3. Extraction of apple peel
For the first treatment, 100 g of dried apple peel powder were
sonicated in 1 l of absolute ethanol, three times for 15 min with
10 min intervals in between sonications (in triplicates). For the
second treatment, 500 g of frozen apple peels were extracted in
2 l of absolute ethanol for 15 min with 10 min intervals three
times. After the extraction, extracts were filtered separately using
Whatman No. 1 filter papers under vacuum. The extracts were
concentrated to 150–200 ml using a rotary evaporator (Rotavapor,
R-200, Buchi, Flawil, Switzerland) at 37 C and filtered through
Whatman No. 1 filter papers under vacuum. The water to ethanol
ratio was adjusted to 1:1 (v/v) with a load volume of 300–400 ml
for the chromatographic column. Both procedures were conducted
in triplicates.