Pharmacognostic standardization and wound healing activity of the leaves and stem bark of entada Africana, Guill. Et. Perr. (leguminosae)

Abstract

The present study sought to validate the folkloric use of a Ghanaian plant, Entada africana (Leguminosae) as a wound healing agent and set benchmarks for correct identification and prevent its adulterations. The leaves of E. africana are compound with an oblong shape, entire margin, an oblique base and emarginated apex. The leaves are oppositely arranged. The stem bark has a simple quill curvature with a scaly outer bark surface and smooth inner bark surface. The leaves are microscopically hypostomatic with paracytic stomata with wavy anticlinal epidermal wall. There are prismatic calcium oxalate crystals present in the leaves and stem bark. Stone cells and pitted vessel are also present in the stem bark. Both plant parts contain the basic phytochemicals with the exception of alkaloids. The percentage yield of pet ether extract of leaves was higher than other solvent and the stem bark, methanol indicating the presence of lipid and polar constituents respectively. The UV analysis suggested similar chemical constituents for the two plant parts. The antioxidant activity of the MeOH extracts of the leaves and stem bark evaluated with DPPH scavenging activity, total phenol, total flavonoid, ferric reducing ability and total antioxidant capacity revealed a higher content of phenols and flavonoids and radical scavenging activity contributing to a higher total antioxidant capacity of 718.80 ± 47.29 mg/g Gallic acid equivalent (GAE) for the stem bark comparable to the leaves (288.10 ± 110.30 mg/g GAE). The MeOH extract of the stem bark showed a broaden spectrum antimicrobial activity comparable to the leaves with its highest activity against S. pyogenes and S. aureus using agar well diffusion and broth dilution assays. The leaves did not show any activity against P. aeruginosa and K. pneumonia but had its highest activity against S. aureus. The anti-inflammatory activity of the extracts were evaluated with carrageenan induced paw oedema in chick at doses of 30, 100 and 300 mg/kg against diclofenac (10, 30, and 100 mg/kg) and dexamethasone (0.3, 1.and 3 mg/kg). The extracts had a significant (P < 0.001) dose dependent activity with the stem bark inhibiting oedema by 60.49 ± 8.80 % comparable to the leaves, 50.89 ± 11.92%. Creams were formulated with the extractsvi and were used to evaluate the wound healing activity of the stem bark (5, 10 and 15%) and leaves (10, 15 and 20%) against 1% silver sulphadiazine using excisional dermal wound assay for 21 days. The test extracts had a significant (P < 0.001) and induced a progressive reduction of wounded area with 10% stem bark extract closing its wounds within 13 to 14 days with a percentage contraction of 56.49 ± 2.24%. Histopathological examination of the healed tissues showed adequate collagenisation with scanty inflammatory cells infiltrate and thinned overlying epidermal layer (scar formation) indicating an effective healing process for the tissues treated with 10% stem bark extract. The findings above are in keeping with an adequate healing process. The wound treated with a blank cream showed excess exudate formation and diffuse inflammatory cells infiltrate and no evidence of granulation in the dermis. The overlying epidermis shows inadequate and poor epithelial cell proliferation. The morphology is consistent with non-healing wound as compared to the 10% stem bark extract. The results obtained from the biological activities shows that E. africana has wound healing activity with its stem bark having a higher activity than its leaves. The results also obtained from the pharmacognostic studies will be used for correct identification of the plant and serve as a monograph for the plant