Wound healing potential of Terminalia sericea

Abstract

A wound occurs when the integrity of the tissue is compromised, resulting in the breakdown of its protective functions. Wound healing is a complex sequential overlapping process. The progression of the wound healing process is hindered by bacterial infections and free radicals. Treatments for wounds are available but are accompanied by an increasing resistance. It is for this reason that new sources of treatment are constantly being sought. Plants have been used ethnomedicinally to treat wounds and one such plant is Terminalia sericea Burch. ex DC. (Combretaceae). The aim of this study was to assess the wound healing activity of T. sericea. Hot water (HW), methanol (MeOH), ethyl acetate (EtOAc) and hexane (HE) extracts were prepared. Thin layer chromatography (TLC) and ultra-performance liquid chromatography time of flight mass spectrometry (UPLC-TOF-MS) were used to determine the phytochemical classes and genus specific compounds present in the plant. Antioxidant activity was assessed using the ABTS + and DPPH radical scavenging assays as well as the cellular antioxidant assay. Antibacterial activity was determined using the broth microdilution assay and the biofilm inhibition assay. The extracts were assessed for cytotoxicity after 24 h and 72 h in the SC-1 (fibroblasts) and EA.hy926 (endothelial) cell lines using the sulphorhodamine B (SRB) assay. The ability of the extracts to enhance proliferation and migration in the SC-1 and EA.hy926 cell lines was assessed using the fibroblast proliferation and scratch assays. The major phytochemical classes detected in the extracts using TLC were alkaloids, coumarins, flavonoids, glycosides, phenolics, saponins, sterols and terpenoids. The genus specific compounds punicalagin, sericoside, anolignan B and arjunic acid were identified in the extracts by means of UPLC-TOF-MS. The MeOH and EtOAc extracts as well as Trolox displayed radical scavenging ability with IC50 values of 0.525, 0.387 and 0.694 ?g/mL, and 9.080, 12.660 and 13.800 ?g/mL against ABTS + and DPPH, respectively. All extracts exhibited a protective dose dependent decrease in intracellular ROS in response to oxidative damage by AAPH. A noteworthy MIC of 1 mg/mL against Staphylococcus epidermidis, Pseudomonas aeruginosa and Vibrio parahaemolyticus was noted for the HE extracts. The MeOH, HW and EtOAc extracts displayed antimicrobial activity at concentrations > 3.13 mg/mL. Most extracts were found to significantly enhance biofilm growth. A low cytotoxic trend was observed overall. None of the extracts displayed cytotoxic effects after a 24 h exposure period, however after 72 h the MeOH and EtOAc extracts exhibited a prominent reduction in cell density at the higher concentrations. The IC50 s (72 h) for the MeOH and EtOAc extracts were 33.77 and 53.04 ?g/mL in the SC-1 cell line and 51.82 and 57.83 ?g/mL in the EA.hy926 cell line, respectively. A significant (p < 0.05) enhancement of cell migration in both the fibroblast and endothelial hybrid cell lines were displayed in the scratch assay. However, no significant increase in cell density was noted with the fibroblast proliferation assay, with the exception of the EtOAc extract at 1 ?g/mL (p ? 0.05). The results from the in vitro wound healing assays indicated that the extracts of T. sericea enhanced migration but not proliferation. The overall wound healing effect of T. sericea has been attributed to a combination of the effects that it elicits on the multiple processes involved in the wound healing process which include antimicrobial, antioxidant, migratory and proliferative activity. Based on these results, the ethnomedicinal usage of T. sericea in the treatment of wounds is validated. Further studies involving the isolation and testing of the active compounds contained within EtOAc and HE extracts are warranted.