Taninos e flavonoides em lotus spp.

Abstract

The present study aimed to quantify the content of condensed tannins (CT) and flavonoids in Lotus spp. in response to soil acidity and the relationship to morphological components of the plants harvested in different phenological stages. Two experiments were performed: in the Experiment I, the concentration of tannins and flavonoids of L. corniculatus (cv. São Gabriel, cv. Ganador and population UFRGS), L. uliginosus (cv. Serrano) and L. subbiflorus (cv. El Rincón), grown in pots, under two soil pH (4.7 to 6.4), was determined. In Experiment II, the components leaf+stem and flower+fruit of cv. São Gabriel plants harvested in vegetative and reproductive stages were evaluated as for tannins and flavonoids. In both experiments, the plant material was subjected to extraction hydroalcoholic. For identification and quantification of the tannins and flavonoids, methods for separation and quantification by High Performance Liquid Chromatography were developed and validated, using catechin, epicatechin, gallic acid, rutin, quercetin and kaempferol as reference standards. There was a significant interaction between genotype and soil acidity, showing intraspecific and interspecific variability. The largest variation of condensed tannins was observed in acid soil, from 5.6 g CT/kg DM (cv. Serrano) to 23.1 g CT/kg DM (population UFRGS). In soil with pH 6.4 the concentration varied from 2.3 g CT/kg DM (cv. El Rincón) to 7.5 g CT/kg DM (cv. Ganador). At the reproductive stage, the concentrations of condensed tannins and flavonoids in leaf+stem were higher (16.3 g/kg) than that found in the vegetative stage (10.0 g/kg). The component flower+fruit showed 120% more rutin, 333% more quercetin, 76% more epicatechin and 47% more CT compared to leaf+stem. The results of the study indicate the importance of the evaluation of these metabolites in breeding programs of Lotus spp. and the relationship of these compounds with the phenological stage of the plants and the soil acidity