Development of a natural anthocyanin-based food colorant obtained from the fruit epicarp of Prunus spinosa L.
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resumo
Prunus spinosa L. is a wild shrub with bitter and astringent fruits with poor commercial value. Nevertheless, they are rich sources of anthocyanins, more specifically cyanidin 3-rutinoside and peonidin 3-rutinoside, which are concentrated in the epicarp. These compounds possess recognized colouring properties and have been increasingly explored for substitution of artificial colorants, for being safer alternatives. In this context, the present work aimed to develop an anthocyanin-based food colorant obtained from P. spinosa fruit epicarp. The conditions that maximize the extraction were optimized, comparing heat (HAE) and ultrasound (UAE) assisted extraction techniques. For that purpose, a response surface methodology was applied, using a circumscribed central composite design with three variables and five levels, being the relevant variables time, temperature (HAE) or power (UAE), and ethanol concentration. The anthocyanin compounds were quantified by HPLC-DAD-ESI/MS. Furthermore, the bioactivity of the optimal extract was assessed through antioxidant, antimicrobial, and cytotoxic activity assays. UAE was the most efficient method, under optimal conditions of 5.0 ± 0.2 min, 400 ± 32 W, and 48 ± 3% ethanol, where the extraction yield was 68.60 ± 2.1%, with a total anthocyanin content of 18 ± 2 mg/g (dried extracted residue-basis) and 11,8 ± 0,8 mg/g (dried epicarp-basis). Additionally, these response values were slightly improved when the solid-to-liquid ratio effect at the optimal conditions in a dose-response format was tested, showing a steady decreasing pattern in the range of 5 to 250 g/L. Regarding bioactive properties, the obtained extract presented antioxidant activity, with EC50 values of 204.22 ± 0.02 μg/mL for the TBARS assay and 296 ± 4 and 509 ± 3 μg/mL for OxHLIA method at 60 and 120 min of reaction, respectively; and antimicrobial properties, allowing the growth inhibition of 9 bacteria strains of public health interest in concentrations from 2.5 to 20 mg/mL. Besides, the obtained extract did not show hepatotoxic effects on a porcine liver primary cell culture (PLP2), being thus safe for incorporation into foodstuff. Lastly, the anthocyanin-based extract was introduced in a traditional Brazilian confectionary product, “beijinho”, where its colouring capacity was confirmed.
