In this review the qualitative and quantitative occurrence of flavonols and flavones, particularly in fruit and vegetables, are considered. They occur practically in all plants. Their formation normally depends on light so that they are mainly concentrated in the outer tissues. the concentration of flavonols in free standing leaves exceeds that in other parts of the same plant considerably, except in onions.
Flavonols act as antioxidants and protect the ascorbic acid from auto-oxidation, for example in fruit juices. On the other hand, flavonols can lead to discolourations. Beneficial effects on the human organism have also been described.