1,8-Cineol, a Food Flavoring Agent, PreventsEthanol-Induced Gastric Injury in Rats

F.A. SANTOS, PhD and V.S.N. RAO, PhD

This study investigated the gastroptrotective effect of 1,8-cineole (cineole) on ethanol-induced gastric mucosal damage in rats and the possible mechanisms involved. 1,8-Cineole(50–200 mg/kg), given orally 1 hr before administration of 1 ml of absolute ethanolsignificantly attenuated the ethanol-induced gastric injury in a manner similar to nordihy-droguairetic acid, a known lipoxygenase inhibitor. 1,8-Cineole showed a tendency to restorethe ethanol-associated decreases in nonprotein sulfhydryls, suggesting a possible antioxidanteffect. In gastric secretion studies, 1,8-cineole, similar to cimetidine, a known histamine-2receptor antagonist, demonstrated significant inhibitions of both gastric juice volume as wellas total acid output. The protection offered by 1,8-cineole was found to be unaltered by8-phenyltheophylline or L-NAME, indicating that its effect is not mediated by endogenousadenosine or nitric oxide. These results, taken together with the earlier reports, suggest thatthe antioxidant and lipoxygenase inhibitory actions of 1,8-cineole are of prime importance inaffording gastroprotection against ethanol injury in the rat.

KEY WORDS: 1,8-cineole; ethanol; gastric mucosal lesions; gastric mucus; nonprotein sulfhydryls.

1,8-Cineole (cineole), also known as eucalyptol orcajeputol, is a terpene oxide found in many plantessential oils (1–3). It is often used as a flavoringagent for food products (4, 5). Traditionally, it hasbeen used for treating symptoms of airway diseasesexacerbated by infection, and a growth inhibitoryeffect of 1,8-cineole on several microorganisms hasrecently been documented (6). It is also frequentlyemployed by the pharmaceutical industry in drugformulations as a percutaneous enhancer and for itsdecongestant and antitussive effects and in aroma-therapy as a skin stimulant in the form of skin baths(7–10). Recent studies have shown its inhibitory effecton the production of inflammatory mediators such ascytokines, prostaglandins, and leukotrienes from li-popolysaccharide-stimulated human blood mono-

cytes both in vitro as well as ex vivo (11, 12). Morerecently, we provided evidence to show that 1,8-cineole possesses antiinflammatory and analgesicproperties (13).

Ethanol-induced gastric mucosal damage in rats isoften used as an experimental model when screeningcompounds for antiulcer activity because it representsthe most common cause of gastric ulcer in man.Absolute ethanol rapidly promotes the formation ofhyperemic blisters in the stomach mucosa, which isessentially an acute inflammatory reaction whereinincreased vascular permeability is a common feature(14). Some plant substances, such as flavonoids, ter-penoids and xanthines, known for their antiinflamma-tory activity have been shown to prevent gastric le-sions induced by ethanol (15–17). Theantiinflammatory effects of these compounds havebeen attributed to their ability to scavenge oxygenfree radicals (5, 18, 19). On the other hand, nonste-roidal antiinflammatory drugs that inhibit prostaglan-din biosynthesis actually promote gastric lesions (20,21). Keeping in view the reputed usefulness of 1,8-

Manuscript received March 31, 2000; accepted July 31, 2000.From the Department of Physiology and Pharmacology, Faculty

of Medicine, Federal University of Ceara, C.P-3157, 60430-270Fortaleza, Ceara, Brazil.

Address for reprint requests: Dr. V.S.N. Rao, Departamento deFisiologia e Farmacologia, Rua Cel Nunes de Melo, 1127, C.P.3157, Porangabussu, 60430-270 Fortaleza, CE, Brasil.

Digestive Diseases and Sciences, Vol. 46, No. 2 (February 2001), pp. 331–337

331Digestive Diseases and Sciences, Vol. 46, No. 2 (February 2001)0163-2116/01/0200-0331$19.50/0 © 2001 Plenum Publishing Corporation

cineole as a flavoring agent for foods, its widespreaduse by the pharmaceutical industry in drug formula-tions, and the established antiinflammatory potential,the present study was designed to verify whether ornot 1,8-cineole prevents ethanol-induced gastric dam-age in rats.

