Lignans from the Bark of Machilus thunbergii and Their DNA Topoisomerases I and II Inhibition and Cytotoxicity

Abstract

DNA topoisomerases are enzymes involved in the relaxation of DNA during a number of critical cellular processes, including replication, recombination and transcription by transiently breaking one or two strands of DNA, passing a single-or double-stranded DNA through the break, and finally resealing the breaking.1-3) Currently, only a camptothecin (CPT) family of compounds as DNA topoisomerase I-directed drugs has been introduced into the clinic to date, 4,5) though many topoisomerase II-directed drugs have been in clinical use for many years.6) DNA topoisomerases have been established as important molecular targets for anticancer drugs.7) During our search for new DNA topoisomerase inhibitors from natural products by activity-guided fractionation, several solvent extracts of more than 100 Korean folk medicines were screened for their DNA topoisomerase I inhibitory activities. Among them, the CH 2 Cl 2 extract of the bark of M. thunbergii showed strong DNA topoisomerase I inhibitory activity (94.1% inhibition at 25 mg/ml), and was subjected to the isolation of compounds with DNA topoisomerase inhibitory activity from the CH 2 Cl 2 extract of the bark of M. thunbergii.The bark of M. thunbergii has been used as a folk medicine for the treatment of leg oedema, abdominal pain and abdominal distension in Korea. 11,19) and inhibitory activity on nitric oxide synthesis in activated macrophages. 16) In this study, we isolated ten lignans from the bark of the M. thunbergii, and investigated their DNA topoisomerases I and II inhibitory effects and cytotoxicity. MATERIALS AND METHODS General ProceduresOptical rotations were measured using a JASCO DIP-1000 (Tokyo, Japan) automatic digital polarimeter. The NMR spectra were recorded on a Bruker 250 MHz (DMX 250) spectrometer using Bruker's standard pulse program. Samples were dissolved in CDCl 3 -d 1 or CD 3 OD-d 4 , and chemical shifts were reported in ppm downfield from TMS. FAB-MS spectra were measured with a VG TRIO 2A mass spectrometer. Stationary phases for column chromatography (Silica gel 60, 70-230 and 270-400 mesh and Lichroprep RP-18 gel, 40-63 mm, Merck) and TLC plates (Silica-gel 60 F 254 and RP-18 F 254 , Merck) were purchased from Merck KGaA (Darmstadt, Germany). Spots were detected under UV radiation and by spraying with 10% H 2 SO 4 , followed by heating. The camptothecin (CPT) and etoposide were purchased from Sigma Chemical Co. (St. Louis, MO, U.S.A.). Supercoiled pBR 322 plasmid DNA and calf thymus topoisomerase I were purchased from MBI Fermentas, Inc. (Hanover, MD, U.S.A.). The human topoisomerase II was purchased from TopoGEN, Inc. (Columbus, OH, U.S.A.). All other chemicals and solvents were of analytical grade, and used without further purification.Plant Material The bark of M. thunbergii was purchased in September 1999 from a folk medicine market, "Yak-ryong-si" in Daegu, Republic of Korea. These materials were confirmed taxonomically by Professor Gi-Hwan Bae, of Chungnam National University, Taejeon, Republic of Korea. A voucher specimen has been de...

Acalypha wilkesiana extracts induce apoptosis by causing single strand and double strand DNA breaks

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Chemical diversity and pharmacological significance of the secondary metabolites of nutmeg (Myristica fragrans Houtt.)

“…The observed bone anabolic activity occurred in a dose-dependent manner. Other activities for machilin A include inhibition of proliferation of blood lymphocytes, human leukemia HL-60 cells, and topoisomerase I and II inhibition, suggesting potential anticancer properties (Hirano et al 1991, Hirano et al 1994, Li et al 2004). Follow-up studies and proper clinical evaluation of these properties remain uninvestigated.…”

Meso-dihydroguaiaretic acid isolated from Saururus chinensis inhibits cyclooxygenase-2 and 5-lipoxygenase in mouse bone marrow-derived mast cells

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