Colour is an important factor influencing the consumer appeal of food products. As most natural colours also have health attributes, there is increasing consumer demand for foods and supplements containing efficacious amounts of these substances. In addition, several countries have already banned the use of a number of synthetic food colorants, promoting further interest in natural pigments.

Most of the edible natural colours are either water-soluble or lipid-soluble. Beetroot contains water-soluble betacyanins such as betanin, which contribute to the red colour, and has been used as a traditional folk medicine and natural food colour. Anthocyanins from beetroot exhibit antioxidant and anti-inflammatory activities while the lipid-soluble lycopene in tomatoes has preventive activity against cancer and cardiovascular diseases.

Another important lipid-soluble natural colour is the carotenoid bixin from annetto seeds. The consumption of carotenoid-rich fruits and vegetables is associated with a lower incidence of cancer and cardiovascular diseases.  In particular, β-carotene exhibits potent antioxidant, cyclooxygenase and cell proliferation inhibitory activities on selected human cancer cell lines. The green pigment chlorophyll is abundant in leafy vegetables and its consumption could prevent or delay the onset of certain types of cancers.

A study by Reddy et al.¹, investigated the relative efficacies of betanin, bixin, chlorophyll, β-carotene, lycopene and cyanidin-3-O-glucoside, alone and in combination, as inhibitors of lipid peroxidation, cyclooxygenase enzymes and human tumour cell proliferation. The pigments were isolated from beetroot, annetto seeds, spinach, carrot, tomatoes and cherries, respectively. All of the pigments showed inhibition against cyclooxygenase enzymes and a dose-dependent growth inhibition against breast, colon, stomach, central nervous system and lung tumour cells. The lipid-soluble pigments exhibited higher antioxidant, anti-inflammatory and anticancer activities than the hydrophilic pigments, except at higher concentrations. However, a combination of betanin and anthocyanin reduced their respective bioactivities, as did a combination of lycopene, β-carotene and bixin.

¹ Reddy, MK; Alexander-Lindo, RL; Nair, MG (2005). Relative inhibition of lipid peroxidation, cyclooxygenase enzymes, and human tumor cell proliferation by natural food colors. Journal of Agricultural and Food Chemistry 53 (23) 9268–9273.

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