aureus , E. faecalis based on broth microdilution assay Table 2. Monoacylated anthocyanins in dark purple-fleshed potatoes consist of more hydroxyl groups compared to anthocyanin sources, with nonacylated anthocyanins having higher MIC values. In a study by Sun et al.

Lam] had lower MIC against Staphylococcus aureus and Salmonella typhimurium compared to the MIC values of nonacylated anthocyanins, indicating that the acylation increases the antibacterial properties of anthocyanins. Interestingly, Zhang et al.

Lam] enhanced the growth of Lactobacillus spp. and Bifidobacterium , but inhibited the abundance of Clostridium histolyticum and Prevotella. This indicates that the acylated anthocyanins impart their antibacterial effect only against harmful bacteria.

Considering nonacylated anthocyanins, anthocyanin fractions from dark roselle petals Hibiscus sabdariffa and eggplant peels Solanum melongena demonstrated higher disc diffusion diameters against B. subtilis than onion peel Allium ascalonicum anthocyanins Table 2.

Main anthocyanin from both dark roselle petals delphinidin O -sambubioside and cyanidin O -sambubioside and eggplant peels delphinidin O -rutinoside consists a higher number of hydroxyl groups compared to onion peel anthocyanins cyanidin O -glucoside. The higher antimicrobial activity was related to the presence of hydroxyl groups phenolic and alcohol compounds , whereas hydrocarbons resulted in less activity of compounds in essential oils [ 70 ].

However, anthocyanins from blue pea flower Clitoria ternatea which contains polyacylated anthocyanins with a large number of hydroxyl groups did not show higher disc diffusion diameters compared to nonacylated anthocyanins Table 2.

This could be due to the steric hindrance imparted by the acyl groups in the polyacylated anthocyanins. Acylation decreases the polarity of the anthocyanin molecule and causes steric hindrance [ 71 ].

The search for alternative agents or approaches apart from antibiotics is urgent to tackle the rise of multidrug-resistant bacterial infections. Therefore, various strategies are being explored to target the virulence factors of pathogens to impair their ability to cause infections such as those associated with biofilms.

The antibiofilm properties displayed by anthocyanins from various sources are shown in Table 3 and Fig. The anthocyanin-enriched extract of black plum was found to have potential antibiofilm activity against K.

It was also found to have antibacterial growth inhibition activity Table 2. Among the underlying mechanisms for the effects observed was its ability to inhibit the quorum sensing signalling pathway, which is essential for bacterial growth, virulence factors, and biofilm formation [ 63 ].

pneumonia [ 64 ]. Grape marc anthocyanin extract was determined for its potential in preventing dental caries in vivo in white rats Rata albicans infected with S. mutans and were fed with a cariogenic diet.

Another study reported the anthocyanin extract of soybean and walnuts to have antibiofilm activity against various Pseudomonas and Klebsiella bacterial species.

It was found to have inhibited biofilm formation by reducing bacterial cell hydrophobicity having the capacity to inhibit attachment to surfaces [ 73 ]. Some studies have shown the proanthocyanidins for their potential antibiofilm activity. The proanthocyanidin fraction of red wine was reported by a study for potent antibiofilm activity against Streptococcus mutans.

mutans is known to colonize tooth surfaces and form biofilm dental plaque that leads to the development of oral infectious diseases, such as caries, gingivitis and periodontal inflammation [ 74 ]. The proanthocyanidin fraction inhibited the adhesion mutans to saliva coated hydroxyapatite HA beads in the presence of sucrose and the activity was found to be much higher than dealcoholized red wine.

The proanthocyanidin fraction was also able to detach S. mutans attached to HA beads and had a very high biofilm inhibitory activity The proanthocyanidin fraction of cranberry was determined by another study for its antibiofilm activity against S.

mutans [ 75 ]. It reduced the biomass dry weight and the total amount of extracellular insoluble polysaccharides of S. The glucosyltransferase GtfB enzyme activity either in solution or adsorbed on the sHA surface was also effectively inhibited.

mirabilis , and P. aeruginosa [ 58 ]. It also exerted a synergistic antibiofilm activity when combined with the antibiotic sulfamethoxazole which had minimal effect on biofilms when used alone. The A-type proanthocyanidins was found in a study to have potential biofilm inhibitory activity against Porphyromonas gingivalis , a key oral bacterium for periodontitis [ 76 ].

gingivalis to epithelial cells The proanthocyanidins also decreased the secretion of IL-8 and chemokine ligand 5 CCL5 of P. gingivalis -induced inflammatory response in oral epithelial cells and decreased the activity of NF-κB p65 pathway. Various other anthocyanin sources or its fraction, such blueberry, chokeberry, purple barley and blue pea flowers have been shown to have antibiofilm activity Table 3.

