An investigation on polyphenolic compounds of the cacao leaf in connexion with a chemical method for detecting virus infection

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Abstract
Polyphenolic substances in acid extracts of cacao leaves have been separated by paper partition chromatography. The substance which gives a red colour when cacao leaf extracts are heated with alkali, a reaction which has been used as the basis of a ‘colour‐test’ for detecting infection with swollen shoot virus, has the properties of a leuco‐anthocyanin. The amount of red‐producing leuco‐anthocyanin varies with the total tannin content of the leaf. In addition to virus infection, other factors such as age of leaf and variety of cacao which affect the total tannin content also affect the leuco‐anthocyanin content. The bearing of this on the applicability of the ‘colour‐test’ is discussed.