Identification and Quantification of Polymethoxylated Flavonoids in Different Citrus Species Using UPLC-QTOF-MS/MS and HPLC-DAD

An integrated multi-system to screen quality markers of blossom of Citrus aurantium L. var. amara Engl. via combining lipid-lowering and expectorant assays

The present research demonstrated that an integrated multi-system based on the assays of lipid-lowering and expectorant effects was used to screen quality markers of an edible and medical material-the blossom of Citrus aurantium L. var. amara Engl. (BCAVA)-and a portion of active constituents were quantified in multiple batches to provide scientific data to establish a quality standard for BCAVA. Mouse models were developed to evaluate the lipid-lowering and expectorant effects, facilitating the investigation of medicinal parts through different polar extractions of BCAVA. Subsequently, ultra-high-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry was utilized for the in vivo and in vitro identification of chemical profiles within the medicinal parts of BCAVA. This methodological approach led to the selection and quantification of several active compounds from 21 batches of BCAVA sourced from different geographical regions samples. Notably, the ethanol extract of BCAVA exhibited significant lipid-lowering and expectorant effects while 183 compounds were identified in vitro and 109 in vivo, respectively. Then, five key ingredients were quantified, and the quantitative data were subjected to statistical analysis to discriminate between samples from various geographical regions. Overall, the findings underscore the significance of an integrated, assay-based approach for the characterization and quality assessment of BCAVA.

Recent advances in the therapeutic potential of nobiletin against respiratory diseases

BACKGROUND

Nobiletin is a natural polymethoxylated flavonoid widely present in citrus fruit peels. It has been demonstrated to exert the effects of anti-tumor, anti-inflammation, anti-oxidative, anti-apoptotic and improve cardiovascular function. Increasing evidences suggest that nobiletin plays an important role in respiratory diseases (RDs) treatment.

OBJECTIVE

This review aimed to investigate the therapeutic potential of nobiletin against RDs, such as lung cancer, COPD, pulmonary fibrosis, asthma, pulmonary infection, acute lung injury, coronavirus disease 2019, and pulmonary arterial hypertension.

METHODS

We retrieved extensive literature of relevant literatures in English until June 26, 2023 from the database of PubMed, Web of Science, and Scopus databases. The keywords of "nobiletin and lung", "nobiletin and respiratory disease", "nobiletin and chronic respiratory diseases", "nobiletin and metabolites", "nobiletin and pharmacokinetics", "nobiletin and toxicity" were searched in pairs. A total of 298 literatures were retrieved from the above database. After excluding the duplicates and reviews, 53 were included in the current review.

RESULTS

We found that the therapeutic mechanisms are based on different signaling pathways. Firstly, nobiletin inhibited the proliferation and suppressed the invasion and migration of cancer cells by regulating the related pathway or key target, like Bcl-2, PD-L1, PARP, and Akt/GSK3β/β-catenin in lung cancer treatment. Secondly, nobiletin treats COPD and ALI by targeting classical signaling pathway mediating inflammation. Besides, the available findings show that nobiletin exerts the effect of PF treatment via regulating mTOR pathway.

CONCLUSIONS

With the wide range of pharmacological activities, high efficiency and low toxicity, nobiletin can be used as a potential agent for preventing and treating RDs. These findings will contribute to further research on the molecular mechanisms of nobiletin and facilitate in-depth studies on nobiletin at both preclinical and clinical levels for the treatment of RDs.

Compositional Analysis of Four Kinds of Citrus Fruits with an NMR-Based Method for Understanding Nutritional Value and Rational Utilization: From Pericarp to Juice

Citrus is one of the most important economic crops and is widely distributed across the monsoon region. Citrus fruits are deeply loved by consumers because of their special color, fragrance and high nutritional value. However, their health benefits have not been fully understood, especially the pericarps of citrus fruits which have barely been utilized due to their unknown chemical composition. In the present study, the pericarp and juices of four typical varieties of citrus fruits (lemon, dekopon, sweet orange and pomelo) were analyzed by NMR spectroscopy combined with pattern recognition. A total of 62 components from the citrus juices and 87 components from the citrus pericarps were identified and quantified, respectively. The different varieties of the citrus fruits could be distinguished from the others, and the chemical markers in each citrus juice and pericarp were identified by a combination of univariate and multivariate statistical analyses. The nutritional analysis of citrus juices offers favorable diet recommendations for human consumption and data guidance for their potential medical use, and the nutritional analysis of citrus pericarps provides a data reference for the subsequent comprehensive utilization of citrus fruits. Our results not only provide an important reference for the potential nutritional and medical values of citrus fruits but also provide a feasible platform for the traceability analysis, adulteration identification and chemical composition analysis of other fruits.

Characterization of a Caffeic Acid 8-O-Methyltransferase from Citrus and Its Function in Nobiletin Biosynthesis

Nobiletin (3',4',5,6,7,8-hexamethoxyflavone) is a polymethoxylated flavonoid specifically accumulated in citrus fruit with numerous beneficial effects to human health. In this study, a novel O-methyltransferase (CitOMT2) was isolated from three citrus varieties, Ponkan mandarin (Citrus reticulata Blanco), Nou 6 ("King mandarin" × "Mukaku-kishu"), and Satsuma mandarin (Citrus unshiu Marc.), and its functions were characterized in vitro. The gene expression results showed that CitOMT2 was highly expressed in the two nobiletin abundant varieties of Ponkan mandarin and Nou 6. However, the expression level of CitOMT2 was low in the flavedo of Satsuma mandarin, in which only a small amount of nobiletin was accumulated. Functional analysis suggested that CitOMT2 was a caffeic acid 8-O-methyltransferase, and it catalyzed the O-methylation of 7,8-dihydroxyflavone at 8-OH. As the methylation of flavone at 8-OH was required for nobiletin biosynthesis, the results presented in this study suggested that CitOMT2 was a key gene regulating nobiletin accumulation in citrus fruit.