The results of extraction yield obtained by the three groups of
assays: SE (with EtAc and EtOH) and SFE (with CO2, CO2/AcEt and
CO2/EtOH) are presented in Table 1. The highest extraction yields in
SE were obtained using EtOH as solvent, especially for the phenolic
fraction, a result of the higher polarity of this solvent compared with
EtAc. The yield of the SFE process in terms of phenolic fraction is
also lower than the value obtained by SE-EtOH, although the total
extraction yields for SFE with CO2/EtOH are mainly higher. This
behavior is explained by the non-polar characteristic of the carbon
dioxide, which increases the extraction of low polarity compounds,
compared with polar ones (particularly found in the phenolic fraction).
In SFE the yield results (phenolic and total) increase directly
with solvent polarity (CO2, CO2/EtAc and CO2/EtOH), particularly,
the use of EtOH as co-solvent is useful to enhance the phenolic
fraction yield. The highest yield in SFE with CO2/EtOH was at
30MPa and 40 ◦C (1.738%, w/w phenolic fraction and 19.033%, w/w
total extract). The effect of extracting conditions in SFE is presented
in Fig. 2 by the yield isotherms for phenolic fraction and
total extract. At constant temperature, the increase in pressure
increases the yield due to the density enhancement. At constant
pressure, the phenolic and the total yield decrease with temperature
increase due to the solvent density reduction, although, at
30MPa the variation of temperature from 50 to 60 ◦C produce an
increase in phenolic yield, probably due to the enhancement in
the solute vapor pressure, the ANOVA show significant differences
between each data. This behavior is an indication of a crossover
pattern, nearly to 25MPa [10,28].