Studies on the Inhibition of Ectonucleotide Pyrophosphatase/Phosphodiesterase 1 (ENPP1) by 2-(3,4-Dihydroxyphenyl)-7,8-dihydroxy-3-methoxychromen-4-one, a Flavonoid from Pistacia chinensis

Ectonucleotide pyrophosphatase/phosphodiesterase 1 (ENPP1) regulates skeletal and soft tissue mineralization by hydrolyzing nucleotide triphosphates and cyclic nucleotides, and is involved in the modulation of immune system. In fact, ENPP1 degrades 2 ',3 '-cyclic GMP-AMP dinucleotide (2 ',3 '-cGAMP), which is an agonist of surface receptor stimulator of interferon genes (STING), thus downregulating immune response. Consequently, ENPP1 inhibitors are being studied as adjuvant agents in infections and cancer. Pistacia chinensis is a medicinal plant endowed with several biological activities and traditional uses. In the current study, we report the isolation of transilitin (2-(3,4-dihydroxyphenyl)-7,8-dihydroxy-3-methoxychromen-4-one) from the methanolic extract of P. chinensis barks and the investigation of its activity as ENPP1 inhibitor. The compound was tested in vitro against snake venom phosphodiesterase, which is structurally related to ENPP1, and dose-dependently inhibited the enzyme. Moreover, molecular modeling studies were employed to assess the binding motif of the transilitin with the macromolecular target. Our findings support the traditional medical application of P. chinensis and its extracts by shedding new light on the mechanisms underlying their biological action.