Inhibition of myeloperoxidase activity by an isolated product from Piper crassinervium (Piperaceae)
Vellosa, JCR; Khalil, NM; Barbosa, VF; Brunetti, IL; Furlan, M; Oliveira, OMMF
Departamento de Bioquímica e Tecnologia Química, Instituto de Química, UNESP-Araraquara (SP)
Introduction: The myeloperoxidase (MPO) is an enzyme that participates in the oxidative burst, which produces highly oxidative species (e.g. hypochlorous acid-HOCl). These species can promote tissue damage and its exacerbated activation has been linked to many diseases (Atherosclerosis, Arthritis, Alzheimer disease).
Objective: Many natural products have been used efficiently against different diseases. The aim of this study is evaluate the MPO inhibition by 1,4-dihydroxy-2-(3',7'-dimetyl,-1'oxo-2'-E-octadienyl) benzene (DDOOB), isolated from Piper crassinervium (Piperaceae).
Methods: Reactions were followed, in phosphate buffer 50mM, pH7,0 (Vf=1mL; 250C), by the absorbance raise at 470nm, during 1 minute after initiate the reaction with hydrogen peroxide. Studies: i) IC50 (compared to quercetin, an standard MPO inhibitor): guaiacol 20mM, MPO 100mU, H2O2 0,2mM; ii) inhibition characterization by double-reciprocal graphs.
Results: It was compared media+DP, considering p<0,05: i) IC50: quercetin (0,0014mg/mL) and DDOOB (0,0031mg/mL); ii) inhibition: both, DDOOB (0,0025mg/mL [vmax: 0,0013s-1; kM: 31 mM]; 0,005mg/mL [vmax: 0,0009s-1; kM: 40mM]) and quercetin (0,0005mg/mL [vmax:0,0009 s-1; kM:73mM]; 0,0025mg/mL [vmax: 0,0005s-1; kM:93 mM]) were characterized as mixed inhibitors compared to reactions in absence of them (vmax: 0,0021s-1; kM: 21mM).
Conclusions: In this work, DDOOB inhibited the catalytic action of MPO over guaiacol, promoting a v0 decreasing, expressed as inhibition percentage, which was used to determine IC50 values. Quercetin is more powerful myeloperoxidase inhibitor than DDOOB, but this is a good one too. Quercetin and DDOOB, by our results, are mixed myeloperoxidase inhibitors. These are really important results because MPO has relevant participation on tissue damage.
e-mail: josevellosa@yahoo.com.br
Supported by: FAPESP/BIOTA and CAPES
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