Chemical nature, stability and bioefficacies of anthocyanins from fruit peel of syzygium cumini Skeels

In the present study, anthocyanin pigments from Syzygium cumini fruit peels were characterized and evaluated for their antioxidant efficacy, and stability as extract and in formulation. Total anthocyanin content was 216 mg/100 ml of extract which is equivalent to 230 mg/100 g fruit on a dry weight basis. Three anthocyanins were identified as glucoglucosides of delphinidin (1), petunidin (2) and malvidin (3) by HPLC–ESI–MS. The antioxidant capacity of the extract was tested using models, such as DPPH-scavenging, reducing power assay, lipid peroxidation in rat brain, liver, liver mitochondria, testes and human erythrocyte ghosts. The extract showed 78.2% DPPH-scavenging at 2.5 ppm, while BHA exhibited only 41.6% activity at the same concentration, thus proving it to be a more efficient free radical-scavenger than the widely used BHA. One ppm of the extract was equivalent to 3.5 μM ascorbic acid, as estimated by reducing power assay. Inhibition of rat brain lipid peroxidation was 94.4% at 5.0 ppm concentration. It was almost equally active in all the biological models, except human erythrocyte ghost cells, where it showed only 48% inhibition at 5.0 ppm. The extract was quite stable at 0 °C with 11% loss in 4 weeks, while the pigment loss in the antitussive formulation was only 13% at 30 °C at the end of 8 weeks. The high antioxidant activity and relatively high stability of the pigments make S. cumini a potential source of natural colourant as well as antioxidants.