Larvicidal activity of medicinal plant extracts and lignan identified in Phryma leptostachya var. asiatica roots against housefly (Musca domestica L.)

Synthesis and biological profile of substituted hexahydrofuro[3,4-b]furans, a novel class of bicyclic acyl-acyl carrier protein (ACP) thioesterase inhibitors

BACKGROUND

Weed control is a significant challenge for farmers around the globe. Of the various methods available for combatting weeds, small molecules remain the most effective and versatile technology to date. In the search for novel chemical entities with new modes of action toward herbicide-resistant weeds, we have investigated hexahydrofuro[3,4-b]furan-based acyl-acyl carrier protein (ACP) thioesterase inhibitors inspired by X-ray co-crystal structure-based modeling studies.

RESULTS

By exploiting scaffold hopping concepts and molecular modeling studies we were able to identify new hexahydrofuro[3,4-b]furan-based lead structures showing promising activity in vivo against commercially important grass weeds in line with strong target affinity.

CONCLUSION

The present work covers a series of novel herbicidal lead structures that possess a hexahydrofuro[3,4-b]furan scaffold as a structural key feature, carrying ortho-substituted aryloxy side chains. Based on an optimized synthetic approach a broad structure-activity relationship (SAR) study was carried out. The new compounds emerging from our modeling-inspired structural variations show good acyl-ACP thioesterase inhibition in line with promising initial herbicidal activity. Glasshouse trials showed that the hexahydrofuro[3,4-b]furans outlined herein display good control of cold and warm season grass-weed species in pre-emergence application. Remarkably, some of the novel acyl-ACP thioesterase-inhibitors also showed promising efficacy against warm season weeds that are difficult to control. © 2024 The Author(s). Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Functional validation of CYP304A1 associated with haedoxan A detoxification in Aedes albopictus by RNAi and transgenic drosophila

BACKGROUND

Insect cytochrome P450 monooxygenases play important roles in the detoxification metabolism of endogenous and exogenous compounds. Haedoxan A (HA) from Phryma leptostachya L. is a highly efficient natural pesticide used to control houseflies and mosquitos. CYP4C21 and CYP304A1 were previously demonstrated to be transcriptionally increased in Aedes albopictus in response to HA exposure, but their involvement in HA metabolism is unknown.

RESULTS

Our data showed that CYP304A1 expression levels in A. albopictus were highest in third-instar larvae, and the expression level of CYP4C21 decreased significantly with the growth of instars, with the lowest occurring in the pupal stage. Compared with the control, the silencing of CYP304A1 and CYP4C21 genes by chitosan nanoparticle-mediated RNA interference could deplete 58.2% and 54.0% of the expression of corresponding genes, respectively. The bioassay data showed that knocking down the expression of CYP304A1 increased the mortality of A. albopictus when exposed to HA at LC₃₀ and LC₅₀ doses, but did not significantly increase mortality after silencing CYP4C21. Our data demonstrated that CYP304A1, but not CYP4C21, may be involved in HA detoxification. Moreover, the resistance ratio of CYP304A1 overexpressing flies was approximately 2-fold higher than that of the control line. The metabolized product of HA by CYP304A1 needs to be further confirmed by in vitro expression.

CONCLUSION

This finding showed that inducibility was not always linked to detoxifying capabilities, and enhanced our understanding of the molecular basis of HA metabolic detoxification in A. albopictus. © 2022 Society of Chemical Industry.

