Detached banana leaves are one of the by-products of banana production. In this study, the absorption and metabolism of formaldehyde (HCHO) in solutions by detached banana leaves was investigated under submergence conditions. The results showed that banana leaves could effectively absorb HCHO in the treatment solutions, and the relationship between HCHO absorption and treatment time appeared to fit a radical root function model. C-13 nuclear magnetic resonance analysis was used to investigate the ability of detached banana leaves to metabolise (HCHO)-C-13, and the results indicated that the (HCHO)-C-13 absorbed from the treatment solutions was converted into non-toxic compounds. High amounts of [U-C-13]glucose, [U-C-13]fructose, [3-C-13]serine and [3-C-13]citrate were produced as a result of (HCHO)-C-13 metabolism in banana leaves, and the production of a small amount of [2,4-C-13]citrate and [2,3-C-13]alanine was also observed. These results suggest that detached banana leaves can metabolise (HCHO)-C-13 and convert it to non-toxic compounds. The metabolic pathways that produce these intermediates in detached banana leaves are postulated based on our C-13 nuclear magnetic resonance data. (C) 2013, The Society for Biotechnology, Japan. All rights reserved.