Metabolite Extraction From Placental Samples

Placental samples in quintuplicate were collected and sent for metabolon-associated energy metabolism analysis (Applied Protein Technology, Shanghai, China). A homogenate of 100 mg of sample mixed with 1 mL of cold methanol/acetonitrile/H2O (2:2:1, v/v/v) was sonicated at a low temperature (30 min/once, twice) and then centrifuged for 20 min (14,000 g, 4°C). The supernatant was dried in a vacuum centrifuge. The dried samples were dissolved in 100 μL of acetonitrile/water (1:1, v/v), adequately vortexed and then centrifuged (14,000 rpm, 4°C, 15 min). The supernatants were collected for LC-MS/MS analysis.