Combining selected medicinal plant extracts to improve wound healing of the skin

Abstract

Throughout history plant-based medicines have been used for the treatment and management of wounds and some of these natural remedies are still very popular. Aloe vera gel is a well-known medicinal plant widely used in cosmetic and medicinal products. Bulbine frutescens, a plant indigenous to South Africa, has been used as a wound healing agent since ancient times and contains phytochemicals with antioxidant activity that contributes to its wound healing effects. Turmeric (Curcuma longa) is an Indian spice, which has been used in remedies all over the world for its wound healing effects. Curcumin is the main curcuminoid extracted from turmeric rhizomes. Numerous studies have been done to investigate the wound healing properties of medicinal plants such as A. vera gel, C. longa extract (curcumin) and B. frutescens gel individually. Medicinal plants, namely A. vera gel, C. longa extract (curcumin) and both B. frutescens gel and aqueous extract, were included in this study. Nuclear magnetic resonance spectroscopy was utilised to chemically characterise and quantify marker molecules present in the A. vera gel. An HPLC analytical method was used to analyse the C. longa extract (curcumin) raw material’s purity against a curcumin reference standard. The nuclear magnetic resonance (both 1H-NMR and 13C-NMR) spectra for B. frutescens gel and B. frutescens aqueous extract was utilised to obtain the chemical fingerprints of these plant materials. The wound healing potential of A. vera gel, C. longa extract (curcumin) and both B. frutescens gel and aqueous extract were determined by means of the wound healing scratch assay on HaCaT cell monolayers after 24 h and 48 h treatment periods. A. vera gel, B. frutescens aqueous extract and B. frutescens gel exhibited pronounced wound healing effects when tested individually, while C. longa extract (curcumin) showed less favorable results. C. longa extract (curcumin) did not exhibit any wound healing properties when tested individually and therefore, it was not included in any combinations for further wound healing studies. B. frutescens aqueous extract and B. frutescens gel showed significant increases in wound closure and migration rate values when tested individually. The methylthiazol tetrazolium (MTT) and neutral red (NR) cytotoxicity assays were performed prior to wound healing scratch assays at a range of concentrations to evaluate the percentage cell viability of both HaCaT and 84BR cells after 24 h and 48 h exposure to selected plant materials. The aim of this study was to determine the in vitro wound healing potential of binary combinations of the selected plant materials that improved wound healing individually by conducting the wound healing scratch assay on HaCaT cell monolayers after 12 h and 24 h treatment periods. The iv combinations consisted of two of the selected plant materials in different concentration combinations of the individually tested treatment concentration and were evaluated to determine if a more enhanced wound healing effect could be observed as compared to their individual performances. The percentage wound closure and migration rate (um2/h) for all the experimental values of the individually tested plant materials, as well as the binary combinations, were expressed as a ratio to the untreated control group (the untreated control = 1). All the B. frutescens aqueous extract and B. frutescens gel combinations demonstrated an increased tendency to enhance wound closure as compared to their individual performances. A. vera gel and B. frutescens gel exhibited wound healing properties when tested individually, but combinations of these plant materials showed unfavourable results and lowered the wound healing properties of these individual plant materials. Therefore, it can be concluded that A. vera gel and B. frutescens gel are better used as individual wound healing agents, than in combination with each other. Combinations of B. frutescens extract with A. vera gel showed excellent wound healing results. Combinations of B. frutescens extract (0.25, 0.50 and 0.75 mg/ml) with A. vera gel (0.25 mg/ml) showed significant wound healing results and more than a 2-fold increase in wound closure and migration rate was obtained at 24 h. B. frutescens extract and A. vera gel