Optimisation of microwave-assisted enzymatic extraction of corilagin and geraniin from Geranium sibiricum Linne and evaluation of antioxidant activity

Plant polyphenols exhibit effective bio-activities, particularly antioxidant activities. Previous studies showed that Geranium sibiricum Linne contains high levels of polyphenolic compounds such as corilagin (CG) and geraniin (GE). In this study, a microwave-assisted enzymatic extraction (MAEE) method was evaluated for the simultaneous extraction of CG and GE only with deionised water. The optimal extraction conditions were as follows: irradiation power 500 W, ratio of solvent to material 40 ml/g, irradiation temperature 33 °C, pH 5.2, amount of cellulase 3600 U/g and irradiation time 9 min. Under these conditions, the extraction yields of CG and GE achieved were 6.79 and 19.82 mg/g, which increased by 64.01% and 72.95%, respectively, as compared with the control ones. Furthermore, the antioxidant activities of crude extracts were 2.61 mmol FeSO₄/g DW and 0.118 mg/ml (IC₅₀), according to the FRAP and DPPH assays, which indicated G. sibiricum Linne possesses good potential for natural antioxidants.