Melatonin levels, determined by HPLC-ESI-MS/MS, deeply fluctuate during the day in Vitis vinifera cv Malbec. Evidences of its antioxidant role

BOCCALANDRO, HERNÁN ESTEBAN; GONZALEZ, CARINA VERONICA; WUNDERLIN, DANIEL; BOTTINI, RUBÉN; SILVA, MARÍA FERNANDA

Montevideo, Uruguay

Congreso; XII Congreso Latinoamericano de Viticultura y Enología; 2009

Asociación de Enólogos del Uruguay

<!-- /* Style Definitions */ p.MsoNormal, li.MsoNormal, div.MsoNormal {mso-style-parent:""; margin:0in; margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:12.0pt; mso-bidi-font-size:10.0pt; font-family:"Times New Roman"; mso-fareast-font-family:"Times New Roman"; mso-ansi-language:FR; mso-fareast-language:EN-AU;} h1 {mso-style-next:Normal; margin:0in; margin-bottom:.0001pt; mso-pagination:widow-orphan; page-break-after:avoid; mso-outline-level:1; font-size:14.0pt; mso-bidi-font-size:10.0pt; font-family:"Times New Roman"; mso-font-kerning:0pt; mso-ansi-language:EN-GB; mso-fareast-language:EN-AU; font-weight:normal;} p.MsoBodyText, li.MsoBodyText, div.MsoBodyText {margin:0in; margin-bottom:.0001pt; mso-pagination:widow-orphan; border:none; mso-border-alt:solid windowtext .5pt; padding:0in; mso-padding-alt:1.0pt 4.0pt 1.0pt 4.0pt; font-size:12.0pt; mso-bidi-font-size:10.0pt; font-family:"Times New Roman"; mso-fareast-font-family:"Times New Roman"; mso-ansi-language:EN-GB; mso-fareast-language:EN-AU;} p.MsoBodyText2, li.MsoBodyText2, div.MsoBodyText2 {margin:0in; margin-bottom:.0001pt; text-align:justify; mso-pagination:widow-orphan; border:none; mso-border-alt:solid windowtext .5pt; padding:0in; mso-padding-alt:1.0pt 4.0pt 1.0pt 4.0pt; font-size:12.0pt; mso-bidi-font-size:10.0pt; font-family:"Times New Roman"; mso-fareast-font-family:"Times New Roman"; mso-ansi-language:EN-GB; mso-fareast-language:EN-AU;} @page Section1 {size:8.5in 11.0in; margin:70.85pt 85.05pt 70.85pt 85.05pt; mso-header-margin:.5in; mso-footer-margin:.5in; mso-paper-source:0;} div.Section1 {page:Section1;} --> Melatonin (MT), the often called ‘hormone of darkness’ is a ubiquitous molecule widely distributed in nature, produced by unicellular organisms, fungi, plants and animals. It plays a significant role, as a mediator, in the regulation of many physiological cycles. It has been proven that is an effective antioxidant, presents inhibitory effects on some cancer forms and shows beneficial effects on neuronal disorders. In plants, it has been speculated that MT protect them from intrinsic and environmental oxidative stress. The latter offers an interesting perspective associated to the plethora of health benefits related to the moderate consumption of wine. The objective of this work was to study if MT levels fluctuate during the day and correlate them with the oxidative damage suffered by berries along a typical day at harvest in the Valle de Uco where there are environmental stressful conditions, like higher UV-B radiation and very cold nights and mornings at harvest.The experiment was carried out on 26th April 2008, in a commercial vineyard located in Gualtallary (1.500 m a.s.l.), province of Mendoza, Argentina. Berry samples were collected during the whole day every three hours. Light exclusion treatment consists in covering clusters with black  ethylene vinyl acetate. Melatonin determination was performed by HPLC-ESI-MS/MS and MDA (malondialdehyde), a product of lipid peroxidation, was measured according to Zhang et al. (2005). Low content of MT in berry skins were found at night (10,9 and 8,9 ng.g-1 at 2.5 and 6h respectively) and a strong peak was detected at dawn (158,9 ng.g-1 at 9.5h). After this peak, melatonin levels deeply decayed to undetectable values (noon and afternoon). MT content in berry skins of covered clusters was significantly higher (14.2 ng.g-1) than those exposed to natural radiation (N/D). Taking into account that vines were suffering oxidative stress, MDA levels clearly fluctuated during the day, reaching a maximum at 17.5h. Minima MDA content was coincident with the higher MT  amounts, suggesting a negative correlation between MDA and MT. Our results suggest the antioxidant role of MT in grape, in agreement with the evidence found for other species (Posmik et. al., 2009). Indeed, such finding was supported by the fact that MDA content in covered bunches was significantly lower.