olid phase extraction (SPE)
All
crude extracts (obtained by Soxhlet, USAE, and ASE) were
purified by SPE. 10 mL of every sample was passed through a
Bakerbond C 18 SPE column (previously conditioned). The retained
polyphenols were eluted with 15 mL of 80% aqueous solution of
methanol using a SPE vacuum. Fractions for analysis were trans-
ferred into volumetric flask, filled up to their volume with 80%
aqueous solution of methanol, and injected into the HPLC system.
The whole procedure was repeated three times for each solvent.
Matrix solid-phase dispersion (MSPD)
0.25 g of dried Equisetum herb powder was placed in a glass
mortar, and mixed with 0.5 g of sorbent (previously conditioned),
and 1 mL of 80% aqueous solution of methanol. The mixture was
then homogenized in the glass mortar using a pestle to obtain a
homogenous mixture. The blend was then transferred into a 3 mL
syringe with a paper frit on the bottom. The sample was covered
with another paper frit, and compressed using the syringe plunger.
Polyphenols were eluted with 5 mL of 80% aqueous solution of
methanol. Fractions for analysis were transferred into volumet-
ric flask, filled up to their volume with 80% aqueous solution of
methanol, and injected into the HPLC system. The whole procedure
was repeated three times for each solvent.