engleski

Antioxidant capacity of medicinal plants: a comparative study using five in vitro antioxidant assays

In addition to playing an important role in the growth, development and protection of plant organisms, natural antioxidants may account for the recognized health benefits of various plants and plant-based foods. The overall antioxidant potency of plant extracts is influenced by many factors, such as their reducing capacity, free radical scavenging potential, metal chelating ability and the ratio of lipophyllic-hydrophillic antioxidants present in the sample. It is difficult to develop a single measure that will account for multiple mechanisms of action of natural antioxidants, therefore, it is necessary to perform more than one type of antioxidant assay when attempting to deduce the antioxidant potency of a sample. In the present study we measured the antioxidant capacity of Jiaogulan (Gynostemma pentaphyllum) – a traditional Chinese remedy for diabetics and two Croatian endemic plants used in traditional medicine to treat mange, skin diseases, inflammation and as purgatives and for blood detoxication - Micromeria croatica (Pers.) Schott. and Rhamnus intermedia Steud. et Hochst, respectively. We compared the results obtained from five different antioxidant tests: three spectrophotometric assays (Ferric Reducing/Antioxidant Power assay (FRAP), 2, 2-diphenyl-1-picrylhydrazyl (DPPH) assay, and 2, 2´-azinobis (3-ethylbenzthiazoline-6-sulphonic acid) (ABTS) assay), as well as cyclic voltammetry and oxygen radical absorbance capacity (ORAC). The antioxidant potency composite index was calculated (ACI) for all tested medicinal plants as a way of incorporating the absolute values from all four antioxidant capacity assays into one measure. We will discuss the differences between the results obtained from different tests and between different plant species. Correlations will be drawn between various assay results.

antioxidant; medicinal plant

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