The DMACA-HCl protocol and the threshold proanthocyanidin content for bloat safety in forage legumes
1996
Li, Y.G. | Tanner, G. | Larkin, P.
A protocol using HCl-acidified 4-dimethylaminocinnamaldehyde (DMACA) was developed for screening proanthocyanidins (PA) in plants. Individual PA-containing cells could be observed following staining of decolourised leaves with DMACA. The quantitative assay using DMACA-HCl to detect soluble PA and butanol-HCl to detect insoluble PA could detect PA content lower than 0.4 mg g-1 dry matter (DM). The DMACA-HCl protocol is recommended for PA detection in low-PA plants because of its higher sensitivity than vanillin-acid protocols. Twenty-two forage legume species, most of which had been reported free of leaf PA but bloat-safe, were re-examined using the DMACA-HCl protocol. PA-positive cells were observed in leaves of 15 species. Measurable amounts of PA were detected in leaves of seven species, with the PA content ranging from 0.6 to 11 mg g-1 DM. White clover (Trifolium repens L), red clover (T pratense L) and lucerne (Medicago sativa L) were also found to have PA-positive leaf trichomes. By analysis of these data and the literature, the threshold PA content for bloat safety in forage legumes was estimated to be 1-5 mg PA g-1 DM.
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