engleski

Antioxidant properties of Teucrium arduini L. flower and leaf infusions

Phytochemicals are extensively found at different levels in many medicinal plants. Numerous plants used in traditional medicine are effective in treating various ailments caused by oxidative stress, bacterial and/or viral infections. Previous research has shown that Croatian medicinal plants exhibit antioxidant activity. Croatia has approximately 500 varieties of endemic herbs, which are commonly used in traditional medicine. One of them is Teucrium arduini L, prepared as an infusion, it is used in treatment of stomach ailments. Antioxidant activity as well as total phenol (TP, Folin-Ciocalteu method) content of leaf and flower infusions of Teucrium arduini L. from six different mountainous localities (Učka, Vošac, Sveti Jure, Snježnica, Vaganac, Sušanj) were analyzed in this study. Antioxidant capacity was evaluated using the ferric reducing/antioxidant power (FRAP) assay, as well as 2, 2-diphenyl-1-picrylhydrazyl (DPPH), and 2, 2´-azinobis (3-ethylbenzthiazoline-6-sulphonic acid) (ABTS) radical scavenging assays. Randomly selected samples of wild growing plants T. arduini were collected during the blooming period in Croatia in the summer of 2008 and were air-dried and saved until analysis. Infusions were prepared on the day of measurement by adding 2 g of dried powdered plant material to 30 mL of deionised water heated to 95°C. The extraction proceeded for 8 minutes in a closed plastic vial at room temperature, with periodic stirring. Flower and leaf infusions from Učka showed the highest TP content and exhibited the highest reducing power. Our results point to significantly (p < 0.05) different TP content between leaf and flower infusions, as well as across localities. The DPPH• radical scavenging ability of leaf infusions can be ranked as follows: Vošac > Učka > Sveti Jure > Snježnica > Sušanj > Vaganac and that of flower infusions: Učka > Vošac > Sveti Jure > Sušanj > Vaganac > Snježnica. The flower infusions from Učka (8.47 ± 0.33 mmol/L TEAC) and Vošac (8.44 ± 0.43 mmol/L TEAC) showed the best ABTS• + scavenging efficiency, while among leaf infusions the sample from Učka exhibited the highest antiradical acitivity (6.46 ± 0.67 mmol/L TEAC). The antioxidant potency composite index (ACI), giving equal weight to all three methods used to quantify antioxidant capacity, was the highest for the infusion from Vošac (96.7) among flower infusions, while maximum ACI (100) was determined for the infusion from Učka among leaf infusions. Strong positive correlation was found between the total phenols and ACI for leaf (r= 0.953) and flower (r= 0.977) infusions indicating that polyphenolic content is highly correlated with the overall antioxidant capacity of T. arduini infusions.

Teucrium arduini L.; antioxidant activity; total phenols; Croatia

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