Mangiferin is a new potential antimalarial and anticancer drug for targeting serine hydroxymethyltransferase

Mangiferin, a polyphenolic xanthone glycoside found in various botanical sources, including mango (Mangifera indica L.) leaves, can exhibit a variety of bioactivities. Although mangiferin has been reported to inhibit many targets, none of the studies have investigated the inhibition of serine hydroxymethyltransferase (SHMT), an attractive target for antimalarial and anticancer drugs. SHMT, one of the key enzymes in the deoxythymidylate synthesis cycle, catalyzes the reversible conversion of l-serine and (6S)-tetrahydrofolate (THF) into glycine and 5,10-methylene THF. Here, in vitro and in silico studies were used to probe how mangiferin isolated from mango leaves inhibits Plasmodium falciparum and human cytosolic SHMTs. The inhibition kinetics at pH 7.5 revealed that mangiferin is a competitive inhibitor against THF for enzymes from both organisms. Molecular docking and molecular dynamic (MD) simulations demonstrated the inhibitory effects of the deprotonated forms of mangiferin, specifically the C₆-O^- species and its resonance C₉-O^- species appearing at pH 7.5, combined with two docked poses, either a xanthone or glucose moiety, placed inside the THF-binding pocket. The MD analysis revealed that both C₆-O^- and its resonance-stabilized C₉-O^- species can favorably bind to SHMT in a similar fashion to THF, supporting the THF competitive inhibition of mangiferin. In addition, characterization of the proton dissociation equilibria of isolated mangiferin revealed that only three hydroxy groups of the xanthone moiety, C₆-OH, C₃-OH, and C₇-OH, underwent varying degrees of deprotonation with pK_a values of 6.38 ± 0.11, 8.21 ± 0.35, and 12.37 ± 0.30, respectively, while C₁-OH remained protonated. Altogether, our findings demonstrate a new bioactivity of mangiferin and provide the basis for the future development of mangiferin as a potent antimalarial and anticancer drug.