Antioxidant Activities of the Extracts and Components of Teucrium orientale L. var. orientale
The effects of the developing stages of Teucrium orientale L. var. orientale on the antioxidant and DPPH radical scavenging activities of the extracts obtained with different organic solvents were investigated. The aerial parts of the plant samples were collected at the budding, flowering and vegetative stages and then the plant samples were extracted separately with petroleum ether, chloroform, acetone and methanol. The antioxidant activities of the extracts were evaluated using 2 different tests: the thiocyanate method and scavenging of the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical. The acetone and methanol extracts of all of the harvesting stages and chloroform extracts of the budding and flowering stages had antioxidant activities. Nevertheless, the acetone extracts of the budding and flowering stages showed the highest antioxidant activity. Higher DPPH radical scavenging activities were found in only acetone and methanol extracts in all of the harvesting stages. The flavonoid contents of all of the extracts were also determined. Similar to antioxidant and DPPH radical scavenging activities, the amounts of total flavonoids were higher in acetone and methanol extracts of the flowering and budding stages. The acetone extract of the flowering stage, which contained the highest amount of total flavonoids, was subjected to chromatographic methods for the isolation of the active compounds. Thus, a new iridoid along with 4 known flavonoids and 1 known iridoid were isolated. The structures of isolated compounds were characterized by UV, IR, 1H, 13C NMR, and 2D-NMR spectroscopic methods as cirsilineol (1), luteolin-7-O-rutinoside (2), luteolin-7-O-glucoside (3), hesperetin-7-O-rutinoside (4), 8-O-acetyl harpagide (5) and 8-O-methyl harpagide (6). These isolated compounds were also tested for their antioxidant and DPPH radical scavenging activities. Flavonoids showed potent antioxidant and DPPH radical scavenging activities, but iridoids did not. The highest antioxidant activity was shown by luteolin-7-O-glucoside.
Teucrium orientale, Labiatae, antioxidant, DPPH radical scavenging, Harvesting stage, Flavonoids, Iridoids