Antioxidant activity of some Mexican medicinal plants extracts
Phytochemicals are extensively found at different levels in many medicinal plants. This work had two objectives: the first, to evaluate the total phenolic and flavonoid contents of four Mexican medicinal plants (Penstemon barbatus, Pedicularis mexicana, Castilleja tenuiflora and Bacopa monnierii) and second, to determine whether these compounds have an antioxidant capacity towards free radical propagation. The polyphenolic extractions of the dried powdered samples have been performed using methanol. The total phenolic content, analyzed using Folin-Ciocalteu reagent, of the samples varied from 20.7 to 187.8mg/g dry weight, expressed as gallic acid equivalents (GAE). The total flavonoid concentrations, detected using 2% aluminum chloride, varied from 4.56 to 10.1mg catechin equivalents (CE)/g dry weight. To analyze the antioxidant activity, common stable radicals chromogens, 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS(.+)) and DPPH (1,1-Diphenyl-2-picrylhydrazyl) were used. The antioxidant activity measurement, expressed as Trolox equivalent antioxidant capacity (TEAC), ranged from 306.7 to 927.7 mmol Trolox equivalents. P. barbatus and B. monnieri showed the highest antioxidant activities, while C. tenuiflora and P. mexicana the lowest activities.
These results suggest that the level of antioxidant activity in these plants varies to a great extent. They also suggest that phenolics in these plants provide substantial antioxidant activity. Upon achievement of this survey, and using more samples, an extra benefit of these medicinal plants may be found. Flora of Mexico appears to be a rich and interesting source for supplementary ethnomedicinal and phytochemical studies.
Acknowledgements: This study was financed by grants from CONACyT (Convenio SEP-2003-CO2–43440/280). Bazaldúa G. S., and Goytia P. S acknowledge scholarship from CONACyT.