Citrus limonoids (CLs) are a group of highly oxygenated terpenoid secondary metabolites found mostly in the seeds, fruits and peel tissues of citrus fruits such as lemons, limes, oranges, pumellos, grapefruits, bergamots, and mandarins. Represented by limonin, the aglycones and glycosides of CLs have shown to display numerous pharmacological activities including anticancer, antimicrobial, antioxidant, antidiabetic and insecticidal among others. In this review, the chemistry and pharmacology of CLs are systematically scrutinised through the use of medicinal chemistry tools and structure-activity relationship approach. Synthetic derivatives and other structurally-related limonoids from other sources are include in the analysis. With the focus on literature in the past decade, the chemical classification of CLs, their physico-chemical properties as drugs, their biosynthesis and enzymatic modifications, possible ways of enhancing their biological activities through structural modifications, their ligand efficiency metrics and systematic graphical radar plot analysis to assess their developability as drugs are among those discussed in detail.

https://www.mdpi.com/1420-3049/21/11/1530/pdf/1

The Chemistry and Pharmacology of Citrus Limonoids

The viewpoints of “medicine food homology” (MFH) conform to today's food requirements of returning to a natural and green healthy life. This paper aims to introduce the concept of MFH and its origin and evolution, and analyze the relationship between food and Chinese medicine. In this review, more than 80 MFH materials approved by China's Ministry of Health are listed and their effective ingredients are summarized in detail. Their treatment mechanism in TCM and western medicine are summarized too. Moreover, some new MFH resources that have been gradually developed are also introduced. MFH materials are a treasure house of functional factors for current functional foods. Innovative ideas for the development of MFH resources in current functional foods are prospected and discussed, such as taking advantage of Chinese diet theory, building a database for MFH varieties and developing new methods and technologies. At present, modern research for the development of MFH functional foods is still in its primary stage, there is still much work required in the popularization of the MFH concept and the development of new products. Knowledge and technological innovations in this area should be accelerated in the future to promote the modernization of MFH.

Origin and concept of medicine food homology and its application in modern functional foods

Citrus aurantium L. (Rutaceae), commonly known as bitter orange, possesses multiple therapeutic potentials. These biological credentials include anticancer, antianxiety, antiobesity, antibacterial, antioxidant, pesticidal, and antidiabetic activities. The essential oil of C. aurantium was reported to display marked pharmacological effects and great variation in chemical composition depending on growing locations but mostly contained limonene, linalool, and β-myrcene. Phytochemically, C. aurantium is rich in p-synephrine, an alkaloid, and many health-giving secondary metabolites such as flavonoids. Animal studies have demonstrated a low affinity of p-synephrine for adrenergic receptors and an even lower affinity in human models. The present review focuses on the different biological activities of the C. aurantium in animal and human models in the form of extract and its pure secondary metabolites. Finally, it is concluded that both the extract and isolated compounds have no unwanted effects in human at therapeutic doses and, therefore, can confidently be used in various dietary formulations.

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An Overview on Citrus aurantium L.: Its Functions as Food Ingredient and Therapeutic Agent.

Relationship between volatile components, antimicrobial and antioxidant properties of the essential oil, hydrosol and extracts of Citrus aurantium L. flowers.

SARS-CoV-2 infection (COVID-19) is in focus over all known human diseases, because it is destroying the world economy and social life, with increased mortality rate each day. To date, there is no specific medicine or vaccine available against this pandemic disease. However, the presence of medicinal plants and their bioactive molecules with antiviral properties might also be a successful strategy in order to develop therapeutic agents against SARS-CoV-2 infection. Thus, this review will summarize the available literature and other information/data sources related to antiviral medicinal plants, with possible ethnobotanical evidence in correlation with coronaviruses. The identification of novel antiviral compounds is of critical significance, and medicinal plant based natural compounds are a good source for such discoveries. In depth search and analysis revealed several medicinal plants with excellent efficacy against SARS-CoV-1 and MERS-CoV, which are well-known to act on ACE-2 receptor, 3CLpro and other viral protein targets. In this review, we have consolidated the data of several medicinal plants and their natural bioactive metabolites, which have promising antiviral activities against coronaviruses with detailed modes of action/mechanism. It is concluded that this review will be useful for researchers worldwide and highly recommended for the development of naturally safe and effective therapeutic drugs/agents against SARS-CoV-2 infection, which might be used in therapeutic protocols alone or in combination with chemically synthetized drugs.

Plants-derived biomolecules as potent antiviral phytomedicines: new insights on ethnobotanical evidences against coronaviruses

Bioactivity evaluations of ingredients extracted from the flowers of Citrus aurantium L. var. amara Engl.

Fourteen Zingiberaceae species, widely used in China for both food and medicine, were selected to evaluate and compare their antioxidant, antimicrobial and cytotoxic activities. Results indicated that seven species displayed high antioxidant activity, while eight species exhibited different degrees of antimicrobial activities (minimum inhibitory concentrations were 2.00–40.00 μg/ml), and six species exhibited cytotoxicity on the SMMC-7721 cells. Alpinia officinarum and Alpinia oxyphylla showed a broader antimicrobial spectrum, while Curcuma phaeocaulis and Zingiber officinale displayed specific inhibition on Escherichia coli. Amomum villosum showed strong radical scavenging capacity. Amomum kravanh and Curcuma longa exhibited significant cytotoxicity. Overall, the antioxidant, antimicrobial and cytotoxic activities of the 14 species showed obvious diversities. It is hoped that, from the results, the biological activity of ginger plants can be used more rationally and effectively in future.

Hai-Yan Zhao

Papers

Bioactivity evaluations of ingredients extracted from the flowers of Citrus aurantium L. var. amara Engl.

Evaluation of multi-activities of 14 edible species from Zingiberaceae

Protective effect of compounds from the flowers of Citrus aurantium L. var. amara Engl against carbon tetrachloride-induced hepatocyte injury.