ABSTRACT
Phytochemical studies of Cespedesia spathulata (Ochnaceae) leaves using 1H, 13C NMR, and GC-MS have led to the isolation of some metabolites identified for the first time in these species such as cathechin, epicatechin, vitexin, orientin, 6''-O-acetyl-vitexin, sitosterol, stigmasterol, phytol, 4,5-dihydrovomifoliol and a mixture of aliphatic methyl esters, together with ochnaflavone, which was previously isolated from this plant. The modulating activity of some fractions and compounds from Cespedesia spathulata towards tyrosinase enzyme was assayed by spectroscopic and theoretical means/experiments. The dichloromethane fraction (133 µg mL-1) and ochnaflavone (333 µM) inhibited tyrosinase activity by 20 % and 2.0 %, respectively, whereas the ethyl acetate fraction (666 µg mL-1) and ±catechins (catechin and epicatechin - 800 µM) activated it by 104 % and 384 %, respectively. Quantum chemical calculations suggested that catechin and epicatechin are better activators than L-DOPA by interacting with Cu (II) ions. Molecular docking results suggested that hydrogen bonding and hydrophobic interactions are the main binding forces between each tyrosinase activator and the amino acid residues inside the active protein binding pocket.
