title: Phytotoxicity of sarmentine isolated from long pepper (Piper longum) fruit.
abstract: 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.
authors.affiliation: Marrone Bio Innovations, 2121 Second Street, Suite B-107, Davis, California 95618, USA. hhuang@marronebio.com
authors.forename: Huazhang
authors.initials: H
authors.lastname: Huang
authors.forename: Christy M
authors.initials: CM
authors.lastname: Morgan
authors.forename: Ratnakar N
authors.initials: RN
authors.lastname: Asolkar
authors.forename: Marja E
authors.initials: ME
authors.lastname: Koivunen
authors.forename: Pamela G
authors.initials: PG
authors.lastname: Marrone
mesh_terms: D005638:Fruit / Q000737:chemistry*; D006540:Herbicides / Q000032:analysis / Q000737:chemistry / Q000302:isolation & purification; D031701:Piper / Q000737:chemistry*; D011090:Polyenes / Q000032:analysis / Q000737:chemistry / Q000302:isolation & purification; D036226:Seedlings
chemical_list: D006540:Herbicides; D011090:Polyenes; C554966:sarmentine