Optimization of microwave-assisted extraction of cajaninstilbene acid and pinostrobin from pigeonpea leaves followed by RP-HPLC-DAD determination

In the present study, a microwave-assisted extraction (MAE) method followed by reversed-phase high-performance liquid chromatography-photodiode array detector (RP-HPLC-DAD) was developed for the determination of cajaninstilbene acid (CSA) and pinostrobin (PI) in pigeonpea leaves. Compared to conventional extraction methods, MAE showed higher efficiency and better recovery yields. The effect of microwave irradiation on cell destruction of plant material was observed by scanning electron microscopy (SEM). The optimum MAE conditions were as follows: sample diameter ≤0.5 mm, extraction solution 80% ethanol, liquid to solid ratio 30:1 (mL g−1), temperature 65 °C, and 2 extraction cycles with each cycle 1 min. The relative standard deviations (RSDs) for intra-day repeatability and inter-day reproducibility were <5% and <6%, respectively. The recoveries for CSA and PI were 96 ± 3% and 95 ± 4%. The developed MAE method, followed by RP-HPLC-DAD technique, was successfully applied in the rapid extraction and accurate determination of CSA and PI in pigeonpea leaves.