One samplewas untreated and served as control. Samples
were heated for 1–4 h and 24 h at 50 °C and 60 °C (±2 °C) in the heating
block. Following the heat treatment, samples were cooled down to room
temperature and diluted with an equal amount of methanol (1/2;
v/v). HPTLC analysis and post-chromatographic derivatization
with p-anisaldehyde sulphuric acid were carried out as mentioned
previously