RESUMO
Geckos and their products have been used in Asian traditional medicine. Medicinal properties of desert-dwelling Gecko species, Crossobamon orientalis remain unexplored. In this study, natural bioactive macromolecules present in oil extracted from C. orientalis (COO) and their biological activities were evaluated. Chemical constitution of COO was explored by using gas chromatography mass spectrometry. Antioxidant, antiviral, and antibacterial activities of COO extracts were assessed using various assays, including DPPH free-radical-protocol, HET-CAM method, in ovo-antiviral technique, and disc-diffusion method. GC-MS study reported 40 different compounds in COO. n-hexane and methanol extracts of COO demonstrated highest DPPH radical inhibition, with values of 70 and 63.3%, respectively. Extracts of COO in solvents, namely 1-butanol, methanol, diethyl ether, and n-hexane significantly inhibited the proliferation of four pathogenic viruses. Maximum zone of inhibition was observed for Escherichia coli (13.65 ± 0.57 mm). These findings suggest that COO possesses potent antioxidant and antimicrobial properties against viral and bacterial strains, thanks to its biologically active components having no side effects. Further studies are essential to isolate and identify individual bioactive compounds present in COO and to investigate their potential as therapeutic agents.
RESUMO
RNA interference (RNAi) triggered by exogenous double-stranded RNA (dsRNA) is a powerful tool to knockdown genetic targets crucial for the growth and development of agriculturally important insect pests. Helicoverpa armigera is a pest feeding on more than 30 economically important crops worldwide and a major threat. Resistance to insecticides and Bt toxins has been gradually increasing in the field. RNAi-mediated knockdown of H. armigera genes by producing dsRNAs homologous to genetic targets in bacteria and plants has a high potential for insect management to decrease agricultural loss. The acetylcholinesterase (AChE), ecdysone receptor (EcR) and v-ATPase-A (vAA) genes were selected as genetic targets. Fragments comprising a coding sequence of < 500 bp were cloned into the L4440 vector for dsRNA production in bacteria and in a TRV-VIGS vector in antisense orientation for transient expression of dsRNA in Solanum tuberosum leaves. After ingesting bacterial-expressed dsRNA, the mRNA levels of the target genes were significantly reduced, leading to mortality and abnormal development in larva of H. armigera. Furthermore, the S. tuberosum plants transformed with TRV-VIGS expressing AChE exhibited higher mortality > 68% than the control plants 17%, recorded ten days post-feeding and significant resistance in transgenic (transient) plants was observed. Moreover, larval lethality and molting defects were observed in larva fed on potato plants expressing dsRNA specific to EcR. Analysis of transcript levels by quantitative RT-PCR revealed that larval mortality was attributable to the knockdown of genetic targets by RNAi. The results demonstrated that down-regulation of H. armigera genes involved in ATP hydrolysis, transcriptional stimulation of development genes and neural conduction has aptitude as a bioinsecticide to control H. armigera population sizes and therefore decreases crop loss.