Characterization and Metabolic Diversity of Flavonoids in Citrus Species

Abstract

Flavonoids are widely distributed in plants and play important roles in many biological processes. Citrus fruits are rich dietary sources of flavonoids. However, there have been very few reports about the comprehensive metabolic profile and natural diversity of flavonoids in different tissues of various Citrus cultivars. In this study, based on the 7416 metabolic signals detected with non-targeted metabolomics approach, Principal Component Analysis revealed the flavedo has the largest differences from other tissues in metabolite levels; as many as 198 flavonoid signals were then detected in 62 Citrus germplasms from 5 species mainly cultivated worldwide, while 117 flavonoids were identified, including 39 polymethoxylated flavonoids (PMFs), 7 flavones, 10 C-O-glycosylflavonoids, 44 O-glycosylflavonoids, 10 C-glycosylflavonoids and 7 newly annotated O-glycosylpolymethoxylated flavonoids. Tissue-specific accumulations were observed: O-glycosylated flavonoids were abundant in all fruit tissues, while PMFs were accumulated preferentially in the flavedo. Among different species, mandarins had the highest levels of PMFs and O-glycosylpolymethoxylated flavonoids, followed by sweet oranges. Based on the flavonoid profiles, 62 germplasms could be clearly grouped into five distinct clusters via hierarchical clustering analysis, which were perfectly matched with their species, with sweet oranges and mandarins clustering closely and being further away from other three species.

Identifying candidate detoxification genes in the ecdysteroid kinase-like (EcKL) and cytochrome P450 gene families inDrosophila melanogasterby integrating evolutionary and transcriptomic data

“…Phytoecdysteroids and mycoecdysteroids are present in various plant and fungal species as anti-insect secondary metabolites (Dinan, 2001; Kovganko, 1999), and some are likely detoxified by phosphorylation (Rharrabe et al, 2007). Other hydroxylated toxins that could be X-class EcKL substrates include withanolides, cardenolides, cucurbitacins and flavonoids (Agrawal et al, 2012; Dinan et al, 1997; Glotter, 2011; S. Wang et al, 2017). X-class EcKLs may also phosphorylate the products of phase I hydroxylation reactions or phase II glucosidation reactions, as is speculated to occur in locusts and moths (Boeckler et al, 2016; Olsen et al, 2015; 2014).…”

Ohmic Heating of Lemon and Grapefruit Juices Under Vacuum Pressure— Comparison of Electrical Conductivity and Heating Rate

“…Lemon ( Citrus limon ) and grapefruit ( Citrus paradisi ) are two major citrus fruits that are extremely interesting for the food industry. Although they are mostly consumed as fresh fruit, some of them are processed into various products, particularly juice (Ye, Chen, Xu, & Chen, ). In terms of nutritional value, lemon and grapefruit juices are good sources of flavonoids, vitamin C, folate, dietary fiber, and carotenoids (Wang et al., ).…”

“…Although they are mostly consumed as fresh fruit, some of them are processed into various products, particularly juice (Ye, Chen, Xu, & Chen, ). In terms of nutritional value, lemon and grapefruit juices are good sources of flavonoids, vitamin C, folate, dietary fiber, and carotenoids (Wang et al., ). These phytochemicals are useful compounds to enhance the level of human health (Guimarães et al., ).…”

UHPLC‐MS Analyses of Plant Flavonoids

“…The use of high-resolution mass spectrometry (HRMS) such as time-offlight (TOF), Fourier transform ion cyclotron resonance (FT ICR) and the Orbitrap mass spectrometers enables accurate mass measurement and further increases the level of identification confidence for plant metabolites. UHPLC-MS has been successfully adopted Table. for flavonoid analyses in many plant species including a number of economically important crops (Cho, Howard, Prior, & Clark, 2004;Farag et al, 2007;Li et al, 2016;Wang et al, 2017). The utility of UHPLC-MS in plant flavonoid analyses is further enhanced by the development of mass spectral libraries as well as informatics tools (Akimoto et al, 2017;Qiu, Fine, Wherritt, Lei, & Sumner, 2016).…”