title: High body clearance and low oral bioavailability of alantolactone, isolated from Inula helenium, in rats: extensive hepatic metabolism and low stability in gastrointestinal fluids.
abstract: Alantolactone (ALA) is a major bioactive sesquiterpene lactone present in the roots of Inula helenium L. (Asteraceae) which has been used widely in traditional medicine against various diseases such as asthma, cancer and tuberculosis. The pharmacologic activities of alantolactone have been well characterized, yet information on the physicochemical and pharmacokinetic properties of alantolactone and their mechanistic elucidation are still limited. Thus, this study aims to investigate the oral absorption and disposition of alantolactone and their relevant mechanisms. Log P values of alantolactone ranged from 1.52 to 1.84, and alantolactone was unstable in biological samples such as plasma, urine, bile, rat liver microsomes (RLM) and simulated gastrointestinal fluids. The metabolic rate of alantolactone was markedly higher in rat liver homogenates than in the other tissue homogenates. A saturable and concentration-dependent metabolic rate profile of alantolactone was observed in RLM, and rat cytochrome P450 (CYP) 1 A, 2C, 2D and 3 A subfamilies were significantly involved in its hepatic metabolism. Based on the well-stirred model, the hepatic extraction ratio (HER) was estimated to be 0.890-0.933, classifying alantolactone as a drug with high HER. Moreover, high total body clearance (111 ± 41 ml/min/kg) and low oral bioavailability (0.323%) of alantolactone were observed in rats. Taken together, the present study demonstrates that the extensive hepatic metabolism, at least partially mediated by CYP, is primarily responsible for the high total body clearance of alantolactone, and that the low oral bioavailability of alantolactone could be attributed to its low stability in gastrointestinal fluids and a hepatic first-pass effect in rats. Copyright © 2016 John Wiley & Sons, Ltd.
authors: College of Pharmacy and Research Institute of Pharmaceutical Sciences, Seoul National University, Seoul, Republic of Korea.
authors: Jae-Young
authors: JY
authors: Lee
authors: College of Pharmacy and Research Institute of Pharmaceutical Sciences, Seoul National University, Seoul, Republic of Korea.
authors: Sang-Bum
authors: SB
authors: Kim
authors: Natural Products Research Institute, College of Pharmacy, Seoul National University, Seoul, Republic of Korea.
authors: Jaemoo
authors: J
authors: Chun
authors: Natural Products Research Institute, College of Pharmacy, Seoul National University, Seoul, Republic of Korea.
authors: Kwang Ho
authors: KH
authors: Song
authors: Natural Products Research Institute, College of Pharmacy, Seoul National University, Seoul, Republic of Korea.
authors: Yeong Shik
authors: YS
authors: Kim
authors: College of Pharmacy and Research Institute of Pharmaceutical Sciences, Seoul National University, Seoul, Republic of Korea.
authors: Suk-Jae
authors: SJ
authors: Chung
authors: College of Pharmacy, Kangwon National University, Gangwon, Republic of Korea.
authors: Hyun-Jong
authors: HJ
authors: Cho
authors: College of Pharmacy and Natural Medicine Research Institute, Mokpo National University, Jeonnam, Republic of Korea.
authors: In-Soo
authors: IS
authors: Yoon
authors: College of Pharmacy and Research Institute of Pharmaceutical Sciences, Seoul National University, Seoul, Republic of Korea.
authors: Dae-Duk
authors: DD
authors: Kim
mesh_terms: D020003:1-Octanol / Q000737:chemistry; D061605:Administration, Intravenous; D000284:Administration, Oral; D000818:Animals; D001682:Biological Availability; D001921:Brain / Q000378:metabolism; D005750:Gastric Juice / Q000737:chemistry; D007413:Intestinal Mucosa / Q000378:metabolism; D007419:Intestinal Secretions / Q000737:chemistry; D038143:Inula; D007668:Kidney / Q000378:metabolism; D007783:Lactones / Q000008:administration & dosage / Q000097:blood / Q000737:chemistry / Q000493:pharmacokinetics*; D008099:Liver / Q000378:metabolism; D008168:Lung / Q000378:metabolism; D008297:Male; D008862:Microsomes, Liver / Q000378:metabolism; D009132:Muscles / Q000378:metabolism; D009206:Myocardium / Q000378:metabolism; D018517:Plant Roots; D017207:Rats, Sprague-Dawley; D045787:Sesquiterpenes, Eudesmane / Q000008:administration & dosage / Q000097:blood / Q000737:chemistry / Q000493:pharmacokinetics*; D013154:Spleen / Q000378:metabolism; D014867:Water / Q000737:chemistry
chemical_list: D007783:Lactones; D045787:Sesquiterpenes, Eudesmane; D014867:Water; C004363:alantolactone; D020003:1-Octanol
keywords: Alantolactone; GI stability; cytochrome P450; hepatic metabolism; oral bioavailability