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Natural Products as Effective Biopesticides and Antiprotozoal Agents

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A special issue of Molecules (ISSN 1420-3049). This special issue belongs to the section "Natural Products Chemistry".

Deadline for manuscript submissions: closed (31 December 2019) | Viewed by 32612

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Dr. Stefano Dall'Acqua

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Pharmaceutical and Pharmacological Sciences, Universita degli Studi di Padova, Padua, Italy
Interests: bioactive natural products; terpenoids; phenolics; saponins; alkaloids; NMR; LC-MS; GC-MS
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Dear Colleagues,

There is currently a need to identify new pest control active agents which exhibit efficient activity as well as increased safety, and this need has accentuated the extremely rich resource of natural products. “Biopesticides” can be defined as an agent that destroys or controls harmful organisms or diseases, or that is able to protect plants or plant products during the different phases of production, conservation storage, and transport. Biopesticides can come in different forms: For example, microorganisms, natural substances, or the so called plant-incorporated protectants (PIPs). The strict relationship that exists between some protozoal diseases and the possibility to, in part, control the diffusion of these illnesses by pest control agents suggests a further area of interest of biopesticide and, specifically, of naturally derived antiprotozoal agents.

This Special Issue aims to attract significant contribution describing the discovery, identification, or study of the molecular mode of action of active natural agents as biopesticide and antiprotozoal agents. Particularly appreciated will be contribution describing in detail new chemical structures by the means of MS and NMR approaches. Articles describing the activity of natural mixtures, such as plant extracts, will be welcomed, but with mandatory accurate characterization by chromatographic and spectroscopic techniques. Papers related to the use of in vitro and in vivo assays for the demonstration of activity and efficacy of biopesticides and antitrypanosomal agents, as well as papers focusing on the identification of mode of action, will be appreciated.

Dr. Stefano Dall'Acqua
Guest Editor

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Keywords

natural products
biopesticides
antiprotozoal
terpenoids
Phenolics
alkaloids

Published Papers (6 papers)

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Research

15 pages, 800 KiB

Open AccessArticle

Efficacy of Origanum syriacum Essential Oil against the Mosquito Vector Culex quinquefasciatus and the Gastrointestinal Parasite Anisakis simplex, with Insights on Acetylcholinesterase Inhibition

by Víctor López, Roman Pavela, Carlota Gómez-Rincón, Francisco Les, Fabrizio Bartolucci, Veronica Galiffa, Riccardo Petrelli, Loredana Cappellacci, Filippo Maggi, Angelo Canale, Domenico Otranto, Stefania Sut, Stefano Dall’Acqua and Giovanni Benelli

Molecules 2019, 24(14), 2563; https://doi.org/10.3390/molecules24142563 - 15 Jul 2019

Cited by 25 | Viewed by 9357

Abstract

Developing effective and eco-friendly antiparasitic drugs and insecticides is an issue of high importance nowadays. In this study, we evaluated the anthelminthic and insecticidal potential of the leaf essential oil obtained from Origanum syriacum against the L3 larvae of the parasitic nematode Anisakis simplex and larvae and adults of the mosquito Culex quinquefasciatus. Tests on A. simplex were performed by standard larvicidal and penetration assays, while mosquito toxicity was assessed relying on larvicidal, tarsal contact, and fumigation tests. To shed light on the possible mode of action, we analyzed the oil impact as acetylcholinesterase (AChE) inhibitor. This oil was particularly active on L3 larvae of A. simplex, showing a LC₅₀ of 0.087 and 0.067 mg mL⁻¹ after 24 and 48 h treatment, respectively. O. syriacum essential oil was highly effective on both larvae and adults of C. quinquefasciatus, showing LC₅₀ values of 32.4 mg L⁻¹ and 28.1 µg cm⁻², respectively. Its main constituent, carvacrol, achieved larvicidal LC₅₀₍₉₀₎ of 29.5 and 39.2 mg L⁻¹, while contact toxicity assays on adults had an LC₅₀₍₉₀₎ of 25.5 and 35.8 µg cm⁻², respectively. In fumigation assays, the LC₅₀ was 12.1 µL L⁻¹ after 1 h and decreased to 1.3 µL L⁻¹ in 24 h of exposure. Similarly, the fumigation LC₅₀ of carvacrol was 8.2 µL L⁻¹ after 1 h of exposure, strongly decreasing to 0.8 µL L⁻¹ after 24 h of exposure. These results support the folk usage of Lebanese oregano as an antiparasitic agent, providing new insights about its utilization for developing new effective and eco-friendly nematocidal and insecticidal products. Full article

