Free-radical-scavenging and antioxidant capacities with special emphasis on enzyme activities and in vitro studies in Caralluma flava N. E. Br.

Caralluma flava is a perennial, succulent edible plant distributed in the hillsides of the United Arab Emirates. In order to validate its use in the traditional system as an edible and medicinal source, we evaluated the antioxidant and in vitro free-radical-scavenging properties of its ethanol extract. The antioxidant activity of the extract was evaluated in vitro by 2,2'-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS⁺), 2,2-diphenyl-1-picrylhydrazyl radical (DPPH), hydroxyl radical and nitric oxide radical scavenging assays. The antioxidant enzyme activities (superoxide dismutase, catalase and glutathione peroxidase) and non-enzymatic antioxidant contents (total reduced glutathione, and Vitamin E and Vitamin C) in the extracts were also determined. The total phenolics content of the plant extract was 10.14 mg/g and the flavonoid content was 4.13 mg/g. The results showed a positive linear correlation between these phytochemicals and the free-radical-scavenging activities. The C. flava extract exhibited significant radical-scavenging properties in the ABTS(^+•), DPPH(^•), hydroxyl radical and nitric oxide radical assays. The study revealed that C. flava could be considered an excellent source of enzymatic and non-enzymatic antioxidants. The results indicate that the plant extract has potent free-radical-scavenging activity and ability to prevent radical chain reactions. Based on the results obtained, C. flava seems to be a very promising species for further investigation in order to identify the compounds responsible for its biological activity.