Prevention of Acetaminophen-induced Hepatotoxicity by Ternatin, A Bioflavonoid from Egletes viscosa Less M. F. Souza, 1 V. S. N. Rao 1 * and E. R. Silveira 2 1 Departmento de Fisiologia e Farmacologia, Universidade Federal do Ceara ´, C. P. 3157, 60 430 - 270 Fortaleza, Ce, Brazil 2 Departamento de Quimica Orga ˆnica, e Inorga ˆnica, Universidade Federal do Ceara ´, Fortaleza, Ce, Brazil The hepatoprotective effect of ternatin, a tetramethoxyflavone from Egletes viscosa L. was investigated in mice against acetaminophen-induced hepatic damage and lethality. Hepatotoxicity was assessed by quan- tifying serum activities of alanine aminotransferase (ALT), aspartate aminotransferase (AST), lactic de- hydrogenase (LD) and malondialdehyde (MDA) concentration in liver homogenates as well as by histopathological examination of liver tissue. Acetaminophen (300 mg/kg) produced liver damage in mice as manifested by a 29-, 23- and 7-fold rise in serum levels of ALT, AST and LD, respectively, compared with controls. Ternatin (25 and 50 mg/kg) was able to prevent significantly (p < 0.05) acetaminophen-in- duced acute increase in serum enzymes. In addition, the severity of histological alterations induced by acetaminophen as evidenced by centrilobular necrosis and cellular infiltration were greatly diminished in animals that received ternatin. The data suggest a hepatoprotective activity of ternatin in mice against toxicity induced by acetaminophen. # 1998 John Wiley & Sons, Ltd. Phytother. Res. 12, 557–561 (1998) Keywords: Egletes viscosa; tetramethoxyflavone; hepatoprotection; acetaminophen toxicity; serum enzymes. INTRODUCTION Many plant flavonoids are claimed to have hepatopro- tective properties (Siegers and Younes, 1981; Cholbi et al., 1991; Galvez et al., 1995; Ubeda et al., 1995). Their protective effects have been related to free radical scavenging and interference with cytochrome P-450 activity (Bors and Saran, 1987; Ubeda et al., 1995). Previous studies from this laboratory have shown that ternatin (4 1 ,5-dihydroxy-3,3 1 ,7,8 tetramethoxyflavone), a flavonoid isolated from the flowering tops of Egletes viscosa Less. exerts antiinflammatory, antianaphylactic, antithrombotic and antihepatotoxic properties (Souza et al., 1992, 1994; Rao et al., 1994). Recently, an antiperoxidative action of ternatin has also been de- scribed (Souza et al., 1997). Acetaminophen (N-acetyl-p-aminophenol, Paraceta- mol), a widely used analgesic and antipyretic drug is known to cause hepatotoxicity in experimental animals and humans (Prescott et al., 1971; Mitchell, 1988; Kumar and Rex, 1991; Eriksson et al., 1992; Thompsen et al., 1995). It is established that following an oral therapeutic dose, a fraction of acetaminophen is converted via the cytochrome P-450 pathway to a highly toxic metabolite, N-acetyl-p-benzoquinoneimine (NAPQI) (Dahlin et al., 1984) which is normally conjugated with glutathione and excreted in the urine as conjugates. Overdoses of acetaminophen deplete glutathione stores, leading to accumulation of NAPQI, mitochondrial dysfunction (Parmar et al., 1995), and the development of acute hepatic necrosis (Janes and Routledge, 1992). Also depletion of glutathione enhances the expression of tumour necrosis factor alpha (TNFa) (Agarwal and Piesco, 1994). TNFa primes phagocytic NADPH oxidase to the enhanced production of oxygen free radicals and contributes to liver damage (Gupta et al., 1992). Since hepatotoxicity caused by acetaminophen involves cyto- chrome P-450-mediated reactions, we have investigated in the present study the possible protective action of ternatin in a mouse model of hepatitis induced by acetaminophen. MATERIALS AND METHODS Chemical. Acetaminophen (Aldrich Chemical Co., Milwaukee, USA), thiobarbituric acid (Sigma Chemical Co., St. Louis, Mo., USA) and Vitamin E (Ephymal 1 , Roche, Brazil) were purchased from the sources indicated. All other chemicals were of analytical grade. Ternatin was isolated from dried flower buds of E. viscosa L. as per procedures and methods described previously (Lima et al., 1996). PHYTOTHERAPY RESEARCH, VOL. 12, 557–561 (1998) CCC 0951–418X/98/080557–05 $17.50 # 1998 John Wiley & Sons, Ltd. * Correspondence to: V. S. N. Rao, Departamento de Fisiologia e Farmacologia, Universidade Federal do Ceara ´, Rua Cel Nunes de Melo, 1127, Porangabussu, C.P.3157, 60430-270 Fortaleza, CE, Brazil.. Contract/grant sponsor: CNP q , Brazil. Contract/grant sponsor: FINEP, Brazil. Contract/grant sponsor: CAPES, Brazil. Received 16 December 1997 Revised 15 April 1998 Accepted 5 June 1998