MATERIALS AND METHODS

Animals. Male Wistar rats weighing 180–200 g were usedin the study. They were housed in polypropylene cages andmaintained under normal laboratory conditions at 22 6 1°Con a 12-hr light–dark cycle and fed a standard diet (PurinaChow) and water ad libitum. All the experimental protocolswere approved by the University Committee for the Careand Use of Laboratory Animals. The animals were deprivedof food but had free access to tap water 24 hr beforeexperimentation.

Drugs and Chemicals. The following drugs were used:1,8-cineole, nordihydroguiaretic acid (NDGA), 8-phenyl-theophylline (8-PT), and L-NAME (Sigma Chemical Co.,St. Louis, Missouri, USA); cimetidine (Tagamet, Smith-Kline), and Tween 80 (Synth). The chemicals used were allof analytical grade.

Gastric Mucosal Damage. Gastric mucosal damage wasinduced in conscious rats by intragastric instillation of 1.0ml/rat of absolute ethanol (99.5%) as previously described(22). The test drug 1,8-cineole was emulsified in Tween 80(5% in water) and administered at doses of 25, 50, 100, and200 mg/kg body weight by oral gavage 45 min before etha-nol. Nordihydroguairetic acid (75 mg/kg) was used as areference drug for comparison. Control rats received onlythe vehicle (5% Tween 80). The animals were killed 60 minafter ethanol and their stomachs removed and openedalong the greater curvature to observe the lesions macro-scopically. Lesion severity was determined by measuring thearea of lesions with a transparent grid (consisting of 1-mmsquares) placed on the glandular mucosal surface (23),which was expressed in percentage of the total area ofgladular stomach. In a few experiments, rats were simulta-neously treated with 8-phenyltheophylline (8 mg/kg, intra-peritoneally) or L-NAME (20 mg/kg) to verify a possibleinfluence of endogenous adenosine or nitric oxide (NO) on1,8-cineole effect.

Gastric Wall Mucus. The ethanol-induced changes ongastric mucus was indirectly analyzed by determining theamount of Alcian blue bound to the gastric wall (24). Theglandular segments from the stomachs of rats treated with1,8-cineole (100 and 200 mg/kg) or vehicle were collectedand weighed. Each segment was transferred to 1% Alcianblue solution (0.1 M sucrose in 0.05 M sodium acetate, pH5.8). Excess dye was removed by washing the segments with0.25 M sucrose solution. The mucus–dye complex wasextracted by placing the segments in 10 ml of 0.5 M mag-nesium chloride for 2 hr. Four milliliters of dye extract wasmixed with an equal volume of diethyl ether, centrifuged at3000 rpm for 10 min, and the absorbance of supernatentwas measured at 598 nm. The quantity of Alcian blueextracted per gram of glandular tissue was then calculated.

Gastric Secretary Studies. The pylorus of each rat wasligated under light ether anesthesia to study the basal

gastric secretion (25). Cineole (100 and 200 mg/kg) andcimetidine (60 mg/kg) were administered intraduodenallyimmediately after pylorus ligation. Control animals weregiven the vehicle instead of test drugs. The animals werekilled after 4 hr. The stomachs were removed and thevolume of gastric juice was determined after centrifugation(3000g for 10 min). Total acidity was assessed by titrationagainst 0.01 N NaOH to pH 7.0, and expressed as micro-equivalents per hour.

Gastric Mucosal Nonprotein Sulfhydryls (NP-SH). Gas-tric mucosal NP-SH was measured according to the methoddescribed earlier (26). The glandular stomachs from ratstreated with 1,8-cineole (100 and 200 mg/kg) or vehiclewere removed and homogenized in ice-cold 0.02 M ethyl-enediaminetetraacetic acid. The homogenate was mixedwith distilled water and 50% trichloroacetic acid and thencentrifuged. The supernatents were mixed with Tris buffer,5,59-dithio-bis(2-nitrobenzoic acid) (DTNB) was added,and the sample was shaken. The absorbance was read,within 5 min of addition of DTNB, at 412 nm, against areagent blank with no homogenate.

