Anti-inflammatory activity of a new cyclic peptide, citrusin XI, isolated from the fruits of Citrus unshiu

作者：Noh Hyung Jun; Hwang Dukhyun; Lee Eun Suk; Hyun Jae Wook; Yi Pyoung Ho; Kim Geum Soog; Lee Seung Eun; Pang Changhyun; Park Yong Joo; Chung Kyu Hyuck; Do Kim Gun^*; Kim Ki Hyun

来源：Journal of Ethnopharmacology, 2015, 163(11): 106-112.

DOI：10.1016/j.jep.2015.01.024

• Citrus unshiu
• Rutaceae
• Peptide
• Citrusin XI
• Anti-inflammation
• RAW264.7 cells

Ethnopharmacological relevance: Citrus unshiu (Rutaceae) is an easy-peeling citrus fruit, which has been used as a traditional Korean medicine for improving skin elasticity, relieving fatigue and cough, and preventing bronchitis, flu, and various cancers. However, its active components associated with anti-inflammation and underlying mechanisms remain unknown. In this study, we investigated the active constituents from the fruits of Citrus unshiu and evaluated the anti-inflammatory activity in order to support the traditional usage of Citrus unshiu.
Material and methods: Repeated column chromatography, together with a semi-preparative HPLC purification was used to separate the bioactive constituent from the EtOAc soluble fraction of the EtOH extract of Citrus unshiu fruits. Anti-inflammatory effects of the isolated compounds on lipopolysaccharide (LPS)-induced production of pro-inflammatory mediators were examined using RAW264.7 macrophage cells.
Results: A new cyclic peptide, citrusin XI (1), was isolated and identified from the fruits of Citrus unshiu. The structure of compound 1 was elucidated by spectroscopic analysis, including 1D and 2D nuclear magnetic resonance (NMR) (H-1, C-13, COSY, HMQC and HMBC experiments), and high resolution (HR)-mass spectrometry, and its absolute configurations were further confirmed by the Marfey's method. Compound 1 decreased NO production in LPS-stimulated RAW264.7 cells in a dose-dependent manner with an IC50 value of 70 mu M. Compound 1 suppressed NO production by decreasing iNOS expression but COX-2 expression was slightly associated with the reduction by compound 1 in LPS-induced RAW264.7 cells. Furthermore, compound 1 inhibited NF-kappa B activation by blocking I kappa B alpha degradation and NF-kappa B phosphorylation in LPS-stimulated RAW264.7 cells.
Conclusions: These results indicate that a new cyclic peptide, citrusin XI, from Citrus unshiu fruits has anti-inflammatory properties that inhibit the release of pro-inflammatory mediators. Compound 1 decreases NO production by decreasing iNOS expression and NF-kappa B activation associated with I kappa B alpha degradation and NF-kappa B phosphorylation in LPS-induced RAW264.7 cells. This is the first study to clarify the underlying mechanism of the anti-inflammatory effect exerted by a pure isolated compound from Citrus unshiu in LPS-stimulated RAW264.7 macrophage cells. The phytochemical, citrusin XI of Citrus unshiu may serve as lead compound in the design of new agents for preventing and treating inflammatory diseases.

• 出版日期2015-4-2