13.

Antioxidant Flavonoids from Nepeta floccosa Benth.

Liaqat Ali, Samina Ali, Tania Shamim Rizvi, Abdul Latif Khan, Zahid Hassan, Ahmed Al-Harrasi, and Javid Hussain

UoN Chair of Oman’s Medicinal Plants and Marine Natural Products, University of Nizwa, P. O. Box 616, Nizwa, Oman

Department of Chemistry, Kohat University of Science and Technology, Kohat-26000, Pakistan

Department of Biological Sciences and Chemistry, College of Arts and Sciences, University of Nizwa, P. O. Box 616, Nizwa, Oman

Abstract: Antioxidants are the substances which significantly delay or prevent the development of age-related degenerative and chronic diseases caused by oxidative damage. Due to this, there is a considerable interest in the identification of lead molecules, which can inhibit the oxidation process or slow it down considerably. Based on the spectrofluorimetric analysis of superoxide and diphenylpicrylhydrazyl radical scavenging ability, the bio-assay guided isolation of methanolic extract of Nepeta floccosa Benth. was carried out. As a result of this study, one new flavanonol named nepetavanol (1) and four known flavonoids; dihydrokaempferol (2), naringenin (3), caulesnarinside (4), and poncirin (5) have been isolated. The structure of the new flavanonol was assigned on the basis of 1H- and 13C-NMR spectra including two-dimensional NMR techniques such as COSY, HMQC, and HMBC experiments and FABMS, EIMS, HR-MS data. Compound 1 , 2, and 3 showed significant activity whereas compounds 4 and 5 showed moderate activity against antioxidant assays.

Keywords: Flavonoids; Structure Elucidation; Lamiaceae; Antioxidant Activity.