Statistical Analysis. All results were expressed as themean 6 SEM. Data were analyzed using analysis of variancefollowed by Fisher’s or Student-Newman-Keuls multiplecomparison tests. Values of P , 0.05 were taken as signif-icant.

RESULTS

Gastric Lesions. Intragastric administration of ab-solute ethanol to the control group of rats treatedwith vehicle (5% Tween 80) produced large bandlikehemorrhagic erosions in the glandular stomach. Thelesion area in control rats was 16.91 6 2.56 mm2.1,8-Cineole at oral doses of 25, 50, 100, and 200 mg/kgprevented the gastric mucosal injury by 21, 74, 90, and92%, respectively (Figure 1). NDGA at an oral doseof 75 mg/kg also prevented the mucosal damage by84%. The gastroprotective effect of 1,8-cineole (200mg/kg, per os) against ethanol injury was not signifi-cantly altered in rats treated with 8-PT (8 mg/kg,intraperitoneally) or L-NAME (20 mg/kg, intraperi-toneally) (Figure 2).

Gastric Wall Mucus and Mucosal Sulfhydryls. Thecontent of gastric mucus as measured by Alcian bluebinding was slightly, but not significantly, elevated inthe ethanol-treated animals (53.91 6 7.05 mg/g) com-pared to that in the mucosa of normal rats (31.39 65.42 mg/g) (Table 1). 1,8-Cineole at 50 mg/kg signifi-cantly enhanced the gastric mucus content (91.06 616.56 mg/g), but at higher doses it showed no signifi-cant effect. Treatment of animals with 1 ml of abso-lute ethanol significantly lowered the gastric NP-SHconcentration (187.66 6 16.46 mmol/g) by 37% com-pared to vehicle-treated rats (296.77 6 16.46 mmol/g).The group of animals treated with absolute ethanol 1

SANTOS AND RAO

332 Digestive Diseases and Sciences, Vol. 46, No. 2 (February 2001)

1,8-cineole (50, 100, and 200 mg/kg) showed lesserreductions (31, 22, and 5%, respectively) than thegroup treated with ethanol alone. In rats that receivedethanol 6 1,8-cineole (200 mg/kg), the levels ofNP-SH were almost similar to those found in vehicle-treated control.

Gastric Secretion. Figure 3 shows the effects of1,8-cineole on gastric secretory volume and total acidoutput in 4-hr pylorus-ligated rats. The gastric secre-tory volume and total acid output in rats that receivedthe vehicle were 1.80 6 0.09 ml/hr and 229.92 6 20.17meq/hr, respectively. 1,8-Cineole at 50 mg/kg caused aslight increase in the above parameters; higher doses(100 and 200 mg/kg) significantly reduced the gastricsecretory volume (41 and 52%) as well as the totalacid output (40 and 84%), respectively. Cimetidine(100 mg/kg), the reference standard used in the study,also showed significant inhibition of gastric secretoryvolume (85%) and total acid output (81%).

DISCUSSION

This study demonstrates that 1,8-cineole has a gas-troprotective property. It was found to be active, at

oral doses ranging from 50 to 200 mg/kg, in theprevention of ethanol-induced gastric damage. At 200mg/kg, its potency was almost the same as that pro-duced by NDGA (75 mg/kg), a known lipoxygenaseinhibitor (27). Studies have shown a role for leuko-triene C4 (LTC4), a lipoxygenase-derived metaboliteof arachidonic acid (28), mast cell-derived histamine(29), and oxygen-derived free radicals (30, 31) in thepathogenic mechanism of gastric injury induced byethanol. Ethanol causes constriction of submucosalvenules with subsequent stasis of blood flow in mu-cosal microcirculation as well as arteriolar dilatationand plasma leakage from the vascular bed (32–34),events that could lead to the formation of bandlikeblisters in the gastric mucosa.