(This article belongs to the Special Issue Natural Products as Effective Biopesticides and Antiprotozoal Agents)

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11 pages, 1642 KiB

Open AccessArticle

In Vitro and In Vivo Effectiveness of Carvacrol, Thymol and Linalool against Leishmania infantum

by Mohammad Reza Youssefi, Elham Moghaddas, Mohaddeseh Abouhosseini Tabari, Ali Akbar Moghadamnia, Seyed Mohammad Hosseini, Bibi Razieh Hosseini Farash, Mohammad Amin Ebrahimi, Niki Nabavi Mousavi, Abdolmajid Fata, Filippo Maggi, Riccardo Petrelli, Stefano Dall’Acqua, Giovanni Benelli and Stefania Sut

Molecules 2019, 24(11), 2072; https://doi.org/10.3390/molecules24112072 - 30 May 2019

Cited by 51 | Viewed by 5796

Abstract

Background: One of the most important causative agents of visceral leishmaniasis (VL) is Leishmania infantum, which is mainly spread by Phlebotomus and Lutzomyia sandflies in the Old and New World, respectively. Novel and effective drugs to manage this neglected vector-borne disease are urgently required. In this study, we evaluated the toxicity of carvacrol, thymol and linalool, three common essential oil constituents, on amastigotes and promastigotes of L. infantum. Methods: in vitro experiments were performed by 24 h MTT assay. Carvacrol, thymol and linalool at concentrations ranging from 1.3 to 10 μg/mL were tested on promastigotes of L. infantum. For in vivo test, two groups of hamsters (Mesocricetus auratus) received 100 mg/kg of body weight/day of carvacrol and thymol as intraperitoneal injection on day 7 post-infection, followed by a 48 h later injection. The third group was treated with the glucantime as standard drug (500 mg/kg) and the last group (control) just received normal saline. On the 16th day, the number of parasites and histopathological changes in liver and spleen were investigated. Results: 24 h MTT assay showed promising antileishmanial activity of thymol and carvacrol, with IC₅₀ values of 7.2 (48 μM) and 9.8 μg/mL (65 μM), respectively. Linalool at all concentrations did not affect L. infantum promastigote viability. In vivo toxicity data of carvacrol and thymol showed that the former at 100 mg/kg was the safest and most effective treatment with little side effects on the liver. Conclusions: Overall, thymol and carvacrol are highly promising candidates for the development of effective and safe drugs in the fight against VL. Full article

(This article belongs to the Special Issue Natural Products as Effective Biopesticides and Antiprotozoal Agents)

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11 pages, 880 KiB

Open AccessArticle

Efficacy of Two Monoterpenoids, Carvacrol and Thymol, and Their Combinations against Eggs and Larvae of the West Nile Vector Culex pipiens

by Mohammad Reza Youssefi, Mohaddeseh Abouhosseini Tabari, Aryan Esfandiari, Sohrab Kazemi, Ali Akbar Moghadamnia, Stefania Sut, Stefano Dall’Acqua, Giovanni Benelli and Filippo Maggi

Molecules 2019, 24(10), 1867; https://doi.org/10.3390/molecules24101867 - 15 May 2019

