*4.1. Chemicals*

All materials and reagents employed for the histological analyses were supplied by Bio-Optica Milano S.p.a. (Milan, Italy). The following reagents were all provided by Sigma-Aldrich (Milan, Italy): sulfuric acid (95–98% purity), sodium hydroxide, boric acid, hydrogen chloride, benzoic acid, and phosphate-buffered saline (PBS). The Kjeldahl catalyst was supplied by Carlo Erba (Milan, Italy). n-Heptane was purchased from PanReac AppliChem (Barcelona, Spain). Potassium hydroxide, chloroform, methanol, sodium carbonate anhydrous, Folin Ciocalteau's reagent, stock standard solution of Re (1000 mg L−<sup>1</sup> in 2% HNO3), gallic acid, and stock standard solutions of Sc, Ge, In, and Bi (1000 mg L−<sup>1</sup> in 2% HNO3) were from Fluka (St. Gallen, Switzerland). Nitric acid (65%, *v*/*v*) was of Suprapur grade (Mallinckrodt Baker, Milan, Italy). Ultrapure water (<5 mg L−<sup>1</sup> TOC) was obtained from a Barnstead Smart2Pure 12 water purification system (Thermo Scientific, Milan, Italy).
