CHROMATOGRAPHIC ISOLATION OF INSECTICIDAL AMIDES FROM PIPER-GUINEENSE ROOT

Fractionation of a light petroleum (b.p. 40-60-degrees-C) extract from the male roots of Piper guineense Schum and Thonn was carried out by thin-layer chromatography (TLC) followed by reversed-phase high-performance liquid chromatography (HPLC). Fractions were monitored by their insecticidal activity, and five different active amides were purified. The amides were identified by spectral and chemical methods as N-isobutyl-11-(3,4-methylenedioxyphenyl)-2E,4E,10E-undecatrienamide (1), N-pyrrolidyl-12-(3,4-methylenedioxyphenyl)-2E,4E,9E,11Z-dodecatetraenamide (2), N-isobutyl-13-(3,4-methylenedioxyphenyl)-2E,4E,12E-tridecatrienamide (3), N-isobutyl-2E,4E-decadienamide (4) and N-isobutyl-2E,4E-dodecadienamide (5). Some of these (4 and 5) have not hitherto been identified in P. guineense, and one (2) appears to be novel from any plant source. TLC-HPLC is suggested to be more suitable than other chromatographic methods used earlier for isolating minor insecticidal components from Piper plants.