Reduced L-glutathione, sodium borohydride, 2-methyl-2-butene solution (2.0 M in THF), sodium chlorite, tert-butanol, glutathione reductase from baker’s yeast (250 units/ml. Sigma catalogue #G3664), 5,5’-dithio-bis(2-nitrobenzoic acid) (DTNB), and NADPH were purchased from Sigma-Aldrich (St. Louis, MO). HOHA-lactone (1) was prepared as described previously.1 (link) N,O-Bis(trimethylsilyl)trifluoroacetamide (BSTFA) was obtained from Acros Organics (Thermo Fisher, New Jersey). Dulbecco’s modified Eagle’s medium, high glucose (DMEM/F12), fetal bovine serum, penicillin–streptomycin and L-glutamine were obtained from Gibco (Life Technologies, Grand Island, NY). ARPE-19 cells were obtained from American Type Culture Collection (ATCC, Rockville, MD). The hRPE cells were obtained from Lonza Walkersville, Inc., Walkersville, MD, catalog # 00194987, lot # 0000424472. According to the manufacturer, they exhibited pan-cytokeratin staining (95%), anti-fibroblast staining (0%) and ZO-1 staining (strongly positive), and they have viability >70%, average doubling time 22 hrs. Retinal pigmented epithelial cell basal medium, an optimized mixture of growth factors and supplements for primary hRPE cells (SingleQuots™ Kit), was obtained from Lonza (Allendale, NJ).