Metabolomic profile and allelopathy effects of Calotropis procera and Nicotiana tabacum extracts used as pesticidal agents on germination of maize seeds.

Abstract

Calotropis procera and Nicotiana tabacum leaves are among the natural pesticides that are generally used on various crops at various stages. However, many of these natural pesticides affect plant growth. This study determined the metabolomic profile and the allelopathic effects of Calotropis procera and Nicotiana tabacum leaf extracts (CPLE and NTLE) on germination of maize seed. The allelopathic activities of n-hexane, ethylacetate and methanol of CPLE and NTLE were determined on maize seed using concentration of 2.5%, 5.0% and 10% for 12 days. On days 3, 6, 9 and 12, the root and shoot development, germination percentage, and seedling vigour of maize seeds were determined. All CPLE contained calotropin, calotoxin, calactin, caffeic acid, thioacetate, alpha-amyrin, beta-sitosterol, stigmasterol, isoquercitrin, quercetin, kaempferol, rhamnetin, luteolin, lineolone, voruscharin, uscharin and uscharidin, while azeleatin, tyranton were present in only the ethylacetate extracts. The NTLE revealed the presence of nicotine, chlorogenic acid, nornicotine, 4-hydroxybenzaldehyde, catechin, catechol, protocatechuic acid, vanillin, vanillic acid, nicotelline, nicotianine, tabacine, tabacinine, harmine and anabasine while ajmalicine, pyridine and cotinine are absent in methanol extracts of NTLE. All seedlings show a reduction in germination percentage when compared to the control from the 3rd to the 12th day of germination. However, only 2.5% of both extracts exhibit concentrations 5% and 10%. Hence, high concentrations (5 and 10%) of CPLE and NTLE should be avoided when using as insecticide during germination stage of maize to prevent growth inhibition. of maize.