The organic acids in banana leaves

Abstract

The concentration of total non-volatile organic acids in eleven banana leaf samples was found to be 93·2 (± 10·2) m-equiv./100 g dry weight ; with a twelfth sample containing only 57·5 m-equiv. The leaf tissue represented three cultivars of banana and various stages of plant maturation, grown either in the tropics or the greenhouse. Oxalic acid constituted 83 per cent of the total acidity, malic acid about 2 per cent and “citric peak” acidity (citric acid plus certain phosphates) about 9 per cent. The remaining acidity consisted of a series of acids, each present in trace quantities. These included glutamic, aspartic, glutaric, glyceric, glycolic, glyoxylic, shikimic, succinic, pyruvic, malonic, and α-ketoglutaric acids. At least nine trace acids, including five keto acids, remain unidentified. Approximately 50 per cent of the oxalate in field-grown leaves is in water-soluble form; the greenhouse leaves contained 28 per cent soluble oxalates. The results are compared with those obtained with the leaves of temperate-zone plants.