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. Chengdu Institute of Biology Prof. ZHANG Guolin’s team present study aims to investigate the osteogenic compounds in TSZ, and to evaluate their antiosteoporotic effects in osteoblastic cells.
In this research, 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. While 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 (ER alpha or ER beta) expression vectors and 5 x ERE luciferase reporter plasmid.
Additionally, 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 (ER alpha or ER beta) expression vectors and 6 x AP-1 luciferase reporter plasmid.
Subsequently, 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 ERP agonist activity.
However, compared with their ER agonist activity, only quercetin and kaempferol showed potent ER antagonist activity by activating ER alpha/beta-mediated AP-1 reporter expression. CIB researchers 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.
ZHANG’s research were supported by Chinese Academy of Sciences, West Light Foundation and National Natural Science Foundation of China. More results have been published in JOURNAL OF ETHNOPHARMACOLOGY in May 2011.
