Phloridzin dihydrate

Methanol and ethanol were from VWR (Darmstadt, Germany) and were like all other solvents used of HPLC grade. Trolox, 2,2′-azinobis-(3-ethylbenzothiazoline-6-sulphonic acid) diammonium salt (ABTS), Folin-Ciocalteu reagent, quercetin, (−)-epicatechin, procyanidin B1, procyanidin B2, procyanidin C1, p-coumaric acid, trans-cinnamic acid and phloridzin dihydrate were from Sigma–Aldrich (Taufkirchen, Germany). Gallic acid, (+)-catechin, chlorogenic acid, ferulic acid, coffeic acid, rutin trihydrate and acetic acid were purchased from Carl Roth (Karlsruhe, Germany). Avicularin was used from Phytolab (Vestenbergsgreuth, Germany). Protocatechuic acid, hyperoside, isoquercitrin, quercitrin and procyanidin A2 were from Extrasynthese (Genay, France). Reynoutrin was purchased from Carbosynth Limited (Berkshire, UK). 2,2′-Azobis(2-amidinopropane) dihydrochloride (AAPH) was from Fisher Scientific (Nidderau, Germany). HPLC grade water (18 MΩ) was prepared using a MicroPure purification system (Thermo Electron LED GmbH, Niederelbert, Germany). Sodium hydroxide, hydrochloric acid (Merck, Darmstadt, Germany), meta-phosphoric acid (Sigma–Aldrich) and all other chemicals were of analytical grade.

All standards, reagents, and solvents were of analytical grade. The standards were: phloridzin dihydrate 99%, phloretin ≥99%, chlorogenic acid ≥95%, quercitrin hydrate ≥78%, and rutin hydrate ≥94%, which were purchased from Sigma-Aldrich Chemie GmbH, Darmstadt, Germany. All other chemicals and reagents (acetonitrile, methanol, phosphoric acid, formic acid) were also obtained from Sigma-Aldrich (St. Louis, MO, USA, Merck KGaA, Darmstadt, Germany). The ultrapure water was purified through a Milli-Q system (Millipore, Bedford, MA, USA).

Sodium carbonate, potassium chloride, potassium persulfate, ferric chloride, sodium acetate, potassium acetate, aluminum chloride, and hydrochloric acid were purchased from Qualigens (Mumbai, India). 2,2-azinobis (3-ethylbenzothiazoline-6-sulphonic acid) (ABTS), 2,4,6-tripyridyl-s-triazine (TPTZ), orthophosphoric acid, Folin-Ciocalteu reagent, formic acid, acetonitrile and methanol were purchased from Merck KGaA (Darmstadt, Germany). Ascorbic acid, tannic acid, Folin-Denis reagent and all phenolic standard compounds (rutin hydrate, phloridzin dihydrate, p-coumaric acid, (+)-catechin hydrate, gallic acid, 3-hydroxybenzoic acid, 4-hydroxybezoic acid, ellagic acid, vanillic acid, caffeic acid, m-coumaric acid, ferulic acid, trans-cinnamic acid and chlorogenic acid) and anthocyanins (malvidin, cyanin, cyanidin, delphinidin and pelargonidin) were procured from Sigma-Aldrich (St. Louis, Missouri, United States). All chemicals were of analytical and HPLC grade and the solutions were prepared with methanol and lab ultra-pure water (Rions India Lab Water Systems, India).

For apical receptor inhibition, the SGLT1 competitive inhibitor phloridzin dihydrate (Sigma) or the sweet taste receptor inhibitor (T1R2/T1R3) gurmarin (Peptides International) were dissolved into 1 M sucrose, 45 mM sucralose or 450 mM α-MGP. Following recording of a preinhibitor response to the selected ligand, sucrose, sucralose or α-MGP were perfused with the apical receptor inhibitors for a final phloridzin concentration of 3 mM (ref. ^{14 (link)}) and a final gurmarin concentration of 7 μΜ (refs. ^{27 ,52 (link)}). SGLT2 inhibitor dapagliflozin (3 nM) in PBS was perfused through the lumen.

Sinigrin hydrate, vanillic acid, amygdalin, L-canavanine, phloridzin dihydrate,
umbelliferone, rutin hydrate, salicin, gallic acid, naringin, sinapic acid,
gramine, caffeine, sucrose, allyl isothiocyanate, coumarin, methyl jasmonate,
brilliant blue FCF and sulforhodamine B were purchased from Sigma-Aldrich (St.
Louis, MO, USA). Glucoiberin potassium salt and glucobrassicin potassium salt
were purchased from Extrasynthese (Lyon, France). Gluconapin potassium salt and
gluconasturtiin potassium salt were purchased from ChromaDex (Irvine, CA, USA).
Quinine, chloroquine, denatonium and indole were purchased from Aladdin
(Shanghai, China). Salicylic acid and jasmonic acid were purchased from TCI (TCI
Shanghai, China). Berberine was purchased from Macklin (Shanghai, China).