(W1030-06-35) Development of Terminalia avicennioides Extract-Hyaluronic Acid Hydrogel Formulation for the Treatment of Methicillin-Resistant MStaphylococcus aureus in Wound Infections

Purpose: The rising incidence of failure of conventional antibiotics to treat methicillin-resistant Staphylococcus aureus (MRSA) pathogen, common in postoperative wound infections, is a public health concern that has led to prolonged hospitalization, lower extremity amputations, and mortality. Since ancient times, medicinal plants have been used to treat wound infections and serve as alternatives to the currently used antibiotics to combat the incidence of antimicrobial resistance. Of interest is the Terminalia avicennioides plant that has been used to treat sores, ulcers, and other skin infections, exhibiting antimicrobial activity against MRSA and other pathogens. Functional hydrogels incorporating therapeutic agents are versatile wound dressings that provide a moist environment, eliminate bacterial load at the site of infection, and promote wound healing. Therefore, this study aims to formulate a hydrogel containing Terminalia avicennioides extract and evaluate its antimicrobial activity against MRSA wound infections.

Methods: The dried bark of Terminalia avicennioides Guill. and Perr. (Combretaceae) with voucher specimen number FHI 114121 was blended and macerated in 96% ethanol for 72 h. The in vitro antimicrobial activity of the extract obtained against MRSA isolate was carried out using the agar diffusion technique to determine the zones of inhibition and minimum inhibitory concentration (MIC) of the extract. Different concentrations of the T. avicennioides (TA) extract and hyaluronic acid polymer (HA) were formulated into hydrogels to obtain formulations F1 (3%HA, 1%TA), F2 (4% HA, 1% TA), F3 (5% HA, 1% TA), F4 (4% HA, 0% TA), and F5 (4% HA, 10% TA). The physicochemical properties of the hydrogels, such as the organoleptic properties, pH, viscosity, spreadability, extrudability, moisture content, swelling index were determined. The antimicrobial activity of F2, F4, and F5 hydrogel formulations against the MRSA strain was evaluated.

Results: The T. avicennioides ethanolic extract exhibited antimicrobial activity against methicillin-resistant Staphylococcus aureus, having a zone of inhibition of 21.5 mm ± 0.50, 23.83 mm ± 1.04, and 26.33 mm ± 1.04 at 100, 200, and 400 mg/mL respectively. The extract inhibited MRSA growth at a minimum concentration of 0.20 mg/mL. All formulated hydrogels with the extracts were light to dark brown in colour, smooth to touch, easy to spread on the skin, and easily dispensed from collapsible tubes. The pH, viscosity, and moisture content of all formulations ranged from 4.54 – 5.45, 25366 – 86133cP, and 80.0 – 86.5% respectively. All formulations fall within the acceptable skin pH of 4-6 and can be applied to the skin without causing irritation. The incorporation of the extract decreased the viscosity of the formulation (86133cP for 0%TA and 25366cP for 10%TA), however, an increase in the shear speed caused a decrease in the viscosity of all formulations, thus demonstrating the shear-thinning behaviour of the formulations which will improve the flow of the formulations when applied to the skin. An increase in the concentration of the hyaluronic acid polymer resulted in an increase in moisture content and swelling capacity of the hydrogels with about 120% increase in swelling observed in 5% HA (450 ± 1.52%) when compared with the 4% HA (205 ± 1.76%) formulation, thus having the capacity to absorb wound exudates. The hyaluronic acid hydrogel possesses intrinsic antimicrobial activity comparable to the T. avicennioides extract with zones of inhibition of 24.83 ± 0.29 mm and 21.5 ± 0.50 mm for the HA hydrogel and TA extract, respectively. However, the incorporation of the T. avicennioides extract exhibited enhanced activity against MRSA (zone of inhibition 38.33 ± 3.21mm). In addition, an increase in the extract concentration (10%TA) increased the activity of the formulation against MRSA, exhibiting zones of inhibition of 61.00 ± 1.0 mm.

Conclusion: The ethanol extract of Terminalia avicennioides bark showed antibacterial activity against methicillin-resistant Staphylococcus aureus. Hydrogels made with the extract and hyaluronic acid had desirable physicochemical properties, and formulation F5 containing 4% hyaluronic acid and 10% TA extract, was the most active against the MRSA strain studied. The study underscores the potential of T. avicennoides-loaded hyaluronic acid hydrogel for treating methicillin-resistant wound infections, providing an alternative wound care option. Further evaluations and optimization are needed to assess its potential as a topical antibiotic for treating wound infections.

References: 1. Abebe M, Alemkere G, Ayele G. Methicillin and vancomycin-resistant Staphylococcus aureus and associated risk factors among patients with wound infection in East Wallaga Zone, Western Ethiopia. Infection Prevention in Practice. 2024, 6(4), 100409.
2. Albahri G, Badran A, Hijazi A, Daou A, Baydoun E, Nasser M, et al. The Therapeutic Wound Healing Bioactivities of Various Medicinal Plants. MDPI Life, 2023, 13, 317.
3. Musa FM, Muhammad-Idris ZK, Abdulfatai K, Wartu JR, Shuaibu SB. Antibacterial Activities of Ethanol Leaf and Bark Extracts of Terminalia Avicennioides against Methicillin-Resistant Staphyloccocus Aureus. Science World Journal. 2020,15(3).
4. Ilomuanya MO, Seriki ZA, Ubani-Ukoma UN, Oseni BA, Silva BO. Silver Sulphadiazine- xanthan gum- hyaluronic Acid Composite Hydrogel for Wound Healing: Formulation Development and in vivo Evaluation. Nigerian Journal of Pharmaceutical Research. 2020,16(1):21–9.

Acknowledgements: We thank Mr. Usman Abulrahman of the Department of Pharmaceutical Microbiology and Biotechnology, University of Lagos, for providing his technical expertise during this study. Conflict of Interest: The authors declare no conflict of interest in this study.

Funding: This research received no external funding


Table 1: Physicochemical properties of T. avicennioides – hyaluronic acid hydrogel formulations. Results are expressed as mean ± SD (n=3).
KEY: F1 - Hyaluronic acid 3% w/v, Extract 1% w/v; F2 - Hyaluronic acid 4% w/v, Extract 1% w/v; F3 - Hyaluronic acid 5% w/v, Extract 1% w/v; F4 - Hyaluronic acid 4% w/v; 0% Extract; F5 – Hyaluronic acid 4%w/v, Extract 10%w/v


Figure 1: Viscosity of Terminalia avicennioides -hyaluronic acid hydrogel formulations at varying shear rates. Result is expressed as mean ± SD (n=3).
KEY: F1 - Hyaluronic acid 3% w/v, Extract 1% w/v; F2 - Hyaluronic acid 4% w/v, Extract 1% w/v; F3 - Hyaluronic acid 5% w/v, Extract 1% w/v; F4 - Hyaluronic acid 4% w/v; 0% Extract; F5 – Hyaluronic acid 4%w/v, Extract 10%w/v


Table 2: In vitro antimicrobial activity of T. avicennioides extract and hydrogels against methicillin-resistant Staphylococcus aureus (MRSA). Results are expressed as mean ± SD (n=3).
KEY: F2 - Hyaluronic acid 4% w/v, Extract 1% w/v; F4 - Hyaluronic acid 4% w/v; 0% Extract; F5 – Hyaluronic acid 4%w/v, Extract 10%w/v; MIC- minimum inhibitory concentration