A new pyranoflavone, methoxycyclocommunol (1) together with four known flavonoids, artonin F (2), heteroflavanone A (3), cudraflavone C (4) and cyclocommunol (5) were isolated from the bark of Artocarpus integer var. silvestris Corner. Their structures were elucidated through extensive spectroscopic- techniques (UV, IR, MS, 1D-NMR and 2D-NMR) and by comparison with literature data. All the pure compounds were tested for their anti-inflammatory activities by using screening kit and radioimmunoassay methods. In a 15-lipoxygenase (15-LOX) inhibitory assay, compounds 1, 2, 4 and 5 gave weak percentages of inhibition, 16.5, 18.3, 17.6, 10.2%, respectively at the concentration of 100 μM. Compounds 1, 3 and 4, however, showed strong dose- dependent inhibition towards prostaglandin E₂ (PGE₂) production in lipopolysaccharide-induced human whole blood using a radioimmunoassay method with IC₅₀ values of 4.3, 0.8, and 0.07 μM, respectively suggesting that they strongly exhibited cyclooxygenase-2 (COX-2) activity.
Acetylmelodorinol, chrysin and polycarpol, together with benzoic acid, benzoquinone and stigmasterol were isolated from the leaves of Mitrella kentii (Bl.) Miq. The compounds were evaluated for their ability to inhibit prostaglandin E₂ (PGE₂) and thromboxane B₂ (TXB₂) production in human whole blood using a radioimmunoassay technique. Their inhibitory effect on platelet activating factor (PAF) receptor binding to rabbit platelet was determined using ³H-PAF as a ligand. Among the compounds tested, chrysin showed a strong dose-dependent inhibitory activity on PGE(2) production (IC₅₀ value of 25.5 µM), which might be due to direct inhibition of cyclooxygenase-2 (COX-2) enzymatic activity. Polycarpol, acetylmelodorinol and stigmasterol exhibited significant and concentration-dependent inhibitory effects on TXB₂ production with IC₅₀ values of 15.6, 19.1 and 19.4 µM, respectively, suggesting that they strongly inhibited COX-1 activity. Polycarpol and acetylmelodorinol showed strong dose-dependent inhibitory effects on PAF receptor binding with IC₅₀ values of 24.3 and 24.5 µM, respectively.
The in vivo and in vitro mechanistic anti-inflammatory actions of cucurbitacin E (CE) (Citrullus lanatus var. citroides) were examined. The results showed that LPS/INF-γ increased NO production in RAW264.7 macrophages, whereas L-NAME and CE curtailed it. CE did not reveal any cytotoxicity on RAW264.7 and WRL-68 cells. CE inhibited both COX enzymes with more selectivity toward COX-2. Intraperitoneal injection of CE significantly suppressed carrageenan-induced rat's paw edema. ORAC and FRAP assays showed that CE is not a potent ROS scavenger. It could be concluded that CE is potentially useful in treating inflammation through the inhibition of COX and RNS but not ROS.