The anti-inflammatory activities of twelve Nigerian medicinal plants: Inhibition of NfkB, activation of Nrf2, and antioxidant content

Chronic non-communicable diseases are responsible for a large majority of deaths worldwide. These include cardiovascular and respiratory diseases, diabetes and cancer. Inflammation has been reported to be involved in the initiation or progression of these conditions. Populations in developing or low to middleincome countries often rely on traditional medicine using locally available herbs and plants for their medical care. This study examined the anti-inflammatory potential of aqueous extracts of twelve medicinal plants used in Nigeria. The antioxidant activity was estimated using the total radical-trapping antioxidant parameter (TRAP) and ferric reducing ability (FRAP) assays. The abilities to inhibit nuclear factor kappa light chain enhancer of activated B cells (NfkB), a key regulator of the inflammatory response, and to activate nuclear factorE2 related factor 2 (Nrf2), a transcription factor that regulates cellular antioxidant defense systems, were determined using in vitro cell based assays. Extracts of Erythrina senegalensis (leaves), Sclerocarya birrea (bark), Boswellia dalzielli (leaves and bark), Pseudrocedrila kotschyi (bark), Sterculia setigera (stem bark), and Sarcocephalus esculentus (bark) contained the highest levels of antioxidant activity. Extracts that showed the greatest inhibition of NfkB were S. esculentus (bark), 91.8%; E. senegalensis (leaves), 81.4%; S. birrea (stem bark), 77.5%; and S. setigera (stem bark), 75.5%. B. dalzielli (leaves) and Xylopia aethiopica (leaves) gave 7.4 and 7.7 fold activation of Nrf2, respectively. These were comparable to activation by sulphorophane.