Optimisation of Pueraria isoflavonoids by response surface methodology using ultrasonic-assisted extraction

•Optimising ultrasonic-assisted extraction with maximal cyto-protective effect.•Optimised parameters: time 16.02 min, ethanol 41.41% and L/S ratio 44.35 mL/g.•Pueraria extract effectively protect human endothelial cells against oxidative stress.•Identified five putative cyto-protective isoflavonoids.

Puerariae Lobatae Radix (PLR) exerts cyto-protective effect against oxidative stress due to its high isoflavonoid content. In this study, the ultrasonic-assisted extraction condition for the maximum recovery of isoflavonoids with high cyto-protective effect was optimised by response surface methodology (RSM). A second-order polynomial fitted the experimental data (R2: 0.9736; p-value <0.0001). The optimal extraction parameters were determined as: extraction time 16.02 min, ethanol concentration 41.41% and liquid-to-solid ratio 44.35 mL/g. Practical experiments with extraction time 16.00 min, ethanol concentration 41.00% and liquid-to-solid ratio 44.00 mL/g were carried out in triplicate. This subsequently yielded a cell viability of 82.90 ± 0.78% against hydrogen peroxide-induced oxidative stress on EA.hy926, and was comparable to the predicted of 85.60%. Five chemical constituents in the extract were identified to exert cyto-protective effect. Taken together, this method successfully integrated RSM and the partial least squares regression method to optimise the PLR extract with highest cyto-protective activity.