Insecticidal constituents from four species of the Zingiberaceae
1993
Pandji, C. | Grimm, C. | Wray, V. | Witte, L. | Proksch, P.
Rhizomes of four species from the Zingiberaceae including Curcuma xanthorrhiza, C. zedoaria, Kaempferia galanga and K. pandurata were analysed for insecticidal constituents. Seventeen major compounds including flavonoids, sesquiterpenoids and cinnamic acid derivatives were isolated and identified based on their NMR and mass spectra, and by comparison with published data. All compounds were studied for contact toxicity against larvae of the polyphagous pest insect Spodoptera littoralis. Nine compounds including the most active sesquiterpenoids xanthorrhizol and furanodienone showed pronounced toxicity against neonate larvae of S. littoralis in a contact residue bioassay. The LD50 of xanthorrhizol following topical application was found to vary between 6.92 and 8.13 micromoles kg-1 fresh weight irrespective of the larval stages studied. In a time course experiment significant mortality of the larvae following topical contact with xanthorrhizol was observed as early as one hour following treatment, whereas all of the moribund larvae died within the first six hours of observation. None of the compounds studied, however, including xanthorrhizol caused significant mortality of neonate larvae of S. littoralis when incorporated into artificial diet, suggesting inactivation of the compounds in the larval gut.
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