Phytotoxicity of Sarmentine Isolated from Long Pepper (<i>Piper longum</i>) Fruit
作者:Huazhang Huang、Christy M. Morgan、Ratnakar N. Asolkar、Marja E. Koivunen、Pamela G. Marrone
DOI:10.1021/jf102087c
日期:2010.9.22
Discovery of novel natural herbicides has become crucial to overcome increasing weed resistance and environmental issues. In this article, we describe the finding that a methanol extract of dry long pepper (Piper longum L.) fruits is phytotoxic to lettuce (Lactuca sativa L.) seedlings. The bioassay-guided fractionation and purification of the crude extract led to isolation of sarmentine (1), a known compound, as the active principle. Phytotoxicity of 1 was examined with a variety of seedlings of field crops and weeds. Results indicated that 1 was a contact herbicide and possessed broad-spectrum herbicidal activity. Moreover, a series of sarmentine analogues were then synthesized to study the structure-activity relationship (SAR). SAR studies suggested that phytotoxicity of sarmentine and its analogues was specific due to chemical structures, i.e., the analogues of the acid moiety of 1 were active, but the amine and its analogues were inactive; the ester analogues and amide analogues with a primary amine of 1 were also inactive. In addition, quantification of 1 from different resources of the dry P. longum fruits using liquid chromatography-mass spectrometry showed a wide variation, ranging from almost zero to 0.57%. This study suggests that 1 has potential as an active lead molecule for synthesized herbicides as well as for bioherbicides derived from natural resources.