Fig 2. Typical ¹H NMR spectrum of an aqueous extract (in deuterated water) of a NR capsule obtained on a bruker AVANCE III 800 MHz nuclear magnetic resonance (NMR) spectrometer.

NMR signals that arise from NR are labeled with the corresponding location of the hydrogen atom(s) as shown in the molecular structure of NR (inset). TSP [3-(trimethylsilyl)propionic acid-2,2,3,3-d₄ sodium salt] was used as an internal standard to quantify the amount and purity of NR in the capsules. The purity of NR was calculated based on integration of all the peaks and was in the range of 98–99%.