Methoxsalen (NCI-C55903) is a Photoactivated Radical Generator and Psoralen. The mechanism of action of methoxsalen is as a Photoabsorption. The physiologic effect of methoxsalen is by means of Photosensitizing Activity.

Methoxsalen inhibits CYP2A6 (Ki = 0.8 μM) with about 3.5- 94-fold greater potency than other P450s, except for CYP1A2 (Ki = 0.2 μM). Methoxsalen shows noncompetitive inhibition of nicotine metabolism, with an apparent Ki value of 0.1 μM in cDNA-expressing microsomes. [1] Methoxsalen is metabolized in human liver microsomes at the rate of 50-100 pmol/mg protein/min (approx. 30% of the activity in mouse liver microsomes). Methoxsalen is a very potent inhibitor of human cytochrome P450 2A6 (CYP2A6) and mouse Cyp2a-5-mediated coumarin 7-hydroxylation in vitro. [2]

Methoxsalen results in a significant decrease in the following factors: number and diameter of corpus lutei, Graafian follicles, diameter of granulosa cell layer and oocytes, number of primordial and primary and growing follicles, while the number of atretic follicle is increased. Methoxsalen also significantly reduces circulating estrogen levels in blood serum of oogenesis Balb/C mice. [3] Methoxsalen dose-dependently stimulates a sustained increase in short-circuit current in the mouse jejunum. Methoxsalen increases the open probability of the basolateral IK(Ca) channel of isolated crypts in the mouse jejunum. [4] Methoxsalen effectively reverses trimethyltin (TMT)-induced memory impairment on both Y-maze and passive avoidance tests in mice. Methoxsalen inhibits brain AchE activity. Methoxsalen significantly ameliorates the level of oxidative stress. [5]