Insecticide and antifeedant activity of different plant parts of Melia azedarach on Xanthogaleruca luteola

Insecticidal Triterpenes in Meliaceae: Plant Species, Molecules, and Activities: Part II (Cipadessa, Melia)

Plant-originated triterpenes are important insecticidal molecules. Research on the insecticidal activity of molecules from Meliaceae plants has always been a hotspot due to the molecules from this family showing a variety of insecticidal activities with diverse mechanisms of action. In this paper, we discussed 116 triterpenoid molecules with insecticidal activity from 22 plant species of five genera (Cipadessa, Entandrophragma, Guarea, Khaya, and Melia) in Meliaceae. In these genera, the insecticidal activities of plants from Entandrophragma and Melia have attracted substantial research attention in recent years. Specifically, the insecticidal activities of plants from Melia have been systemically studied for several decades. In total, the 116 insecticidal chemicals consisted of 34 ring-intact limonoids, 31 ring-seco limonoids, 48 rearranged limonoids, and 3 tetracyclic triterpenes. Furthermore, the 34 ring-intact limonoids included 29 trichilin-class chemicals, 3 azadirone-class chemicals, and 1 cedrelone-class and 1 havanensin-class limonoid. The 31 ring-seco limonoids consisted of 16 C-seco group chemicals, 8 B,D-seco group chemicals, 4 A,B-seco group chemicals, and 3 D-seco group chemicals. Furthermore, among the 48 rearranged limonoids, 46 were 2,30-linkage group chemicals and 2 were 10,11-linkage group chemicals. Specifically, the 46 chemicals belonging to the 2,30-linkage group could be subdivided into 24 mexicanolide-class chemicals and 22 phragmalin-class chemicals. Additionally, the three tetracyclic triterpenes were three protolimonoids. To sum up, 80 chemicals isolated from 19 plant species exhibited antifeedant activity toward 14 insect species; 18 chemicals isolated from 17 plant species exhibited poisonous activity toward 10 insect species; 16 chemicals isolated from 11 plant species possessed growth-regulatory activity toward 8 insect species. In particular, toosendanin was the most effective antifeedant and insect growth-regulatory agent. The antifeedant activity of toosendanin was significant. Owing to its high effect, toosendanin has been commercially applied. Three other molecules, 1,3-dicinnamoyl-11-hydroxymeliacarpin, 1-cinnamoyl-3-methacryl-11-hydroxymeliacarpin, and 1-cinnamoyl-3-acetyl-11-hydroxymeliacarpin, isolated from Meliaazedarach, exhibited a highly poisonous effect on Spodoptera littoralis; thus, they deserve further attention.

Combining next-generation sequencing and single-molecule sequencing to explore brown plant hopper responses to contrasting genotypes of japonica rice

BACKGROUND

The brown plant hopper (BPH), Nilaparvata lugens, is one of the major pest of rice (Oryza sativa). Plant defenses against insect herbivores have been extensively studied, but our understanding of insect responses to host plants' resistance mechanisms is still limited. The purpose of this study is to characterize transcripts of BPH and reveal the responses of BPH insects to resistant rice at transcription level by using the advanced molecular techniques, the next-generation sequencing (NGS) and the single-molecule, real-time (SMRT) sequencing.

RESULTS

The current study obtained 24,891 collapsed isoforms of full-length transcripts, and 20,662 were mapped to known annotated genes, including 17,175 novel transcripts. The current study also identified 915 fusion genes, 1794 novel genes, 2435 long non-coding RNAs (lncRNAs), and 20,356 alternative splicing events. Moreover, analysis of differentially expressed genes (DEGs) revealed that genes involved in metabolic and cell proliferation processes were significantly enriched in up-regulated and down-regulated sets, respectively, in BPH fed on resistant rice relative to BPH fed on susceptible wild type rice. Furthermore, the FoxO signaling pathway was involved and genes related to BPH starvation response (Nlbmm), apoptosis and autophagy (caspase 8, ATG13, BNIP3 and IAP), active oxygen elimination (catalase, MSR, ferritin) and detoxification (GST, CarE) were up-regulated in BPH responses to resistant rice.

CONCLUSIONS

The current study provides the first demonstrations of the full diversity and complexity of the BPH transcriptome, and indicates that BPH responses to rice resistance, might be related to starvation stress responses, nutrient transformation, oxidative decomposition, and detoxification. The current result findings will facilitate further exploration of molecular mechanisms of interaction between BPH insects and host rice.

Daphnauranins C⁻E, Three New Antifeedants from Daphne aurantiaca Roots

Daphnauranins C–E (compounds 1–3), two sesquiterpenoids and one monoterpenoid were isolated from the roots of Daphne aurantiaca Diels. Daphnauranin C is a 9-O-13 etherified and hydroperoxy-substituted guaiane sesquiterpenoid, daphnauranin D is a guaiane sesquiterpenoid ketal, and daphnauranin E is a monoterpenoid lactone. Their structures were elucidated by comprehensive analyses of MS, 1D NMR, and 2D NMR spectroscopic data. In an anti-feeding activities test, daphnauranins C–E showed activity against male fruit fly with anti-feeding indexes (AI) up to 39.1, 39.2, and 27.8% respectively, at 1 mM.

