Anti-inflammatory and anti-bacterial activity of South African Erythrina species.

Abstract

An investigation was undertaken to determine whether Erythrina species indigenous to South Africa contained the same type of compounds as Erythrina species not found in South Africa and to determine whether they displayed any anti-inflammatory and antibacterial activity. Phytochemical analysis was conducted using thin layer chromatography. A great similarity was found in the leaf profiles of the species being studied. The leaf and bark extracts of E. caffra and E. lysistemon appear to have similar profiles when viewed under normal light and ultraviolet light, (254 and 366 nm). These two species have similar banding patterns when stained with fast blue reagent for flavonoids and potassium hydroxide reagent for coumarins. The five species that were tested appear to contain alkaloids, flavonoids, coumarins and triterpenes just like the species not found in South Africa from this genus. Dried bark and leaves from E. caffra, E. humeana, E. latissima, E. lysistemon and E. zeyheri were screened for anti-inflammatory and anti-bacterial activity. Ethanol, ethyl acetate and water extracts were screened for both anti-inflammatory and anti-bacterial activity. The cyclooxygenase bioassay was used to test for anti-inflammatory activity. The ethanol and ethyl acetate extracts generally displayed activity while the water extracts displayed no activity for both the bark and the leaves. The bark generally displayed more cyclooxygenase inhibitory activity than the leaves. The bark of E. caffra and E. lysistemon displayed the highest cyclooxygenase inhibitory activity. The disc diffussion bioassay was used to screen for anti-bacterial activity. Anti-bacterial activity was only detected in the water extracts of the leaves. The water extracts of the bark showed very little or no activity. The bark yielded more anti-bacterial activity than the leaves. Anti-bacterial activity was mainly displayed against Gram positive bacteria. The bark of E. caffra and E. lysistemon displayed the highest anti-bacterial activity. On the basis of the screening results it was decided to use bioasssay guided fractionation in an attempt to isolate putative anti-inflammatory and anti-bacterial compounds. A hexane extract from the bark of E. lysistemon was prepared and purified using a range of chromatographic methods. Vacuum liquid chromatography, separation using a chromatotron, thin layer chromatography and high performance liquid chromatography were used to isolate anti-inflammatory compound(s). The isolation proved to be unsuccessful as the pure compound had no cyclooxygenase inhibitory activity. It was subsequently determined that the compounds were lost during the HPLC procedure. An ethanolic extract of the bark of E. Iysistemon was purified in an attempt to isolate an anti-bacterial compound(s). Vacuum liquid chromatography and separation using the chromatotron was used to purify the crude extract. The more sensitive microtitre bioassay was used to test for anti-bacterial activity against S. aureus. The isoflavone, Wighteone was isolated.