Dual antibacterial and pro-healing effects of thymoquinone in an experimental infected diabetic wound model

Impaired wound healing and persistent infection are major challenges in diabetic wounds. This study aimed to investigate the therapeutic effects of topical thymoquinone formulated in peanut oil on wound healing and bacterial burden in an infected diabetic wound model.

Diabetes was induced in rats using streptozotocin, followed by creation of standardized full-thickness excisional wounds that were subsequently infected with Staphylococcus aureus. Animals were randomly assigned to four groups: untreated negative control, vehicle (peanut oil), thymoquinone, and positive control (topical mupirocin). Treatments were applied topically once daily for 14 days. Wound closure was assessed at predefined time points, bacterial load was quantified as log₁₀ CFU/g tissue, and histopathological evaluation was performed using semi-quantitative scoring of re-epithelialization, inflammatory cell infiltration, granulation tissue formation, and collagen deposition.

Mean wound closure rates in the thymoquinone group were 27.6 ± 6.1% on day 3, 55.1 ± 8.4% on day 7, 72.4 ± 7.5% on day 10, and 88.2 ± 5.6% on day 14, which were significantly higher than those observed in the untreated negative control group (12.4 ± 4.6%, 28.7 ± 6.9%, 41.9 ± 8.1%, and 58.6 ± 9.3%, respectively) and the vehicle (peanut oil) group (18.9 ± 5.2%, 36.4 ± 7.3%, 52.7 ± 8.6%, and 69.8 ± 8.9%, respectively; p = 0.004 on day 3, p = 0.002 on day 7, p = 0.001 on day 10, and p = 0.001 on day 14), while remaining comparable to the positive control (mupirocin) group without demonstrating statistical superiority. Mean bacterial counts were 5.94 ± 0.46 log₁₀ CFU/g on day 3 and 4.73 ± 0.51 log₁₀ CFU/g on day 7 in the thymoquinone group, compared with 7.62 ± 0.41 and 6.89 ± 0.44 log₁₀ CFU/g in the negative control group and 7.18 ± 0.38 and 6.32 ± 0.40 log₁₀ CFU/g in the peanut oil group (p = 0.003 on day 3 and p = 0.002 on day 7). Histopathological evaluation revealed significantly improved re-epithelialization (3.8 ± 0.4 vs. 1.6 ± 0.5 in controls, p = 0.002), increased granulation tissue formation (4.0 ± 0.5 vs. 1.8 ± 0.6, p = 0.003), and enhanced collagen deposition (3.9 ± 0.4 vs. 1.5 ± 0.5, p = 0.002), together with reduced inflammatory cell infiltration (1.9 ± 0.4 vs. 4.1 ± 0.4, p = 0.001) in thymoquinone-treated wounds compared with controls.

Topical thymoquinone formulated in peanut oil improved wound closure, reduced bacterial burden, and enhanced histopathological indicators of tissue repair in this experimental infected diabetic wound model. Further studies are warranted to confirm these findings and explore their translational relevance.