Quantitative Analysis of NDP via HPLC

High-performance liquid chromatography was used to investigate NDP (HPLC; model Jasco PU-2089 equipped with detector model Jasco UV-2070 plus multi-wavelength UV–vis, Jasco, Tokyo, Japan). According to a prior publication, the separation and analytical method were used [23 (link)]. A C18 column was used (5 µm, 4.6 mm × 250 mm) ACE^® column. The detector wavelength was 235 nm. To illustrate NDP, an isocratic flow (1 mL/min) condition was used. A mobile phase containing methanol–acetonitrile–water (25:25:50 v/v) was filtered via a 0.45 μm nylon membrane filter and degassed in a sonicator bath before use. A 20 μL of sample was injected. NDP peak was computed using ChromNav software (Jasco, Tokyo, Japan). These analyses were performed in triplicate.