Antimicrobial
Polyphenolic compounds including anthocyanins possess antimicrobial activity against a wide range of microorganisms, especially in inhibiting the growth of food-borne pathogens [
129]. Anthocyanins exhibit antimicrobial activity through several mechanisms, such as induced cell damage by destroying the cell wall, membrane, and intercellular matrix [
101].
Based on a previous study, maqui berry extracts had antibacterial activity with the highest sensitivity to
Aeromonas hydrophilia and
Listeria innocua [
102]. These bacteria are commonly associated with refrigerated foods as indicators of pathogenic microorganisms or as spoilage microorganisms [
130]. Côté et al. [
103] report that cranberry extract had antibacterial activity towards
Enterococcus faecium resistant to vancomycin,
Pseudomonas aeruginosa, Staphylococcus aureus, and
Escherichia coli. The antibacterial activity of cranberry extract is not based on its low pH, but it is believed due to the other specific bioactive components, such as anthocyanins and flavonols in cranberry extracts after pH adjusted to 7.
Anthocyanin-rich extracts, such as blueberry, raspberry, blackcurrant, and strawberry extracts, inhibit Gram-negative bacteria but not Gram-positive bacteria [
104]. This variation may be due to the different structures of cell wall between Gram-negative and Gram-positive bacteria, in which the outer membrane of Gram-negative bacteria acts as a preventive barrier against hydrophobic compounds but not on hydrophilic compounds [
131]. These antimicrobial activities of anthocyanin-containing extracts are possibly due to the multiple mechanisms and synergistic effects of various phytochemicals in the extracts, including anthocyanins, weak organic acids, phenolic acids, and their mixtures of different chemical forms [
132]. Thus, the antimicrobial effect of chemically complex compounds instead of solely anthocyanins should be extensively analyzed. Also, anthocyanins in purple, red, and blue-colored fruits and vegetables are the main bioactives in preventing microbial infection by several mechanisms.
Neuroprotective effect of anthocyanins
The term, ‘neuroprotection’, has been defined as the protection of nerve cells from oxidative injury and neurotoxicity, which interferes with the ischemic cascade. A neuroprotective agent is a drug or natural compound that prevents the nervous system from secondary injuries. The neuroprotective effects of anthocyanins have been evaluated based on the
in vitro and
in vivo studies. Most of the
in vitro studies are performed by applying cell cultures, whereas
in vivo studies are carried out based on animal models.
The neuroprotective findings from selected studies are reported in this review. An
in vitro study [
133] shows the neuroprotective effect of cyanidin-3-glucoside and its aglycone against hydrogen peroxide-induced oxidative stress in human neuronal cells (SH-SY5Y). The results demonstrate that SH-SY5Y cells pretreated with 100 µM cyanidin and cyanidin-3-glucoside significantly increased total antioxidant activity of membrane and cytosolic fraction from the cells; cyanidin also significantly increased the percentages of mitochondrial functioning and inhibited DNA fragmentation induced by hydrogen peroxide.
Based on a previous study, cyanidin-3-glucoside (2 mg/kg body weight) isolated from
Prunus cerasus fruit inhibited apoptosis-inducing factor from mitochondria under oxidative stress but did not block the release of cytochrome c against permanent middle cerebral artery occlusion in the cortical neurons isolated from adult mice brain [
134]. Besides the reported findings, the cyanidin-3-glucoside treated mice had brain superoxide level lower than the control (0.9% normal saline), as well as with better neurological test scores.
In another study, male Sprague-Dawley rats with traumatic spinal cord injury that received 400 mg/kg body weight of cyanidin-3-glucoside had a significantly improved blood-brain barrier score by 16.7%, platform hang by 40.0%, and hind foot bar grab by 30.8% compared to vehicle treated control, as well as significant reductions in superoxide level of the spinal cords and lesion volume in the lesion periphery, and a significant increased in motor neuron cell numbers of the anterior horn in lesion periphery [
135]. The data from a mouse model of late pregnancy reveals that intraperitoneal injection of cyanidin-3-glucoside blocks ethanol-mediated glycogen synthase kinase-3β by inducing phosphorylation at serine 9 and reduces the phosphorylation at tyrosine 216 [
136]. The compound also ameliorates ethanol-induced oxidative stress by inhibiting expression of malondialdehyde (MDA). The study concludes that cyanidin-3-glucoside prevents neurotoxicity of ethanol.
As reported in the literature, cyanidin-3-O-ß-d-glucopyranoside isolated from mulberry extract had a neuroprotective effect on PC12 pheochromocytoma cells through inhibiting cerebral ischemic damage induced by oxygen-glucose deprivation when the cells were exposed to hydrogen peroxide (150 µM) for 24 h [
137]. The researchers also developed a mouse-brain-injury model of transient middle-cerebral artery occlusion, where the mice were supplemented with cyanidin-3-O-β-d-glucopyranoside and mulberry fruit extract. The result demonstrates a reduction in the infarct volume of the brain by 18% and 26%, respectively, and both supplemented groups had a lesser number of myeloperoxidase-positive cells than the ischemic control group in the striatum and cortex of the injured brain.
Based on the previous findings, most of the studies report the neuroprotective effects of cyanidin and its glycosides. Limited study has been done to determine the neuroprotective benefits of other anthocyanidins and anthocyanins. Kim et al. [
138] show the neuroprotective effect of three major anthocyanins (a mixture of cyanidin-3-glucoside, delphinidin-3-glucoside, and petunidin-3-glucoside) isolated from black soybean, against hydrogen peroxide-induced cell death. They conclude that the human brain neuroblastoma SK-N-SH cells treated with the purified anthocyanin mixture (1–25 μg/ml) had a significant reduction in intracellular ROS level in a dose-dependent manner. The anthocyanins also inhibited ROS-dependent activation of apoptosis signal-regulating kinase 1 (ASK1)–JNK/p38 pathways, stimulated expression of heme oxygenase 1, and upregulated sialidase 1 (also known as Neu1) gene expression. Based on this evidence, anthocyanins obtained from plants have a neuroprotective effect.
Source:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5613902/