Anti-inflammatory coumarins from Paramignya trimera

Abstract

Context: Paramignya trimera (Oliv.) Burkill (Rutaceae) has been used to treat liver diseases and cancer. However, the anti-inflammatory effects of this medicinal plant and its components have not been elucidated.

Objective: This study investigated chemical constituents of the P. trimera stems and evaluated anti-inflammatory effects of isolated compounds.

Materials and methods: Cytotoxicity of isolated compounds (5-40 μM) toward BV2 cells was tested using 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) for 24 h. Inhibitory effects of isolated compounds (5-40 μM) on nitrite and PGE₂ concentrations were determined using Griess reaction and PGE₂ ELISA kit, respectively (pretreated with the compounds for 3 h and then stimulated for 18 h with LPS). Inhibitory effects of compounds (5-40 μM) on iNOS and COX-2 protein expression were evaluated by Western blot analysis (pretreated with the compounds for 3 h and then stimulated for 24 h with LPS).

Results: Seven coumarins were isolated and identified as: ostruthin (1), ninhvanin (2), 8-geranyl-7-hydroxycoumarin (3), 6-(6',7'-dihydroxy-3',7'-dimethylocta-2'-enyl)-7-hydroxycoumarin (4), 6-(7-hydroperoxy-3,7-dimethylocta-2,5-dienyl)-7-hydroxycoumarin (5), 6-(2-hydroxyethyl)-2,2-dimethyl-2H-1-benzopyran (6), and luvangetin (7). Compounds 1-4 and 7 inhibited NO and PGE₂ production in LPS-stimulated BV2 cells, with IC₅₀ values ranging from 9.8 to 46.8 and from 9.4 to 52.8 μM, respectively. Ostruthin (1) and ninhvanin (2) were shown to suppress LPS-induced iNOS and COX-2 protein expression.

Discussion and conclusion: The present study provides a scientific rationale for the use of P. trimera in the prevention and treatment of neuroinflammatory diseases. Ostruthin and ninhvanin might have potential therapeutic effects and should be considered for further development as new anti-neuroinflammatory agents.

Keywords: 6-(2-hydroxyethyl)-2,2-dimethyl-2H-1-benzopyran; 6-(6′,7′-dihydroxy-3′,7′-dimethylocta-2′-enyl)-7-hydroxycoumarin; 6-(7-hydroperoxy-3,7-dimethylocta-2,5-dienyl)-7-hydroxycoumarin; 8-geranyl-7-hydroxycoumarin; BV2 microglia; Rutaceae; luvangetin; ninhvanin; ostruthin.

Figure 1.

Chemical structures of compounds 1–7 from P. trimera.

Figure 2.

Effects of compounds 1–4, and 7 on nitrite production in LPS-stimulated BV2 microglia (A−E). Cells were pretreated for 3 h with the indicated concentrations of the compounds, then stimulated for 18 h with LPS (1 μg/mL). The concentrations of nitrite were determined using a Griess reaction. Data represent the mean ± S.D. of three experiments. #p < 0.05, as compared with the control group; *p < 0.05, as compared with the group treated with LPS only. Butein was used as the positive control.

Figure 3.

Effects of compounds 1–4, and 7 on PGE₂ production in LPS-stimulated BV2 microglia (A−E). Cells were pretreated for 3 h with the indicated concentrations of the compounds and then stimulated for 18 h with LPS (1 μg/mL). The concentrations of PGE₂ were determined using a PGE₂ ELISA kit. Data represent the mean ± S.D. of three experiments. #p < 0.05, as compared with the control group; *p < 0.05, as compared with the group treated with LPS only. Butein was used as the positive control.

Figure 4.

Effects of compounds 1 and 2 on iNOS and COX-2 protein expression in LPS-stimulated BV2 microglia. Cells were pretreated for 3 h with indicated concentrations of compounds 1 and 2, then stimulated for 24 h with LPS (1 μg/mL). Western blot analyses (A and B) were performed as described in ‘Materials and methods’ section.