title: Bioassay-guided isolation and identification of cytotoxic compounds from Bolbostemma paniculatum.
abstract: BACKGROUND
  Bolbostemma paniculatum (Maxim.) Franquet (B. paniculatum), also named "Tu-bei-mu" in Chinese folk medicines, has been described in application for the treatment of tumors, warts, inflammation and toxication in traditional Chinese medicinal books. The major constituents in B. paniculatum are triterpenoid saponins, which have been proved to possess dramatically cytotoxic activity and antivirus activity. The aim of this study is to isolate and identify the active triterpenoid saponin from the bulb of B. paniculatum by a bioassay-guided method.
  
  
  METHODS
  Four cucurbitacine triterpenoid sapogenins and 11 triterpenoid saponins were isolated from the active EtOAc and n-BuOH extract of B. paniculatum by using bioassay-guided screening. Their structures were elucidated based on the spectroscopic methods and compared with published data. Cytotoxic activities of isolated compounds were determined by MTT assay.
  
  
  RESULTS
  Four cucurbitacine triterpenoid sapogenins, isocucurbitacin B(1), 23,24-dihydroisocucurbitacin B(2), cucurbitacin E(3), 23,24-dihydrocucurbitacin E(4), and 11 triterpenoid saponins, tubeimosideI(5), tubeimoside III(6), tubeimoside V(7), dexylosyltubeimoside III(8), lobatoside C(9), tubeimoside A(10), tumeimoside B(11), lobatoside A(12), tubeimoside C(13), tubeimoside IV(14), 7β,18,20,26-tetrahydroxy-(20S)-dammar-24E-en-3-O-α-L-(4-acetyl)arabinopyranosyl-(1→2)-β-D-glucopyranoside(15) were isolated from the active EtOAc and n-BuOH extracts. Of them, compounds 2, 4, 9 and 12 were firstly isolated from the Bolbostemma genus. MTT assay revealed that compounds 1, 3 and 4 had significantly activities against HeLa and HT-29 human cancer cells with IC50 values ranging from 0.93 to 9.73μM. It is worth mentioning that compound 4׳s activities against the two cell lines are 12- and 8-fold that of the positive control drug (5-Fu). Whereas, the cyclic bisdesmosides 5-9 exerted significantly activities on BGC-823, HeLa, HT-29 and MCF-7 cancer cells with IC50 values ranging from 1.30 to 15.64μM. And 6׳s activities against the four cell lines are 6-, 3-, 10- and 16-fold that of 5-Fu and 8׳s activities against the four cell lines are 5-, 3-, 14- and 9-fold that of 5-Fu.
  
  
  CONCLUSIONS
  The cytotoxic activity of the bulbs of B. paniculatum is mainly ascribable to cucurbitacine triterpenoid sapogenins (1-4) and the cyclic bisdesmosides (5-9). The cyclic bisdesmosides are the main anti-cancer active compounds of B. paniculatum. The above results provide scientific evidence to support, to some extent, the ethnomedicinal use of B. paniculatum as anticancer remedies in traditional Chinese medicine.
authors.affiliation: Key Laboratory of Natural Active Pharmaceutical Constituents of Jiangxi Province, Yichun University, Yichun 336000, PR China; School of Traditional Chinese Materia Medica, Shenyang Pharmaceutical University, Shenyang 110016, PR China.
authors.forename: Yun
authors.initials: Y
authors.lastname: Tang
authors.affiliation: Key Laboratory of Natural Active Pharmaceutical Constituents of Jiangxi Province, Yichun University, Yichun 336000, PR China.
authors.forename: Wei
authors.initials: W
authors.lastname: Li
authors.affiliation: School of Traditional Chinese Materia Medica, Shenyang Pharmaceutical University, Shenyang 110016, PR China; Key Laboratory of Structure-Based Drug Design & Discovery (Shenyang Pharmaceutical University), Ministry of Education, Shenyang 110016, PR China.
authors.forename: Jiaqing
authors.initials: J
authors.lastname: Cao
authors.affiliation: School of Traditional Chinese Materia Medica, Shenyang Pharmaceutical University, Shenyang 110016, PR China; Key Laboratory of Structure-Based Drug Design & Discovery (Shenyang Pharmaceutical University), Ministry of Education, Shenyang 110016, PR China.
authors.forename: Wei
authors.initials: W
authors.lastname: Li
authors.affiliation: School of Traditional Chinese Materia Medica, Shenyang Pharmaceutical University, Shenyang 110016, PR China; Key Laboratory of Structure-Based Drug Design & Discovery (Shenyang Pharmaceutical University), Ministry of Education, Shenyang 110016, PR China. Electronic address: zyq4885@126.com.
authors.forename: Yuqing
authors.initials: Y
authors.lastname: Zhao
mesh_terms: D001681:Biological Assay / Q000379:methods; D019662:Cucurbitaceae; D003603:Cytotoxins / Q000737:chemistry* / Q000302:isolation & purification*; D004365:Drugs, Chinese Herbal / Q000737:chemistry* / Q000302:isolation & purification*; D019073:HT29 Cells; D006367:HeLa Cells; D006801:Humans; D061986:MCF-7 Cells; D018517:Plant Roots
chemical_list: D003603:Cytotoxins; D004365:Drugs, Chinese Herbal
keywords: Bolbostemma paniculatum; Cyclic bisdesmosides; Cytotoxicity; Triterpenoid; Tubeimoside