Flies (Musca domestica, Calliphora vomitoria, Sarcophadigae) and Cokroaches (Periplaneta americana) Control Based on Botanical Insecticides in Outdoor Food Processing Areas

Abstract Background Pathogenic agents can be spread by flies and cockroaches. Food processing areas are favored by insects, Control is carried out to prevent contamination of food. The use of synthetic insecticides causes environmental damage, resistance, and contamination of food that is processed and served. Natural ingredients containing active ingredients can be used as insect repellents that are safer because they can be decomposed by nature. Research Objective This study aims to determine the ability to use the concentration formula and duration of exposure to clove flower extract and bay leaf extract against the repelling capability of flies and cockroaches in outdoor restaurants. Method This research is field experiment research, which studies the effect of concentration formulations and exposure time of clove flower extract and bay leaf extract in repelling flies and cockroaches in food processing facilities. Experiments were carried out with 3 levels of formulation: Clove flower extract and bay leaf extract, namely 20%: 25%, 20%: 30%, 25%: 30% with 3 levels of exposure  time, namely 30 minutes, 45 minutes and 60 minutes. Outdoor restaurant as a place to observe the density of flies and the density of cockroaches, the temperature and humidity of the dining room/food serving room. Data analysis using two-way ANOVA analysis and Tukey's test. Results: The results of this study indicate that the formula of clove flower extract and bay leaf extract has an effect on the density of flies and cockroaches in outdoor restaurants. The mixed formula of 25% -30% extract with 60 minutes of exposure can repel flies by 100% in the outdoor dining area.   Conclusion The mixed formula of Clove flower extract and bay leaf extract can be used to control the density of flies and cockroaches in outdoor food processing areas.  

Total Synthesis and Anti-Tobacco Mosaic Virus Activity of the Furofuran Lignan (±)-Phrymarolin II and Its Analogues

Phrymarolin II, a furofuran lignan isolated from Phryma leptostachya L., features a 3,7-dioxabicyclo[3.3.0]octane skeleton. Herein, we report an alternative total synthesis of (±)-phrymarolin II (2), which was performed in 9 steps from commercially available sesamol. The key steps of the synthesis included a zinc-mediated Barbier-type allylation and a copper-catalyzed anomeric O-arylation. Our total synthesis allowed the synthesis of analogues of (±)-phrymarolin II. Most derivatives displayed good to excellent in vivo activity against tobacco mosaic virus (TMV). (±)-Phrymarolin II (2) and compounds (±)-31d and (±)-31g exhibited similar or higher activity than commercial ningnanmycin, which indicated that phrymarolin lignans are a promising new class of plant virus inhibitors.

Ethnobotanical survey of plants traditionally used against hematophagous invertebrates by ethnic groups in the mountainous area of Xishuangbanna, Southwest China

Hematophagous invertebrates such as mosquitoes, leeches, mites, ticks, lice and bugs cause various problems for humans. Considering reports on insecticide resistance and requirements for improved environmental and toxicological profiles, there is a continuing need to discover and develop new insecticides and repellents. Ethnobotanical surveys of traditional plant-based repellents provide a direct method of identifying plants for potential use. During five field surveys in Bulang, Jinuo and Lahu villages between August 2018 and July 2019, semi-structured interviews were conducted with 237 informants (151 male, 86 female; mean age 63). Frequency of citation, use value, informant consensus factor and Jaccard index were employed to statistically analyze the collected data. A total of 709 use reports relating to 32 plant species and 71 remedies were collected. Similarities and differences between the three groups, as well as the Dai and Hani of Xishuangbanna, who were studied earlier, were shown through network analysis. These five ethnic groups living in the same area have a common understanding of traditional botanical knowledge against hematophagous invertebrates, but each group also possesses unique knowledge. Recording and protecting this traditional knowledge is potentially useful for protecting this cultural diversity and related biodiversity and can also have important practical applications. In this study, traditional knowledge provided us with many new potential plants for follow-up research for the development of new insecticides and repellents, among which Artemisia indica, Nicotiana tabacum and Clausena excavata are the most promising.

