Effects of Cold-Pressing and Hydrodistillation on the Active Non-volatile Components in Lemon Essential Oil and the Effects of the Resulting Oils on Aging-Related Oxidative Stress in Mice

Abstract

The aim of this study was to analyze the non-volatile composition and antioxidant differences of lemon essential oils (LEOs) obtained by cold-pressing vs. hydrodistillation. Pathological observations showed that LEO effectively inhibited liver injury caused by oxidative stress, and CPLEO was more effective than HDLEO. CPLEO increased serum T-AOC, SOD, GSH, and GSH-Px levels while decreasing NO, COX-2, IL-6, IL-1β, IFN-γ, and TNF-α levels in mice with oxidative damage. The effects of CPLEO were stronger than those of HDLEO and similar to those of vitamin C. CPLEO upregulated mRNA and protein expressions of Cu/Zn-SOD, Mn-SOD, CAT, HO-1, Nrf2, and NQO1 while downregulating nNOS, iNOS, IL-1β, COX-2, TNF-α, and NF-κB mRNA expression and nNOS, eNOS, iNOS, and COX-2 protein expression in mice with oxidative damage. The results demonstrate that LEO has good antioxidant effects and that CPLEO has a better antioxidant effect than HDLEO as it retains more active non-volatile substances.

Keywords: antioxidant; cold-expression; coumarins; furocoumarins; oxidative stress.

Figure 1

High-performance liquid chromatography (HPLC) chromatograms of cold-pressed and hydrodistilled lemon essential oils. The peak assignment corresponds to that in Table 1. IS1 (coumarin) and IS2 (psoralen) are internal standards.

Figure 2

Pathological observation of hematoxylin-eosin (H&E)-stained sections of liver tissue from mice with oxidative damage. The area indicated by the arrow is inflammatory infiltration. (A) 100 × ,(B) 600 × .

Figure 3

Total antioxidant capacity (T-AOC), superoxide dismutase (SOD), glutathione (GSH) and glutathione peroxidase (GSH-Px) levels in the serum of mice with oxidative damage. ^a−dMean values with different letters in the same bar are significantly different (p < 0.05) according to Duncan's multiple range test.

Figure 4

Nitric oxide (NO), cyclooxygenase-2 (COX-2), interleukin-6 (IL-6), interleukin-1 beta (IL-1β), interferon gamma (IFN-γ) and tumor necrosis factor alpha (TNF-α) levels in the serum of mice with oxidative damage. ^a−eMean values with different letters in the same bar are significantly different (p < 0.05) according to Duncan's multiple range test.

Figure 5

Copper/zinc superoxide dismutase (Cu/Zn SOD), manganese superoxide dismutase (Mn SOD), catalase (CAT), heme oxygenase-1 (HO-1), nuclear factor E2-related factor 2 (Nrf2) and NAD(P)H quinone dehydrogenase 1 (NQO1) mRNA expression in the liver tissues of mice with oxidative damage. ^a−fMean values with different letters in the same bar are significantly different (p < 0.05) according to Duncan's multiple range test.

Figure 6

Copper/zinc superoxide dismutase (Cu/Zn SOD), manganese superoxide dismutase (Mn SOD), catalase (CAT), heme oxygenase-1 (HO-1), nuclear factor E2-related factor 2 (Nrf2) and NAD(P)H quinone dehydrogenase 1 (NQO1) protein expression in the liver tissues of mice with oxidative damage. ^a−fMean values with different letters in the same bar are significantly different (p < 0.05) according to Duncan's multiple range test. β-actin is the internal reference expression. As the same experiment, the β-actin internal parameters of this Figure 6 and the β-actin internal parameters of Figure 8 is the same.

Figure 7

Neuronal nitric oxide synthase (nNOS), inducible nitric oxide synthase (iNOS), interleukin-1 beta (IL-1β), cyclooxygenase-2 (COX-2), tumor necrosis factor alpha (TNF-α), and nuclear factor kappa-B (NF-κB) mRNA expression in the liver tissues of mice with oxidative damage. ^a−eMean values with different letters in the same bar are significantly different (p < 0.05) according to Duncan's multiple range test.

Figure 8

Neuronal nitric oxide synthase (nNOS), endothelial nitric oxide synthase (eNOS), inducible nitric oxide synthase (iNOS), and cyclooxygenase-2 (COX-2) protein expression in the liver tissues of mice with oxidative damage. ^a−fMean values with different letters in the same bar are significantly different (p < 0.05) according to Duncan's multiple range test. β-actin is the internal reference expression. As the same experiment, the β-actin internal parameters of Figure 6 and the β-actin internal parameters of this figure is the same.