Ch3oh

Silibinin (purity ≥98% by HPLC) was purchased from Sigma-Aldrich (Milan, Italy). HPLC grade CH₃CN and CH₃OH were purchased from Carlo Erba Reagents (Milan, Italy) and Sigma-Aldrich. Hydrogen peroxide (H₂O₂) (30%) was purchased from Fluka (Milan, Italy). Unless otherwise indicated, all other chemicals were obtained from Sigma Aldrich, and their purity was >98%. Fresh aqueous solutions of hydrogen peroxide, Rose Bengal and tryptophan were prepared prior to each experiment. The concentration of the stock solution of H₂O₂ in Milli-Q H₂O (for the laser flash photolysis experiments) was determined using a molar absorption coefficient of 38.1 ± 1.4 M⁻¹·cm⁻¹ at 240 nm [20 (link)].

Silibinin 1 was purchased from Sigma-Aldrich (Milano, Italy). HPLC-grade ACN and CH₃OH were purchased from Carlo Erba Reagents and Sigma-Aldrich. Unless otherwise indicated, other chemicals were obtained from Sigma Aldrich. For the experimental synthesis procedures of tyrosol-based building blocks 6–8, see Romanucci et al. 2021 [37 (link)]. It must be noted that the experimental procedures for the synthesis of compounds 10–12 and 13–15 were described in detail only for the stereoisomer of silybin A (SilA, 1a): the same reaction conditions (temperature, stoichiometric ratios, and time of reaction) were used for silybin B (SilB, 1b) and silibinin (Sil, 1ab) as a natural mixture. Reactions were monitored by TLC (precoated silica gel plate F254, Merck, Upper Gwynedd, PA, USA) and column chromatography: Merck Kieselgel 60 (70–230 mesh). The analysis was performed with a Shimadzu (Tokyo, Japan) LC-8A HPLC system equipped with a Shimadzu SCL-10A VP System control and Shimadzu SPD-10A VP UV-VIS Detector. HPLC purifications were carried out on a Phenomenex Gemini RP18 column (10 μm particle size, 21.20 mm × 250 mm i.d.) using a linear gradient of ACN in 0.1 M NH₄Ac in H₂O, pH 7.0, from 20% to 100% over 30 min at a flow rate of 8 mL/min, with detection at 288 and 260 nm. MALDI spectral data were acquired on a MALDI TOFTOF AB Sciex 5800 mass spectrometer.