Caffeine and rutin standards

Caffeine and rutin standards, HPLC grade acetonitrile, methanol, acetic acid, formic acid, dimethyl sulfoxide, Phosphate Buffer Saline (PBS), porcine polar brain lipid extract, cholesterol, phosphatidylcholine, and deuterated methanol (methanol-d₄, 99.8 atom% D, contains 0.03% (v/v) TMS) were purchased from Merck (Darmstadt, Germany). Ethyl acetate, methanol, and n-dodecane of reagent grade were purchased from Reanal-Ker (Budapest, Hungary). HPLC-grade water was prepared with a Millipore Direct Q5 water purification system (Merck, Darmstadt, Germany). All aqueous eluents for HPLC were filtered through MF-Millipore membrane filters (0.45 μm, mixed cellulose esters) (Merck, Darmstadt, Germany) and degassed in an ultrasonic bath before use.

HPLC grade acetic and formic acid, myricetin-3-O-rhamnoside, quercetin-3-O-rhamnoside, hirsutenone, oregonin, caffeine and rutin standards, dimethyl sulfoxide-d₆ (99.8 atom% D with 0.03 vol.% TMS) and methanol-d₄ (99.8 atom% D), phosphatidylcholine, cholesterol and the porcine polar brain lipid extract were purchased from Merck (Darmstadt, Germany). Ethyl acetate, n-hexane and methanol of reagent grade, HPLC-MS grade acetonitrile, methanol, n-dodecane, dimethyl sulfoxide, NaCl, HCl, Na₂HPO₄·7H₂O and NaH₂PO₄·H₂O were obtained from Reanal-Ker (Budapest, Hungary). HPLC-grade water was prepared with a Millipore Direct Q5 water purification system (Bedford, MA, USA). All aqueous eluents for HPLC were filtered through MF-Millipore membrane filters (0.45 μm, mixed cellulose esters) (Billerica, MA, USA) and degassed in an ultrasonic bath before use.