Tannins are made of polyphenolic compounds and they exist
widely in plants. In order to determine the total free phenolic
group, i.e., total soluble phenols present in the extract, the colorimetric
assay (Folin–Ciocalteau method) was carried out.
The total phenolic content of the extract was 365.12 mg/g
gallic acid equivalent, respectively. The extracts confirmed
the presence of phenolic (–OH) groups and thus can be effectively
used as mordants for natural dyes on all the three
substrates.