Effect of shading and nitrogen fertilization on nitrogen metabolism, essential oil content and antimicrobial activity of Achillea millefolium

The Achillea millefolium L. is a perennial herb with important antibacterial, antifungal, anti-inflammatory, antitumoral, and antioxidant properties. This research aimed to investigate the effect of shading (75%; black net) and nitrogen fertilization (0, 75 and 150 kg urea ha-1) on the nitrogen metabolism, essential oil yield and antimicrobial activity of A.millefolium at vegetative- and reproductive-stage. The evaluated parameters varied depending on the organ and the phenological stage of the plant considered. Overall, our findings indicated that shading decreased nitrogen assimilation. Decreased activities of nitrate reductase and glutamine synthetase were observed on shaded plants during reproductive and vegetative stages, respectively. Nitrate and total amino acid levels increased in shaded plants at the vegetative stage. Regarding nitrogen supply, the improved nitrogen metabolism and essential oil yield values were accompanied by intermediate concentrations of urea (75 kg ha-1). Plants fertilized with 75 kg urea ha-1 produced the highest amino acids concentration (vegetative stage), ammonium concentration (vegetative stage) and essential oil yield (reproductive stage). Shading or nitrogen supply did not influence the microbial activity of A. millefolium essential oil.However, the essential oil of leaves and flowers were highly effective against fungi and bacteria, especially gram-positive bacteria. In conclusion, the current study showed that full light and 75 kg urea ha-1 enhanced the nitrogen metabolism of A. millefolium in both vegetative and reproductive stages.

[Antibacterial activity of hydroalcoholic extract of Salvia officinalis and Achillea millefolium against cariogenic microorganisms: an in vitro investigation]

There is an increasing global tendency to use traditional medicines and drug-extracts from natural plant materials. This in-vitro study was conducted in order to evaluate the cariostatic effect of hydroalcoholic extract of Salvia officinalis and Achillea millefolium. In this experimental study, hydroalcoholic extracts were prepared from Salvia officinalis and Achillea millefolium using maceration method. The antibacterial activity of these two extracts against Streptococcus mutans, Lactobacillus rhamnosus, and Actinomyces viscosus were evaluated through broth macrodilution method. Data was analyzed with Mann-Whitney test. The Minimum Inhibitory Concentration [MIC] of Salvia officinalis and Achillea millefolium for streptococcus mutans were 6.25 and 50 micro gram per milli liter, respectively. The corresponding figures for Lactobacillus rhamnosus were 1.56 and 12.5 micro gram per milli liter; and for Actinomyces viscosus the value were 12.5 and 50 micro gram per milli liter, respectively. The differences between the two extracts were statistically significant. Both extracts had growth inhibitory effect on all three bacteria. Salvia officinalis showed greater inhibitory effect on growth of all three bacteria. Both extracts had bactericidal effect in the considered concentration range