Toxicity of the essential oil from Thymus serpyllum and thymol to larvae and pupae of the housefly Musca domestica L. (Diptera: Muscidae)

The essential oil (EO) of Thymus serpyllum and thymol were evaluated for their insecticidal activity against the housefly (Musca domestica) larvae and pupae. Contact toxicity and fumigation bioassays were used. Chemical composition analysis of T. serpyllum EO by gas chromatographic mass spectrometry (GC-MS) revealed that thymol (41.6%), p-cymene (21.9%), and γ-terpinene (19.2%) were the major components. For larval assays, the LC50 value of T. serpyllum EO was 0.4 μl/cm2 for contact toxicity and 20.9 μl/l for fumigation toxicity. For thymol, the contact toxicity LC50 value was 0.035 μl/cm2 and the fumigation LC50 value was 2.0 μl/l. For the pupal assay, T. serpyllum EO had a percentage inhibition rate (PIR) value of 100% for both contact toxicity (1.0 μl/cm2) and fumigation toxicity assay (25 μl/l), whereas thymol had a PIR of 100% for contact toxicity (0.1 μl/cm2) and fumigation assay (5 μl/l). This study shows that T. serpyllum EO and thymol are toxic to housefly larvae and pupae and have the potential for use in the population control of this species.

A Synthetic View on Haedoxans and Related Neolignans From Phryma leptostachya

Haedoxans are a series of sesquilignan natural products isolated from the traditional insecticidal plant Phryma leptostachya. Given their significant insecticidal activity, haedoxans and related analogs have been considered as potential agents for plant defense. Moreover, these compounds also exhibit promising antifungal, antibacterial, and anticancer activities. The present paper is a review of the structure, biological activity, and chemical synthesis of naturally occurring haedoxan-like molecules.

Two novel alkaloids from Corydalis curviflora Maxim. and their insecticidal activity

BACKGROUND

Botanical pesticide plays an essential role in the control of agricultural pests. Corydalis curviflora Maxim. is used as a cholagogue and larvicide in the rural areas of Northwest China. In this study, our objective was to identify the insect active ingredients of C. curviflora extract.

RESULTS

Bioassay-guided isolation of the high active fraction led to the identification of two novel N-demethyl hexahydrobenzophenanthridine-type alkaloids, Curviflorain A (1) and Curviflorain B (2), together with nine known alkaloids, ambiguanine A (3), ambiguanine B (4), ambiguanine C (5), 6-acetylambinine (6), 1,1-dimethyl-6-methoxy-7-hydroxyl-1,2,3,4-tetrahydroisoquinoline (7), hendersine B (8), coryximine (9), isochotensine (10) and corysolidine (11). Compounds 1, 2, and 6 showed promising activity to the larvae of Culex pipiens pallens Coq. and Aedes albopictus Skuse. These compounds were also tested against the insect pests, Mythimna separata walker. and Schizaphis graminum Rondani.

CONCLUSION

These findings provide a better understanding of the insecticidal activity of C. curviflora extract and the active compounds. This has the potential to lead to a more effective botanical insecticide.

Efficacy of Origanum vulgare essential oil and carvacrol against the housefly, Musca domestica L. (Diptera: Muscidae)

The toxicity of Origanum vulgare essential oil to the housefly Musca domestica L. was evaluated. The major constituents of the O. vulgare essential oil by gas chromatographic mass spectrometry (GC-MS) analysis were carvacrol (58.13%), p-cymene (17.85%), thymol (8.15%), γ-terpinene (4.96%), and linalool (3.69%). Toxicity of O. vulgare essential oil against larvae and pupae was evaluated using fumigation and contact assays. The contact toxicity (LC₅₀) of O. vulgare essential oil and carvacrol for larvae was 0.23 and 0.03 μL/cm², respectively. The fumigation toxicity (LC₅₀) of O. vulgare essential oil and carvacrol for larvae was 9.52 and 2.78 μL/L, respectively. Pupal toxicity was evaluated by percentage inhibition rate (PIR). PIR of O. vulgare essential oil at 0.25 μL/cm² was 90.9% for the contact assay and 100% at 20 μL/L for the fumigation assay. PIR of carvacrol was 29.5% (0.025 μL/cm²) and 81.8% (1.25 μL/L) for the contact toxicity and fumigation assay, respectively. O. vulgare essential oil and carvacrol have significant toxicity to the housefly and are potential insecticides for housefly control.