Cited by 58 | Viewed by 4654

Abstract

Background: Insect vector control is facing the challenges of resistance development and environmental hazards caused by synthetic pesticides. This has led to a considerable market opportunity for botanical insecticides. In this scenario, our study investigated the potential of selected bioactive monoterpenoids, carvacrol and thymol, as safe and effective tools to control the West Nile vector Culex pipiens. Furthermore, the combined effect of thymol-carvacrol mixtures and their possible interactions were assessed. Methods: For determining larvicidal and ovicidal 50% lethal concentration (LC₅₀), each monoterpenoid was tested at different concentrations (5–500 mg/L). Then, the fixed ratio method was used for evaluating their combinational efficacy. Results: Carvacrol was more toxic against larvae of Cx. pipiens, with a LC₅₀ value of 14 mg/L, whereas thymol exhibited a LC₅₀ value of 49 mg/L. Comparable trends of efficacy were observed when toxicity on Cx. pipiens eggs was investigated, with LC₅₀ values of 7 and 13 mg/L for carvacrol and thymol, respectively. In combinational toxicity assays, the mixture thymol-carvacrol at 1:4 ratio achieved a synergistic effect against larvae of Cx. pipiens, whereas an additive effect was observed on eggs. Other ratios showed antagonistic effects. Conclusions: Overall, our findings pointed out that the 1:4 ratio of thymol-carvacrol blend can enhance the insecticidal efficacy on Cx. pipiens young instars and can be considered further as active ingredient for developing botanical insecticides to be used in mosquito control operations. Full article

(This article belongs to the Special Issue Natural Products as Effective Biopesticides and Antiprotozoal Agents)

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13 pages, 1220 KiB

Open AccessArticle

Lethality of Sesquiterpenes Reprogramming Red Palm Weevil Detoxification Mechanism for Natural Novel Biopesticide Development

by Abid Hussain, Muhammad Rizwan-ul-haq, Ahmed Mohammed AlJabr and Hassan Al-Ayedh

Molecules 2019, 24(9), 1648; https://doi.org/10.3390/molecules24091648 - 26 Apr 2019

Cited by 21 | Viewed by 3114

Abstract

Natural biopesticide development for invasive populations of red palm weevils is mainly responsible for the destruction of date palms and demands an extensive screening program of plant secondary metabolites. In the current study, the pesticidal potential of sesquiterpenes (C₁₅ H₂₄), an important class of plant secondary metabolites primarily composed of three isoprene units, was evaluated by laboratory toxicity, feeding performance bioassays, and host detoxification gene expression patterns. Dose-mortality response bioassays performed against mid-aged eighth-instar red palm weevil larvae revealed dose-dependent mortality. Only three sesquiterpenes, including Farnesol (LD₅₀ = 6559 ppm) and Farnesyl acetate (LD₅₀ = 7867 ppm), are considered to have significant toxicity, with Picrotoxin (LD₅₀ = 317 ppm) being the most toxic. Furthermore, highly toxic sesquiterpene (Picrotoxin) established in the current study tremendously reduced the feeding performance indices, including the efficacy of conversion of digested food (ECD) (81.74%) and the efficacy of conversion of ingested food (ECI) (73.62%). The least toxic sesquiterpenes, including β-Caryophyllene, (+)-Cedrol, Nerolidol, (+)-Nootkatone, and Parthenolide, observed in the current study failed to impart significant reductions of ECI and ECD indices. Lethality of the least toxic sesquiterpenes was overcome by greatly inducing gene expressions of Glutathione S transferase (GST) and Cytochrome P450. These encouraging results enabled us to suggest Picrotoxin as a promising biopesticide for the control of red palm weevil infestations. Full article

(This article belongs to the Special Issue Natural Products as Effective Biopesticides and Antiprotozoal Agents)

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15 pages, 1213 KiB

Open AccessFeature PaperArticle

Exploring the Insecticidal Potential of Boldo (Peumus boldus) Essential Oil: Toxicity to Pests and Vectors and Non-target Impact on the Microcrustacean Daphnia magna

by Roman Pavela, Giovanni Benelli, Riccardo Petrelli, Loredana Cappellacci, Giulio Lupidi, Stefania Sut, Stefano Dall’Acqua and Filippo Maggi

Molecules 2019, 24(5), 879; https://doi.org/10.3390/molecules24050879 - 1 Mar 2019

