*2.1. Chemicals*

DCFH-DA (2,7-Dichlorodihydrofluorescein diacetate), mercuric chloride (HgCl2), and DTNB (5,5-dithiobis (2-nitrobenzoic acid), or Ellman's reagent) were from Sigma Chemical Co. (St. Louis, Missouri, USA). Anti-Glicophorin A antibody (FITC) was purchased from antibodies-online.com (ABIN6253946, antibodies-online GmbH, Aachen, Germany).

#### *2.2. Pulp and Peel Acetonic Extraction of Feijoa Fruits*

A total of 60 g of fruit, subdivided into pulp and peel, either fresh or after storage at −5 ◦C, were treated with 0.8% water solution of Triton X-100 to remove epiphytic hosts normally found on the surface. They were then extensively washed in tap and distilled water and dried on filter paper. Peel and pulp separately underwent extraction with acetone for 15 min in a liquefier blender until homogenized. The resulting homogenate was centrifuged at 1800× *g* for 10 min; the supernatant was filtered, and the solvent was evaporated under reduced pressure at 45 ◦C for about 24 h. The dry extracts were solubilized with pure dimethyl sulfoxide (DMSO).

#### *2.3. Preparation of Red Blood Cells and Treatment with HgCl2*

Whole blood was obtained with informed consent from healthy volunteers at Campania University "Luigi Vanvitelli" in Naples, Italy. It was deprived of leucocytes and platelets by filtration in a nylon net and washed twice with isotonic saline solution (0.9% NaCl); the resulting intact RBC were resuspended in bu ffer A (5 mM Tris-HCl pH 7.4, 0.9% NaCl, 1 mM MgCl2, and 2.8 mM glucose) to obtain a 10% hematocrit, as previously described [41]. Intact RBC were incubated at 37 ◦C with 40 μM HgCl2 for 4 h or 24 h. For experiments with *Feijoa* pulp and peel extracts, stock solutions, prepared in DMSO as above described, were diluted in bu ffer A to a final DMSO concentration of about 0.02%, in order to avoid DMSO cytotoxicity. As a control, the e ffect of this volume of DMSO on RBC was evaluated and found to be negligible (data not shown). RBC from each donor were used for a single assay in triplicate. Each experiment was repeated on RBC obtained from three di fferent donors.
