Insecticidal effects of the dichloromethane, ethyl acetate, acetone, ethanol and methanol extracts of Humulus lupulus (hops) L. cones and its principal components, xanthohumol was investigated on five stored pests, Sitophilus granarius (L.), Sitophilus oryzae (L.), Acanthoscelides obtectus (Say.), Tribolium castaneum (Herbst) and Lasioderma serricorne (F.). The mortality of adults of the insects treated with 2, 5, 5, 10 and 20 mg ml̠-1 concentrations of the extracts and xanthuhumol was counted after 24, 48, 72, 96 and 120 h. In order to determine the toxic effects of the substances tested against all tested insects, durations for 50% mortality of the adults, and LD50 values were also determined in the first 48 h by probit analysis. Our results also showed that xanthohumol was more toxic against the pests in comparison with the extracts applications. LD50 values for xanthohumol were found to be low dose as compared with the extracts. Xanthohumol was more toxic against S. granarius (L.) with 6.8 µg of LD50 value. Among the extracts, methanol extract was less effective than other extracts against all tested insects. The ethyl acetate extract of H. lupulus cones was the most effective extract against the tested pests. The quantitative amounts of xanthohumol in the extracts were determined using a high-performance liquid chromatography. The quantitative data indicated that amount of xanthohumol in the extracts increased with increase of polarity of the solvents used from methanol to dichloromethane. The methanol extract contained the high amount of xanthohumol with 5.74 g/100 g extract (0.46 g/100 g plant sample).

The dried rhizomes of Veratrum album were individually extracted with CHCl3 , acetone, and NH4 OH/benzene to test the toxic effects against the Colorado potato beetle, Leptinotarsa decemlineata, which is an important agricultural pest. Fifteen compounds in various amounts were isolated from the extracts using column and thin-layer chromatography. The chemical structures of 14 compounds were characterized as octacosan-1-ol (1), β-sitosterol (2), stearic acid (3), diosgenin (4), resveratrol (5), wittifuran X (6), oxyresveratrol (7), β-sitosterol 3-O-β-D-glucopyranoside (8), diosgenin 3-O-α-L-rhamnopyranosyl-(1 → 2)-β-D-glucopyronoside (9), oxyresveratrol 3-O-β-D-glucopyranoside (10), jervine (11), pseudojervine (13), 5,6-dihydro-1-hydroxyjervine (14), and saccharose (15) using UV, IR, MS, (1) H- and (13)C-NMR, and 2D-NMR spectroscopic methods. However, the chemical structure of 12, an oligosaccharide, has not fully been elucidated. Compounds 4, 6, 9, and 10 were isolated from V. album rhizomes for the first time in the current study. The toxic effects of three extracts (acetone, CHCl3 , and NH4 OH/benzene) and six metabolites, 2, 2+4, 5, 7, 8, and 11, were evaluated against the Colorado potato beetle. The assay revealed that all three extracts, and compounds 7, 8, and 11 exhibited potent toxic effects against this pest. This is the first report on the evaluation of the toxic effects of the extracts and secondary metabolites of V. album rhizomes against L. decemlineata. Based on these results, it can be concluded that the extracts can be used as natural insecticides.

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