54
New xanthone derivatives as potent anti-inflammatory agents Tadeusz Librowski, Ryszard Czarnecki, Teresa Czekaj1, Henryk Marona1 Department of Pharmacodynamics, 1 Department of Chemical Technology of Drugs, Jagiellonian University, Krakow, Poland
Key words: alkanoic derivatives of xanthone, anti-inflammatory activity. Summary. A series of novel xanthone derivatives were synthesized as potential anti-inflammatory compounds. The compounds were examined for anti-inflammatory and analgesic properties. Aspirin and ketoprofen were used as reference compounds. Material and methods. Acute inflammation was induced by subplantar injection of 0.1 ml of 1% carrageenan solution to the right rat paw, 1 hour after oral administration of the investigated compound. The development of paw edema was measured plethysmographically. Pain threshold in the hind paw of rat affected by inflammation was measured using an analgesimeter 4 hours after oral administration of the compounds. Mean pain thresholds were calculated for treated and control groups and the percent change from control was determined. Thus we observed irritation of gastric mucosa after use of compounds, which showed significant anti-inflammatory activity. The mucosa of the glandular part of the stomach was inspected using a binocular microscope. Results. The preliminary investigation of the anti-inflammatory activity of the novel xanthone derivatives showed uneven anti-inflammatory and analgesic activity. The highest anti-inflammatory and analgesic activity was provided by compound MH-44. The compounds MH-41, MH43 and MH-48 potentiated the carrageenan edema and lowered the threshold pain in comparison with control. Side effects of the active compound were examined on gastric mucosa and stomach and none of the active compounds showed significant side effects compared with nonsteroidal anti-inflammatory drugs. Conclusions. None of the active compounds showed significant side effects compared with nonsteroidal anti-inflammatory drugs. Introduction Investigations of many naturally occurring xanthones as well as their synthetic derivatives, resulted in numerous publications described their broad spectrum of biological activities namely antiallergic (1), anti-inflammatory (2–5), anti-tumor (6, 7), antimycobacterial (8), cardiovascular (9–12) and neuropharmacological effects (13–16). Some of natural and synthetic xanthones have shown anti-inflammatory and analgesic activity. In this group of compounds special mention deserves compound norathyriol, widely investigated and described (17). We have recently described the preliminary pharmacological screening of a series of aminoalkanolic derivatives of xanthone. Within this series of compounds the chiral 2-N-methylamino-1-butanol derivatives of 7-chloro-2-methylxanthone displayed action on the cardiovascular system. They attenuated or prevented the adrenaline-,
calcium-, and/or barium-induced arrhythmias in rats. In case of adrenaline-induced arrhythmia, the tested compounds considerably diminished arrhythmia causing blocks and extrasystoles. In the barium model of arrhythmia the racemate diminished mortality by 43% and in the calcium-induced arrhythmia inhibited ventricular block (25%), extrasystoles (37%) and bigeminy (20%) (18). Taking this into account and also the fact that the above mentioned compounds have structural elements of known anti-inflammatory drugs like ketoprofen or fenoprofen, we try to find an active anti-inflammatory compounds in this chemical group. A series of novel xanthone derivatives, MH41, MH-43, MH-44 and MH-48, were synthesized as potential anti-inflammatory compounds (compounds in the patent – conduct). The relationship between the pharmacological activity and chemical structure of compounds with an anti-inflammatory activity has
Correspondence to T. Librowski, Department of Pharmacodynamics, Jagiellonian University, Faculty of Pharmacy, Medical College, Medyczna 9, 30-688 Kraków, Poland. E-mail:
[email protected]
New xanthone derivatives as potent anti-inflammatory agents been a subject of pharmacological investigations for many years (2–5, 19). Some authors suggest the existence of a close correlation between the potency of non-steroidal anti-inflammatory drugs as the inhibitors of prostaglandin synthetase activity and the degree of irritating action on the mucosa (20–22). A definite dependence between the anti-inflammatory activity and lesion of gastric mucosa had been found (23). Material and methods Male albino Wistar rats (150–200 g) and male albino mice (18–26 g) were used for anti-inflammatory and analgesia tests, respectively. The animals were housed and fed in a laboratory kept at constant temperature of 22°C under the standard conditions (12:12 h L:D cycle, standard pellet diet, tap water). Each experimental group consisted of 8 animals / dose and all the animals were used only once. Treatment of the used laboratory animals in the present study was in full accordance with the respective Polish and European regulations and was approved by the Local Ethics Committee. Determination of anti-inflammatory activities of investigated compounds using carrageenan-induced hind paw edema test Male albino Wistar rats (100–150 g) were used in “hind paw edema” test. Rats were divided into four groups, one of them being the control. In order to produce inflammation, 0.1 ml of 1% carrageenan solution in water was injected into hind paws subplantar tissue of rats, according to the modified method of C. A. Winter (24) and P. Lence (25). The development of paw edema was measured plethysmographically. Prior to this administration, paw diameters were measured by dividers and recorded. After carrageenan injections, the investigated compounds were administered orally (po). Physiological saline was administered by the same route, to the control group. After these administrations, paw diameters were measured at 1, 2, and 3 hours, % of edema and edema inhibition was calculated according to the formulas given below. Edema % = (N’×100)/N. Edema inhibition % = (N–N’×100)/N. N: paw diameters measured 1, 2 and 3 hours after injection of carrageenan to the control group – paw diameters at the beginning. N’: paw diameters measured 1, 2, and 3 hours after injection of carrageenan to the test groups – paw diameters at the beginning. Medicina (Kaunas) 2005; 41(1)
55
Analgesic activity Analgesic activity was determined by assessing the inhibition of pain provoked by compression of carrageenan-inflamed rat paw and by the method of L. O. Randall and J. J. Selitto (26). In L. O. Randall’s test, pain threshold in the hind paw of rat affected by inflammation was measured using an analgesimeter 4 hours after intraperitoneal administration of the compounds. Mean pain thresholds were calculated for treated and control groups and the percent change in relation to the control was determined. Ulcerogenic effect Ulcerogenic effect was determined by the method of T. Komatsu et al (27). The tested compounds were administered to fasted rats having free access to drinking water. Four hours after administration of the compounds, the rats were sacrificed, the stomach was removed and, after incision along the lesser curvature, rinsed with a tap soaked in warm (37oC) saline and spread on a corkboard and pinned down. The mucosa of the glandular part of the stomach was inspected using a binocular microscope (10-fold magnification). Thus we observed irritation of gastric mucosa after used compounds, which they showed significant antiinflammatory activity. The mucosal lesions were evaluated using 0–5 gradation (0 – no lesions, 1 – erythema, 2 – punctiform ulcers, 3 – small ulcers, 4 – large ulcers, 5 – perforation). Statistical analysis The data were expressed as means ± SEM. The obtained data were evaluated by the one-way analysis of variance (ANOVA), followed by Bonferroni’s multiple comparison test; p
