Antioxidant and anticancer effects and bioavailability studies of the flavonoid baicalin and its oxidovanadium(IV) complex

JUAN J. MARTÍNEZ MEDINA; ALBERTO RIZZI; ANA L. PÉREZ; WILLIAMS, PATRICIA A.M.; L.G. NASO; E.G. FERRER

JOURNAL OF INORGANIC BIOCHEMISTRY

ELSEVIER SCIENCE INC

Lugar: Amsterdam; Año: 2017 vol. 166 p. 150 - 161

0162-0134

Based on the known antioxidant effect of flavonoids, baicalin (baic) found in roots ofScutellaria has been selected. Its coordination complex with the oxidovanadium(IV)cation, Na4[VO(baic)2].6H2O (VIVO(baic)), was synthesized at pH 9 in ethanol andcharacterized by physicochemical methods. Spectrophotometric studies at pH 9 showeda ligand: metal stoichiometry of 2:1. By vibrational spectroscopy a coordination modethrough the cis 5-OH and 6-OH deprotonated groups is inferred. EPR spectroscopyshows an environment of four aryloxide (ArO-) groups in the equatorial plane of theV=O moiety, both in solution and in the solid complex. The antioxidant capacity againstsuperoxide and peroxyl radicals of VIVO(baic) resulted greater than for baicalin andcorrelated with previous results obtained for other VOflavonoid complexes. Thecoordination mode produces delocalization of the electron density and the stabilizationof the radical formed by interaction with external radicals. The complex and the liganddisplayed no toxic (Artemia salina test) and no mutagenic (Ames test) effects. Thecomplex improved the ability of the ligand to reduce cell viability of human lung cancercell lines (A549) generating reactive oxygen species (ROS) in cells, being this effectreversed by pre-incubation of the cells with antioxidants such as vitamins C and E. Theaddition of NAC (N-acetyl-L-cysteine, a sequestering agent of free radicals) suppressesthe anticancer effect, confirming the oxidative stress mechanism. The complexinteracted with bovine serum albumin (BSA) with stronger binding than baicalin andthe mechanisms involved H bonding and van der Waals interactions.