Structural Diversity and Biological Activity of the Genus Pieris Terpenoids

Secondary metabolites, particularly the grayanane diterpenoids produced by the members of genus Pieris, have been investigated in past decades for their remarkable antifeedant and insecticidal activities and toxicity. Grayanoids exhibit diverse biological properties such as antifeedant, insecticidal, cAMP regulatory, and sodium-channel-modulating activities. Structural complexity and diverse bioactivity of grayanoids have made them attractive targets for chemical, biological, and synthetic purposes. The current review synthesized findings published from 1966 to 2017, which include 135 reports that describe 130 terpenoids, including 103 grayanoids. The distribution, structure, skeleton, as well as the antifeedant and insecticidal activity of terpenoids, particularly the grayanane diterpenoids, are discussed in detail in this review. In cases where sufficient information is available, the structure-activity relationships of their antifeedant activity are also presented. We hope that this contribution will prompt more scientists to pay attention to these diterpenoids, which may be potentially applied in the agricultural field.

Highly Oxygenated Grayanane Diterpenoids from Flowers of Pieris japonica and Structure-Activity Relationships of Antifeedant Activity against Pieris brassicae

Six new highly oxygenated grayanane diterpenoids, neopierisoids G-L, 1-6, together with 10 known related compounds, 7-16, were identified from the flowers of the poisonous plant Pieris japonica. The structures were elucidated on the basis of comprehensive NMR spectroscopy and mass analysis. The relative configurations of 1-6 were elucidated by analysis of ROESY spectra and comparison of NMR data with the analogues. The absolute configurations of 1-6 were established by the X-ray diffraction analysis of 1 and comparison of the CD spectra of 1-6. Compared with the skeleton of the normal grayanane diterpenoids, compounds 1-6 shared an unusual seco A ring moiety. The antifeedant activities of compounds 1-16 against Pieris brassicae were evaluated by using a dual-choice bioassay, and compounds 1-10 with a normal grayanane skeleton showed potent antifeedant activity against P. brassicae. The structure-activity relationships of antifeedant activities of 1-16 against P. brassicae are discussed.

Insecticidal Properties of a Highly Potent Wax Isolated from Dolichandra cynanchoides Cham

Bioassay-guided fractionation of an ethanolic extract of the aerial parts of Dolichandra cynanchoides Cham. (Bignoniaceae) led to the isolation of a natural wax with anti-insect activity against Spodoptera frugiperda (Noctuidae) and Epilachna paenulata (Coleptera). The compound was identified spectroscopically as an ester of a C27 fatty acid and a C25 alcohol, pentacosyl heptacosanoate (1). The effective doses of 1 for 50% feeding inhibition (ED50) of S. frugiperda and E. paenulata were 0.82 and 8.53 µg/cm², respectively, in a choice test, while azadirachtin showed ED50 of 0.10 and 0.59 µg/cm², respectively. In a no-choice test, both insects refused to feed on leaves treated with 1 at doses of 0.1 µg/cm² or greater inhibiting larval growth and dramatically reducing survival. The lethal doses 50 (LD50) of 1 were 0.39 and 0.68 µg/cm² for S. frugiperda and E. paenulata, respectively. These results indicate that 1 has potential for development as botanical insecticides. Similar esters might be obtainable in large quantities as many edible crops produce wax esters that are discarded during food processing. Research on these materials could lead to the detection of similar waxes with insecticidal activity.

Antifeedant activity of Jatropha gossypifolia and Melia azedarach senescent leaf extracts on Spodoptera frugiperda (Lepidoptera: Noctuidae) and their potential use as synergists

BACKGROUND

To reduce rates of synthetic insecticide applications, natural product alternatives and synergists are needed. A study has been made of the toxicity of ethanolic senescent leaf extracts (SLEs) of Jatropha gossypifolia and Melia azedarach on larvae of the noctuid pest Spodoptera frugiperda. Their effects as syngergists and inhibitors of several enzyme activities are also reported.

RESULTS

When added to the diet, M. azedarach SLE showed lower toxicity than J. gossypifolia SLE. However, after 2 weeks on the diet, the M. azedarach SLE proved to be lethal to 100% of the larval population. Artificial diets with both SLEs have an antifeedant effect on armyworm larvae. Acute toxicity after topical application in a dipping assay was relatively low for both J. gossypifolia and M. azedarach SLEs (LC(50) of 2.6 and 1.4 g L(-1), respectively, after 24 h). However, mixtures of the SLEs of M. azedarach and J. gossypifolia had a strong synergistic effect with cypermethrin. Synergism was higher with the J. gossypifolia SLE, perhaps because it contains several natural products with a methylenedioxyphenyl moiety. Both extracts inhibited P450, general esterase and acetylcholinesterase activities in vitro and in vivo.

