Method for preparing an extract of centella asiatica

A method for preparing a refined extract of Centella asiatica comprising more than 50% wt. of a mixture of madecassoside and terminoloside in relation to the total weight of the extract, said method comprising the following steps:

• a. maceration under stirring of the aerial parts of leaves of the Centella asiatica plant in water or in a solvent mixture, comprising at least water and optionally an alcoholic solvent, at a temperature of 20 to 90° C., for 20 and 180 minutes in a Centella asiatica to solvent mixture ratio of between 1:2 and 1:20, followed by
• filtration of the maceration mixture, whereby an aqueous solution is obtained;
• α. passage of the aqueous solution obtained over an adsorbent resin suitable for adsorbing triterpene heterosides;
• β. elution of said adsorbent resin with an eluent comprising at least 30% wt. of an alcoholic solvent and optionally water, whereby an eluate is obtained, followed by:
• treatment of the eluate obtained with activated carbon;
• b. passage of the treated eluate over a strong anionic styrene-chloride type discoloring resin followed by treatment by means of successive passage(s) over a strong cationic ion exchange resin comprising sulfonate type functional groups, and over a strong anionic ion resin comprising quaternary ammonium type functional groups, or passage of the eluate over said mixed resins, whereby a discolored aqueous phase is obtained;
• c. vacuum-concentration of the discolored aqueous phase using tangential filtration membrane techniques on an organic or mineral membrane, using media having a cut-off threshold between 200 kDa and 100 kDa, whereby an extract is obtained, followed by
• recrystallization of the extract obtained by:
• d. solubilization of the extract obtained in a solvent mixture comprising water and an alcoholic solvent, carried to a temperature between 40° C. and 70° C., whereby a solution is obtained;
• e. slow and gradual reduction of the temperature for 1 to 250 hours to a cooled mixture temperature between −20° and 30° C., whereby a cooled mixture is obtained;
• f. filtration of the cooled mixture, whereby a filtrate is obtained;
• and
• g. concentration of the filtrate by distillation, whereby a refined extract comprising less than 15% wt. of asiaticoside in relation to the total weight of the extract is obtained.