Evaluation of the antioxidant and cytotoxic activity of arzanol, a prenylated α-pyrone-phloroglucinol etherodimer from Helichrysum italicum subsp. microphyllum

Various phenolics and (mero)terpenoids from Helichrysum italicum subsp. microphyllum, a plant endemic to Sardinia, were investigated for their capacity to inhibit non-enzymatic lipid peroxidation. These compounds were studied in simple in vitro systems, under conditions of autoxidation and of iron (EDTA)-mediated oxidation of linoleic acid at 37 °C. Arzanol, a pyrone-phloroglucinol etherodimer, and helipyrone, a dimeric pyrone, showed antioxidant activity, and could protect linoleic acid against free radical attack in assays of autoxidation and EDTA-mediated oxidation. Methylarzanol, as well as the sesquiterpene alcohol rosifoliol, showed a decreased, but still significant, protective effect against linoleic acid oxidation. Arzanol and helipyrone were also tested in an assay of thermal (140 °C) autoxidation of cholesterol, where arzanol showed significant antioxidant activity. The cytotoxicity of arzanol was further evaluated in VERO cells, a line of fibroblasts derived from monkey kidney. Arzanol, at non-cytotoxic concentrations, showed a strong inhibition of TBH-induced oxidative stress in VERO cells. The results of the present work suggest that the natural compound arzanol exerts useful antioxidant properties in different in vitro systems of lipid peroxidation.