Trans-4-aminoproline, a phytotoxic metabolite with herbicidal activity produced by Ascochyta caulina Antonio Evidente a, *, Anna Andol® a , Maurizio Vurro b , Maria Chiara Zonno b , Andrea Motta c a Dipartimento di Scienze Chimico-Agrarie, Universita  di Napoli Federico II, Via Universita  100, I-80055 Portici, Italy b Istituto Tossine e Micotossine da Parassiti Vegetali, CNR, Viale L. Einaudi 51, I-70125 Bari, Italy c Istituto per la Chimica di Molecole di Interesse Biologico, CNR, Via Toiano 6, I-80072 Arco Felice, Italy Received 8 July 1999; received in revised form 14 September 1999; accepted 15 September 1999 Abstract A phytotoxic metabolite, characterized through NMR techniques and synthetic methods as trans-4-aminoproline, was isolated from the culture ®ltrates of Ascochyta caulina, a promising mycoherbicide for biological control of Chenopodium album. The metabolite, which shows interesting phytotoxic properties, together with ascaulitoxin (recently characterized as N 2 -b-D-glucoside of the unusual bis-amino acid 2,4,7-triamino-5-hydroxyoctandioc acid) and another unidenti®ed compound, compose an active fraction of A. caulina culture ®ltrates with promising herbicidal properties. When assayed on leaves of host and non host dicots, including wild and cultivated plants, the trans-4-aminoproline showed a wide range of toxicity, with leaves of C. album being the most sensitive. Other interesting aspects were its inecacy on several monocots, both cultivated and wild, and its lack of antifungal, antibiotic and zootoxic activities. This is the ®rst report on trans-4-aminoproline as naturally occurring compound and phytotoxic metabolite produced by A. caulina. # 2000 Elsevier Science Ltd. All rights reserved. Keywords: Chenopodium album; Ascochyta caulina; Phytotoxins; Nonproteigenic amino acids; Trans-4-aminoproline; Weed biocontrol 1. Introduction The perthotrophic fungal species Ascochyta caulina (P. Karst.) v.d. Aa and v. Kest. has been proposed as a mycoherbicide against Chenopodium album (L.) (Kempenaar, 1995). This is known as common lambs- quarter or fat hen and is a common world-wide weed of many arable crops as sugar beet and maize (Holm, Pluckett, Pancho & Herberger, 1977). The application of pycnidiospores of the fungus to C. album plants causes the appearance of large necrosis of leaves and stems, and depending on the amount of necrosis devel- oped, plants show retarded growth or death. Preliminary experiments had showed that A. caulina produced in vitro phytotoxic hydrophilic low molecu- lar weight metabolites (Scheepens, Kempenaar, Adreanas, Eggers, Netland & Vurro, 1997), which could be relevant for an alternative, or in addition, to the use of pathogens in weed biocontrol (Strobel, Kien®eld, Bunkers, Sugawara & Clardy, 1991). Recently, the main phytotoxin, named ascaulitoxin, has been isolated and characterized as N 2 -b-D-gluco- side of the unusual bis-amino acid 2,4,7-triamino-5- hydroxyoctandioc acid (Evidente et al., 1998). Considering that the other toxic metabolites also exhibited an amino acidic nature, the culture ®ltrates were preliminarily fractionated by cationic-exchange chromatography obtaining a mixture of phytotoxins. The puri®cation of this mixture by gel ®ltration chro- matography allowed isolation of a further phytotoxin which, together with ascaulitoxin and other still unknown metabolites, is responsible for the high phy- totoxicity of the fungal culture ®ltrate. Phytochemistry 53 (2000) 231±237 0031-9422/00/$ - see front matter # 2000 Elsevier Science Ltd. All rights reserved. PII: S0031-9422(99)00507-5 www.elsevier.com/locate/phytochem * Corresponding author. Tel.: +39-081-7885224; fax: +39-081- 7755130. E-mail address: evidente@unina.it (A. Evidente).