Total Phenolic Content, Antioxidant and Antibacterial Activities of Three Verbascum Species from Iran

Abstract

The genus <em>Verbascum</em> L. belongs to the family Scrophulariaceae and includes plants that have been used widely in traditional medicine for a long time. Methanolic extracts of three <em>Verbascum</em> species from flora of Iran were <em>in vitro</em> screened for their possible antioxidant activities by three complementary test systems, namely DPPH free radical-scavenging, metal chelating activity and β-carotene/linoleic acid. The total phenol and flavonoid contents of the methanolic extracts from the aerial parts were measured by Folin Ciocalteu and AlCl₃ assays, respectively. In addition, antibacterial activities of the methanolic extracts were studied by disc diffusion method against 3 Gram positive and Gram negative bacteria. Results showed that the methanolic extract of <em>V. sinuatum</em> contains the highest amount of phenolic compounds and of <em>V. speciosum</em> represents the highest flavonoid content. Results from antioxidant activity assays showed that the studied extracts are more active than ascorbic acidas a synthetic antioxidant in DPPH radical scavenging assay, but represent lower activity in metal-chelating assay. In β-carotene/linoleic acid system, oxidation of linoleic acid was effectively inhibited by <em>V. speciosum</em> extract (58.4±18.1mg/g), followed by <em>V. sinuatum</em> (51.41±2.28 mg/g). In addition, methanolic extracts of three <em>Verbascum</em> species showed strong antibacterial activity against all tested bacteria.