Extract of greyia radlkoferi and use thereof

Abstract

This invention relates to the isolation, and use of a plant extract in the treatment of skin hyper-pigmentation. More particularly, this invention relates to the isolation of a tyrosinase inhibitor in an extract of plant material from the Greyia radlkoferi ( G. radlkoferi ) plant, the extract including 5,7-dihidroxyflavone[(2S)-pinocembrin]; 2′, 6′-dihydroxy-4′-methoxydihydrochalcone; 2′,4′,6′-trihydroxyhydrochalcone; 3,5,7-trihydroxyflavone and 4′,5′7-thhydroxyisoflavone.

1 . A method for preparing a plant extract having tyrosinase inhibitor activity, the method including the steps of:
 drying leaves of  Greyia radikoferi  ( G. radikoferi );   pulverising the dried leaves;   mixing the pulverised leaves with a solvent to allow phenolic compounds to leach into the solvent; and   removing the pulverised leaves from the solvent, such that the plant extract remains in the solvent.   
     
     
         2 . A method according to  claim 1 , wherein the solvent is selected from the group consisting of water and ethanol. 
     
     
         3 . A method according to  claim 1 , wherein the step of mixing the pulverised leaves with solvent includes the further step of agitating the mixture to improve leaching of phenolic compounds from the leaves into the solvent. 
     
     
         4 . A method according to  claim 1 , wherein the step of removing the pulverised leaves from the solvent includes the step of passing the solvent through a vacuum filter system. 
     
     
         5 . A method according to  claim 1 , including the further step of adding a preservative to the plant extract. 
     
     
         6 . A method according to  claim 5  wherein the preservative is in the form of 1% of a mixture of phenoxyethanol and ethylhexylglycerin added to the plant extract on a weight per weight basis. 
     
     
         7 . A method according to  claim 1 , including the further step of preparing the plant extract in a topical dosage form selected from the group consisting of creams; lotions; aqueous solutions; balms; sunscreens; skin-oils and ointments. 
     
     
         8 . A plant extract for inhibiting tyrosinase activity prepared in accordance with a method of  claim 1 , characterised in that the extract includes 5,7-dihidroxyflavone[(2S)-pinocembrin]; 2′,6′-dihydroxy-4′-methoxydihydrochalcone; 2′,4′,6′-trihydroxyhydrochalcone; 3,5,7-trihydroxyflavone and 4′,5′7-trihydroxyisoflavone. 
     
     
         9 . A plant extract according to  claim 8  displaying tyrosinase inhibitory activity by exhibiting a 50% inhibitory concentration (IC50) ranging from 17,96 μg/ml to 32.62 μg/ml when using L-tyrosine and dihydroxyphenylalanine (DOPA) as substrates. 
     
     
         10 . Use of a plant extract according to  claim 8  in the treatment of skin hyper-pigmentation. 
     
     
         11 . Use of a plant extract according to  claim 8  in the preparation of a topical dosage form for use in a method of treating a patient suffering from skin hyper-pigmentation. 
     
     
         12 . A topical dosage form selected from any one of the group consisting of a cream; lotion; aqueous solution; balm; sunscreen; skin-oil; and an ointment, for the treatment of skin hyper-pigmentation comprising a plant extract according to  claim 8 , in a suitable dermatologically acceptable carrier. 
     
     
         13 . A method for preparing a plant extract having tyrosinase inhibitor activity for the treatment of skin hyper-pigmentation from leaves of  Greyia radlkoferi  ( G. radlkoferi ) substantially as herein described. 
     
     
         14 . A plant extract from the leaves of  Greyia radlkoferi  ( G. radlkoferi ) having tyrosinase inhibitor activity for the treatment of skin hyper-pigmentation substantially as herein described.