Solvent extraction
The betel leaves were washed with tap water, dried at 40 oC for 3 days and grounded to rough powder. One hundred gram dried powder was incubated with 1 L of different solvents, including hexane, dichloromethane (DCM), ethyl acetate (EtOAc) and ethanol (EtOH) at 4 oC for 48 hr with interval shaking. Afterwards, the suspension was filtered through Whatman paper No.1. The filtrate was collected and evaporated with a rotary evaporator at 40 oC. The crudes were collected, weighted and stored at 4 oC in dark. Percentage of recovery yield (% yield) was calculated and reported as extracts weight to dried-leaf weight.