Abstract
Aims: To characterize the antioxidant properties of twelve selected medicinal plants commonly used in Jordan in traditional medicine.
Methodology: The following in vitro antioxidant assays were used: total antioxidant capacity, DPPH free radical scavenging, ferric reducing, ferrous chelating, total phenols and flavonoids.
Results: Considering the overall antioxidant activities (aeg AA equivalent /mg extract), the studied plants were arranged in the following decreasing order of their extract strength: Pistacia palaestina Boiss. (232) > Arbutus andrachne L. (197) > Hypericum triquetrifolium Turra (186) > Zingiber officinale Roscoe (185) > Mentha spicata L. (184) > Rosmarinus officinalis L. (183) > Salvia triloba L. f. (154) > Verbena triphylla L(H(er. (117) > Origanum syriacum L. (109) > Teucrium polium L. (96) > Nigella sativa L. (80) > Ceratonia siliqua L. (69). When the antioxidant capacity of the dry weights (g AA equivalent / 100g dry weight) of tested plants was calculated, the plants were arranged from the strongest to the weakest as follows: Pistacia palaestina Boiss. (7.1%) > Arbutus andrachne L. (6.1%) > Hypericum triquetrifolium Turra (4.3%) > Salvia triloba L. f. (2.4%) > Rosmarinus officinalis L. (2.2%) > Ceratonia siliqua L. (1.9%) > Zingiber officinale Roscoe (1.4%) > Nigella sativa L. (1.1%) > Origanum syriacum L. (0.8%) > Mentha spicata L. (0.7%) > Teucrium polium L. (0.6%) > Verbena triphylla L'H'er. (0.5%). The antioxidant activities of studied plants were explained by their content of total phenols and flavonoids. Nigella sativa L. had the lowest antioxidant activity and the lowest total phenols and flavonoids, but the highest metal chelating activity. This plant however, could be used as a good source for new agents for iron chelating drugs.
Conclusion: Medicinal plants commonly used in Jordan varied widely in their antioxidant and metal chelating abilities. Both abilities should be tested when characterizing the antioxidant properties of medicinal plants. The ability of the dry weight of plant should also be noted.