1. A generic term for a group of compounds that are widely distributed in plants and that are concerned with maintenance of a normal state of the walls of small blood vessels.
2. A biologically active compound found in the rinds of citrus fruits and some other plants.

Any of a group of water-soluble yellow compounds, present in citrus fruits, rose hips, and other plants, that in mammals maintain the resistance of capillary walls to permeation and change of pressure.