Plant extract containing diketopiperazine and method for producing same

Abstract

Provided are a diketopiperazine mixture suitable for mixing with a food or drink and a method for producing the mixture. High-temperature and high-pressure treatment of plant peptides in a liquid allows production of a plant extract containing a high concentration of diketopiperazines including cyclo-leucyl-leucine and cyclo-leucyl-phenylalanine. The present invention can provide diketopiperazines having excellent flavor derived from a plant natural product and can produce a food or drink provided with the functions of the diketopiperazines by directly mixing the diketopiperazines with the food or drink.

1 - 10 . (canceled) 
     
     
         11 . A plant extract comprising at least one of cyclo-alanyl-glutamine, cyclo-alanyl-alanine, cyclo-seryl-tyrosine, cyclo-glycyl-leucine, cyclo-glycyl-tryptophan, cyclo-valyl-valine, cyclo-tryptophanyl-tyrosine, cyclo-leucyl-tryptophan, and cyclo-phenylalanyl-phenylalanine at a concentration of 10 μg/100 g/Bx or more. 
     
     
         12 . The plant extract according to  claim 11 , wherein the total amount of diketopiperazine(s) per Bx is 900 μg/100 g/Bx or more. 
     
     
         13 . The plant extract according to  claim 11 , being a tea extract, a soybean extract, or a malt extract. 
     
     
         14 . A plant extract prepared by subjecting a protein-containing plant to decomposition treatment to generate a plant peptide and subjecting the plant peptide to high-temperature and high-pressure treatment in a liquid. 
     
     
         15 . A method for producing a plant extract containing a high concentration of diketopiperazines including cyclo-leucyl-leucine and cyclo-leucyl-phenylalanine, the method comprising a step of subjecting a plant peptide to high-temperature and high-pressure treatment in a liquid. 
     
     
         16 . The method according to  claim 15 , wherein the high-temperature and high-pressure treatment is performed in a liquid of 100° C. to 170° C. for from 30 minutes to several hours as heating conditions. 
     
     
         17 . The method according to  claim 15 , wherein the plant peptide is an oligopeptide. 
     
     
         18 . The method according to  claim 15 , wherein the plant peptide is prepared by subjecting a plant-derived protein or a protein-containing plant to decomposition treatment. 
     
     
         19 . The method according to  claim 18 , wherein the decomposition treatment is heat treatment or enzyme treatment. 
     
     
         20 . The method according to  claim 19 , wherein the decomposition treatment is enzyme treatment, and the enzyme is endo-type protease.