Effects of flavonoid on calcium content in femoral tissue culture and parathyroid hormone-stimulated osteoclastogenesis in bone marrow culture in vitro

The effect of various flavonoids, which are present in food and plants, on bone calcium content and osteoclastogenesis were investigated to compare action of flavonoid on bone formation and bone resorption in vitro. Rat femoral-diaphyseal (cortical bone) and -metaphyseal (trabecular bone) tissues were cultured for 48 h in Dulbecco’s modified Eagle’s medium (high glucose) supplemented with antibiotics and bovine serum albumin. Amoung quercetin, myricetin, kaempferol, isorhamnetin, curcumin, hesperidin, or astaxanthin in the range of 10−7–10−5 M, culture with quercetin (10−6 or 10−5 M) caused a significant increase in diaphyseal calcium content. Such an effect was not seen in other compounds. Mouse bone marrow cells were cultured for 7 days in the presence of parathyroid hormone (PTH; 10−7 M), a bone-resorbing factor, in vitro. Culture with PTH caused a significant increase in osteoclast-like cell formation. This increase was significantly inhibited in the presence of quercetin, myricetin, kaempferol, isorhamnetin, or curcumin in the range of 10−8–10−6 M. Such an effect was not seen in the case of hesperidin or astaxanthin. In addition, culture with PTH (10−7 M) caused a significant decrease in diaphyseal calcium content. This decrease was completely prevented in the presence of quercetin, myricetin, kaempferal, or isorhamnetin of 10−6 M. This study demonstrates that various flavonoids have a potent inhibitory effect on osteoclastogenesis and bone resorption rather than bone formation in vitro. Among various flavonoids, quercetin had a stimulatory effect on bone formation and an inhibitory effect on bone resorption in vitro.