linalool, a Piper aduncum essential oil component, has selective activity against Trypanosoma cruzi trypomastigote forms at 4°C.

BACKGROUND Recent studies showed that essential oils from different pepper species (Piper spp.) have promising leishmanicidal and trypanocidal activities.OBJECTIVES In search for natural compounds against Trypanosoma cruzi, different forms of the parasite were incubated for 24 h at 28ºC or 4ºC with Piper aduncum essential oil (PaEO) or its main constituents linalool and nerolidol.METHODS PaEO chemical composition was obtained by GC-MS. Drug activity assays were based on cell counting, MTT data or infection index values. The effect of PaEO on the T. cruzi cell cycle and mitochondrial membrane potential was evaluated by flow cytometry.FINDINGS PaEO was effective against cell-derived (IC50/24 h: 2.8 μg/mL) and metacyclic (IC50/24 h: 12.1 μg/mL) trypomastigotes, as well as intracellular amastigotes (IC50/24 h: 9 μg/mL). At 4ºC - the temperature of red blood cells (RBCs) storage in blood banks - cell-derived trypomastigotes were more sensitive to PaEO (IC50/24 h = 3.8 μg/mL) than to gentian violet (IC50/24 h = 24.7 mg/mL). Cytotoxicity assays using Vero cells (37ºC) and RBCs (4ºC) showed that PaEO has increased selectivity for cell-derived trypomastigotes. Flow cytometry analysis showed that PaEO does not affect the cell cycle of T. cruzi epimastigotes, but decreases their mitochondrial membrane potential. GC-MS data identified nerolidol and linalool as major components of PaEO, and linalool had trypanocidal effect (IC50/24 h: 306 ng/mL) at 4ºC.MAIN CONCLUSION The trypanocidal effect of PaEO is likely due to the presence of linalool, which may represent an interesting candidate for use in the treatment of potentially contaminated RBCs bags at low temperature.

Combining the essential oil of Piper aduncum L. with commercial insecticides

The use of synergists is important to minimize the amount of chemical insecticide required for insect control. Their use may contribute to reducing environmental contamination and preserving beneficial insects. The aim of this study was to evaluate the synergy and uniformity of the response of Spodoptera frugiperda (Noctuidae) larvae to doses of an essential oil of an Amazon chemotype, Piper aduncum (Piperaceae), when combinationed with the following commercial insecticides: cypermethrin, zeta-cypermethrin, permethrin and esfenvarelate, compared to piperonyl butoxide (PBO). Through the relationship between CL50 and DL50 of insecticides taken separately and their synergistic combinations with the essential oil and PBO, synergism factors (SF) were obtained for comparison with each other. With residual contact, there was a significant enhancement of commercial insecticides formulated with cypermethrin (SF = 73.03), zeta-cypermethrin (SF = 16.51) and permethrin (SF = 8.46-17.22), when combined with the P. aduncum essential oil; in turn, with topical application, there was only an observed significant enhancement for zeta-cypermethrin (SF = 0.40-4.26), permethrin (SF = 2.10-4.79) and esfenvarelate (SF = 3.80) insecticides when combined with the essential oil. With the exception of esfenvarelate, the other synergistic combinations showed homogeneous responses for topical application and residual contact for at least one synergistic combination with P. aduncum essential oil. The significance of the SF values from combining P. aduncum essential oil with cypermethrin, zeta-cypermethrin, permethrin and esfenvarelate insecticides may indicate that this essential oil is an alternative option to PBO.

The formulation of the essential oil of Piper aduncum Linnaeus (Piperales: Piperaceae) increases its efficacy as an insect repellent.

The essential oil (EO) of Piper aduncum Linnaeus, known as 'sireh lada' to locals Malaysian, has the potential to be used as an alternative to synthetic insect repellents such as N,N-diethyl-meta-toluamide. However, the EO's efficacy as a repellent decreases after application due to the high volatility of its active ingredients. A number of studies have showed that optimizing the formulation of plant-based EOs can improve their efficacy as repellents. The present study sought to evaluate the effectiveness of 10% P. aduncum EO in ethanol and in three different semisolid formulations: ointment, cream and gel. These formulations were tested on Aedes aegypti under laboratory conditions. Each formulation was applied to the subject's hands, which were then inserted into a cage containing 25 nulliparous A. aegypti. The number of mosquitoes landing on or biting each subject's hand was recorded, and the repellency percentage, landing/biting percentage and protection time for each of the formulations were compared. There were no statistically significant differences between the semisolid EO formulations with regards to the repellency percentage and the landing/biting percentage at 4 h post-application. All three semisolid EO formulations were able to repel >65% of the A. aegypti at 4 h post-application. The EO ointment formulation provided a protection time (182.5 ± 16.01 min) that was statistically significantly longer than that associated with the EO gel formulation (97.5 ± 14.93 min). Meanwhile, the EO cream formulation provided a protection time of 162.5 ± 6.29 min. As the EO cream and ointment formulations displayed better repellent properties than the EO gel formulation, they appear to be the most promising P. aduncum EO formulations to be developed and commercialized as alternatives to synthetic repellents.