From an aqueous extract of the fruit of the tropical plant Thaumatococcus ohniellii &frtfh, -two sweet-tasting basic proteins, here named thaumatin I and thaumatin 11, were isolated by ultrafiltration, gel filtration on Sephadex (2-50 and ion-exchange chromatography on SE-Sephadex C-25, using a sodium chloride concentration gradient.The proteinaceous character of the two sweet-tasting compounds was proven by the characteristic ultraviolet absorption spectrum, the presence of almost 100 polypeptide material as determined by the biuret method, the yield of 100°/o amino acids on hydrolysis with hydrochlorid acid, the positive reaction with amido black colouring agent (as used in the analysis of the fractions by polyacrylamide gel and starch gel electrophoresis) and by the disappearance of the sweet taste of the compounds after incubation with trypsin.The basic character of the two proteins appears from their isoelectric points of almost 12, as estimated by starch gel electrophoresis a t M e r e n t p H values, and from the precipitation of the proteins a t pH 12.

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