Metabolite Profiles and Biological Activity of Extracts from Alternaria sonchi S-102 Culture Grown by Different Fermentation Methods

Abstract

Five compounds, 4-chloropinselin, chloromonilinic acids B and C, alternariol, and emodin, are the first to be identified in the metabolite composition of Alternaria sonchi, a pathogen of field sowthistle (Sonchus arvensis L.). The metabolite profiles of extracts have been significantly influenced by fermentation and extraction techniques. Solid-state fermentation of A. sonchi S-102 on millet was preferable for the production of alternethanoxin A, chloromonilicin, and 4-chloropinselin with a yield of about 460, 70, and 2760 mg/kg respectively, while the use of pearl barley was optimal for the production of alternethanoxin B (215 mg/kg) and alternethanoxin D (29 mg/kg). Extracts from the culture broth and mycelium of A. sonchi obtained after surface cultivation of the fungus contained 4-chloropinselin, alternariol, emodin, and a number of unidentified biologically active compounds. The extracts display relatively low phytotoxic and antimicrobial activity and only trace levels of alternariol. Thus, there is low toxicological risk for the application of this fungus as a bioherbicide producer.