Purine

A mixture of hexane and ethyl acetate was used for column preparation and fractionation. Silica gel (SiO₂) and normal phase thin layer chromatography plate were obtained from Merck, Germany. Developed TLCs were visualized using 5 per cent molybdophosphoric acid in ethanol was purchased from Nacalai, Japan. Formalin (37 per cent aqueous formaldehyde solution) was bought from Sigma, Leica, Microsystem (Darmstadt, Germany), Methanol (HPLC grade) was purchased from Merck (Darmstadt, Germany). LCMS-grade acetonitrile was obtained from J. T. Baker (Philipsburg, NJ, USA). Polyvinylidene fluoride (PVDF) syringe filters (0.22 µm pore size and 13 mm diameter) were bought from Merck (Darmstadt, Germany). Deionized water was acquired via a Milli-Q system (Merck, Darmstadt, Germany) at a resistivity of >18.2 MΩ·cm. Reference mass solution containing 5.0 mM of purine and 2.5 mM of Hexakis [1H,1H,3H-tetrafluoropropoxy] phosphazine, was procured from Agilent Technologies (Santa Clara, CA, USA). LCMS-grade formic acid (HCOOC) was acquired from Fisher Scientific (Fair Lawn, NJ, USA).

Acetonitrile, isopropanol, methanol (all LC-MS grade) as well as chloroform (HPLC grade), and ammonium formate (≥95% puriss.) were purchased from Carl Roth GmbH (Karlsruhe, Germany). Acetic acid (≥99.5% p.a.) was bought from Merck KGaA (Darmstadt, Germany). Ultrapure water (18 MΩ cm) was obtained from a millipore water purification system (Direct-Q 3 UV-R system, Merck KGaA, Darmstadt, Germany). Hexakis(1H,1H,3H-perfluoropropoxy)phosphazene, purine and LC/MS calibration standard for ESI-TOF were purchased from Agilent Technologies (Santa Clara, CA, USA). Hesperetin reference standard was obtained from Sigma-Aldrich (Steinheim, Germany), blumeatin reference standard from Cayman Chemical (Ann Arbor, MI, USA) and divanillin reference standard from Sigma-Aldrich.

Ultrapure water was obtained by purifying demineralized water in a Direct-Q 3 UV-R system (Merck, Millipore, Darmstadt, Germany). LC-MS-grade acetonitrile, methanol, ammonium formate, and HPLC-grade chloroform were purchased from Carl Roth GmbH and Co. KG (Karlsruhe, Germany). LC-MS-grade isopropanol was from Merck KgaA (Darmstadt, Germany). LC-MS tuning mix and hexamethoxyphosphazine, used as tuning standards, as well as hexakis(1H,1H,3H-tetrafluoropropoxy)phosphazine, and purine, used as lock masses, were purchased from Agilent Technologies (City of Santa Clara, CA, USA). Acetic acid, ethanol, sodium carbonate, disodium hydrogen phosphate, sodium chloride, potassium chloride, and potassium dihydrogen phosphate (all analytical-grade) were from Carl Roth GmbH and Co. KG (Karlsruhe, Germany). 2,2’-Azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS), fluorescein, and trolox (all analytical-grade) were from Sigma-Aldrich Chemie GmbH (Deisenhofen, Germany). 2,2’-Azobis(2-methylpropionamidine) dihydrochloride (AAPH), potassium peroxodisulphate, and gallic acid (both of analytical-grade) were purchased from Fisher Scientific GmbH (Schwerte, Germany). Folin-Ciocalteu phenol reagent (analytical-grade) was obtained from Merck KgaA (Darmstadt, Germany). Acetone (analytical-grade) was obtained from VWR International LLC (Fontenay-sous-Bois, France).