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.

ABSTRACT This study aims to identify special metabolites in polar extracts from Urochloa humidicola (synonym Brachiaria humidicola) that have allelopathic effects and induce secondary photosensitization in ruminants. The compounds were isolated and identified via chromatographic and spectroscopic techniques. The compounds 4-hydroxy-3-methoxy-benzoic acid, trans-4-hydroxycinnamic acid, and p-hydroxy-benzoic acid; the flavonols isorhamnetin-3-O-β-d-glucopyranoside and methyl quercetin-3-O-β-d-glucuronate; and kaempferitrin, quercetin-3-O-α-l-rhamnopyranoside, and tricin were identified in the extract from the leaves of Urochloa humidicola. Two furostanic saponins, namely, dioscin and 3-O-α-l-rhamnopyranosyl-(1-4)-[α-l-rhamnopyranosyl-(1-2)]-β-d-glucopyranosyl-penogenin, as well as catechin-7-O-β-d-glucopyranoside were identified in the methanolic extract obtained from the roots of this plant. This species features a range of metabolites that may be toxic for animals if used in food and may interfere with the growth medium, thereby inhibiting the development of other species.

ABSTRACT A new lactone, 7-epi-griffonilide (1), and six known compounds, 2, 3a - 3c, 4a and 4b, were isolated from the leaves of Bauhinia pentandra (Fabaceae). The structures elucidation of 1 and 2 were based on detailed 2D NMR techniques and spectral comparison with related compounds, leading to complete assignment of the 1H and 13C NMR spectra.