Facultad de Farmacia, Universidad de Castilla-La Mancha, Campus Universitario s/n, Albacete, Spain ; Instituto Botánico, Universidad de Castilla-La Mancha, Campus Universitario s/n, Albacete, Spain.
PLoS One. 2013 Sep 13;8(9):e71946. doi: 10.1371/journal.pone.0071946. eCollection 2013.
Crocus sativus is the source of saffron spice, the processed stigma which accumulates glucosylated apocarotenoids known as crocins. Crocins are found in the stigmas of other Crocuses, determining the colourations observed from pale yellow to dark red. By contrast, tepals in Crocus species display a wider diversity of colours which range from purple, blue, yellow to white. In this study, we investigated whether the contribution of crocins to colour extends from stigmas to the tepals of yellow Crocus species. Tepals from seven species were analysed by UPLC-PDA and ESI-Q-TOF-MS/MS revealing for the first time the presence of highly glucosylated crocins in this tissue. β-carotene was found to be the precursor of these crocins and some of them were found to contain rhamnose, never before reported. When crocin profiles from tepals were compared with those from stigmas, clear differences were found, including the presence of new apocarotenoids in stigmas. Furthermore, each species showed a characteristic profile which was not correlated with the phylogenetic relationship among species. While gene expression analysis in tepals of genes involved in carotenoid metabolism showed that phytoene synthase was a key enzyme in apocarotenoid biosynthesis in tepals. Expression of a crocetin glucosyltransferase, previously identified in saffron, was detected in all the samples. The presence of crocins in tepals is compatible with the role of chromophores to attract pollinators. The identification of tepals as new sources of crocins is of special interest given their wide range of applications in medicine, cosmetics and colouring industries.
番红花是藏红花香料的来源，其加工柱头积累了糖基化的类胡萝卜素，称为藏红花素。藏红花素存在于其他番红花的柱头中，决定了从浅黄色到深红色的观察到的颜色。相比之下，番红花属植物的花被片显示出更广泛的颜色多样性，从紫色、蓝色、黄色到白色。在这项研究中，我们研究了藏红花素对颜色的贡献是否从柱头扩展到黄色番红花属植物的花被片。通过 UPLC-PDA 和 ESI-Q-TOF-MS/MS 分析了来自七个物种的花被片，首次在该组织中发现了高度糖基化的藏红花素。β-胡萝卜素被发现是这些藏红花素的前体，其中一些含有鼠李糖，这是以前从未报道过的。当将花被片中的藏红花素图谱与柱头中的图谱进行比较时，发现了明显的差异，包括在柱头上存在新的类胡萝卜素。此外，每个物种都表现出一种特征性的图谱，与物种之间的系统发育关系无关。虽然花被片中参与类胡萝卜素代谢的基因的表达分析表明，类胡萝卜素合酶是花被片中类胡萝卜素生物合成的关键酶。在所有样品中都检测到了以前在藏红花中鉴定出的藏红花酸葡萄糖基转移酶的表达。花被片中藏红花素的存在与其作为吸引传粉者的色素的作用是一致的。鉴于其在医学、化妆品和着色工业中的广泛应用，将花被片鉴定为新的藏红花素来源具有特殊意义。