1,8-Cineole was shown to inhibit arachidonic acidmetabolism and the generation of prostaglandins andleukotrienes (11, 12, 35). Our previous results (un-published) demonstrate that 1,8-cineole has the abil-ity to protect gastric mucosa against indomethacin-induced gastric ulcers also, but only at a high dose(400 mg/kg). Since 1,8-cineole prevented ethanol-induced gastric injury at relatively smaller doses (50–

Fig 1. Effects of 1,8-cineole and nordehydroguiaretic acid (NDGA) on gastric lesions induced by absolute ethanol in rats.Drugs or vehicle (control) were administered orally 1 hr before absolute ethanol (1 ml/rat). Each column denotes mean 6SEM for six rats. ***P , 0.001 compared to control.

1,8-CINEOLE AND ETHANOL-INDUCED GASTRIC DAMAGE

333Digestive Diseases and Sciences, Vol. 46, No. 2 (February 2001)

200 mg/kg), it might be a preferential inhibitor of thelipoxygenase enzyme.

The gastric mucosa possesses a high basal concen-tration of glutathione, which functions as an antioxi-dant (36). Glutathione accounts for the majority ofsoluble reduced sulfhydryl compounds (37) and eth-anol-induced gastric damage has been shown to beassociated with a significant decrease in mucosal lev-

els of sulfhydryl compounds (38). Therefore we inves-tigated whether 1,8-cineole can mitgate the ethanol-induced decreases in gastric NP-SH. The resultsobtained reveal that 1,8-cineole abrogates ethanol-induced depletion of NP-SH in a dose-related man-ner, suggesting a possible antioxidant activity.

Studies in the past have shown that adenosine, apurine metabolite, inhibits gastric acid secretion (39),

Fig 2. Effects of 8-phenyltheophylline (8-PT, 8 mg/kg, intraperitoneally) and L-NAME (20 mg/kg, intraperitoneally) treatments on1,8-cineole (200 mg/kg, per os)-induced gastroprotection against ethanol in rats. Drugs and vehicle were administered 1 hr beforeabsolute ethanol (1 ml/rat). Each column denotes 6SEM for six rats. ***P , 0.001 compared to control.

TABLE 1. EFFECT OF 1,8-CINEOLE ON ABSOLUTE ETHANOL-INDUCED CHANGESIN GASTRIC WALL MUCUS AND NONPROTEIN SULFHYDRYLS

(NP-SH) CONCENTRATION*

Treatment and dose(mg/kg)

Gastric wall mucus(mg Alcian blue/g)

Gastric NP-SH concentration(mmol/g)

Vehicle control 31.39 6 5.42 296.77 6 16.46Ethanol control 53.91 6 7.05 187.66 6 7.30†1,8-Cineole

50 91.06 6 16.56† 204.98 6 18.86†100 58.81 6 9.06 231.40 6 14.18200 50.38 6 16.87 282.81 6 21.27‡

*Values denote mean 6 SEM from six rats.†P , 0.05 vs vehicle control.‡P , 0.05 vs ethanol control.

SANTOS AND RAO

334 Digestive Diseases and Sciences, Vol. 46, No. 2 (February 2001)

increases gastric mucosal blood flow and stimulatesantioxidant enzymes (40), and protects against etha-nol-induced gastric damage in rats (41). Adenosinemay also stimulate vascular endothelium to producenitric oxide (NO) and play a role in the maintenance

of gastric mucosal integrity (42). The possibility that1,8-cineole-mediated gastroprotection is a result of itsability to release endogenous adenosine and NO wastested by treating rats with the adenosine antagonist,8-PT (8 mg/kg) and the calcium-dependent nitric

Fig 3. Effects of 1,8-cineole and cimetidine on gastric secretory volume (A) and total acid output (B) in 4-hr pylorus-ligatedrats. Drugs and vehicle (control) were administered intraduodenally, immediately after pyloric ligation. Each columndenotes the mean 6 SEM for six rats. **P , 0.01; ***P , 0.001 compared to control.

