Composition of alkaloids in seeds of Lupinus mexicanus (FABACEAE) and antifungal and allelopathic evaluation of the alkaloid extract [Composición de alcaloides en semillas de Lupinus mexicanus (FABACEAE) y evaluación antifúngica y alelopática del extracto alcaloideo]

Abstract

Plants synthesize secondary metabolites that can be isolated and used in agriculture as an alternative for the control of pests and diseases. Capillary gas chromatography mass spectrometry (CG-MS) was used to analyze the composition of alkaloids in seeds of Lupinus mexicanus. In addition, an in vitro study was made of the antifungal and allelopathic activity of the crude extract of alkaloids. The antifungal action of the extract was evaluated based on the inhibition of the mycelial growth of the phytopathogenic fungi Sclerotium rolfsii, Rhizoctonia solani and Fusarium oxysporum, while the allelopathic activity was evaluated on the germination of seeds of Amaranthus hybridus and Echinochloa crus-galli. The analysis of alkaloids from the extract revealed the presence of lupanine, 3β-hydroxylupanine, multiflorine aphylline, epiaphylline and α-isolupanine as majority compounds. The extract, at the concentration of 3 mg mL-1, significantly inhibited the mycelial growth of R. solani by 87.7%, whereas the mycelial growth of S. rolfsii was only inhibited 72.5% with the highest concentration. Only the germination of seeds of A. hybridus showed significant differences from the effect of the extract, and inhibition of germination was 80% with the highest concentration (1 mg mL-1). Lupanine was the most abundant alkaloid (76.2%) in the extract of seeds of L. mexicanus. The extract showed inhibitory activity of the mycelial growth of R. solani and S. rolfsii, and a phytotoxic or inhibitory effect on the germination of seeds of A. hybridus.