Evaluation of the antioxidant activity of selected non-food plants traditionally used in the treatment of arthritis

Objective

The aim of this study was to evaluate the antioxidant activity of selected non-food plants traditionally used in the treatment of arthritis.

Materials and methods

The inhibition of lipid peroxidation by crude plant extracts was investigated in vitro using two assays; the first using linoleic acid as the oxidising substrate and the second, the 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay, for evaluation of free radical scavenging activity. Chromatographic analysis of selected plant extracts was performed.

Results

All crude plant extracts tested showed free radical scavenging activity at higher or comparable levels to the reference compound, propyl gallate. Results from the DPPH assay showed the highest levels of antioxidant activity at a concentration of crude extract of 2.5 mg/ml giving the following free radical scavenging activity at 2 min: burdock 89%, hawthorn (berry) 86%, hawthorn (flowers/leaves) 87%, dandelion 86%, white willow 84%, celery 85%, marigold 83% and milk thistle 72% (results as per cent of control). Results for the inhibition of lipid peroxidation showed an overall variation according to concentration (0.02% w/v and 0.05% w/v) of burdock 83%/60%, hawthorn (berry) 84%/34%, hawthorn (flowers/leaves) 83%/88%, dandelion 65%/87%, white willow 26%/73%, celery 68%/71%, marigold 71%/40% and milk thistle 63%/80%. The free radical scavenging activity of the known antioxidant (propyl gallate) was 30% (50 µM).

Chromatographic analysis confirmed the presence of a number of flavonoids.

Conclusion

Crude extracts of all the selected plants showed a high level of antioxidant activity. Although the flavonoids may not be the only active antioxidant compounds, it is likely that they play a role.