EFFECT OF SOLVENT AND SOLVENT-TO-SOLID RATIO ON THE PHENOLIC EXTRACTION AND THE ANTIOXIDANT CAPACITY OF EXTRACTS FROM Pinus durangensis AND Quercus sideroxyla BARK

Bark from timber species might be a promising target of therapeutical interest due to its content of bioactive, phenolic compounds. However, the extraction efficiency of these metabolites depends on the type of solvent chosen and the process variables analyzed. Traditional medicine only uses ethanol and water mixtures for therapeutical purposes. Therefore, in this study extractions of Pinus durangensis and Quercus sideroxyla bark were realized. In order to study the effect of the hydroethanolic solutions of 20, 50 and 80% and the relation mass/solvent volume ratio of 1/10, 1/20 and 1/30, an experiment design of 2x3x3 was followed, over the extract yield; where 28,72 +/- 0,9% corresponded to P. durangensis (PdE50-1/20) and 24,95 +/- 1,2% to Q. sideroxyla (QsE50-1/30). The highest content of phenolic compounds was obtained with ethanol 80%-1/10 in both species (PdE80-1/10 with 712,36 +/- 13,4 mg of gallic acid equivalent (GAE)/g) and QsE80-1/10 of 592,97 +/- 10,6 (GAE/g); while the antioxidant capacity evaluated through DPPH, ABTS and FRAP showed that PdE20-1/30 and QsE50-1/10 presented the strongest activity. Significant statistical differences (p< 0,05) were found among the treatments analyzed. The ethanol concentration had a higher effect than the relation mass/solvent volume ratio. More importantly, P. durangensis showed the highest phenol and flavonoid concentration respect to Q. sideroxyla. However, the proanthocyanidin amount was similar in both species. Finally, the flavonoid content of P. durangensis is mainly composed by flavanone and flavonol type compounds, while Q. sideroxyla contains gallic acid and flavan-3-ol (catechins).