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A valine carbamate prodrug of naringenin (NAR) called 4'V was synthesized to enhance its oral bioavailability because of low water solubility and poor membrane permeability of NAR. This study developed and fully validated a sensitive, rapid, and robust HPLC-MS/MS method for the simultaneous determination of NAR and 4'V in plasma. The analytes were treated using liquid-liquid extraction, separated on a Phenomenex Kinetex XB-C 18 column, and detected using a triple-quadrupole tandem mass spectrometer equipped with an electrospray ionization interface. The analytes were eluted within only 4 min by gradient procedure. The excellent linear correlations were validated over the range of 4-400 ng/mL (r = 0.9990) for NAR and 2-2000 ng/mL (r = 0.9951) for 4'V, with lower limits of quantification of 4 and 2 ng/mL, respectively. For all quality control samples, the intra-day and inter-day precision and accuracy were within ±15%. The validated method was economical, high throughput, and reliable and was first successfully applied to a pharmacokinetic study of NAR and 4'V after oral administration to Sprague-Dawley rats. The results of the pharmacokinetic study demonstrated that the idea of amino acid carbamate prodrug is a promising strategy to improve the bioavailability of NAR.

Introduction Glucosinolates (1–5) are important secondary metabolites found in Isatis indigotica roots. Due to their high hydrophilic and ionic nature, purified glucosinolates often contain salt impurities and moisture. Accurate assessment of their purities is important for glucosinolates being utilised as chemical markers. Objective To develop and validate quantitative proton (1H) nuclear magnetic resonance (qHNMR) methods for purity assessments of aliphatic and indole glucosinolates (1–5). Method Several NMR parameters such as pulse program, relaxation time, and delay time were optimised. Three qHNMR methods were developed using gluconapin (3), neoglucobrassicin (4), and sinigrin (5) for method validation and with maleic acid as internal standard. Results The quantification was based on the integrated area ratios of an olefinic proton (H‐4 for 1–3; H‐6 for 4; and H‐3 for 5) of the side chain from glucosinolates relative to the olefinic proton from the internal standard using deuterated water (D2O) as the solvent. The qHNMR methods were successfully applied for purity assessments of four aliphatic glucosinolates (1–3 and 5: progoitrin, epiprogoitrin, gluconapin, and sinigrin), and an indole glucosinolate (4: neoglucobrassicin). Conclusion The purity of glucosinolates isolated from I. indigotica and commercial sinigrin was accurately assessed using the developed qHNMR method. The qHNMR provides a reliable and superior means to determine the purity of glucosinolates.