Abstract
Furofuran lignans have been identified as the main substances responsible for the biological activities of the plant genus Phryma. Here, four new phrymarolin-type leptolignans A-D (7-10) and eight previously known lignans were isolated from P. leptostachya. Of these, nine exhibited significant antifeedant activity against armyworm (Mythimna separata) through a dual-choice bioassay, with the EC(50) values ranging from 0.58 to 10.08 μg/cm(2). In particular, the newly identified lignan leptolignan A (7) showed strong antifeedant activity, with an EC(50) value of 0.58 ± 0.34 μg/cm(2). Further investigation found that leptolignan A can inhibit the growth and nutritional indicators in the armyworm M. separata. The concentrations of two molting hormones, 20-hydroxyecdysone and ecdysone, were also found to decrease significantly following the treatment of the armyworms with the lignan, implying that the target of the P. leptostachya lignan may be involved in 20-hydroxyecdysone and ecdysone synthesis. These results enrich our knowledge of P. leptostachya metabolite structural diversity, and provide a theoretical basis for the control of armyworm using lignans.