Each sample of Zingiber officinalis rhizomes (1 g) was extractedsubmitted to a solid-liquid extraction with 25 mL of methanol(25◦C at 150 rpm) during 1 h. After filtration with Whatman N◦4paper, the obtained residue was re-extracted in the same conditionsof the ones previously used. The methanol was removed at 40◦C(rotary evaporator Büchi R-210) and the remaining extracts werere-dissolved in methanol (final concentration, 5 mg/mL). Thesefinal solutions were further diluted to different concentrations tobe used in the subsequent assays.