Toxicity of Malaysian Medicinal Plant Extracts Against Sitophilus oryzae and Rhyzopertha dominica

The insecticidal activities of extracts from 22 Malaysian medicinal plant extracts from 8 botanical families were tested against rice weevil: Sitophilus oryzae (L.) and lesser grain borer: Rhyzopertha dominica (F.). The extracts were obtained using hexane, methanol, and dichloromethane to extract potential biopesticides from dried leaves. The toxicity levels were examined periodically based on antifeedant activity and contact toxicity assays using treated grain assay. Hexane extracts of Alpinia conchigera, Alpinia scabra, Curcuma mangga, Curcuma purpurascens, Goniothalamus tapisoides, Piper sarmentosum , and methanol extracts of Curcuma aeruginosa, C. mangga , and Mitragyna speciosa were the most potent extracts against S. oryzae and R. dominica with lethal concentration (LC50) values of ≤ 0.42 mg/mL and ≤ 0.49 mg/mL, respectively. The contact toxicity test results showed that methanol extracts of C. aeruginosa and C. mangga , dichloromethane extracts of Cryptocarya nigra , and hexane extracts of C. mangga, and C. purpurascens resulted in 100% mortality of both pests within 28 days exposure of 5 mg/cm2 concentration

Insecticidal activity and mechanism of action of phenylpropanoids isolated from Piper sarmentosum against storage insect pests and mosquito vectors / Arshia Hematpoor

The phytochemical and biological studies were carried out on medicinal and adible plant known as Piper sarmentosum L. (Piperaceae). Bioassay guided study of the active hexane and methanol extracts from aerial parts and roots of P. sarmentosum L. lead to isolation of four phenylpropanoids namely, asaricin 1, isoasarone 2, trans-asarone 3 and asaraldehyde 4. Their insecticidal activity and mechanism of action was investigated against storage pests (Sitophilus oryzae, Rhizopertha dominica and Plodia interpunctella) and mosquito vectors (Aedes albopictus, Aedes aegypti and Culex quinquefasciatus). Potent insecticidal activity against both species was produced by 1 and 2. Compounds 1 and 2 were highly toxic to S. oryzae with LC50 value of 4.7 and 5.6 respectively. R. dominica was slightly more resistance, P. interpunctella had highest resistant to 1 and 2 with LC50 value of ≤ 17.37 μg/ml and LC95 ≤ 37.7 μg/ml. asaricin 1 and isoasarone 2 exhibited high repellent activity against S. oryzae, R. dominica and P. interpunctella at 10 μg/ml. during the residual toxicity test it was observed that 1 and 2 had consistent activity within 30 days and their activity declined after that but compound 3 activity was consistent with 60 days of experiment. Likewise, 1 and 2 had potent larvicidal activity against Ae. albopictus, Ae. aegypti and Cx. quinquefasciatus. 1 and 2 similarly were highly potent against Ae. aegypti, Ae. albopictus and Cx. quinquefasciatus larvae with LC50 ≤ 8.9 μg/ml and LC95 ≤ 15.1 μg/ml . The ovicidal activity of 1, 2 and 3 were evaluated through egg hatching. 1 and 2 showed potent ovicidal activity. Ovicidal activity for both compounds was up to 90% at 25μg/ml. However repellent and adulticide activities of 1 and 2 against tested female mosquito was moderate. In all insecticidal tests compound 3 had moderate insecticidal activity and compound 4 did not have any insecticidal property. Biochemical investigation revealed that 1, 2 and 3 inhibit the acetylcholinesterase (AChE). Although 1 and 2 inhibition was stronger than 3 but correlation study showed that the toxicity of all three compounds was significantly related with their AChE inhibition activity. Further investigation for insect esterase activity showed that all insects had high GST activity and the level of GST was significantly higher in P. interpunchitela which had the highest resistance against 1, 2 and 3. The levels of non-specific esterases and oxidases activities were not significant between the tested insets. Further the docking studies were done to investigate the binding mode of interaction of 1, 2 and 3 with AChE and GST enzyme using Autodock/Vina. Between three active sites peripheral anionic site (PAS), catalytic and anionic in AChE, 1, 2 and 3 interact with more residues within 3 Å using a lower energy at anionic site. Compound 1 was interacted with TYR 370 pocket while 2 and 3 were more stable in THR 154, GLY 155, SER 156, TYR 162 at very low and stable energy level. Docking study on GST interactions with 1, 2 and 3 suggested that PRO11. GLU64 and TYR105 are more essential residues in GST for 1, 2 and 3 binding besides known active residues SER65 and ARG66. This can explain the high toxicity of 1 and 2. Biochemical and docking clearly showed the GST activity role in binding and detoxifying the 1, 2 and 3. Our result suggested that 1 and 2 were highly toxic to tested insects by inhibiting AChE enzyme and computation work supported and clarified the binding mode of interaction. Although compound 3 activity was not as significant as 1 and 2 but there is possibility of its usage in mixture as formulation in future study since it is more stable in the environment. On the other hand understanding the role of GST enzyme helped to develop knowledge on insects response to 1, 2 and 3. Further studies will warrant possible applications of 1, 2 and 3 as potential natural insecticide for the control of storage pests and mosquito vectors populations

