Fig 1.
The chemical structure for piperlongumine.
Fig 2.
HPLC chromatograms for the separation of piperlongumine (peak at 6.9 minutes) in different stability conditions.
(a) Sample at pH 8. (b) Sample at pH 5. (c) Sample at pH 3. (d) Photo-stability sample.
Fig 3.
Solubility of piperlongumine in different surfactant and complexing systems.
Fig 4.
Solubility of piperlongumine in different cosolvent systems.
Fig 5.
Photomicrographs of piperlongumine (400X).
(a) Original crystals, (b) Crystalline precipitant.
Fig 6.
DSC thermogram of piperlongumine.
Fig 7.
Pattern of X-ray diffraction of piperlongumine crystals.
Fig 8.
Degradation of piperlongumine as a function of pH at 56°C.
Fig 9.
Arrhenius plots for piperlongumine degradation at different pH values.
Table 1.
Summary of stability results.
Fig 10.
Piperlongumine pH degradation rate profiles.
All samples were at an ionic strength of ~0.2 M. Buffer types are: citrate for pH 3 and 4, phosphate for pH 5, 6 and 7, borate for pH 8 and 9.
Fig 11.
Effect of ionic strength (IS) on stability of piperlongumine at pH 3, 5 and 9 at 26°C.
Fig 12.
Major degradation products of piperlongumine.
Table 2.
Summary of photo-stability studies of piperlongumine.
Fig 13.
Stability of piperlongumine with the addition of different excipients.
(a) pH 7 at 26°C. (b) pH 3 at 56°C.
Table 3.
Stability comparisons for piperlongumine with different excipients.