Limonin

Twelve reference standards (purity>98%) were pur-chased from Weikeqi (Sichuan, China). These standardswere  isoscopoletin,  scopoletin,  7-methoxycoumarin,7-hydroxycoumarin,  isomeranzin,  bergapten,  tan-geretin, nobiletin, hesperidin, limonin, ferulic acidand  bergamottin.  Chromatographic-grade  methanoland dichloromethane were purchased from WeikeqiBio-Technology (Sichuan, China). Formic acid and ACN(purity>99.9%) of HPLC-grade were provided by MerckKGaA (Darmstadt, Germany) and Thermo Fisher Scien-tific Inc. (NYSE:TMO), respectively. CO2(purity>99.9%)was provided by Messer Gas (Guangzhou, China).

The reference standards of stachydrine, scopoletin, hesperidin, 5,7-dimethoxycoumarin, limonin, nomilin, nobiletin, and tangeretin were obtained from Weikeqi (Sichuan, China). The compounds had purities higher than 98%. High-performance liquid chromatography (HPLC)-grade formic acid was purchased from Thermo Fisher Scientific (USA). HPLC-grade acetonitrile and n-hexane were obtained from Merck (Germany). Deionized water was prepared by a Milli-Q system (Millipore, USA).

Formic acid was purchased from ACS (Washington DC, USA). Ultrapure water was obtained from a Milli-QB system (Bedford, MA, USA). The reference compounds umbelliferone, 3,5,6,7,8,3′,4′-heptamethylflavone, naringenin-7-O-glucoside and limonin (purity ≥?98%) were purchased from Weikeqi Biotechnology Co., Ltd. (Chengdu, China).

Acetonitrile was of HPLC grade and supplied by Merck Company, Inc. (Merck, Darmstadt, Germany). Ultrapure water was prepared by a Milli-Q50 SP Reagent Water System (Millipore Corporation, MA, USA). All other reagents were of analytical grade. Authentic standards of Phe, Mag, Jat, Pal, Ber, Ob1 and Ob2 were provided by Sichuan WeiKeqi Bio-Tech Co., Ltd (Sichuan, China).