Osthole - also spelled osthol - is a type of coumarin. Osthole is found in cnidium monnieri and several other plants. Osthol could increase androgen, gonadotropin and nitric oxide synthase (NOS) activity.
Osthole is a libido stimulator: researchers investigate the cavernosal relaxant effect of osthole, has been long used in China as a herbal medicine to improve male sexual dysfunction. The data suggested that osthole posseses a relaxant effect on rabbit corpus cavernosal tissues which is attributable to the release of NO from sinusoidal endothelium and to the potentiation of the cGMP and/or cAMP signal mediating relaxation of cavernosal smooth muscle by inhibiting phosphodiesterase". (Corpus cavernosum = one of the columns of erectile tissue forming the dorsum of the penis (one of the two columns of erectile tissue forming the clitoris.
Cnidium Monnier-increases nitric oxide release and inhibits PDE-5, allowing erections to be sustained for longer periods of time.