Characterization of Active Component in Marine Alga Sargassum horneri Extract in Stimulating Bone Calcification in Vitro

Abstract

The marine alga Sargassum horneri (S. horneri) has an anabolic effect on bone metabolism (J. Health Sci., 47, 533-538, 2001). The effect of the fractionated extracts obtained from S. horneri on bone calcium content and osteoclast-like cell formation in vitro was investigated. S. horneri was gathered from various coasts (Shimoda, Iwate, or China). Rat femoral-diaphyseal and -metaphyseal tissues were cultured for 24 hr in a medium containing either vehicle or a water-solubilized extract (25 μg/ml of medium) obtained from S. horneri. Diaphyseal and metaphyseal calcium contents were significantly increased in the presence of S. horneri extract from Shimoda, Iwate, or China. The active component of S. horneri extract in increasing calcium content in diaphyseal tissues was seen in the nearby fraction molecular weight (MW) of 1000. This effect completely disappeared upon heat treatment with 80°C for 30 min. Mouse marrow cells were cultured for 7 days in a medium containing 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] (10-7 M) in the presence or absence of S. horneri extract (1.0 μg/ml of medium). The 1,25(OH)2D3-induced increase in osteoclast-like cell formation was markedly suppressed in the presence of the crude extract or a fraction more than MW 50000 of S. horneri extracts obtained from Iwate or China. This effect was also seen by heat treatment. The present study suggests that the active components of S. horneri extract in stimulating bone formation or suppressing osteoclastic bone resorption are different.