1,8-CINEOLE AND ETHANOL-INDUCED GASTRIC DAMAGE

335Digestive Diseases and Sciences, Vol. 46, No. 2 (February 2001)

oxide synthase inhibitor L-NAME (20 mg/kg), respec-tively. The results show that both these agents wereunable to modify the response of 1,8-cineole on eth-anol injury, suggesting that endogenous adenosineand NO do not participate in its gastroprotectiveeffect.

Ethanol-induced gastric mucosal injury has beenalso suggested to be due to impairments in defensivefactors such as gastric mucus and mucosal blood flow(43). When 1,8-cineole was tested on pylorus-ligatedrats, the smaller dose (50 mg/kg) produced an in-crease in gastric mucus content, gastric secretory vol-ume, and total acidity and higher doses (100 and 200mg/kg) resulted in significant inhibition of gastricsecretory volume and total acidity, suggesting itsmodulatory influence on gastric secretion. The effectof 1,8-cineole on ethanol-induced gastric injury, how-ever, seems to be independent of its effect on gastricsecretion and gastric mucus since gastroprotectionwas observed at almost all doses employed. Interest-ingly, a recent study has observed a global increase incerebral blood flow after prolonged inhalation of1,8-cineole in human subjects (44). It remains to beverified whether such an effect of 1,8-cineole couldaccount for the mitigation of ethanol-induced gastricmucosal injury through an increase in gastric mucosalblood flow.

In conclusion, these data demonstrate that 1,8-cineole offers protection against ethanol damage inthe rat at nontoxic doses. Considering that an oralLD50 of 3.5 g/kg was observed in mice (13), the dosesutilized in this study are safe and demonstrated nountoward behavioral effects in rats. However, 1,8-cineole administered to rats at doses above 600 mg/kghas been shown to be associated with decreased bodyweight gain, even more so after prolonged adminis-tration, but it showed no signs of nephrotoxicity orhepatotoxicity (4). This suggests that 1,8-cineole issafe as a gastroprotective agent and supports its use indrug formulations. It also implies that the gastropro-tection afforded by 1,8-cineole, in part, involves itsantioxidant action, preventing ethanol-induced deple-tion of NP-SH, and also, partly due to lipoxygenaseinhibition, blocking leukotrienes formation. However,further studies are needed to clarify the exact mech-anism of gastroprotective effect of 1,8-cineole.

ACKNOWLEDGEMENTS

This work was supported by grants from Conselho Na-cional de Desenvolvimento Cientıfico e Tecnologico(CNPq), Coordenacao de Aperfeicoamento de Pessoal de

Ensino Superior (CAPES) and Financiadora de Estudos eProjetos (FINEP) of Brasil.

REFERENCES

1. Kovar KA, Gropper B, Friess D, Ammon APT: Blood levels of1,8-cineole and locomotor activity of mice after inhalation andoral administration of rosemary oil. Planta Med 53:315–318,1987

2. Andrade-Neto M, Alencar JW, Cunha AH, Silveira ER: Vol-atile constituents of Psidium pohlianum Berg. and Psidiumguyanensis Pers. J Essen Oil Res 6:299–300, 1994

3. Gobel H, Schmidt G, Dworschak M Heiiss D: Essential plantoils and headache mechanisms. Phytomedicine 2:93–102, 1995

4. De Vincenzi M, Mancini E, Dessi MR: Monographs on botan-ical flavouring substances used in foods. Part V. Fitoterapia67:241–251, 1996

5. al-Sereiti MR, Abu-Amer KM, Sen P: Pharmacology of rose-mary (Rosmarinus officinales Linn.) and its therapeutic poten-tials. Indian J Exp Biol 37:124–130, 1999

6. Pattnaick S, Subramanyam VR, Bapaji M, Kole CR: Antibac-terial and antifungal activity of aromatic constituents of essen-tial oils. Microbios 89:39–46, 1997

