From the extracts of three Papaveraceous plants, i.e., Macleaya cordata (Willd.) R.Br., Corydalis incisa (Thunb.) Pers., and Chelidonium majus L. var. asiaticum (Hara) Ohwi., eight isoquinoline alkaloid compounds, i.e., protopine, allocryptopine, sanguinarine, chelerythrine, coryincine, (±)-corynoline, (+)-chelidonine, and (±)-stylopine, were isolated. Furthermore, their structures were spectroscopically determined. Among them, the absolute structure of coryincine was directly determined by

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... y crystallography for the first time. Seven compounds showed larvicidal activity in the mosquito Culex pipiens pallens Coquillett (1898), with corynoline, chelidonine, and stylopine showing particular activity even at low concentrations (1 ppm). In an antifungal test against rice blast fungus, Pyricularia oryzae Cavara involving six compounds, sanguinarine and chelerythrine exhibited almost the same excellent level of activity as isoprothiolane. The toxicity of the M. cordata extract to the fish Oryzias latipes Temminck & Schlegel (1846) was weaker than that of nicotine, which suggests that the fish toxicity of sanguinarine and chelerythrine are low. We believe that these aromatic quaternary benzo[c]phenanthridine alkaloids, especially sanguinarine and chelerythrine, are potentially highly suited as new treatments against the blast fungi and mosquito larvae in aquatic environments, including paddy fields, because of their efficacy and low fish toxicity.