Insecticidal and antifeedant activities of clerodane diterpenoids isolated from the Indian bhant tree, Clerodendron infortunatum, against the cotton bollworm, Helicoverpa armigera.
Bottom Line: Compound HD also showed very good antifeedant activity, which did not differ significantly from that of azadirachtin.Insecticidal activity of the isolated compounds was not significant compared to the control condition, even at the highest con-concentrations of the compounds.These results suggest that extracts of C. infortunatum have very good antifeedant effects against H. armigera due to the presence of specific compounds.
Affiliation: Horticultural Research Institute, Shahid Bahonar University of Kerman, Iran email@example.com.Show MeSH
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Mentions: The antifeedant activities of different crude extracts and fractions of C. infortunatum were studied using the leaf disc no-choice test method. The methanol fraction of hexane extract showed the highest antifeedant activity against H. armigera (Table 1); activity was recorded as 95%, which was statistically significant (P < 0.05) compared to other extracts, fractions, and azadirachtin. The highly-effective methanol fraction of hexane extract was dissolved in 50 mL of methanol and kept in the refrigerator for two days; crystallization occurred during this time, and crystals were then separated. The purity of the compound was examined via TLC (Rf values of 0.71, solvent system ratio of ethyl acetate to hexane was 60:40) and HPLC (RP-18 column and acetonitrile-water as the solvent system with a ratio of 70:30) at a flow rate of 0.75 mL/min that showed an Rt value of 5.683 min. Then the pure compound was subjected to NMR and MS analyses. The NMR of the compound matched with that of clerodin (CL), as it exhibited peaks characteristic of the CL molecule (Figure 1). In the mass spectrum, the compound exhibited molecular ion peak [M+] at m/z 434, which was typical of the CL molecule. These spectral data confirmed the compound to be CL (Figures 2 and 3). The rest of the methanol fraction of hexane extract was subjected to column chromatography. Among the six fractions obtained, antifeedant activities of fractions 1, 2, and 3 were poor, and they were shown through TLC to be a mixture of various compounds. Fractions 4, 5, and 6 showed very good antifeedant activity with single spots in the TLC trials (Table 2). Fraction 4, collected at mobile phase ratio of 75:25 (hexane:ethyl acetate), was a single compound and showed an Rf value of 0.71 (60:40 hexane: ethyl acetate) when its purity was checked by TLC, which was similar to CL. Its Rf value was confirmed by further purity analysis. Fractions 5 and 6, collected at the mobile phase ratio of 65:35 and 60:40 (hexane:ethyl acetate), respectively, were also single compounds. The purity of these compounds was checked by TLC using ethyl acetate:hexane (60:40) as the mobile phase, which showed Rf values of 0.54 and 0.31, for fractions 5 and 6, respectively. The purity was also checked by HPLC, using RP-18 column and acetonitrile-water with a ratio of 70:30 as the solvent system at a flow rate of 0.75 mL/min, which showed single peaks with Rt values of 4.933 and 1.772 min, for fractions 5 and 6, respectively. When these pure compounds were subjected to NMR and MS analyses, they exhibited molecular ion peaks at 466 and 452 (fractions 5 and 6, respectively), which corresponded to the molecular mass of the compounds (Figures 4 and 5). The NMR spectra of these two compounds also matched those reported in the literature (Figures 6 and 7). These spectral data confirmed that fraction 5 was 15-methoxy-14, 15-dihydrocleodin (MD) and fraction 6 was 15-hydroxy-14, 15-dihyroclerodin (HD) (Figure 8).
Affiliation: Horticultural Research Institute, Shahid Bahonar University of Kerman, Iran firstname.lastname@example.org.