Mechanisms of Anti-Inflammatory and Antioxidant Activity of Extracts of Selected South African Celastraceae and Crassulaceae Plant Species With Known Efficacy Against Bovine Mastitis Bacterial Pathogens.

Inflammation, a complicated reaction to microbial infection or injury, promotes healing under normal circumstances. However, when it becomes uncontrolled, it can result in cell damage or even death. Inflammation is a major feature of infectious mastitis in cattle as well as in humans, with substantial health, welfare and financial challenges. Uncontrolled inflammation is commonly accompanied by excess reactive oxygen species (ROS), which may be harmful. Ethanol and acetone leaf extracts of Bryophyllum pinnatum (Lam.) Oken (synonym: Kalanchoe pinnata (Lam.) Pers.), Kalanchoe gunniae Gideon F. Sm. and Figueiredo, Maytenus undata (Thunb.) Blakelock and Maurocenia frangula Mill. were investigated for their antioxidant and anti-inflammatory activities. In previous work, these plant species had promising antimicrobial activity against mastitis-causing bacteria. In this study, anti-inflammatory activity of the extracts was investigated in terms of their ability to inhibit the action of the enzymes implicated in inflammation, namely 15-lipoxygenase (15-LOX) and cyclooxygenase (COX). Their ability to inhibit the production of nitric oxide (NO) by lipopolysaccharide (LPS)-activated RAW 264.7 macrophages was also tested. Using ELISA kits, the effect of the plant extracts on the regulation of cytokine production was determined. Evaluation of antioxidant activity was done using electron reducing 2, 2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) and radical scavenging 2, 2-diphenyl-1-picrylhydrazyl (DPPH) assays. The best 15-LOX inhibitory activity with IC50 values of 1.25 and 2.03 μg/mL for acetone and ethanol extracts, respectively, was observed with K. gunniae extracts. The best NO inhibition of 80.48% and cell viability of 96.75% was produced by the acetone extract of B. pinnatum at the highest concentration (100 μg/mL). Significant inhibition of COX-2 was observed with both extracts of K. gunniae and B. pinnatum. In this study, the highest inhibitory activity against proinflammatory cytokines and enhanced production of anti-inflammatory cytokines were observed with extracts of B. pinnatum. Kalanchoe gunniae extracts had the best antioxidant activity with IC50 values ranging from 0.06 to 0.42 μg/mL. This research highlights the therapeutic potential of the selected plant species in managing inflammation and oxidative stress associated with bacterial mastitis.