Total condensed tannin content was determined by the Folin–
Ciocalteu procedure, as described above, after their adsorption
onto hide powder of the polyvinyl polypyrrolidone (PVPP)
(Hagerman and Butler, 1978). In brief, samples of plant extract
were homogenized with adsorbent material and the mixture
was stirred for 30–60 min, the obtained preparation was stored
for 1–2 h at +4 C to develop tannin–PVPP complex. Then
the pH was acidified (pH 3) in case of using PVPP. After centrifugation
at 4000 rpm/15 min, no adsorbed phenolics in the
supernatant were determined by the Folin–Ciocalteu procedure
as described above. Calculated values were subtracted
from total polyphenol contents and the amount of total condensed
tannins expressed as mg of gallic acid equivalents per
gram of dry weight (mg GAE/g DW) through the calibration
curve with gallic acid. The calibration curve range was 50–