Yi Debao, Zhang Hongna, Lai Biao, Liu Liqin, Pan Xiaolu, Ma Zhiling, Wang Yicheng, Xie Jianghui, Shi Shengyou, Wei Yongzan
Hainan University, Haikou, Hainan 570228, People's Republic of China.
Engineering Research Center for Longan and Litchi of Upper Yangtze River, School of Advanced Agriculture and Bioengineering, Yangtze Normal University, Chongqing 408100, People's Republic of China.
J Agric Food Chem. 2021 Feb 17;69(6):1806-1815. doi: 10.1021/acs.jafc.0c05023. Epub 2020 Dec 17.
The pericarp of longan ( Lour.) is rich in secondary metabolites and typically yellow-brown or gray-yellow in appearance. Here, we obtained a specific longan type, called red pericarp (RP) longan, which has a strong red pericarp. To understand the coloring mechanism of RP longan, metabolome and transcriptome data were used to analyze its secondary metabolites and molecular mechanism. From the results of liquid chromatography tandem mass spectrometry, 597 substances were identified in RP longan and 'Shixia' (SX) longan. Among these substances, 33 (mostly including flavonoids) were found in RP longan and 23 (mostly containing phenolic acids) were identified in SX longan. We identified five types of anthocyanins in longan pericarp, including three cyanidin derivatives, one delphinidin derivative, and one pelargonidin derivative. Three cyanidin derivatives, which contained cyanidin 3--glucoside, cyanidin 3--6″-malonyl-glucoside, and cyanidin -syringic acid, were the primary components of anthocyanidins, and they only existed in RP longan. Delphinin 3--glucoside existed only in SX longan, and pelargonin -rutinoside existed in RP and SX longan. However, their contents were extremely low. The structural genes , , , and and the controlling genes containing , , , and in the biosynthetic pathway of anthocyanin were significantly upregulated in RP longan. In summary, the strong red hue of RP longan is due to the accumulation of cyanidin derivatives in its pericarp, and the genes and may play an important role in selecting which component of anthocyanins will be synthesized. These results can provide scientific guidance for understanding and developing bioactive compounds from longan fruits.
龙眼（Lour.）的果皮富含次生代谢产物，外观通常为黄褐色或灰黄色。在此，我们获得了一种特殊的龙眼类型，称为红皮（RP）龙眼，其果皮颜色呈深红色。为了解RP龙眼的着色机制，利用代谢组学和转录组学数据对其次生代谢产物和分子机制进行了分析。通过液相色谱串联质谱分析结果，在RP龙眼和‘石硖’（SX）龙眼中共鉴定出597种物质。其中，在RP龙眼中发现了33种（主要包括黄酮类化合物），在SX龙眼中鉴定出23种（主要含有酚酸）。我们在龙眼果皮中鉴定出五种花色苷，包括三种矢车菊素衍生物、一种飞燕草素衍生物和一种天竺葵素衍生物。三种矢车菊素衍生物，即矢车菊素3 - 葡萄糖苷、矢车菊素3 - 6″-丙二酰葡萄糖苷和矢车菊素 - 丁香酸，是花青素的主要成分，且仅存在于RP龙眼中。飞燕草素3 - 葡萄糖苷仅存在于SX龙眼中，天竺葵素 - 芸香糖苷存在于RP和SX龙眼中，但其含量极低。花青素生物合成途径中的结构基因、、、和以及包含、、、和的调控基因在RP龙眼中显著上调。综上所述，RP龙眼深红色的色泽是由于其果皮中矢车菊素衍生物的积累，基因和可能在选择合成哪种花色苷成分方面发挥重要作用。这些结果可为理解和开发龙眼果实中的生物活性化合物提供科学指导。