7. Macht D: The absorption of drugs and poisons through theskin and mucous membranes. J Am Med Assoc 110:409–414,1938

8. Williams AC, Barry BW: Terpenes and the lipid-protein-partitioning theory of skin penetration enhancement. PharmRes 8:17–24, 1991

9. Laude EA, Morice AH, Grattan TJ: The antitussive effects ofmenthol, camphor and cineole in conscious guinea-pigs. PulmPharmacol 7:179–184, 1994

10. Levison KK, Takayama K, Okabe K, Nagai T: Formulationoptimization of indomethacin gels containing a combination ofthree kinds of cyclic monoterpenes as percutaneous penetra-tion enhancers. J Pharm Pharmacol 83:1367–1372, 1994

11. Juergens UR, Stober M, Vetter H: Inhibition of cytokineproduction and arachidonic acid metabolism by eucalyptol(1,8-cineole) in human blood monocytes in vitro. Eur J MedRes 17:508–510, 1998

12. Juergens UR, Stober M, Schmidt-Schilling L, Kleuver T, Vet-ter H: Anti-inflammatory effects of eucalyptol (1,8-cineole) inbronchial asthma: inhibition of arachidonic acid metabolism inhuman blood monocytes ex vivo. Eur J Med Res 17:407–412,1998

13. Santos FA, Rao VSN: Anti-inflammatory and antinociceptiveeffects of 1,8-cineole, a terpenoid oxide present in many plantessential oils. Phytother Res 13:1–5, 2000

14. Szabo S, Trier JS, Brown A, Schnoor J: Early vascular injuryand increased vascularpermeability in gastric mucosal injurycaused by ethanol in the rat. Gastroenterology 88:228–236,1985

15. Alarcon de la Lastra C, Lopez A, Motilva V: Gastroprotectionand prostaglandin E2 generation in rats by flavonoids of Dit-trichia viscosa. Planta Med 59:497–501, 1993

16. Tambe Y, Tsujiuchi H, Honda G, Ikeshiro Y, Tanaka S:Gastric cytoprotection of the non-steroidal anti-inflammatorysesquiterpene, b-caryophyllene. Planta Med 62:469–470, 1996

17. Ares JJ, Outt PE: Gastroprotective agents for the preventionof NSAID-induced gastropathy. Curr Pharm Des 4:17–36, 1998

18. Lonchampt M, Guardiola B, Sicot N, Bertrand M, Perdrix I,Duhault J: Protective effect of a purified fraction against reac-

SANTOS AND RAO

336 Digestive Diseases and Sciences, Vol. 46, No. 2 (February 2001)

tive oxygen radicals. In vivo and in vitro study. Arzneim Forsch39:882–885, 1989

19. Bozkurt A, Yuksel M, Haklar G, Kurtel H, Yegen BC, AlicanI: Adenosine protects against indomethacin-induced gastricdamage in rats. Dig Dis Sci 43:1258–1263, 1998

20. Valcavi U, Caponl K, Brambilla A, Palmira F, Monoja F,Bernini F, Mustani R, Fumagall R: Gastric antisecretory, an-tiulcer and cytoprotectiveproperties of 9-hydroxy. 19,20-bis-nor-prostanoic acid in experimental animals. Arzneim Forsch32:657–663

21. Wallace JL, Bak A, McKnight W, Asfaha S, Sharkey KA,MacNaughton WK: Cyclooxygenase 1 contributes to inflam-matory responses in rats and mice: Implications for gastroin-testinal toxicity. Gastroenterology 15:101–109, 1998

22. Robert A: Cytoprotection by prostaglandins. Gastroenterology77:761–767, 1979

23. Robert A, Nezamis JE, Lancaster C: Mild irritants preventgastric mucosa through adaptive cytoprotection mediated byprostaglandins. Am J Physiol 245:G113–G121, 1983

24. Come SJ, Morrisey SM, Woods KJ: A method for the quanti-tative estimation of gastric barrier mucus. J Physiol 242:116–117, 1974

25. Shay H, Sun DCY, Gruenstein R: A quantitative method formeasuring spontaneous gastric secretion in the rat. Gastroen-terology 26:906–913, 1954

