Process for preparing plant extract, comprises: cooling of the plant or part of fresh plant at -10[deg] C to -80[deg] C; grinding frozen plant; contacting the frozen ground plant with a part of enzymatic solution suitable for digesting pectocellulosic partition of the plant cells; adjusting the value of pH and temperature in which enzymes act; adding rest of enzymatic solution; applying depression and pressure using the inert gas; and sieving and stabilizing the obtained liquid extract, when the digestion is completed.