Anthocyanins in Blueberries Grown in Hot Climate Exert Strong Antioxidant Activity and May Be Effective against Urinary Tract Bacteria

Abstract

Anthocyanins are extensively studied for their health-related properties, including antibacterial activity against urinary tract infections (UTI). Among common fruits, blueberries, with their remarkable antioxidant capacity, are one of the richest sources. Anthocyanin-rich extracts were obtained from four varieties: Snowchaser, Star, Stella Blue and Cristina Blue, grown in the hot climate of Southern Spain. Their total anthocyanins contents (TAC) were determined spectrophotometrically, and the anthocyanin profile by ultra high performance liquid chromatography—tandem mass spectrometer (UHPLC-MS/MS). Their antioxidant activity was assessed by oxygen radical absorbance capacity (ORAC) assay, while antibacterial activity against strains isolated from UTI patients was assessed in vitro, helping to select the varieties with the highest bioactive potential. Star showed the highest TAC and antioxidant activity (1663 ± 159 mg of cyanidin-3-O-glucoside (cy-3-O-glu) equivalents/100 g fresh weight (FW), 6345 ± 601 μmol Trolox equivalents (TE)/100 g FW, respectively), followed by Cristina Blue, Stella Blue and Snowchaser. As far as we know, this is the first time that cyanidin-3-rutinoside has been identified in blueberries. The extracts inhibited all the tested strains, MICs ranging from 0.4 mg/mL (for Stella Blue extract against UTI P. aeruginosa) to 9.5 mg/mL (for all extracts against UTI K. pneumoniae ssp. pneumoniae). This is the first study that assessed in vitro the antibacterial activity of blueberries against Klebsiella pneumoniae, Providencia stuartii and Micrococcus spp. strains isolated from UTI.

Influence of production systems on phenolic characteristics and antioxidant capacity of highbush blueberry cultivars

“…Acylated anthocyanins elute after their corresponding non‐acylated anthocyanins because acylation of the sugar moieties of anthocyanins causes a decrease in polarity and an increase in retention time (Cardeñosa et al., 2016). The chromatograms in Figure 1 were consistent with the previously reported results of anthocyanin analysis of highbush blueberries (Cerezo et al., 2020).…”

Phenolic Compound Content and the Antioxidant and Antimicrobial Activity of Wild Blueberries (Vaccinium stenophyllum Steud.) Fruits Extracts during Ripening

“…This phenomenon was previously reported in berry extracts of Prunus spinosa L., which exhibited the same MIC of 250 µg/mL for Escherichia coli ATCC 25922 and Shigella sonnei ATCC 25931 [51]. Contrarily, Cerezo et al [52]…”

A High-Throughput Metabolic Microarray Assay Reveals Antibacterial Effects of Black and Red Raspberries and Blackberries against Helicobacter pylori Infection

“…Anthocyanins exhibit antimicrobial activity against Gram-negative bacteria by causing damage to the cell walls, membranes, and intercellular matrix [44]. Importantly, anthocyanins have been linked to the antimicrobial effects of berry preparations in previous studies [45][46][47] and are responsible for the major chemopreventive effects of blackberries and black and red raspberries [18,24,[48][49][50]. However, our correlation analysis suggests that the antibacterial effects against H. pylori were independent of anthocyanins and thus must be caused by other active compounds.…”