Cary 300 varian spectrophotometer

The procedure was presented previously by Gabrielska et al. (2006b (link)). Lipid peroxidation in phospholipid liposomes was induced by ultraviolet radiation from a bactericidal UVB lamp at 3.5 mW cm⁻² intensity (UVP radiometer, UK). Lipid peroxidation was measured as the thiobarbituric acid reactive substance (TBARS) level, based on the method of Buege and Aust (1978 (link)). TBARS concentrations were estimated using the molar extinction coefficient ε = 156 mM⁻¹ cm⁻¹. The percentage of PC liposome oxidation inhibition was calculated using the formula: $$\%\text{Inhibition}=\frac{C_0-C}{C_0}·100\%$$ where C₀ is concentration of malondialdehyde (MDA) in a sample without antioxidant added (control) and C is concentration of MDA in a sample with study compound added, measured at λ = 535 nm. All determinations were performed for six independent preparations (n = 6) using a Cary 300 Varian spectrophotometer. The IC₅₀ parameter was calculated on the basis of plots showing the relation between percentage of lipid oxidation and concentration of the antioxidant. Its value expresses the concentration of an antioxidant that inhibits oxidation by 50 %.

The experiment was described previously [36 (link),77 (link)]. In short, peroxidation of PC liposome lipids was initiated with ultraviolet radiation using a bactericidal UVB lamp. Peroxidation was measured as the TBARS level. The percentage of PC liposome oxidation inhibition was calculated using the formula: $$\% \mathit{inhibition}=\frac{C_C -C_E}{C_C} \times 100\%,$$
where C_C refers to the concentration of malondialdehyde (MDA) in a sample without extract (control) and C_E refers to the concentration of MDA in a sample with the appropriate extract added, measured at λ = 535 nm. All determinations were performed with three independent preparations (n = 3) using a Cary 300 Varian spectrophotometer.