Chemical profile and allelopathic potential of Anacardium humile St. Hill. (cajuzinho-do-cerrado) leaf aqueous extract in the seed germination and seedling growth of lettuce, tomato and sicklepod

Abstract

Anacardium genus, Anacardiaceae, stands out for the presence of phenolic compounds. One of its species, investigated for its different potential uses, is Anacardium humile; however, little is known about its allelopathic effects. Therefore, the present study aimed to determine the chemical profile and evaluate the herbicide potential of your leaves in the germination of seeds and growth of seedlings of Lactuca sativa (lettuce), Lycopersicon esculentum (tomato) and Senna obtusifolia (sicklepod), both in vitro and in greenhouse. Leaves of A. humile were obtained from 20 matrices of Cerrado fragments in the municipality of Campo Grande, Mato Grosso do Sul state, Brazil. A voucher specimen was deposited at the herbarium (no. 8448). The aqueous extract was obtained from dried and crushed leaves using the extraction method of ultrasonic bath (30 min) with subsequent static maceration. After solvent evaporation, 12.78 g of extract were obtained. The chemical profile of the aqueous extract included determination of total phenolic and flavonoid contents, pH, electrical conductivity, and soluble solids concentration. For the in vitro bioassays, the extract was used at different concentrations, namely, 25, 50, 100, 150, and 200 mg mL^-1. In greenhouse, the substrates were prepared using 950 g of vermiculite and 50 g of A. humile leaf powder at the following ratios: (950/50) (5%), 900/100 (10%), 800/200 (20%), and a control (100% vermiculite), under a completely randomized experimental design. Phenolic compounds and anthraquinones were predominant in the chemical profile of the extract, which presented different levels of allelopathic effect on seed germination and seedling growth of plants both in germination chamber and in greenhouse, indicating strong allelopathic activity associated with the different compounds found in the leaves. Therefore, the results showed germination and growth inhibition at different levels, indicating that the substances contained in the leaves of Anacardium humile may be a promising alternative for the control of invasive species.