title: Effects of Potassium Sulfate [K2SO4] on The Element Contents, Polyphenol Content, Antioxidant and Antimicrobial Activities of Milk Thistle [Silybum Marianum].
abstract: BACKGROUND
  Silybum marianumL. (Milk thistle) is native to the Mediterranean basin and is now widespread throughout the world. It's sprout is used as a herbal medicine for the treatment of liver disease for centuries. The seeds of milk thistle contain silymarin, an isomeric mixture of flavonolignans [silybin, silychristin, and silydianin]. Silymarin acts as a strong anti-hepatotoxic.
  
  
  OBJECTIVE
  The objective of this study was to evaluate the influences of potassium sulfate [K2SO4] fertilizer doses on polyphenol content, some nutrient elements, antioxidant and antimicrobial activities of milk thistle at experimental fields of Ordu University in Turkey.
  
  
  METHODS
  The antimicrobial activities of seed ethanol extracts and seed oil were testedin vitroagainst Pseudomonas aeruginosa (P. aeruginosa), Escherichia coli, (E. coli) Staphylococcus aureus (S. aureus), Aspergillus niger (A. niger) and Candida albicans (C. albicans) using the disc diffusion method. Free radical scavenging activity of the ethanolic extracts of milk thistle was determined spectrophotometrically by monitoring the disappearance of 2, 2-diphenyl-1-picrylhydrazil (DPPH•) at 517 nm according to the method described by Brand-Williamset al.[17] The phenolic contents in the ethanolic extracts of milk thistle were determined according to the procedure described by Slinkard and Singleton[19] with a slight modification of using a Folin-Ciocalteu phenolic reagent. The amount of total flavonoid in the ethanolic extracts was measured by aluminum chloride [AlCl3] colorimetric assay. The ions in aerosol samples were determined by using Dionex ICS 1100 Series ion chromatography.
  
  
  RESULTS
  Seed and seed oils obtained from obvious doses of potassium sulfate [0, 30, 60, 90 and 120 kg ha-1fertilizer applications showed antimicrobial activities againstE. coli,A. nigerandP. aeruginosa. The application of 90 kg ha-1of K2SO4on seed oil resulted in the highest antimicrobial activities. At 100 µg mL-1and 200 µg mL-1, except the highest potassium application [120 kg ha-1extract, all extracts showed high and similar DPPH scavenging activity. The highest phenolic compounds were obtained with 30 kg ha-1of K2SO4, whereas the use of 60 kg ha-1caused the highest total flavonoid content. This plant is a good source of K+, Ca+2, PO4-3, and Cl-1.
  
  
  CONCLUSIONS
  In this study, increasing doses of potassium sulfate had significant effect on element, polyphenol content, antioxidant and antimicrobial activities of the milk thistle.
  
  
  CONCLUSIONS
  All tested extracts were active against all tested microbial species.All extracts have shown high and similar DPPH scavenging activity.There was a gradual increase in the biological properties of the milk thistle seeds with rising levels of potassium sulfate.The milk thistle seeds are rather rich sources of K+, Ca+2, PO4-3and Cl-1potentially bioavailable for human consumption.Abbreviations used:AlCl3: aluminum chloride, Ca+2: calcium, Cl-: chloride, Cr: chromium CE: catechol equivalents, DPPH: 2,2-diphenylpicrylhydrazyl, ABTS: 2,2'-azino-bis-3-ethylbenzthiazoline-6-sulphonic acid, DAP: diamonyum fosfat, F-: fluoride, Fe: iron, K2SO4: potassium sulfate, K+ : potassium, Li+: lithium, Mg+2: magnesium, NH4+: amonyum, Na+: sodium, NO2-: nitrite, NO3-: nitrate, Ni: nickel, NaNO2:sodium nitrite, NaOH: sodium hidroksit. ND: Not detectable, PO4-3: phosphorus, Zn: zinc.
authors.affiliation: Faculty of Agriculture and Natural Sciences, Department of Field Crops, Abant İzzet Baysal University, Bolu, Turkey.
authors.forename: Gulsum
authors.initials: G
authors.lastname: Yaldiz
keywords: Antimicrobial activity; Silybum marianum; antioxidant activity; elements; potassium sulfate