Insecticidal activity and the mechanism of action of three phenylpropanoids isolated from the roots of Piper sarmentosum Roxb

Abstract Hexane, dichloromethane and methanol extracts of the roots of Piper sarmentosum Roxb. were screened for toxicity towards Sitophilus oryzae (L.), Rhyzopertha dominica (F.), and Plodia interpunctella (Hübner) and the hexane extract exhibited the highest mortality percentage. Bioassay-guided fractionation of the hexane extract resulted in the isolation of asaricin 1, isoasarone 2, and trans-asarone 3. Asaricin 1 and isoasarone 2 were the most toxic compounds to Sitophilus oryzae, Rhyzopertha dominica, and Plodia interpunctella. Sitophilus oryzae and Rhyzopertha dominica exposed to asaricin 1 and isoasarone 2 required the lowest median lethal time. Insecticidal activity of trans-asarone 3 showed consistent toxicity throughout the 60 days towards all three insects as compared to asaricin 1 and isoasarone 2. Asaricin 1 and isoasarone 2 at different doses significantly reduced oviposition and adult emergence of the three insects in treated rice. Trans-asarone 3 had lowest toxicity with highest LC and LT values in all tested insects relative to its mild oviposition inhibition and progeny activity. Moreover, asaricin 1 and isoasarone 2 significantly inhibited acetylcholinesterase in comparison with trans-asarone 3 and the control. Acetylcholinesterase inhibition of Rhyzopertha dominica and Plodia interpunctella by asaricin 1 and isoasarone 2 were lower than that of Sitophilus oryzae, which correlated with their higher resistance

Repellent activity of asaricin 1 on <i>Ae</i>. <i>Aegypti</i>, <i>Ae</i>. <i>albopictus</i> and <i>Cx</i>. <i>quinquefasciatus</i>.

<p>Repellent activity of asaricin 1 on <i>Ae</i>. <i>Aegypti</i>, <i>Ae</i>. <i>albopictus</i> and <i>Cx</i>. <i>quinquefasciatus</i>.</p

Isolation procedures of asaricin 1, isoasarone 2 and <i>trans</i>-asarone 3 as larvicide.

<p>The <i>P</i>. <i>sarmentosum</i> roots hexane extract was fractionated using hexane- dichloromethane. The preliminary test had identify the active fraction and relative active fraction (F2) were further purified using thin layer chromatography (TLC). Isolated asaricin <b>1</b>, isoasarone <b>2</b> and <i>trans</i>-asarone <b>3</b> were tested toward late third early fourth instar larvae from <i>Ae</i>. <i>aegypti</i>, <i>Ae</i>. <i>albopictus</i> and <i>Cx</i>. <i>quinquefasciatus</i>.</p

Chemical constituents; asaricin 1, isoasarone 2 and <i>trans</i>-asarone 3 which were isolated from roots of <i>P</i>. <i>sarmentosum</i>.

<p>Chemical constituents; asaricin 1, isoasarone 2 and <i>trans</i>-asarone 3 which were isolated from roots of <i>P</i>. <i>sarmentosum</i>.</p

HMBC and COSY correlation of asaricin 1, isoasarone 2 and <i>trans</i>-asarone 3.

<p>HMBC and COSY correlation of asaricin 1, isoasarone 2 and <i>trans</i>-asarone 3.</p

Binding residues of three binding sites of AChE enzyme, blue, orange and lime green residues depict the anionic binding site (TRP83), catalytic binding site (SER238, GLU367, HIS480) and peripheral binding site (TRP271) respectively.

<p>Binding residues of three binding sites of AChE enzyme, blue, orange and lime green residues depict the anionic binding site (TRP83), catalytic binding site (SER238, GLU367, HIS480) and peripheral binding site (TRP271) respectively.</p

The interaction energy of phenolic compounds toward AChE catalytic site.

<p>The interaction energy of phenolic compounds toward AChE catalytic site.</p

Acetylcholinesterase inhibitory activities of asaricin 1, isoasarone 2 and <i>trans</i>-asarone 3 from <i>Piper sarmentosum</i>.

<p>Acetylcholinesterase inhibitory activities of asaricin 1, isoasarone 2 and <i>trans</i>-asarone 3 from <i>Piper sarmentosum</i>.</p