Soursop fruits (A. muricata) were harvested at consumption maturity (15-19 • Brix) in Compostela, Nayarit, Mexico. They were manually peeled to obtain the pulp and the by-products (peel, seeds, and columella). The raw materials were freeze-dried at -50 • C under pressure of 0.12 mbar (Labconco 77522020, Kansas City, MO, USA), then ground (Nutribullet NB-101B, Los Angeles, CA, USA), and sieved (500 µm, No. 35, Fisher Scientific, Hampton, NH, USA).
Quinine standard, acetic acid, Dragendorff's reagent, and methanol were purchased from Sigma-Aldrich (St. Louis, MO, USA).
Quinine standard, acetic acid, Dragendorff's reagent, and methanol were purchased from Sigma-Aldrich (St. Louis, MO, USA).