Narcissin

OFI-50E (250 mg) was dissolved in 80% methanol and filtered through a polyvinylidene difluoride syringe filter. HPLC analysis was performed using a Waters Alliance 2695 with 996 photodiode array detector system (Waters Corp., Milford, MA, USA). Samples (10 µL) were separated on a ShiseidoCapcell Pak C18 column MGII (5 μm, 4.6 × 250 mm, 40 °C) at a flow rate of 0.6 mL/min and eluted using a linear gradient of two mobile phases (A, ultrapure water; B, acetonitrile containing 0.1% trifluoroacetic acid). A chromatographic gradient was optimized as follows: 0 min, 90% A; 0–10 min, 70% A; 10–15 min, 67% A; 15–32 min, 60% A; 32–36 min, 0% A; 36–45 min, 0% A; 45–50 min, 90% A; 50–60 min, 90% A. All extraction and chromatographic solvents used were of mass spectrometry grade (Billerica, MA, USA). Narcissin was purchased from Sigma-Aldrich (St. Louis, MO, USA).

Rutin (quercetin 3-O-rutinoside) (2) was purchased from Alchimica s.r.o. (Czech Republic). Hesperidin (hesperetin 7-O-rutinoside) (3), narcissin (isorhamnetin 3-O-rutinoside) (4), diosmin (diosmetin 7-O-rutinoside) (5), and p-nitrophenyl β-d-glucoside (7) were purchased from Sigma-Aldrich. Isoquercitrin (quercetin 3-O-β-d-glucopyranoside) (1) and p-nitrophenyl rutinoside (8) were prepared as previously described (Weignerová et al. 2012 (link); Šimčíková et al. 2015 (link)).

Folin–Ciocalteu reagent was obtained from VWR International (Metz, France). Gallic acid, rutin, catechin, gallocatechin, epigallocatechin, chlorogenic acid, vanillic acid, caffeic acid, epicatechin, narcissin, verbacoside, naringin, Trolox and sodium nitrite (NaNO₂), were obtained from Sigma-Aldrich (Paris, France). Sodium carbonate (Na₂CO₃), aluminum chloride (AlCl₃), and sodium hydroxide (NaOH) from Acros Organics (Brussels, Belgium).