Modelling of polyphenol and flavonoid extraction from bottle gourd fruit using green and cost effective LTTM glycerol-ammonium acetate in neat and diluted forms

The current study investigated the effectiveness of a low-cost, safe and green LTTM (low-transition-temperature mixture) GAA (glycerol-ammonium acetate) for extraction of bioactive biomolecules form bottle gourd ( Lagenaria siceraria ) fruit. Two forms of LTTM, neat and diluted with ethanol, were compared. Response surface methodology (RSM) was employed for optimization using the Box-Behnken design consisting of three-factors, each with three levels. Total polyphenols (TP), total flavonoids (TF), anti-radical activity (ARA), and iron chelating activity (ICA) were dependent variables, while time, temperature, speed, and solvent concentrations were independent variables. Second order polynomial models were well fitted for the responses in both solvent systems. For GAA-ethanol extraction, TP, TF, ICA, and anti-radical activity were 14.47 mg GAE/g, 4.93 mg RE/g, 12.21% and 36.43%, respectively, at optimum conditions of extraction time (42 min), temperature (42 °C), and solvent ratio (56%). For GAA extraction, the values 4.50 mg GAE/g, 2.86 mg RE/g, and 70.21% were obtained for TP, TF, and anti-radical activity, respectively, at optimized extraction conditions of speed 300 RPM, temperature 50 °C and solvent-to-solid ratio 10 mL/g. For anti-radical activity of GAA and GAA-ethanol extracts, the error rates between predicted and observed values were extremely low (3.35% and 3.88%, respectively), which demonstrated the suggested quadratic polynomial models as adequate for predicting this activity under any set of extraction conditions. With the error rate of 15.09%, the extraction of TP with GAA can also be quite adequately modelled. The study demonstrated GAA as a green and efficient solvent for extraction of polyphenols and other antioxidant biomolecules from L. siceraria fruit and the optimized process can be used for maximum extraction of antioxidants from it.