Sulfatase type h 1

Oleuropein (Ole) was obtained from Nacalai Tesque, Inc. (Kyoto, Japan). Hydroxytyrosol (HT, 2-(3,4-dihydroxyphenyl) ethyl alcohol) was purchased from Tokyo Chemical Co. (Tokyo, Japan). Oleuropein aglycone (3,4-DHPEA-EDA, 3,4-dihydroxyphenylethyl elenolate dialdehydic form) was purified using ODS-preparative HPLC according to a previous study [32 (link)]. Homovanillic acid (HVA, 4-hydroxy-3-methoxyphenylacetic acid), homovanillyl alcohol (HVAOH, 4-hydroxy-3-methoxyphenethyl alcohol), MOPS [3-(N-morpholino)propanesulfonic acid], β-glucuronidase Type VII-A, and sulfatase Type H-1 were obtained from Sigma-Aldrich (St. Louis, MO, USA). Trifluoroacetic acid (TFA) was obtained from Wako Pure Chemical Co. (Tokyo, Japan).

The reference standards of quercetin, kaempferol, rutin, kaempferol-3-O-rutinoside, isoquercitrin, hyperoside, N-trans-Feruloyltyramine, and astragalin were purchased from the National Institute for the Control of Pharmaceutical and Biological Products (Beijing, China). Internal standard (IS) d3-quercetin was obtained from Toronto Research Chemicals (North York, ON, Canada). Sulfatase (type H-1) and β-glucuronidase (type H-2) were obtained from Sigma-Aldrich (St Louis, MO, USA). Deionized water was freshly prepared using a Milli-Q purification system (Millipore, Billerica, MA, USA). HPLC-grade acetonitrile and methanol were purchased from Fisher Scientific (Fair Lawn, NJ, USA). EDTA-K₂ containing vacutainer tubes (5 mL) and 22 G IV catheters (0.9 × 25 mm) were obtained from BD Biosciences (Franklin Lakes, NJ, USA). Formic acid, methyl tert-butyl ether (MTBE), and other chemical reagents were of analytical grade. The tartary buckwheat extracts were produced by Jing Brand Co. Ltd. (Daye, China). The contents of rutin, quercetin, kaempferol and, kaempferol-3-O-rutinoside were 61.2%, 4.5%, 0.15%, and 4.84% respectively, which was quantified by HPLC.