5-Methoxytryptophol is a pineal indoleamine derived from serotonin shown to be biologically active in a number of species.
In MC3T3-E1 cells, most of the 5-methoxytryptophol doses reduced slightly the metabolic activity of osteoblasts. After 14 days of cell culture, Rankl mRNA levels were decreased. 5-methoxytryptophol also induced a high osteocalcin secretion and mineralization capacity. In RAW264.7 cells, 5-methoxytryptophol decreased the number of osteoclast formed and its activity. 5-methoxytryptophol promoted activation of the ERK1/2 pathway through the phosphorylation of ERK, while LUZ addition suppressed this effect. In conclusion, 5-methoxytryptophol inhibits osteoclastogenesis and promoting osteoblast differentiation.