Metabolic profiling, antioxidant, and antibacterial activity of some Iranian Verbascum L. species

The first step in introducing a medicinal plant into farming systems and industrial pharmacology is the realization of its metabolic profile and biological features. In the present study, ten Verbascum species including V. cheirantifolium, V. erianthum, V. macrocarpum, V. punalense, V. sinuatum, V. songaricum, V. speciosum, V. stachidiforme, V. thapsus, and V. densiflorum were collected from Iran and their phytochemical characteristics and biological activities were studied. The powdered air-dried aerial flowering parts of the plants were extracted with methanol by maceration. The crude methanolic extracts were further fractionated by solvent-solvent partitioning to obtain various fractions using n-hexane and ethyl acetate. The total phenol and flavonoid, phenolics and iridoids contents and metabolic profiling of the obtained extracts and enriched-fractions were assessed using UV, HPLC-PDA, LC-MS and in silico methods, respectively. Antioxidant activity using DPPH and FRAP methods, and antibacterial activity against Gram-positive and -negative bacteria were also studied. The highest contents of total phenol (51.94 +/- 2.30 mg GAE/g DW) and total flavonoid (22.57 +/- 1.73 mg QE/g DW) were found in V. sinuatum. The range of the highest content (mg/g DW) among the other compounds were found to be rutin (0.11-21.0), rosmarinic acid (0.33-12.16), p-coumaric acid (0.10-10.22), ferulic acid (0.11-7.82), gentisic acid (0.09-5.73), protocatechuic acid (0.09-4.74), salicylic acid (2.45-4.36), quercetin (0.13-3.21), and harpagoside (0.001-0.320) in the studied species. In addition, twenty-eight compounds were qualitatively identified in the plant extracts. The highest content of metabolites supported the observed highest antioxidant activity in V. speciosum and V. songaricum. Phenolic-enriched fraction of V. songaricum showed the highest antibacterial activity (MIC 0.12 mg/mL) against Staphylococcus aureus. Association analysis showed a significant positive correlation between biological properties and phenolic compounds. In conclusion, V. songaricum and V. sinuatum could be selected as adequate species for further exploitation in agricultural systems and pharmaceutical industry.