Antibacterial and Therapeutic Potentials of the Capsicum annuum Extract against Infected Wound in a Rat Model with Its Mechanisms of Antibacterial Action

Abstract

The wound healing process is essential to reform the damaged tissue and prevent its invasion by pathogens. The present study aims at evaluating the antibacterial and therapeutic properties of the Capsicum annuum L. (Solanaceae) extract against infected wound in a rat model with its mechanisms of antibacterial action. The fruit extract was prepared by maceration in methanol. The broth microdilution method was used to investigate the antibacterial activity of the methanol extract of C. annuum fruits. The therapeutic effect of the extract gel was performed on an excision wound infected with Staphylococcus aureus using a rat model. The total phenol, flavonoid, and tannin contents as well as the antibacterial mechanisms of action of the extract were determined using spectrophotometric methods. The C. annuum fruit extract showed antibacterial properties which can be linked to its total phenolic, flavonoid, and tannin contents. The antibacterial activity is due to the inhibition of the biofilm formation, ATPases/H⁺ proton pump, and dehydrogenase activity as well as the alteration of the bacterial cell membrane through the leakage of nucleic acids, reducing sugars and proteins. The extract gel showed a significant (p < 0.05) increase in the percentage of wound closure and eradicated S. aureus at the infection site. The extract gel was nonirritating to the skin and slightly irritating to the eyes and should be used with caution. Overall, the findings of the present study support the traditional use of the studied plant in the treatment of wounds and infectious diseases associated with the tested bacteria.

Figure 1

Bacterial outer membrane permeability to erythromycin induced by the MeOH extract of C. annuum fruits (MECa). Each value represents mean ± SD of three independent assays; (a) Pseudomonas aeruginosa PA01; (b) Staphylococcus aureus 18; (c) Escherichia coli 64R.

Figure 2

Nucleotide leakage from bacterial suspensions treated with MIC of MeOH extract of C. annuum fruits (MECa). Each value represents mean ± SD of three independent assays; (a) Pseudomonas aeruginosa PA01; (b) Staphylococcus aureus 18; (c) Escherichia coli 64R.

Figure 3

Leakage of reducing sugars (a) and proteins (b) from bacterial suspension treated with the MeOH extract of C. annuum fruits. Each value represents mean ± SD of three independent assays; values affected by the different superscript letters (a, b) are significantly different (p < 0.05).

Figure 4

Effect of the MeOH extract of C. annuum fruits on the enzymatic activity of respiratory chain dehydrogenases. Data are average from triplicate experiments. Error bars represent standard deviations of triplicate incubations. The negative and positive controls represent the boiled and unboiled bacteria, respectively. (a) Pseudomonas aeruginosa PA01; (b) Staphylococcus aureus 18; (c) Escherichia coli 64R.

Figure 5

Effect of the MeOH extract of C. annuum fruits on the bacterial ATPase/H⁺ proton pumps. Data are average from triplicate experiments. Error bars represent standard deviations of triplicate incubations. (a) Pseudomonas aeruginosa PA01; (b) Staphylococcus aureus 18; (c) Escherichia coli 64R.

Figure 6

Antibiofilm effect of the MeOH extract of C. annuumfruits against the tested bacteria. Data are expressed as mean ± SD. n = 3. Values with different letters are significantly (p < 0.05) different according to the Waller-Duncan test.

Figure 7

Effect of C. annuum fruit extract gels on the wound area (a) and the percentage of wound contraction (b) in excision wound model on different days after wounding. The data represent the mean ± standard deviation; on the same day, the values earmarked with different superscript letters (a–c) are significantly different at p < 0.05.