Cinchotannic acid explained

Cinchotannic acid is a tannin contained in many cinchona barks, which by oxidation rapidly yields a dark-coloured phlobaphene^[1] called red cinchonic,^[2] cinchono-fulvic acid or cinchona red.^[3]

Notes and References

1. http://chestofbooks.com/health/materia-medica-drugs/Textbook-Materia-Medica/Cinchona-Bark-Cortex-Cinchonae-Part-3.html Cinchona Bark (Cortex Cinchonae). Part 3
2. http://chestofbooks.com/health/materia-medica-drugs/The-Essentials-Therapeutics/Cinchonaceae-Part-2.html Cinchonaceae on chestofbooks.com
3. http://www.1902encyclopedia.com/Q/QUI/quinine.html Quinine on www.1902encyclopedia.com