Enhancing the antimicrobial and antifungal activities of a coloring extract agent rich in betacyanins obtained from Gomphrena globosa L. flowers

Abstract

Although less explored than beetroot (Beta vulgaris L.), the flowers of Gomphrena globosa L. are a very suitable source of betacyanins with strong pigmentation features, together with many other desirable bioactive properties. Thus, the aim of this study was to enhance the antimicrobial and antifungal activities of a pigmented extract obtained from G. globosa flowers by ultrasound assisted extraction (UAE). The procedure was supported with the application of the response surface methodology, a robust optimization technique that allows to study jointly the effects of several variables and responses. To enhance the antimicrobial (Bacillus cereus, Listeria monocytogenes, Escherichia coli and Salmonella typhimurium) and antifungal (Aspergillus flavus, Aspergillus niger, Penicillium ochrochloron and Penicillium verrucosum) activities, the responses were evaluated in terms of the concentrations needed to obtain minimum inhibitory (MIC), minimum bactericidal (MBC) and minimum fungicidal (MFC) concentrations. It was found that the optimal UAE conditions were 10.8 min, 410.5 W, 57.8% of ethanol, and 5 g L⁻¹ of the solid–liquid ratio providing the following response values: (1) from the studied species of bacteria, the MIC ranged from ∼0.15 to 0.35 g L⁻¹ and the MBC ranges were ∼0.30 to 0.65 g L⁻¹; and (2) from the studied fungus species, the MIC ranged from ∼0.20 to 0.30 g L⁻¹ and the MFC ranges were ∼0.40 to 0.65 g L⁻¹. The antibacterial activity dose levels were lower than the antifungal ones. In conclusion, the results obtained in this study highlight extracts from G. globosa flowers as natural sources of betacyanins with application as food colorants with important antimicrobial and antifungal activities.