Coumestrol as well as isoflavones in soybean extract prevent bone resorption in ovariectomized rats.
OBJECTIVE
Soybeans contain an abundance of phytoestrogens such as genistein and daidzein, and these compounds are thought to protect against bone loss under estrogen deficient conditions. It is possible, however, that phytoestrogens other than isoflavones may suppress bone resorption. The objective of the present study was to determine whether there are any phytoestrogens other than isoflavones in soybeans that can act as antiosteoporotic agents.


METHODS
The isoflavones genistein and daidzein, and an extract of soybeans that contained very low levels of isoflavones were tested for their ability to reduce bone resorption in ovariectomized rats. The extract of soybeans was further analyzed for its main components by thin layer chromatography and gas chromatography-mass spectrometry.


RESULTS
The soybean extract, as well as the two isoflavones, were effective to reduce urinary excretion of deoxypyridinoline and pyridinoline, typical markers of bone resorption in ovariectomized rats. However the extract, unlike the isoflavones, increased the uterine weight of ovariectomized rats significantly. Analysis by thin-layer and gas chromatography revealed that the main constituent of this extract exhibited a chromatographic profile corresponding to coumestrol. This substance was positively identified as coumestrol by gas chromatography-mass spectrometry.


CONCLUSIONS
These results suggest that the phytoestrogens including coumestrol and isoflavones in soybeans may exert effective prevention against bone resorption in estrogen deficient conditions.
Department of Biochemistry, Dokkyo University School of Medicine, Mibu, 321-0293 Tochigi, Japan.
She-Fang
SF
Ye
I
I
Saga
K
K
Ichimura
T
T
Nagai
M
M
Shinoda
S
S
Matsuzaki
D000596:Amino Acids / Q000652:urine; D000818:Animals; D001862:Bone Resorption / Q000378:metabolism / Q000517:prevention & control*; D002784:Cholesterol / Q000097:blood; D002855:Chromatography, Thin Layer; D003375:Coumestrol / Q000737:chemistry / Q000494:pharmacology*; D004997:Ethinyl Estradiol / Q000494:pharmacology; D005260:Female; D008401:Gas Chromatography-Mass Spectrometry; D019833:Genistein / Q000494:pharmacology; D007529:Isoflavones / Q000494:pharmacology; D009929:Organ Size; D015675:Osteocalcin / Q000097:blood; D010052:Ovariectomy; D011897:Random Allocation; D051381:Rats; D017208:Rats, Wistar; D013025:Glycine max / Q000737:chemistry*; D014599:Uterus / Q000378:metabolism
D000596:Amino Acids; D007529:Isoflavones; D015675:Osteocalcin; D004997:Ethinyl Estradiol; C004742:daidzein; C015484:pyridinoline; C036020:deoxypyridinoline; D002784:Cholesterol; D019833:Genistein; D003375:Coumestrol