Sample preparation was performed using the method described
by Gonza´lez-Parama ´s et al. (2006). Lyophilized strawberries (0.3 g)
were homogenized in 0.1% HCl in methanol and then filtered
through a Bu¨chner funnel under vacuum (in previous experiments,
it was found that lyophilization was an excellent method, both for
the conservation and for the preparation of the sample before