Origanum majorana L.: A Nutritional Supplement With Immunomodulatory Effects

Abstract

Origanum majorana L. is an aromatic herb that has been grown in several Mediterranean countries since ancient times, but became popular during the Middle Ages as a medicinal plant and seasoning ingredient. O. majorana has many pharmacological effects, but its immunoreactive components and mechanisms are still unclear. In this study, four compounds were isolated and identified from O. majorana by a spectral analysis, including ¹H and ¹³C-NMR. They were 1H-indole-2-carboxylic acid (1), (+)-laricresol (2), (+)-isolaricresol (3), and procumboside B (4, pB), which were isolated for the first time in O. majorana. The immunomodulatory effects of the four compounds were screened, and pB had good immunomodulatory activity on RAW 264.7 cells. The immunomodulatory mechanism of pB was proved, in which pB could increase the secretion of nitric oxide (NO), interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), and reactive oxygen species (ROS) and simultaneously upregulate the expression of CD80 and CD86 on the cell surface. These results suggested that the mechanism of pB may be related to the activation of nuclear factor-kappaB (NF-κB) and mitogen-activated protein kinases (MAPKs)-signaling pathways. O. majorana is rich in nutrients and is commonly used in diets, so it can be used as a nutritional supplement with immunomodulatory effects.

Keywords: MAPKs; NF-κB; Origanum majorana L.; RAW264.7; immune; procumboside B.

Figure 1

Structures of compounds 1–4 from Origanum majorana.

Figure 2

Effects of procumboside B (pB) on the viability of RAW264.7 cells. Data presented are the mean ± SD, n = 6.

Figure 3

Effects of pB on nitric oxide (NO) production (A) and nitric oxide synthase (iNOS) mRNA expression (B) in RAW264.7 cells. Data presented are the mean ± SD, n = 3. Compared with the control, ^***p < 0.001, ^**p < 0.01.

Figure 4

The effects of pB on the expression of IL-6 (A), tumor necrosis factor-α (TNF-α) (B), interleukin-6 (IL-6) (C), and TNF-α (D) mRNA in Raw264.7 cells. Data presented are the mean ± SD, n = 3. Compared with the control, ^***p < 0.001 and ^*p < 0.05.

Figure 5

Effects of pB on the nuclear factor-kappaB (NF-kB) pathway with Western blotting. (A) The expression of p-P65, P65, p-IκBα and IκBα were detected using Western blotting. (B) The ratio of the content of p-P65/P65 and p-IκBα/IκBα. Data presented are the mean ± SD, n = 3. Compared with the control, ^***p < 0.001.

Figure 6

Effects of pB on the mitogen-activated protein kinases (MAPKs) pathway with Western blotting. (A) The expression of p-P38, P38, p-ERK, ERK, p-JNK, and JNK detected using Western blotting. (B) The ratio of the content of p-P38/P38. (C) The ratio of the content of p-ERK/ERK. (D) The ratio of the content of p-JNK/JNK. Data presented are the mean ± SD, n = 3. Compared with the control, ^***p < 0.001.

Figure 7

The effects of pB on reactive oxygen species (ROS) in RAW264.7 cells. (A) The fluorescence intensity was determined by flow cytometry at the FITC channel. (B) The realitive fluoresence intensity of ROS per group. Data presented are the mean ± SD, n = 3. Compared with the control, ^***p < 0.001 and ^*p < 0.05.

Figure 8

Flow cytometric analysis of CD86, CD80, and MHC II expressions on the surface of RAW264.7 cells. (A,D) represent the results of CD86 expression. (B,E) represent the results of CD80 expression. (C,F) represent the results of MHC II expression. Data presented are the mean ± SD, n = 3. Compared with the control, ^***p < 0.001 and ^**p < 0.01.