Evaluation of phenolic compounds and antioxidant activity in leaves of different different Verbascum L. species in West Azerbaijan province

Mullein (Verbascum L.) is a biennial herbaceous medicinal plant belonging to the Scrophulariaceae family. The flowers of this plant are used to treat respiratory disorders. In this study, the genetic diversity of different mullein species from different regions of West Azerbaijan province was investigated based on some phytochemical markers to domesticate this valuable plant. Phytochemical diversity among different species of mullein was evaluated based on the content of carotenoid, beta-carotene, total phenol, total flavonoid, and antioxidant activity (by FRAP and DPPH methods), and identification of phenolic compounds (gallic acid, caffeic acid, chlorogenic acid, rutin, coumaric acid, quercetin, cinnamic acid, and apigenin) by HPLC in leaf. The results showed that all phytochemical characteristics studied were significantly different among species (P<0.01). The highest content of carotenoid (76.27 mg g-1 DW), beta-carotene (5.88 mg 100g-1 DW), total phenol (32.83 mg GAE g-1 DW), total flavonoid (7.13 mg QE g-1 DW) and antioxidant activity by DPPH method (34.66 µg AA mL-1) was observed in V. sinuatum. The results showed that V. erianthum leaves had the highest content of chlorogenic acid, quercetin, cinnamic acid, and apigenin, while the highest content of gallic acid and caffeic acid was observed in V. saccatum. In general, the findings of this research showed that there was a wide variation of mullein species in West Azerbaijan province. Species V. erianthum and V. saccatum had unique phytochemical properties that can be used to design breeding programs and use them in the pharmaceutical industry.