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

摘要

The phytochemical and biological studies were carried out on medicinal and adibleudplant known as Piper sarmentosum L. (Piperaceae). Bioassay guided study of the activeudhexane and methanol extracts from aerial parts and roots of P. sarmentosum L. lead toudisolation of four phenylpropanoids namely, asaricin 1, isoasarone 2, trans-asarone 3 andudasaraldehyde 4. Their insecticidal activity and mechanism of action was investigatedudagainst storage pests (Sitophilus oryzae, Rhizopertha dominica and Plodiaudinterpunctella) and mosquito vectors (Aedes albopictus, Aedes aegypti and Culexudquinquefasciatus). Potent insecticidal activity against both species was produced by 1udand 2. Compounds 1 and 2 were highly toxic to S. oryzae with LC50 value of 4.7 and 5.6udrespectively. R. dominica was slightly more resistance, P. interpunctella had highestudresistant to 1 and 2 with LC50 value of ≤ 17.37 μg/ml and LC95 ≤ 37.7 μg/ml. asaricin 1udand isoasarone 2 exhibited high repellent activity against S. oryzae, R. dominica and P.udinterpunctella at 10 μg/ml. during the residual toxicity test it was observed that 1 and 2udhad consistent activity within 30 days and their activity declined after that butudcompound 3 activity was consistent with 60 days of experiment. Likewise, 1 and 2 hadudpotent larvicidal activity against Ae. albopictus, Ae. aegypti and Cx. quinquefasciatus. 1udand 2 similarly were highly potent against Ae. aegypti, Ae. albopictus and Cx.udquinquefasciatus larvae with LC50 ≤ 8.9 μg/ml and LC95 ≤ 15.1 μg/ml . The ovicidaludactivity of 1, 2 and 3 were evaluated through egg hatching. 1 and 2 showed potentudovicidal activity. Ovicidal activity for both compounds was up to 90% at 25μg/ml.udHowever repellent and adulticide activities of 1 and 2 against tested female mosquitoudwas moderate. In all insecticidal tests compound 3 had moderate insecticidal activityudand compound 4 did not have any insecticidal property. Biochemical investigationudrevealed 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 threeudcompounds was significantly related with their AChE inhibition activity. Furtherudinvestigation for insect esterase activity showed that all insects had high GST activityudand the level of GST was significantly higher in P. interpunchitela which had theudhighest resistance against 1, 2 and 3. The levels of non-specific esterases and oxidasesudactivities were not significant between the tested insets. Further the docking studiesudwere done to investigate the binding mode of interaction of 1, 2 and 3 with AChE andudGST enzyme using Autodock/Vina. Between three active sites peripheral anionic siteud(PAS), catalytic and anionic in AChE, 1, 2 and 3 interact with more residues within 3 Åudusing a lower energy at anionic site. Compound 1 was interacted with TYR 370 pocketudwhile 2 and 3 were more stable in THR 154, GLY 155, SER 156, TYR 162 at very lowudand stable energy level. Docking study on GST interactions with 1, 2 and 3 suggestedudthat PRO11. GLU64 and TYR105 are more essential residues in GST for 1, 2 and 3udbinding besides known active residues SER65 and ARG66. This can explain the highudtoxicity of 1 and 2. Biochemical and docking clearly showed the GST activity role inudbinding and detoxifying the 1, 2 and 3. Our result suggested that 1 and 2 were highlyudtoxic to tested insects by inhibiting AChE enzyme and computation work supported andudclarified the binding mode of interaction. Although compound 3 activity was not asudsignificant as 1 and 2 but there is possibility of its usage in mixture as formulation inudfuture study since it is more stable in the environment. On the other hand understandingudthe role of GST enzyme helped to develop knowledge on insects response to 1, 2 and 3.udFurther studies will warrant possible applications of 1, 2 and 3 as potential naturaludinsecticide for the control of storage pests and mosquito vectors populations.