Briefly, after adding 375 µL of methanol to one million HeLa or H9c2 cells, the mixture was incubated at RT for 1 h while vortexing at 600 rpm. Next, 1.25 mL of MTBE and 313 µL of deionized water were added, followed by centrifugation at 10,000 rpm for 10 min. The upper MTBE phase was carefully collected, dried in a SpeedVac, and stored at -80 °C for subsequent use.