Abstract
Purpose: To investigate the anti-inflammatory activity of the ethanol extract of the immature fruit of a citrus, Shiranuhi, and to identify the active ingredient. Methods: The immature Shiranuhi peel was extracted with 80 % ethanol, and the extract was fractionated with solvents (n-hexane, ethyl acetate and n-butanol) to afford the corresponding fractions and water residue. Among them, the EtOAc-soluble portion was subjected to medium pressure liquid chromatography (MPLC) over a reversed-phase SiO 2 column to give compound 1 . The isolated compound was identified based on the proton and carbon nuclear magnetic resonance (NMR) spectra. The release of nitric oxide, prostaglandin (PG)E2, tumor necrosis factor (TNF)-α, interleukin (IL)-1β, and IL-6 secreted by mouse macrophages was measured using RAW264.7 cell culture supernatant. Results: Shiranuhi (Korean name, Hallabong) is an important citrus species cultivated in Jeju Island, Korea. A polymethoxyflavonoid (PMF), tetramethyl-O-scutellarin ( 1 ), was isolated from the peels of immature Shiranuhi fruit. Upon the evaluation of anti-inflammatory effects, the flavonoid 1 decreased the nitric oxide production in macrophage cells with high efficiency, viz, 50 % inhibition concentration, IC 50 of 57.4 μM. Subsequent studies demonstrated that PMF 1 effectively inhibited the generation of PGE2, TNF-α, IL-1β, and IL-6 cytokine in a dose-dependent manner. Conclusion: Tetramethyl-O-scutellarin ( 1 ) has been successfully isolated from Shiranuhi species for the first time. Thus, Shiranuhi fruit peel extract containing PMF 1 can potentially be applied as an antiinflammatory ingredient in food or cosmetic industries. Keywords: Shiranuhi fruit, Nitric oxide, Tetramethyl-O-scutellarin, Anti-inflammatory
Highlights
Citrus is a genus of trees producing important fruits such as oranges, lemons, grapefruit, and limes
Phytochemical studies of Citrus peels have led to identifying some metabolites including flavonoids [2,3], limonoids [4,5], and coumarins [6]
The ethanol extracts were examined for the anti-inflammatory activities using RAW 264.7 cells
Summary
Citrus is a genus of trees producing important fruits such as oranges, lemons, grapefruit, and limes. The dried peels of Citrus fruits have been used in Chinese medicine for the cure of stomachache, skin inflammation, muscle pain, cough, and high blood pressure [1]. Phytochemical studies of Citrus peels have led to identifying some metabolites including flavonoids [2,3], limonoids [4,5], and coumarins [6]. Polymethoxyflavones (PMFs) have attracted considerable attention as bioactive constituents in Citrus peels [2,7] owing to their antiinflammatory [8], anticarcinogenic [9], and antiatherogenic properties [10]. Antioxidant [11,12] and antitumor properties [13] were identified from the flavonoids of Citrus genus
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