26. Sedlak J, Lindsay RH: Estimation of total, protein bound, andnonprotein sulfhydryl groups in tissue with Ellman’s reagent.Anal Biochem 25:192–205, 1968

27. Peskar BM, Lange K, Hoppe U, Peskar BA: Ethanol stimulatesformation of leukotriene C4 in rat gastric mucosa. Prostaglan-dins 31:283–293, 1986

28. Konturek SJ, Brzozowski T, Drozdowicz D, Beck G: Role ofleukotrienes in acute gastric lesions induced by ethanol, tau-rocholate, aspirin, platelet-activating factor and stress in rats.Dig Dis Sci 33:806–813, 1988

29. Szabo S, Trier JS, Brown A, Schnoor J: Early vascular injuryand increased vascular permeability in gastric mucosal injurycaused by ethanol in the rat. Gastroenterology 88:228–236,1985

30. Szelenyi I, Brune K: Possible role of oxygen free radicals inethanol-induced gastric mucosal damage in rats. Dig Dis Sci33:865–871, 1988

31. Salim AS: Removing oxygen-derived free radicals stimulatehealing of ethanol-induced erosive gastritis in the rat. Diges-tion 47:24–28, 1990

32. Oates PJ, Hakkinen JP: Studies on the mechanism of ethanol-induced gastric damage in rats. Gastroenterology 94:10–21,1988

33. Sato N, Kawano S, Tsuji S, Ogihara T, Yamada S: Gastricblood flow in ulcer diseases. Scand J Gastroenterol 30 (suppl208):14–20, 1995

34. Bou-Abboud CF, Wayland H, Paulsen G, Guth PH: Microcir-culatory stasis precedes tissue necrosis in ethanol-induced gas-tric mucosal injury in the rat. Dig Dis Sci 33:872–877, 1988

35. Beuscher N, Kietzmann M, Bien E, Champeroux P: Interfer-ence of myrtol standardized with inflammatory and allergicmediators Arzneim Forsch 48:985–989, 1998

36. Mutoh H, Hiraishi H, Ota S, Yoshida H, Ivey KJ, Terano A,Sugimoto T: Protective role of intracellular glutathione againstethanol-induced damage in cultured rat gastric mucosal cells.Gastroenterology 98:1452–1460, 1990

37. Robert A, Eberle D, Kaplowitz N: Role of glutathione ingastric mucosal cytoprotection. Am J Physiol 247:G296–G304,1984

38. Szabo S, Trier JS, Frankel PW: Sulfyhdryl compounds maymediate gastric cytoprotection. Science 214:200–202, 1981

39. Puurunen J, Huttunen P: Central gastric antisecretory action ofadenosine in the rat. Eur J Pharmacol 147:59–66, 1988

40. Ramkumar V, Nie Z, Rybak LP, Maggirwar SB: Adenosine,antioxidant enzymes and cytoprotection. TiPS 16:283–285,1995

41. Cho CH, Ogle CW: Modulatory action of adenosine on gastricfunction and ethanol-induced mucosal damage in rats. Dig DisSci 35:1334–1339, 1990

42. Whittle BJR: Nitric oxide in the gastrointestinal physiology andpathology. In Physiology of the Gastrointestinal Tract. LRJohnson (ed) New York, Raven Press, 1994, p 267

43. Kuwata H, Ishihara K, Kakei M, Ohara S, Okabe H, Hotta K:Correlation of quantitative changes of gastric mucosal glycop-roteins with ethanol-induced gastric damage in rats. NipponShokakibyo Gakkai Zasshi 82:28–33, 1985

44. Nasel C, Nasel B, Samec P, Schindler E, Buchbauer G: Func-tional imaging of effects of fragrances on the human brain afterprolonged inhalation. Chem Senses 19:359–364, 1994

1,8-CINEOLE AND ETHANOL-INDUCED GASTRIC DAMAGE

337Digestive Diseases and Sciences, Vol. 46, No. 2 (February 2001)