Evaluation of chemical composition, trace element content, antioxidant and antimicrobial activities of Verbascum pseudoholotrichum

Abstract

Given that some Verbascum species are effective against influenza viruses, an endemic species, Verbascum pseudoholotrichum is thought to have the potential to be used in the treatment of virucidal diseases. It was extensively investigated for its antioxidant and antimicrobial activities, chemical and trace element composition. The soxhlet extraction method was applied in the extraction process of the above-ground parts of the plant using three solvents (methanol, ethanol and water). The total phenolic content of extracts was between 175.7 and 186.1 mg GAE/100 g on the dried weight basis. DPPH radical scavenging activity analysis was performed and IC₅₀ values were 0.539–1.254 mg mL⁻¹. In total, 38 compounds were detected by GC–MS analysis. ICP-MS analysis was applied to identify the total contents of 24 elements in dried samples. The antimicrobial activity of the extracts was evaluated on six different pathogens using the spectrophotometric microdilution technique. The obtained minimum inhibitory concentration values were 17.37 µ–113.9 µg mL⁻¹ at the end of the 24-h incubation. The highest and lowest inhibition zones were 5.0 and 0.3 mm for ethanol extract against Bacillus subtilis and water extract against Enterococcus fecalis, respectively, and no resistance was seen against Escherichia coli using disc diffusion method.

Keywords:

• Antimicrobial activity
• antioxidant activity
• DPPH
• GC–MS
• soxhlet extraction
• Verbascum pseudoholotrichum

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was funded by Mersin University Research Fund (Project No. BAP 2019-1-TP2-3298).