Producing a plant extract of leaves of sweet blackberry ( Rubus chingii var. suavissimus) comprises: (a) performing an aqueous primary extraction of the dried sweet blackberry leaves； (b) alcoholically precipitating the obtained aqueous extract； (c) separating and discarding the obtained precipitate； (d) further precipitating the remaining extract of the steps (b) and (c) with calcium hydroxide； (e) separating and discarding the precipitate obtained in the step (d)； and (f) further processing the remaining extract of the steps (d) and (e) as a liquid-, a paste or a dry extract. An independent claim is also included for the extract of the leaves of sweet blackberry ( Rubus chingii var. suavissimus) comprising (in % based on dry material): water (4.64), protein (NX6.25) (2.79), fat (1.6), carbohydrate (73.61), sugar (19.1), glucose (9.85), fructose (9.25), sucrose (less than o.1), roughage (5.55), ash (11.81), sodium (647.2 mg/kg), an amino acid (4.3 mg/g), L-proline (2.1 mg/g), L-glutamic acid (0.04 mg/g) and rubusoside (18).