CONCLUSION

Both J. gossypifolia and M. azedarach SLEs are antifeedants to armyworm larvae when present in the food, and also have a synergistic effect with cypermethrin in topical assays. Although the synergistic effect is less than with piperonyl butoxide, both SLEs have some inhibitor activity against detoxification enzymes and acetylcholinesterase. Thus J. gossypifolia and M. azedarach SLEs may be considered as ecofriendly approaches for the control of S. frugiperda in order to reduce cypermethrin usage.

Acromyrmex octospinosus (Hymenoptera: Formicidae) management. Part 1: Effects of TRAMIL's insecticidal plant extracts

BACKGROUND

Leaf-cutting ants are considered to be one of the most important pest species of the New World. Until now, control strategies against these leaf-cutting ants have mainly been synthetic chemicals. The aim of the present study was to test the action of several plant extracts quoted as an example by TRAMIL participative surveys for their insecticidal properties on adult major workers of Acromyrmex octospinosus. Three tests were used to that end: contact toxicity, repellent test and ingestion bioassay. Six traditional plant uses recommended by interviewed people in surveys were tested: (1) maceration of Mammea americana fresh crushed seeds; (2) decoction of Nerium oleander fresh leaves; (3) Nerium oleander dried leaf water juice; (4) decoction of Nicotiana tabacum dried leaves; (5) Trichillia pallida dried leaf water juice; (6) decoction of Rollinia mucosa dried seeds.

RESULTS

Two plant extracts with contact toxicity (Mammea americana and Nicotiana tabacum), six plant extracts with repellent activity and four plant extracts with ingestion toxicity (Mammea americana, Nicotiana tabacum and both extracts of Nerium oleander) were found.

CONCLUSION

The data presented in this study showed that plant extracts cited by TRAMIL ethnopharmacological surveys have the potential to control the leaf-cutting ant, Acromyrmex octospinosus. In particular, the Mammea americana extract, with its natural low repellent effect and its high toxicity by ingestion, and Nerium oleander extracts, with their natural delay action, are possibly the best extracts for the control of these ants.

Cold tolerance and supercooling capacity in overwintering adults of elm leaf beetle Xanthogaleruca luteola (Coleoptera: Chrysomelidae)

Elm leaf beetle, Xanthogaleruca luteola (Muller) is one of the key pests of elm trees all over the world, and survives winter in reproductive diapause in sheltered locations. Seasonal variation of whole body supercooling points (SCPs), LT50 (temperature at which 50% of the test individuals die) and survival rate after exposure to subzero temperatures were determined in field collected adults during October 2008 to May 2009 and October 2009 to May 2010. The SCP of adults decreased significantly from October (median=-13.8°C) to January (median=-20.7°C) in first year, relatively similar results was observed in the second year. The lowest LT50 was observed in overwintering adults collected in January (-16.81°C) in the first year and December (-15.59°C) in the second year. Mortality at -15°C for 24 h was >70% in early autumn in both years whereas it decreased to lower than 45% in early winter, the highest mortality (100%) was observed in adults collected in May in both years. Cold acclimated adults (30 d, 5°C) in November 2008 exhibited significantly higher SCP (-12.21±0.64°C) than nonacclimated adults (-15.57±1.35°C). A 30-d exposure to 5°C caused >20% mortality in November, while <9% mortality was observed in adults collected in December and January 2008. Overwintering adults died upon freezing and the lower lethal temperatures were within the range of SCP, indicating that X. luteola is a freeze intolerant insect.

USOS POTENCIAIS DE MELIA AZEDARACH L. (MELIACEAE): UM LEVANTAMENTO

RESUMO Há muito tempo, diversas plantas têm sido utilizadas como medicinais. Além disso, inúmeras pesquisas são realizadas com o intuito de validar os seus princípios ativos. A Melia azedarach, que apresenta uma ampla utilização popular, já teve muitos princípios ativos isolados e várias ações farmacológicas testadas e comprovadas. Entre estas ações destacam-se a atividade antiviral, antimicrobiana, antimalarial, antiparasitária, inseticida, contraceptiva e antifoliculogênica e citotóxica devidamente comprovadas. Portanto, visando contribuir para um maior conhecimento a respeito desta planta, apresentamos um levantamento enfocando suas principais ações farmacológicas, biológicas e químicas. Evidenciando desta forma o seu potencial medicinal e fitoquímico, portanto sua utilização na medicina popular.

Leaf extracts of Melia azedarach Linnaeus (Sapindales: Meliaceae) act as larvicide against Aedes aegypti (Linnaeus, 1762) (Diptera: Culicidae)

The objective of this study was to compare the larvicidal effect of hydroethanolic extracts of fresh and dry leaves of Melia azedarach Linnaeus (Sapindales: Meliaceae) on Aedes aegypti (Linnaeus, 1762) (Diptera: Culicidae). All the extracts evaluated induced mortality among the third and fourth instar larvae of Aedes aegypti after 24 and 48 hours of exposure to the products. Although previous studies had demonstrated the action of seeds and fruits of Melia azedarach against the larvae of different Aedes aegypti populations, the present report is the first to show the larvicidal effect of the fresh and dry leaves of this plant.