title: Structural analysis of isosteviol and related compounds as DNA polymerase and DNA topoisomerase inhibitors.
abstract: Isosteviol (ent-16-ketobeyeran-19-oic acid) is a hydrolysis product of stevioside, which is a natural sweetener produced in the leaves of Stevia rebaudiana (Bertoni) Bertoni. In this report, we prepared isosteviol and related compounds from stevioside by microbial transformation and chemical conversion and assayed the inhibitory activities toward DNA metabolic enzymes and human cancer cell growth. Among twelve compounds obtained, only isosteviol (compound 3) potently inhibited both mammalian DNA polymerases (pols) and human DNA topoisomerase II (topo II), and IC50 value for pol alpha was 64.0 microM. This compound had no inhibitory effect on higher plant (cauliflower) pols, prokaryotic pols, human topo I, and DNA metabolic enzymes such as human telomerase, T7 RNA polymerase, and bovine deoxyribonuclease I. With pol alpha, isosteviol acted non-competitively with the DNA template-primer and nucleotide substrate. Isosteviol prevented the growth of human cancer cells, with LD50 values of 84-167 microM, and 500 microg of the compound caused a marked reduction in TPA (12-O-tetradecanoylphorbol-13-acetate)-induced inflammation (inhibitory effect, 53.0%). The relationship between the structure of stevioside-based compounds and these activities were discussed.
authors.affiliation: Laboratory of Food and Nutritional Sciences, Department of Nutritional Science, Kobe-Gakuin University, Nishi-ku, Kobe, Hyogo 651-2180, Japan. mizushin@nutr.kobegakuin.ac.jp
authors.forename: Yoshiyuki
authors.initials: Y
authors.lastname: Mizushina
authors.forename: Toshihiro
authors.initials: T
authors.lastname: Akihisa
authors.forename: Motohiko
authors.initials: M
authors.lastname: Ukiya
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Hamasaki
authors.forename: Chikako
authors.initials: C
authors.lastname: Murakami-Nakai
authors.forename: Isoko
authors.initials: I
authors.lastname: Kuriyama
authors.forename: Toshifumi
authors.initials: T
authors.lastname: Takeuchi
authors.forename: Fumio
authors.initials: F
authors.lastname: Sugawara
authors.forename: Hiromi
authors.initials: H
authors.lastname: Yoshida
mesh_terms: D000818:Animals; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000737:chemistry / Q000494:pharmacology*; D000972:Antineoplastic Agents, Phytogenic / Q000737:chemistry / Q000494:pharmacology*; D001937:Brassica / Q000201:enzymology; D002417:Cattle; D002470:Cell Survival / Q000187:drug effects; D045786:Diterpenes, Kaurane / Q000737:chemistry / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000737:chemistry / Q000494:pharmacology*; D006801:Humans; D007700:Kinetics; D051379:Mice; D019384:Nucleic Acid Synthesis Inhibitors; D051381:Rats; D013329:Structure-Activity Relationship; D013950:Thymus Gland / Q000201:enzymology; D059004:Topoisomerase I Inhibitors; D059005:Topoisomerase II Inhibitors; D059003:Topoisomerase Inhibitors
chemical_list: D000894:Anti-Inflammatory Agents, Non-Steroidal; D000972:Antineoplastic Agents, Phytogenic; D045786:Diterpenes, Kaurane; D004791:Enzyme Inhibitors; D019384:Nucleic Acid Synthesis Inhibitors; D059004:Topoisomerase I Inhibitors; D059005:Topoisomerase II Inhibitors; D059003:Topoisomerase Inhibitors; C012042:steviol