Improving the desorption of Inga edulis flavonoids from macroporous resin: Towards a new model to concentrate bioactive compounds

The cumulative recovery of Inga edulis flavonoids from a fixed-bed adsorber was evaluated using an empirical sigmoid model, aiming at optimise the maximum solute desorption. Ethanol:water mixtures (20-100%, v/v) were applied to desorb the bioactive compounds from the column filled with Amberlite XAD-7 resin. Flavanol and flavonol content of the eluate were monitored with fast spectrophotometric measurements and these determinations were then validated using chromatographic analysis. The modelling results showed that a three-parameter sigmoid model fitted well to the cumulative flavonoid recovery data and the coefficients of multiple determination were higher than 0.99 for all ethanol proportions. Moreover, the estimated parameters of the model provided qualitative and quantitative desorption information, including the rate of desorption and the maximum recovery value. Interestingly, the rate of desorption presented a linear relationship with the ethanol proportion, while a quadratic behaviour was observed for the maximum recovery. In the optimised condition, four bed volumes of an 80% ethanol-water mixture permitted the desorption of almost 100% of the flavonoids from the column. All fractions presented particularly elevated antioxidant capacity (17.84 ± 5.23 μmol TE/mg GAE), when measured by the oxygen radical antioxidant capacity per total phenolic content. This modelling procedure appears to be useful when one is focusing on rapidly concentrating bioactive compounds