The effect of arbutin on membrane integrity during drying is mediated by stabilization of the lamellar phase in the presence of nonbilayer-forming lipids

Arbutin (4-hydroxyphenyl-beta -glucopyranoside) is a solute accumulated to high concentrations in drought and frost resistant plants, Arbutin can inhi bit membrane lysis, both free radical-mediated and enzymatic in nature, and it has been suggested that arbutin might contribute to membrane stabilizat ion in these plants. However, we found that arbutin destabilized phosphatid ylcholine vesicles during drying and rehydration, which appears to be incon sistent with the proposed protective function of arbutin for membranes. We also found, however, that arbutin stabilizes membranes containing nonbilaye r-forming lipids during freezing. We now report that, in liposomes containi ng the nonbilayer-forming lipids monogalactosyldiacylglycerol (MGDG) or pho sphatidylethanolamine (PE), arbutin served a protective Function during dry ing, as measured by retention of carboxyfluorescein (CF) and extent of vesi cle fusion. In hydrated samples containing these lipids, arbutin stabilized the lamellar liquid crystalline phase. Therefore. the interaction between arbutin and lipid membranes and the resulting effects on membrane stability depend, in a complex manner, on the lipid composition of the membrane. (C) 2001 Elsevier Science Ireland Ltd, All rights reserved.