The aim of this study was to analyze the non-volatile composition and antioxidant differences of lemon essential oils (LEOs) obtained by cold-pressing vs. hydrodistillation. Pathological observations showed that LEO effectively inhibited liver injury caused by oxidative stress, and CPLEO was more effective than HDLEO. CPLEO increased serum T-AOC, SOD, GSH, and GSH-Px levels while decreasing NO, COX-2, IL-6, IL-1β, IFN-γ, and TNF-α levels in mice with oxidative damage. The effects of CPLEO were stronger than those of HDLEO and similar to those of vitamin C. CPLEO upregulated mRNA and protein expressions of Cu/Zn-SOD, Mn-SOD, CAT, HO-1, Nrf2, and NQO1 while downregulating nNOS, iNOS, IL-1β, COX-2, TNF-α, and NF-κB mRNA expression and nNOS, eNOS, iNOS, and COX-2 protein expression in mice with oxidative damage. The results demonstrate that LEO has good antioxidant effects and that CPLEO has a better antioxidant effect than HDLEO as it retains more active non-volatile substances.

The publication of several high‐quality genomes has contributed greatly to clarifying the evolution of citrus. However, due to their complex genetic backgrounds, the origins and evolution of many citrus species remain unclear. We assembled de novo the 294‐Mbp chromosome‐level genome of a more than 200‐year‐old primitive papeda (DYC002). Comparison between the two sets of homologous chromosomes of the haplotype‐resolved genome revealed 1.2% intragenomic variations, including 1.75 million SNPs, 149,471 insertions and 154,215 deletions. Using this genome as a reference, we resequenced and performed population and phylogenetic analyses of 378 representative citrus accessions. Our study confirmed that the primary origin center of core Citrus species is in South China, particularly in the Himalaya–Hengduan Mountains. Papeda species are an ancient Citrus type compared with C. ichangensis. We found that the evolution of the Citrus genus followed two radiations through two routes (to East China and Southeast Asia) along river systems. Evidence for the origin and evolution of some individual citrus species was provided. Papeda probably played an important role in the origins of Australian finger lime, citrons, Honghe papeda and pummelos; Ichang papeda originated from Yuanjiang city of Yunnan Province, China, and C. mangshanensis has a close relationship with kumquat and Ichang papeda. Moreover, the Hunan and Guangdong Provinces of China are predicted to be the origin center of mandarin, sweet orange and sour orange. Additionally, our study revealed that fruit bitterness was significantly selected against during citrus domestication. Taken together, this study provides new insight into the origin and evolution of citrus species and may serve as a valuable genomic resource for citrus breeding and improvement.

Pomelo flowers emit a strong fragrance and give aromatic odors. Volatile compounds from pomelo flowers were analyzed at three developmental stages and in the main organs by molecular sensory science. A total of 134 volatiles including 25 odorants, were analyzed by gas chromatography-mass spectrometry/pulsed flame photometric detector (GC-MS/PFPD) and multidimensional GC-MS/olfactory (MDGC-MS/O). The total volatile content varied among pomelo flowers at different developmental stages (stage-III > stage-II > stage-I) and among different organs of pomelo flowers (petal > pistil > stamen). Linalool was an important odorant with a high OAV, and floral/fruity comprised the predominant aroma profile. Four odorants, ethyl 2-methylbutanoate, linalool, β-myrcene, and 2-butenal, were selected based on variable importance in projection (VIP) values and contributed mainly to the discrimination of pomelo flowers at three different developmental stages. Linalool, β-myrcene, d-limonene, and ethyl hexanoate were potential markers for evaluating flavor differences in pomelo floral organs.