Studies on the antibiofilm activity of acylated anthocyanins are limited. However, when comparing the available literature, the polyacylated anthocyanins from blue pea flowers demonstrated lower antibiofilm activity compared to nonacylated anthocyanins against gram-negative bacteria.

For instance, the biofilm inhibition of anthocyanins from blue pea flowers at 5. However, the mode of action of biofilm inhibition activity of acylated anthocyanins is not fully understood. Therefore, further in-depth studies looking into its mechanism of action would be beneficial in understanding the activity observed.

Various research studies are being done to obtain alternatives to antibiotics to treat bacterial infections with the rise of antimicrobial resistance. Many studies investigating anthocyanins against the Gram-positive or Gram-negative bacterial strains have shown much better activity against the Gram-positive strains.

However, some studies have also shown it to be equally potent against Gram-positive and Gram-negative strains. The findings of these studies serve as a guide for the potential application of anthocyanins in treating bacterial infections in clinical settings.

At the same time, infections involving a mix of Gram-positive and Gram-negative bacterial strains may be treated with anthocyanins which are effective against both strain types. Some of the studies have explored the combination treatment of anthocyanins with antibiotics and which had a potentiating effect.

This effect is highly beneficial as anthocyanins alone do not affect bacterial viability but are able to synergise the effect when combined with antibiotics to further reduce bacterial growth and viability. This combination approach would be beneficial in clinical settings as it may help prevent the unnecessary increase in the antibiotic concentration for treatment of infections which may eventually lead to antibiotic resistance.

These anthocyanins at concentrations that do not affect bacterial growth have potential antibiofilm activity. Most of the current antibiotics are only effective against the planktonic growth mode of bacteria but not against biofilms, making it challenging for the antibiotics to penetrate into the biofilms to target their growth.

Therefore, the combinatorial approach serves as an arsenal to target two different areas of bacterial cell communication and signalling pathway, thus providing a much more significant effect and leading to better treatment outcomes. Research studies looking further into the combinatorial approach of various other anthocyanins to treat different bacterial infections would provide useful information for its potential application for treatment in clinical settings.

Several in vivo studies have been done so far, especially in the treatment and prevention of dental caries which was found to have a positive impact. Future in vivo studies looking at different infection models would also be needed to understand the potential of anthocyanins, especially in chronic wounds and biofilm infections involving medical implants or devices.

Most studies have used the anthocyanin fractions of various sources to study its antibacterial or antibiofilm properties. However, quite a number have not characterised the anthocyanin composition.

It is also unknown if the cocktail of anthocyanins or some impurities in the fraction may have potentiated or reduced the observed effect.

Further isolation of the anthocyanins major compounds would be needed to determine the compound most possibly being responsible for the activity, and it may even have much better activity. Obtaining the pure compound responsible for the effect would be important to standardise the potential application e.

concentration and dosage of anthocyanins in clinical settings. Some studies have also shown the potential activity of individual commercial anthocyanins. Thus further studies exploring the chemical structure modification and synthesis of these anthocyanin compounds may yield compounds with improved activity.

With the growing interest and knowledge of the health benefits of anthocyanins, consumers are also looking forward to health or food products containing these active compounds. Incorporating anthocyanins in the food and beverages industries will represent an important value.

Focusing on improving formulations and packaging together with consumption safety and compound stability studies is beneficial. Findings obtained from these studies further support the anthocyanins natural compounds as alternative sources of antibacterial or anti-infective agent, which has the potential for application in treating bacterial infections and may have the possibility of preventing the development of antimicrobial resistance.

Further research into these compounds would be highly beneficial and recommended and their incorporation into health supplements and food products for general well-being.

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Effect of Hydrolysable Tannins and Anthocyanins on Recurrent Urinary Tract Infections in Nephropathic Patients: Preliminary Data. Author s. Noce, A; Di Daniele, F; Campo, M; Di Lauro, M; Pietroboni Zaitseva, A; Di Daniele, N; Marrone, G; Romani, A.

Is Peer Reviewed? Nutrients ISSN: Page Numbers. Urinary tract infections UTIs are caused by uropathogenic microorganism colonization.

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 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.