Isolation, identification, and characterization of compounds from acer rubrum capable of oxidizing equine...

To identify compounds in Acer rubrum that cause hemolysis or oxidation of equine erythrocytes and determine whether these toxins are found in other Acer spp.

Equine erythrocytes.

Washed erythrocytes were incubated with extracts and fractions of Acer spp that were separated by thin layer chromatography. Methemoglobin and hemolysis were measured spectrophotometrically. Compounds within Acer spp fractions associated with cell oxidation or hemolysis were identified by gas chromatography-mass spectrometry.

Erythrocytes incubated separately with either A. rubrum, A. saccharum, or A. saccharinum extracts had increased methemoglobin formation, compared with extract-free control samples. Two Acer spp fractions had toxic effects on erythrocytes in vitro. A major component of the Acer fraction that caused a significant amount of methemoglobin formation was identified as gallic acid. An amount of gallic acid equivalent to that found in A. rubrum extract significantly increased methemoglobin, compared with extract-free control erythrocytes, but caused less methemoglobin formation than A. rubrum extracts did. A potential co-oxidant, 2,3-dihydro-3,5-dihydroxy-6-methoxy-4H-pyran-4-one, was found in the A. rubrum extract and may have been responsible for increasing methemoglobin formation. A second A. rubrum fraction caused methemoglobin formation and significant hemolysis. A. saccharum and A. saccharinum extracts caused hemolysis but less than the A. rubrum extracts did.

Oxidants in A. rubrum are also found in A. saccharum and A. saccharinum, and the ingestion of A. saccharum and A. saccharinum poses a potential threat to horses.