Evaluation of some traditional medicinal plants: phytochemical profile, antibacterial and antioxidant potentials

Bioassays provide an authentication of the traditional knowledge of medicinal plants. Antibacterial, antioxidant and phenolic content of nine medicinal plants (Achillea millefolium, Prunella vulgaris, P. laciniata, Lythrum salicaria, Epilobium angustifolium, E. hirsutum, Pedicularis comosa, Agrimonia eupatoria and Verbena officinalis) were investigated in connection with folkloric usages. Aerial parts of nine plant species were extracted with water and methanol (MeOH). Disc diffusion method was performed to evaluate the antibacterial activity of the extracts against ten pathogenic bacteria. Antioxidant activity was determined by using 2,2-diphenyl-1picrylhydrazil (DPPH) radical photometric assay. Total phenolic and flavonoid content were investigated by using Folin-Ciocaltaeu and aluminum chloride (AlCl3) colorimetric method, respectively. Quantitative analysis of phenolic constituents of nine plants species were performed by high performance liquid chromatography-diode array detector (HPLC-DAD) via chosen ten phenolic standards (gallic acid monohydrate, caffeic acid, rutin hydrate, luteolin-7-O-β-D glucoside, kaempferol, rosmarinic acid, myricetin, quercetin, coumarin and apigenin). E. hirsutum showed the best antibacterial activity against gram-positive bacteria (S auerus, S. epidermidis and S. pyogenes). L. salicaria also demonstrated strong and broad spectrum antibacterial activity. P. laciniata, L. salicaria and E. angustifolium showed potent antioxidant activity. The highest phenolic and flavonoid content was observed with E. hirsutum and A. millefolium, respectively. L. salicaria also had very high amount of total phenol and flavonoid content. HPLC-DAD analysis displayed that P. laciniata and A. eupatoria were the best sources of rosmarinic acid. Furthermore, V. officinalis and P. vulgaris also had remarkable amount of rutin. This study revealed the scientific rationale behind the traditional knowledge of the tested plants. Consistent with traditional usages, the most prominent plants were L. salicaria, E. hirsutum and E. angustifolium in regard to strong antibacterial and antioxidant potentials. These plants may be proper natural sources with potential applications in pharmaceutical and food industry.