Betalains, such us indicaxanthin and betacyanins,are nitrogenous pigments present in fruits of many caryophyllales, like Opuntia ficus indica,with potent antioxidant proprieties. However, their biological activities are poorly known. Previously weshowed that the Opuntia ficus indica fruit extract (OFE)induced a concentration-dependent reduction of spontaneous and evoked mechanical activity of mouse ileum, which was mimicked by its pigment indicaxanthin.Therefore, the purpose of this study was to examinethe indicaxanthin mechanism of action, in mouse ileum longitudinal muscle, using organ bath technique.

The inhibitory action of indicaxanthin (3–100 mM) on spontaneous mechanical activity was unaffected by indomethacin (10 mM), inhibitor of cycloxygenase, ODQ (10 mM), selective inhibitor of nitric oxide-dependent guanylyl cyclase, and DDA (10 mM), adenylate cyclase inhibitor, while it was significantly reduced in the presence of IBMX (10 mM), a non selective inhibitor of phosphodiesterases (PDEs). In addition indicaxanthin, as IBMX, increased the inhibitory effects of foskolin (1 nM – 1 mM), an adenylate cyclase activator, while it did not affect the inhibitory action of sodium nitroprusside (1 –100 mM), a soluble guanylil cyclase activator, which was increased only by IBMX. The present data show for the first time that indicaxanthin from OFE is able to reduce the contractility of ileal longitudinal muscle by inhibition of PDEs and likely increase of intracellular cAMP.