Influence of molecular descriptors of plant volatilomics on fumigant action against the three major stored product beetle pests.

Plant volatilomics such as essential oils (EOs) and volatile phytochemicals (PCs) are known as potential natural sources for the development of biofumigants as an alternative to conventional fumigant pesticides. This present work was aimed to evaluate the fumigant toxic effect of five selected EOs (cinnamon, garlic, lemon, orange, and peppermint) and PCs (citronellol, limonene, linalool, piperitone, and terpineol) against the Callosobruchus maculatus, Sitophilus oryzae, and Tribolium castaneum adults. Furthermore, for the estimation of the relationship between molecular descriptors and fumigant toxicity of plant volatiles, quantitative structural activity relationship (QSAR) models were developed using principal component analysis and multiple linear regression. Amongst the tested EOs, garlic EO was found to be the most toxic fumigant. The PCs toxicity analysis revealed that terpineol, limonene, linalool, and piperitone as potential fumigants to C. maculatus (< 20 µL/L air of LC50), limonene and piperitone as potential fumigants to T. castaneum (14.35 and 154.11 µL/L air of LC50, respectively), and linalool and piperitone as potential fumigants to S. oryzae (192.27 and 69.10 µL/L air of LC50, respectively). QSAR analysis demonstrated the role of various molecular descriptors of EOs and PCs on the fumigant toxicity in insect pest species. In specific, dipole and Randic index influence the toxicity in C. maculatus, molecular weight and maximal projection area influence the toxicity in S. oryzae, and boiling point and Dreiding energy influence the toxicity in T. castaneum. The present findings may provide insight of a new strategy to select effective EOs and/or PCs against stored product insect pests.

Profiling of semiochemicals from three stored product beetles by headspace solid-phase microextraction coupled with gas chromatography-mass spectrometry.

This work focuses on the profiling of semiochemicals (SCS) from Callosobruchus maculatus, Sitophilus oryzae and Tribolium castaneum by headspace solid-phase microextraction (HS-SPME) coupled with gas chromatography-mass spectrometry (GC-MS) technique. Totally, 6, 9 and 8 volatile compounds (VCS) were detected from C. maculatus, S. oryzae and T. castaneum, respectively. As a result of pherobase analysis and preference bioassay, stearic acid (C. maculatus); nonanal, lauric acid and stearic acid (S. oryzae); stearic acid (T. castaneum) were identified as new SCS that could be useful for integrated pest management (IPM) practices.

Eugenol nanoemulsion as bio-fumigant: enhanced insecticidal activity against the rice weevil, Sitophilus oryzae adults.

Nanoemulsion is a promising delivery system for delivering the plant bioactive molecules against insect pests. In this study, we aimed to prepare eugenol based nanoemulsions (EL-NE) by ultrasonication method to investigate its fumigant toxicity against Sitophilus oryzae adults and to analyse the residual characteristics of eugenol bioactive on the treated grains and beetles. In EL-NE preparations, 1:1 ratio of eugenol: Tween 80 combination with 5 min of ultrasonication at frequency of 10 kHz and 12 W power output was determined as optimal. In the optimized nanoemulsions, 19.21 to 42.82 d.nm range of mean droplet size, 0.50 to 0.77 range of polydispersity index and -21.80 to -29.83 mV range of zeta potential values were observed with respect to 2.5 to 10.0% of eugenol concentrations. After 72 h of fumigation, enhanced fumigant toxicities (3.5-11.2 fold) were observed against S. oryzae adults for the optimized EL-NEs compared to eugenol alone. Fumigant toxicity results revealed 14.40 µl/L air of least LC50 value for the 10.0% EL-NE. Persistence of eugenol was more (12.46%) in EL-NE treated wheat grains compared to eugenol alone treatments based on Gas Chromatography-Mass Spectroscopy analysis, which indicates the improved fumigation. This study results suggests EL-NEs as promising nano-biofumigant against the S. oryzae adults for eco-friendly Integrated Pest Management (IPM).

Isolation and structural characterization of 2R, 3R taxifolin 3-O-rhamnoside from ethyl acetate extract of Hydnocarpus alpina and its hypoglycemic effect by attenuating hepatic key enzymes of glucose metabolism in streptozotocin-induced diabetic rats.

Hydnocarpus alpina Wt. (Flacourtiaceae) (H. alpina) is a large tree traditionally used to treat leprosy; it also posses antidiabetic property. The present study was undertaken to isolate, characterize and to evaluate the antidiabetic effect of 2R, 3R taxifolin 3-O-rhamnoside. (rhamnoside) and its impact on carbohydrate metabolic key enzymes in control and streptozotocin (STZ)-induced diabetic rats. Diabetes mellitus was induced by a single intraperitoneal injection of streptozotocin (STZ) (40 mg/kg). Oral administration of rhamnoside for 21 days significantly reduced food intake, calorie intake, blood glucose and glycosylated hemoglobin levels, and improved plasma insulin levels. Administration of rhamnoside showed significant increase in the body weight, body composition (Lean body weight (LBW) and retro body fat), glycolytic hexokinase, glucose-6-phophate dehydrogenase and pyruvate kinase levels where as significant decrease was observed in the levels of glucose-6-phosphatase fructose-1, 6-bisphosphatase and lactate dehydrogenase in diabetic treated rats. Further, administration of rhamnoside significantly improved the glycogen content, glycogen synthase and glycogen phosphorylase, suggesting the antihyperglycemic potential of rhamnoside in diabetic rats. The results obtained were compared with glibenclamide a standard hypoglycaemic drug. Immunohistopathological study of pancreas revealed increased number of ß-cells and insulin granules in diabetes-induced rats after treatment with rhamnoside for 21 days. Furthermore, Co-administration of rhamnoside (50 mg/kg) with nifedipine (13.6 mg/kg), a Ca(2+)ion channel blocker, or nicorandil (6.8 mg/kg), an ATP-sensitive K(+) ion channel opener, reveals the insulin secretion property of rhamnoside via a K(+)-ATP channels dependent pathway in diabetic rats. In conclusion, rhamnoside normalized blood glucose, glycosylated hemoglobin, key hepatic enzymes and glycogen content by increasing insulin secretion via K(+)-ATP channels dependent signaling pathway. The results suggest that the rhamnoside from H. alpina could be used as a therapeutic agent to treat diabetes mellitus.

Antifeedant, larvicidal and pupicidal activities of Atalantia monophylla (L) Correa against Helicoverpa armigera Hubner (Lepidoptera: Noctuidae).

Antifeedant, larvicidal and pupicidal activities of hexane, chloroform and ethyl acetate extracts of Atlantia monophylla leaf were studied against third instar larvae of Helicoverpa armigera. All the extracts showed feeding deterrent, larvicidal and pupicidal effects in a dose dependent manner. Significant antifeedant, larvicidal and pupicidal activities were observed only in hexane extract. The hexane extract was subjected to fractionation using silica gel column chromatography. Twelve fractions were obtained. Ninth fraction showed good antifeedant, larvicidal, pupicidal activities and disrupted adult emergence. LC(50) value was at 384.57 ppm for larval mortality. The active fraction at 1000 ppm concentration had 100% pupal mortality.