Anti-inflammatory, antioxidant, anti-cholinesterase activity and mutagenicity of South African medicinal orchids

Abstract

While the role of various processes in inflammatory-related degenerative disorders is still being researched, many avenues of research have concentrated on the treatment and/or prevention of these disorders. Inflammatory-responses, the cholinergic system and oxidative stress have often been linked to the symptoms prevalent in aged persons and Alzheimer's patients. The current research explored the selective inhibition of cyclooxygenase (COX) enzymes, antioxidant and anti-cholinesterase activities of selected South African orchid extracts, currently traded in herbal markets along the east coast of South Africa. Out of a total of 53 evaluated extracts, significant anti-inflammatory activity was observed in nearly 40% of extracts in the COX-1 assay and 25% of extracts in the COX-2 assay. Overall, the DCM root extract of Ansellia africana was the most potent, the DCM tuber extract of Eulophia hereroensis was the only extract to significantly inhibit both COX enzymes, while all Bulbophyllum scaberulum organic root extracts exhibited COX-2 selective inhibitory activity. Bulbophyllum scaberulum DCM root extract was also the most effective anti-cholinesterase extract, performing better than galanthamine. In the single electron transfer (SET) (2,2′-diphenylpicrylhydrazyl (DPPH) free radical scavenging assay and ferric reducing antioxidant power (FRAP) reaction based assays, E. petersii pseudobulb and A. africana root extracts performed better than other extracts. In the hydrogen atom transfer (HAT) (β-carotene/linoleic acid assay) reaction-based assay, the leaf extract of Tridactyle tridentata and root extracts of Cyrtorchis arcuata and E. hereroensis exhibited the best antioxidant effects. The mutagenicity (Salmonella/microsome assay) was also determined. Organic leaf and root extracts of C. arcuata produced no genotoxic effects in comparison to the other tested species. None of the crude extracts tested demonstrated mutagenic effects using S. typhimurium strain TA98 with metabolic activation. The results obtained in this study validate the use of certain orchid species in South African traditional medicine for inflammation-related degenerative disorders.