Insecticidal Activity of Four Lignans Isolated from Phryma leptostachya

A new lignan (T4) and three known lignans (T1, T2, and T3) were isolated from the methanol extract of the roots of Phryma leptostachya using bioassay-guided method, and their structures were identified as phrymarolin I (T1), II (T2), haedoxan A (T3), and methyl 4-((6a-acetoxy-4-(6-methoxybenzo[d][1,3]dioxol-5-yl)tetrahydro-1H,3H-furo[3,4-c]furan-1-yl)oxy)-1-hydroxy-2,2-dimethoxy-5-oxocyclopent-3-ene-1-carboxylate (T4) byNMR and ESI-MS spectral data. Bioassay results revealed that haedoxan A exhibited remarkably high insecticidal activity against Mythimna separata with a stomach toxicity LC₅₀ value of 17.06 mg/L and a topical toxicity LC₅₀ value of 1123.14 mg/L at 24 h, respectively. Phrymarolin I and compound T4 also showed some stomach toxicity against M. separata with KD₅₀ values of 3450.21 mg/L at 4 h and 2807.10 mg/L at 8 h, respectively. In addition, phrymarolin I and haedoxan A exhibited some stomach toxicity against Plutella xylostella with an LC₅₀ value of 1432.05 and 857.28 mg/L at 48 h, respectively. In conclusion, this study demonstrated that lignans from P. leptostachya are promising as a novel class of insecticides or insecticide lead compounds for developing botanical pesticides.

Insight into the Mode of Action of Haedoxan A from Phryma leptostachya

Haedoxan A (HA) is a major active ingredient in the herbaceous perennial plant lopseed (Phryma leptostachya L.), which is used as a natural insecticide against insect pests in East Asia. Here, we report that HA delayed the decay rate of evoked excitatory junctional potentials (EJPs) and increased the frequency of miniature EJPs (mEJPs) on the Drosophila neuromuscular junction. HA also caused a significant hyperpolarizing shift of the voltage dependence of fast inactivation of insect sodium channels expressed in Xenopus oocytes. Our results suggest that HA acts on both axonal conduction and synaptic transmission, which can serve as a basis for elucidating the mode of action of HA for further designing and developing new effective insecticides.

Synthesis and Larvicidal Activity of Phrymarolin Derivatives against Culex Pipiens Pallens

Twenty-eight new phrymarolin derivatives, including twenty-one ethers, six esters and a dehydroxy phrymarolin, were prepared from phrymarolin I and the structures of all the derivatives were confirmed by 1H NMR and 13C NMR spectroscopic and MS data analyses. Larvicidal activities of these phrymarolin analogues were assayed against 4th instar larvae of Culex pipiens pallens. The ester derivatives of phrymarolin showed lower larvicidal activity than phrymarolin I, but some of the ether derivatives and dehydroxy phrymarolin showed much higher activity. Two ether derivatives, 1–18 and 1–19, showed significant larvicidal activity with LC50 values of 1.89 and 7.78 mg/L, respectively.

Synthesis and larvicidal activity against Culex pipiens pallens of new triazole derivatives of phrymarolin from Phryma leptostachya L

Twelve new triazole derivatives of Phrymarolin were prepared from Phrymarolin I and the structures of all the derivatives were fully characterized by ¹H-NMR, ¹³C-NMR and MS spectral data analyses. Larvicidal activities against 4rd instar larvae of Culex pipiens pallens of these Phrymarolin analogues were assayed. Although the triazole derivatives of Phrymarolin showed certain larvicidal activity, they showed lower activity than Phrymarolin I. The typical non-natural groups triazole substituents reduced the larvicidal activity of Phrymarolin derivatives.