title: Antiosteoporotic compounds from seeds of Cuscuta chinensis.
abstract: BACKGROUND
  The seeds of Cuscuta chinensis (Tu-Si-Zi, TSZ) have long been used for the treatment of osteoporosis in China and some Asian countries. The compounds in TSZ responsible for the antiosteoporotic activity are still poorly understood.
  
  
  OBJECTIVE
  The present study was designed to investigate the osteogenic compounds in TSZ, and to evaluate their antiosteoporotic effects in osteoblastic cells.
  
  
  METHODS
  Osteoblast-like UMR-106 cells were used for bioactivity-guided isolation of the active compounds. The activity of alkaline phosphatase (ALP) in UMR-106 cells was measured by p-nitrophenyl sodium phosphate assay. The proliferation of UMR-106 cells was assayed by Alamar-Blue method. Estrogenic activity of the extracts and isolated compounds was evaluated by activation of estrogen response element (ERE) luciferase reporter expression in HeLa cells co-transfected with human estrogen receptor subtypes (ERα or ERβ) expression vectors and 5×ERE luciferase reporter plasmid. Antiestrogenic activity of the extracts and isolated compounds were evaluated by activation of activator protein-1 (AP-1) luciferase reporter expression in HeLa cells co-transfected with human estrogen receptor subtypes (ERα or ERβ) expression vectors and 6×AP-1 luciferase reporter plasmid.
  
  
  RESULTS
  ALP-guided fractionation led to the isolation of five known flavonoids, quercetin, kaempferol, isorhamnetin, hyperoside and astragalin from the crude ethanolic extract of TSZ. Further study showed that kaempferol and hyperoside significantly increased the ALP activity in UMR-106 cells. Astragalin promoted the proliferation of UMR-106 cells whereas other compounds had no such effect. The isolated compounds showed estrogenic activity but quercetin, kaempferol and isorhamnetin showed more potent ERβ agonist activity. However, compared with their ER agonist activity, only quercetin and kaempferol showed potent ER antagonist activity by activating ERα/β-mediated AP-1 reporter expression.
  
  
  CONCLUSIONS
  Our findings validated the clinical use of TSZ in the treatment of osteoporosis, and demonstrated that kaempferol and hyperoside are the active compounds in TSZ for the osteogenic effect.
authors.affiliation: Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu 610041, China.
authors.forename: Lijuan
authors.initials: L
authors.lastname: Yang
authors.forename: Qianfeng
authors.initials: Q
authors.lastname: Chen
authors.forename: Fei
authors.initials: F
authors.lastname: Wang
authors.forename: Guolin
authors.initials: G
authors.lastname: Zhang
mesh_terms: D002460:Cell Line; D049109:Cell Proliferation / Q000187:drug effects; D034182:Cuscuta / Q000196:embryology*; D006801:Humans; D010006:Osteoblasts / Q000166:cytology / Q000187:drug effects; D010024:Osteoporosis / Q000188:drug therapy*; D010936:Plant Extracts / Q000494:pharmacology / Q000627:therapeutic use*; D012639:Seeds / Q000737:chemistry*
chemical_list: D010936:Plant Extracts