Development of analytical techniques for soybean wastes

Soybean grain is the product that represents the highest value of exports in Brazil. The other parts of the plant, such as branches, leaves and pods are left in the ground generating physicochemical and biological improvements to the soil [1]. However, at least a percentage of other plant parts could be collected for higher value-added uses. This project aims to map the specialized metabolites in different soybean crop residues through green analytical methods, estimating potential applications for these residues and their metabolites. Initially, mechanical crop residues of soybean cultivar TMG 7062 IPRO were collected at Santa Fé Farm - Pardinho / SP, Brazil. The plant material obtained directly from the ground after mechanical harvest (leaves, branches, pods and grains) was dried, ground and mixed in equal amounts of each part of the residue. To verify the most appropriate extraction methodology, 150 mg of the mix was extracted with 1.5 ml EtOH: H2O (7: 3) (v / v) by three techniques: (a) dynamic maceration at magnetic stirring speed of 1400 rpm, 30 ° C for 30 min; (b) maceration in ThermoMixer at 1150 rpm, 30 ° C for 30 min; (c) bath ultrasound assisted extraction at room temperature, 15 minutes. Hydroethanolic extract was analyzed by UHPLC-PAD-UV [2,3], with number of peaks and total area under chromatogram peaks being monitored responses. The data were analyzed by analysis of variance (ANOVA), followed by Tukey’s multiple comparisons test, considering 5% level of significance. After verifying that there were no statistically significant differences between the techniques (p > 0.05), it was decided to use the technique (a) to analyze each part of the residue individually, because it has a more precise control of the variables and generated 157,00 ± 6,24 peaks and 4.150.075 ± 729.911 of total area. The resulting chromatograms shown in Fig. 1. As can been seen, each part of the residue left in the ground had a characteristic chromatographic profile and differential distribution of metabolites.