1 Introduction

Flavanones, chalcones and dihydrochalcones are biochemically related compounds of restricted occurrence. For this reason they are described as minor flavonoids despite sometimes being present in foods at a dietary significant concentration.1 This is the case of flavanones in citrus fruits, chalcones in tomato and dihydrochalcones in apple.

Flavanones have a saturated C-ring, chalcones are unsaturated and along with dihydrochalcones have an open structure and a carbon skeleton numbered in a way different from other flavonoids (Figure 1).

Figure 1: Flavanone, chalcone and dihydrochalcone structures and numbering. Flavanone-Chalcone chemical interconversion

These compounds are often responsible for relevant quality characteristics of plant-derived food products (taste, colour and appearance, etc.).2 Thus, some flavanones have an intense bitter taste, being responsible for the characteristic taste of sour orange and grapefruit. In contrast, some dihydrochalcones that are obtained by chemical transformation of the bitter flavanones show an intense sweet taste and they are used as low-calorie sweeteners. Chalcones, together with aurones, are responsible for the pigmentation of many yellow and orange flowers, such as carnations and many flowers of the Compositae family.

Some of these compounds, such as citrus fruits flavanones, are ingested in the diet in very significant concentrations (150 300 mg per serving).1 As orange juice is one of the main fruit-derived products in the diet of European countries,3 flavanones are one of the main phenolic compounds ingested in the diet.

2 Extraction

Some flavanones and chalcones are very difficult...