Larvicidal activity and structure activity relationship of cinnamoyl amides from Zanthoxylum armatum and their synthetic analogues against diamondback moth, Plutella xylostella

Cinnamoyl amides isolated from Zanthoxylum armatum (Rutaceae) and their synthetic analogues were tested for their insecticidal activity against the second instar larvae of diamondback moth, Plutella xylostella (L.) (Lepidoptera: Yponomeutidae) to determine the promising structures with insecticidal activity. Most of the test compounds showed promising activity against larvae of P. xylostella. However, the activities of different compounds varied depending on the presence of different substituents at various positions of both the aromatic rings A and B. Among the tested compounds, 8, N-(3-bromo-4-methoxyphenethyl)cinnamamide showed best larvicidal activity with an LC(50) = 62.13 mg/L followed by 6, N-(3׳-bromophenethyl)cinnamamide (LC(50)=128.49 mg/L) and 2 N-(4׳-methoxyphenylethyl)cinnamamide (LC(50) = 225.65 mg/L).