Determination of secondary metabolites and antioxidant activity of some boraginaceae species growing in Iran

Purpose: To evaluate the antioxidant potential, flavonoids, and total phenols as well as cyanidin 3- glucoside and delphinidin 3-glucoside contents of some Boraginaceae species that grow in Iran.Methods: The aqueous and ethanol extracts of the plants were prepared. The free radical scavenging activity of the extracts was determined using 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical method. Total phenolic and flavonoid contents of the extracts were assessed by Folin-Ciocalteu and aluminium chloride colorimetric assays, respectively. Furthermore, cyanidin 3-glucoside and delphinidin 3- glucoside contents of the extracts were determined using high- performance liquid chromatography (HPLC) method.Results: The most powerful free radical scavenging activity with 50 % inhibitory concentration (IC50) of 23.13 ± 1.90 μg mL-1 was exerted by the ethanol extract of Nonea caspica, while the weakest IC50 of 364.38 ± 14.18 μg mL-1 was shown by the aqueous extract of Onosma sericeum. Total phenolic content varied among the plants, ranging from 270.33 ± 2.60 to 3.40 ± 0.28 mg GAE g-1 dry weight. The ethanol extracts of Nonea caspica and Anchusa arvensis displayed the highest total flavonoid content (252.60 ± 1.80 and 29.13 ± 1.05 mg QE g-1 dry weight, respectively). The highest contents of cyanidin and delphinidin 3-glucosides were found in the ethanol extracts of Nonea caspica and Anchusa arvensis, respectively.Conclusion: The results show that some of the plants have potent antioxidant activities which may justify the ethno-therapeutic usage of these plants by traditional healers.Keywords: Boraginaceae, Polyphenol, Antioxidant activity, Cyanidin 3-glucoside, Delphinidin 3- glucoside, Nonea caspica, Onosma sericeum, Anchusa arvensi