The solubilization properties of PNM and MNM were investigated adding an excess of SLM to 5 mL of empty micellar solutions in sealed glass bottles, which were then kept under magnetic stirring at room temperature. After 24 h, the samples were centrifuged at 14,000 rpm for 10 min, and SLM concentration in the supernatants was determined by HPLC after proper dilution with MeOH [63 (link)]. Then, the solubility factor (Sf) was calculated according the equation,
where Smic is the solubility of SLM in each micellar formulation and Sw is the water solubility of the extract. SLM analyses were performed, employing an HP 1100 Liquid Chromatograph (Agilent Technologies, Santa Clara, CA, USA) equipped with a UV detector and a Luna Omega Polar (150 mm × 3 mm, 5 µm) (all from Agilent Technologies) RP-C18 analytical column. The software was HP 9000 (Agilent Technologies). SLM detection was at a wavelength of 288 nm. The mobile phase consisted of: (A) formic acid/water pH 3.2, (B) acetonitrile and (C) methanol. The following gradient profile was applied: 0–2 min 10% B and 10% C, 2–6 min 15% B and 22% C, 6–11 min 20% B and 30% C, 11–16 min 30% B and 40% C, 16–18 min 30% B and 40% C, 18–20 min 40% B and 40% C, 20–23 min 40% B and 40% C, 23–27 min 10% B and 10% C. The flow rate was 0.5 mL/min. The calibration curve was prepared using standard silibinin dissolved in methanol from a concentration range of 0.001–0.100 μg/μL, and the concentration absorption relationship was above 0.999.
where Smic is the solubility of SLM in each micellar formulation and Sw is the water solubility of the extract. SLM analyses were performed, employing an HP 1100 Liquid Chromatograph (Agilent Technologies, Santa Clara, CA, USA) equipped with a UV detector and a Luna Omega Polar (150 mm × 3 mm, 5 µm) (all from Agilent Technologies) RP-C18 analytical column. The software was HP 9000 (Agilent Technologies). SLM detection was at a wavelength of 288 nm. The mobile phase consisted of: (A) formic acid/water pH 3.2, (B) acetonitrile and (C) methanol. The following gradient profile was applied: 0–2 min 10% B and 10% C, 2–6 min 15% B and 22% C, 6–11 min 20% B and 30% C, 11–16 min 30% B and 40% C, 16–18 min 30% B and 40% C, 18–20 min 40% B and 40% C, 20–23 min 40% B and 40% C, 23–27 min 10% B and 10% C. The flow rate was 0.5 mL/min. The calibration curve was prepared using standard silibinin dissolved in methanol from a concentration range of 0.001–0.100 μg/μL, and the concentration absorption relationship was above 0.999.
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