Studies on Crude Drugs Effective on Visceral Larva Migrans. IV.¹⁾ Isolation and Identification of Larvicidal Principles in Pepper

Eight new amide constituents together with seven known amides were isolated from pepper and their structures were determined by spectroscopic means. They are piperamide-C5:1(2E) (2), -C7:1(6E) (3), -C7:2(2E, 6E) (4), -C9:1(8E) (5), -C9:2(2E, 8E) (6), -C9:3(2E, 4E, 8E) (7), 1-[(2E, 4E)-2, 4-decadienoyl]pyrrolidine (8), and 1-[(2E, 4E)-2, 4-dodecadienoyl]pyrrolidine (9). Among all of the amides isolated, seven (3, 4, 5, 6, 8, 9, and 15) showed larvicidal activity against second-stage larva of Toxocara canis and the others were inactive. The assay results suggested that the strongest activity was exhibited by the tertiary amides (piperidin- and pyrrolidin-amides) possessing a nine-carbon chain between the aromatic group and the amine moiety [for example, piperamide-C9: 1(8E), MLC: 0.05 mM after 24h of incubation]. The aliphatic amides 8 and 9 were also larvicidal. Mass spectra of piperamides are also discussed.