Department of Applied Biological Chemistry, Graduate School of Agriculture, Kinki University, Nara, Japan.
PLoS One. 2012;7(2):e31285. doi: 10.1371/journal.pone.0031285. Epub 2012 Feb 17.
Black rice (Oryza sativa L. Japonica) contains high levels of anthocyanins in the pericarp and is considered an effective health-promoting food. Several studies have identified the molecular species of anthocyanins in black rice, but information about the localization of each anthocyanin species is limited because methodologies for investigating the localization such as determining specific antibodies to anthocyanin, have not yet been developed Matrix-assisted laser desorption/ionization imaging mass spectrometry (MALDI-IMS) is a suitable tool for investigating the localization of metabolites. In this study, we identified 7 species of anthocyanin monoglycosides and 2 species of anthocyanin diglycosides in crude extracts from black rice by matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) analysis. We also analyzed black rice sections by MALDI-IMS and found 2 additional species of anthocyanin pentosides and revealed different localization patterns of anthocyanin species composed of different sugar moieties. Anthocyanin species composed of a pentose moiety (cyanidin-3-O-pentoside and petunidin-3-O-pentoside) were localized in the entire pericarp, whereas anthocyanin species composed of a hexose moiety (cyanidin-3-O-hexoside and peonidin-3-O-hexoside) were focally localized in the dorsal pericarp. These results indicate that anthocyanin species composed of different sugar moieties exhibit different localization patterns in the pericarp of black rice. This is the first detailed investigation into the localization of molecular species of anthocyanins by MALDI-IMS.
黑米（Oryza sativa L. Japonica）的种皮中含有高水平的花色苷，被认为是一种有效的促进健康的食品。已有几项研究鉴定了黑米中花色苷的分子种类，但由于尚未开发出用于研究花色苷定位的方法，如鉴定花色苷的特异性抗体，因此有关每种花色苷种类的定位信息有限。基质辅助激光解吸/电离成像质谱（MALDI-IMS）是一种适合研究代谢物定位的工具。在这项研究中，我们通过基质辅助激光解吸/电离质谱（MALDI-MS）分析，从黑米粗提物中鉴定出 7 种花色苷单糖苷和 2 种花色苷双糖苷。我们还通过 MALDI-IMS 分析黑米切片，发现了另外 2 种花色苷五糖苷，并揭示了由不同糖基组成的花色苷种类的不同定位模式。由戊糖基组成的花色苷种类（矢车菊素-3-O-戊糖苷和锦葵素-3-O-戊糖苷）定位在整个种皮中，而由己糖基组成的花色苷种类（矢车菊素-3-O-己糖苷和芍药素-3-O-己糖苷）则在背侧种皮中局部分布。这些结果表明，由不同糖基组成的花色苷种类在黑米种皮中表现出不同的定位模式。这是首次通过 MALDI-IMS 对花色苷分子种类的定位进行详细研究。
