2.1. Materials and Reagents
All lactating mothers in this study were obtained from the Maternal and Child Health and Family Planning Service Center of Jiangning District, Nanjing, Jiangsu Province, China. From November 2018 to January 2019, breast milk of 121 eligible healthy lactating mothers was included in this study. The project has been approved by the Human Research Ethics Committee of Nanjing Medical University and registered as ChiCTR1800020179 in clinicaltrials.gov. Each participant provided oral and written informed consent. Inclusion criteria: (1) 20-40 years old healthy lactating mothers, 30-50 days postpartum exclusive breastfeeding; (2) singleton pregnancy, full-term delivery (≥ 37 weeks of gestation), birth weight ≥ 2500 g, ≤ 4000 g infants. Mothers with any infectious disease, severe malignant disease, malnutrition, or mental illness; people diagnosed with breast diseases such as mastitis; or people with pregnancy complications such as gestational hypertension and diabetes were excluded. Mothers who had a history of drinking and smoking during pregnancy and lactation, vegetarians, mothers who consumed fatty acid supplements during lactation, or who participated in other studies in the past 30 days were also excluded.
The mixed TAGs standards (8:0, 10:0, 12:0, 14:0 and 16:0, 17811-1AMP) were purchased from Sigma-Aldrich Limited (Shanghai, China). High performance liquid chromatography grade n -hexane, acetonitrile, and iso -propanol were purchased from Shanghai Bailingwei Technology Co., Ltd. (China, Shanghai). Ammonia, ethanol, anhydrous ethyl ether (boiling point of 30 to 60 ℃), and petroleum ether were purchased from Chemical Reagent Co., Ltd. (Shanghai, China).