Metabolic perturbations and key pathways associated with the bacteriostatic activity of Clitoria ternatea flower anthocyanin fraction against Escherichia coli.

Clitoria ternatea flowers are rich in anthocyanins and possess various biological activities. Specifically, the antibacterial mechanism of action of C. ternatea anthocyanins remains unknown and was investigated in Escherichia coli . A time-kill assay was used to assess the antibacterial activity and the metabolic perturbations in E. coli were investigated utilizing liquid chromatography-mass spectrometry (LC-MS)-based metabolomics. Pathway analyses were carried out for metabolites showing ≥2-fold changes. The anthocyanin fraction remarkably reduced the growth of E. coli at 4 h by 95.8 and 99.9 % at minimum inhibitory concentration (MIC) and 2× MIC, respectively. The anthocyanin fraction (MIC) had a bacteriostatic effect and was shown to have perturbed glycerophospholipids (1-acyl-sn-glycero-3-phosphoethanolamine, phosphatidylglycerol, diacylglycerol and cardiolipin), amino acids (valine, tyrosine and isoleucine) and energy (ubiquinone and NAD) metabolites at 1 and 4 h. This study demonstrated significant metabolic perturbations of the glycerophospholipid, amino acid and energy metabolism, with these being the key pathways involved in the bacteriostatic activity of anthocyanins from C. ternatea, which may have promise as bacteriostatic agents for E. coli -related infections.

Antibiofilm properties of Clitoria ternatea flower anthocyanin-rich fraction towards Pseudomonas aeruginosa.

In Asia, Clitoria ternatea flowers are commonly used as a traditional medicinal herb and as a food colourant. Their bioactive compounds have anti-inflammatory, anti-microbial and anti-biofilm activities. Pseudomonas aeruginosa is one of the major pathogens that cause biofilm-associated infections resulting in an increase in antimicrobial resistance. Hence, the aim of this study was to investigate if the anti-biofilm properties of the anthocyanin-rich fraction of C. ternatea flowers were effective against P. aeruginosa . The effect of the anthocyanin-rich fraction of C. ternatea flowers on P. aeruginosa biofilms formed on a polystyrene surface was determined using the crystal violet assay and scanning electron microscopy (SEM). The anthocyanin-rich fraction reduced biofilm formation by four P. aeruginosa strains with a minimum biofilm inhibitory concentration value ranging between 0.625 and 5.0 mg ml-1. We further show that the biofilm-inhibiting activity of C. ternatea flowers is not due to the flavonols but is instead attributed to the anthocyanins, which had significant biofilm inhibitory activity (64.0±1.1 %) at 24 h in a time-response study. The anthocyanin-rich fraction also significantly reduced bacterial attachment on the polystyrene by 1.1 log c.f.u. cm-2 surface based on SEM analysis. Hence, anthocyanins from C. ternatea flowers have potential as an agent to decrease the risk of biofilm-associated infections.

Anthocyanins From Clitoria ternatea Flower: Biosynthesis, Extraction, Stability, Antioxidant Activity, and Applications.

Clitoria ternatea plant is commonly grown as an ornamental plant and possesses great medicinal value. Its flower is edible and also known as blue pea or butterfly pea flower. The unique feature of anthocyanins present in blue pea flowers is the high abundance of polyacylated anthocyanins known as ternatins. Ternatins are polyacylated derivatives of delphinidin 3,3',5'-triglucoside. This review covers the biosynthesis, extraction, stability, antioxidant activity, and applications of anthocyanins from Clitoria ternatea flower. Hot water extraction of dried or fresh petals of blue pea flower could be employed successfully to extract anthocyanins from blue pea flower for food application. Blue pea flower anthocyanins showed good thermal and storage stability, but less photostability. Blue pea flower anthocyanins also showed an intense blue colour in acidic pH between pH 3.2 to pH 5.2. Blue pea flower anthocyanin extracts demonstrate significant in vitro and cellular antioxidant activities. Blue pea flower anthocyanins could be used as a blue food colourant in acidic and neutral foods. The incorporation of blue pea flower anthocyanins in food increased the functional properties of food such as antioxidant and antimicrobial properties. Blue pea flower anthocyanins have also been used in intelligent packaging. A comparison of blue pea flower anthocyanins with two other natural blue colouring agents used in the food industry, spirulina or phycocyanin and genipin-derived pigments is also covered. Anthocyanins from blue pea flowers are promising natural blue food colouring agent.