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Quercetin as the Active Principle of Hypericum hircinum Exerts a Selective Inhibitory Activity against MAO-A: Extraction, Biological Analysis, and Computational Study.

Chimenti F, Cottiglia F, Bonsignore L, Casu L, Casu M, Floris C, Secci D, Bolasco A, Chimenti P, Granese A, Befani O, Turini P, Alcaro S, Ortuso F, Trombetta G, Loizzo A, Guarino I

Dipartimento di Studi di Chimica e Tecnologia delle Sostanze Biologicamente Attive, Università degli Studi di Roma “La Sapienza”, P.le A. Moro 5, 00185 Rome, Italy, Dipartimento Farmaco Chimico Tecnologico, Università degli Studi di Cagliari, Via Ospedale 72, 09124 Cagliari, Italy, Dipartimento di Scienze Chimiche, Università di Cagliari, Complesso di Monserrato, SS 554, Km 4.5, 09042 Monserrato (CA), Italy, Dipartimento di Scienze Biochimiche “A. Rossi Fanelli” and Centro di Biologia Molecolare del CNR Università degli Studi di Roma “La Sapienza”, P.le A. Moro 5, 00185 Rome, Italy, Dipartimento di Scienze Farmaco Biologiche “Complesso Ninì Barbieri”, Università degli Studi di Catanzaro “Magna Graecia”, 88021 Roccelletta di Borgia (CZ), Italy, and Istituto Superiore di Sanità, Viale Regina Elena 299, 00161 Rome, Italy.

The methanol extract from Hypericum hircinum leaves exhibited in vitro inhibition of monoamine oxidases (MAO). Bioassay-guided fractionation led to the isolation of quercetin and five compounds identified for the first time from H. hircinum. Quercetin was the only compound with a selective inhibitory activity against MAO-A, with an IC(50) value of 0.010 muM. To explain MAO selective inhibition at the molecular level, a computational study was carried out by conformational search and docking techniques using recently determined crystallographic models of both enzymatic isoforms. An in vivo study in mice was carried out using the forced swimming test in order to elucidate the behavioral effects of quercetin.

Published 23 June 2006 in J Nat Prod, 69(6): 945-949.
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