Psidium guajava L. leaves as source of proanthocyanidins: Optimization of the extraction method by RSM and study of the degree of polymerization by NP-HPLC-FLD-ESI-MS

Due to the importance of the proanthocyanidins (PAs)bioactivity and its relationship with the PAs degree of polymerization (DP), an experimental design was carried out to establish the best extraction conditions in order to evaluate the proanthocyanidins content and their degree of polymerization in Psidium guajava leaves at different oxidation state. Optimal conditions achieved by response surface methodology were 50% acetone/water (v/v), 48 degrees C, 30 min, and 0% acetic acid (v/v). The highest DP has been found in the low oxidized state (DP 13 plus the polymers). Medium and high oxidized state leaves reported a DP 11 plus the polymers. The total amounts of proanthocyanidins (sum of PAs by HPLC-FLD-ESI-MS) decreased when oxidation state of leaves increased (15.8 +/- 0.4,12.6 +/- 0.4, and 10.5 +/- 0.3 mg/g leaf dry weight (d.w.) in low, medium and high oxidized state leaves, respectively). Guava leaves present an interesting source of low DP-PAs. (C) 2016 Elsevier B.V. All rights reserved.