Preparation of green tea extract
Fresh green tea leaves were collected from tea gardens of Mazandaran
province. Then, were sorted, washed, and were dried under sunlight. The
dried tea leaves were crushed in a blender and then sieved using 70/100
mesh sieve-set (Setyopratomo., 2014). The extraction carried out by
mixing 1000 ml of 70% ethanol in distilled water to 100 g of green tea
powder. The obtained mixture had agitated with a magnetic for 24 hours
at 40 °C temperature. In the next stage, the extract separated by
filtration. Then to obtain to a concentrate extract, the resultant
liquid evaporated by oven at temperature 40 °C. Finally, the extract was
converted to powder by employing a freeze dryer at -50°C and was kept in
air-tight dark bottles in the freezer at -18°C until usage (Vuong et
al., 2011). Nwuha et al. reported the green tea polyphenols solubility
in ethanol solvent was five to seven times higher than in the water
extracts (Nwuha et al., 1999).