Antifungal and toxicological evaluation of the alkaloids fraction from Neltuma nigra leaves

SEQUIN, CHRISTIAN J.; APPELHANS, STEFANIA C.; HEIS, MAGALÍ S.; TORRENT, WALTER A.; TROSSERO, JULIA A.; CATALÁN, CÉSAR A.N.; SAMPIETRO, DIEGO A.; ACEÑOLAZA, PABLO G.

Biocatalysis and Agricultural Biotechnology

Elsevier BV

Año: 2023

1878-8181

The use of synthetic fungicides for control soybean crop diseases has beencuestionated because of its impacts on human health and the environment. This workevaluated the composition, antifungal activity and toxicity of the alkaloids fraction obtainedfrom Neltuma nigra leaves and compared its effect with the fungicide difenoconazole onSclerotium rolfsii, Cercospora kikuchii, and C. sojina. Alkaloids fraction was extracted fromleaves of N. nigra and its composition was analyzed by gas-chromatography coupled to massspectrometry (GC-MS). The antifungal effect was recorded by measuring diameters of halosof inhibition of the growth of the different evaluated fungis. The toxicity of the alkaloidsfraction was carried out using the method of Caenorhabditis elegans toxicity test. Theextracted alkaloids fraction contained the alkaloids tryptamine (63.9%), tetrahydroxyharman(13.8%), phenethylamine (11.1%), cassine (10.4%), and N-formylphenylethylamine (0.8%).The alkaloids fraction was as effective against S. rolfsii as on the Cercospora strains, withminimum inhibitory doses of 25.0 µg disc-1 and inhibitory halos in the range of 8.5-13.0 mm,while difenoconazole had no effect on S. rolfsii. The toxicity of the alkaloid fraction (30.4-68.8mg L-1) and difenoconazole (0.1-2.8 mg L-1) was tested on the reproduction, body length, andfertility of C. elegans. The fraction reduced the reproductive rate by 28.8-72.4% whereasdifenoconazole did it from 12.2% to complete suppression. Neither of them affected thefertility of C. elegans. These findings suggest that the alkaloids fraction of N. nigra leaves isless toxic than difenoconazole and is a promising botanical fungicide against pathogenicsoybean fungi.