Cited by 16 | Viewed by 5214

Abstract

Every year Chile exports about 2000 tons of boldo folium (Peumus boldus), which is used around the world as a traditional herbal medicinal product (THMP), mostly to relieve gastrointestinal disorders. This biomass may be a resource for the agrochemical industry to manufacture botanical insecticides. In this regard, the insecticidal potential of boldo has been poorly investigated. In the present work, hydrodistillation of a commercial boldo folium gave 1.5% (w/w) of a yellowish essential oil (boldo essential oil, BEO) containing 1,8-cineole (20.7%), p-cymene (18.5%), limonene (9.1%), ascaridole (9.1%) and β-phellandrene (6.4%) as the main constituents, as determined by gas chromatography-mass spectrometry (GC-MS). NMR analysis allowed us to determine that ascaridole was mainly represented by the cis-isomer. BEO was toxic to larvae of the filariasis vector Culex quinquefasciatus and adults of the housefly Musca domestica, showing LC₅₀/LD₅₀ values of 67.9 mg·L⁻¹ and 98.5 µg·adult⁻¹, respectively. On the other hand, lower insecticidal activity was observed against larvae of the moth pest Spodoptera littoralis (LD₅₀ of 268.9 µg·larva⁻¹). It is worth noting that, when tested at LC₉₀ concentration, BEO was significantly less toxic to aquatic microcrustacean Daphnia magna than the conventional insecticide α-cypermethrin. Finally, in the attempt to explore the BEO mode of action, we tested it for acetylcholinesterase (AChE) inhibitory properties using the Ellman method, obtaining negligible effects (IC₅₀ = 0.45 mg·mL⁻¹). Taken together, these results gave new insights into the potential of BEO as a future ingredient of botanical insecticides. Full article

(This article belongs to the Special Issue Natural Products as Effective Biopesticides and Antiprotozoal Agents)

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13 pages, 2847 KiB

Open AccessArticle

Cholinergic Agonists and Antagonists Have an Effect on the Metabolism of the Beetle Tenebrio Molitor

by Szymon Chowański, Joanna Pacholska-Bogalska and Grzegorz Rosiński

Molecules 2019, 24(1), 17; https://doi.org/10.3390/molecules24010017 - 20 Dec 2018

Cited by 8 | Viewed by 3996

Abstract

Synthetic insecticides are still widely used in plant protection. The main target for their action is the nervous system, in which the cholinergic system plays a vital role. Currently available insecticides have low selectivity and act on the cholinergic systems of invertebrates and vertebrates. Acetylcholine, a cholinergic system neurotransmitter, acts on cells by two types of receptors: nicotinic and muscarinic. In mammals, the role of muscarinic acetylcholine receptors (mAChRs) is quite well-known but in insects, is still not enough. Based on data indicating that the muscarinic cholinergic system strongly affects mammalian metabolism, we investigated if it similarly occurs in insects. We investigated the influence of agonists (acetylcholine, carbachol, and pilocarpine) and antagonists (tropane alkaloids: atropine and scopolamine) of mAChRs on the level of selected metabolites in Tenebrio molitor beetle trophic tissues. We analyzed the glycogen content in the fat body and midgut, the total free sugar concentration in the hemolymph and the lipid amount in the fat body. Moreover, we analyzed the levels of insulin-like peptides in the hemolymph. The tested compounds significantly influenced the mentioned parameters. They increased the glycogen content in the fat body and midgut but decreased the concentration of free sugars in the hemolymph. The observed effects were tissue-specific, and were also time- and dose-dependent. We used nonligated and neck-ligated larvae (to eliminate the influence of head factors on tissue metabolism) to determine whether the observed changes are the result of direct or indirect impacts on tissues. The obtained data suggest that the cholinergic system affects the fat body and midgut indirectly and directly and a pleiotropic role for mAChRs exists in the regulation of energy metabolism in insects. Moreover, tested compounds significantly affected the level of insulin-like peptides in hemolymph. Our studies for the first time showed that mAChRs are involved in regulation of insect metabolism of trophic tissues, and act on them directly and indirectly. Improved knowledge about insect cholinergic system may help in searching more selective and environment-friendly solutions in pest management. Full article

(This article belongs to the Special Issue Natural Products as Effective Biopesticides and Antiprotozoal Agents)

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