1 Introduction

These compounds are found in nature in flowers as well as in fruits, to which they provide a broad spectrum of colour ranging from orange to blue. They may also occur in roots, stems, leaves and bracts, accumulating in the vacuoles. Anthocyanins are vacuolar pigments found in various plant tissues. In flowers they are principally located in epidermal cells, and rarely in the mesophyll. However, in rye leaves, they are restricted to the mesophyll cells.1

The functions of the anthocyanins in plants are similar to the general functions of all flavonoids: antioxidant functions, photoprotection, defence mechanisms, and other ecological functions (symbiotic phenomena). Since they give colour to different parts of plants, they also play an interesting role in reproductive mechanisms: found in flowers, they serve to attract polinators, and in seeds and fruits to attract seed disseminators. It has also been observed that cyanide-3-glucoside inhibits larval growth in tobacco worms ( Heliothis viriscens), and thus anthocyanins may be considered agents of biological control. It has also been suggested that anthocyanins may serve as taxonomic markers in plants, but up to now research has been carried out only on some levels of species within specific families.

Anthocyanins have been attracting greater interest as food colouring agents as a result of the present tendency toward the use of natural colours. To this end, researchers have been looking for sources in the plant kingdom that can provide sufficient quantities of stable anthocyanins. At the same time, the...