The Chemistry and Pharmacology of Citrus Limonoids

Metabolic profiling and enzyme inhibitory activity of the essential oil of citrus aurantium fruit peel

BACKGROUND

Bitter orange (Citrus aurantium) is a fruiting shrub native to tropical and subtropical countries around the world and cultivated in many regions due to its nutraceutical value. The current study investigated the metabolic profiling and enzyme inhibitory activities of volatile constituents derived from the C. aurantium peel cultivated in Egypt by three different extraction methods.

METHODS

The volatile chemical constituents of the peel of C. aurantium were isolated using three methods; steam distillation (SD), hydrodistillation (HD), and microwave-assisted hydrodistillation (MAHD), and then were investigated by GC-MS. The antioxidant potential was evaluated by different assays such as DPPH, ABTS, FRAP, CUPRAC, and phosphomolybdenum and metal chelating potential. Moreover, the effect of enzyme inhibition of the three essential oils was tested using BChE, AChE, tyrosinase, glucosidase, as well as amylase assays.

RESULTS

A total of six compounds were detected by GC/MS analysis. The major constituent obtained by all three extraction methods was limonene (98.86% by SD, 98.68% by HD, and 99.23% by MAHD). Differences in the composition of the compounds of the three oils were observed. The hydrodistillation technique has yielded the highest number of compounds, notably two oxygenated monoterpenes: linalool (0.12%) and α-terpineol acetate (0.1%).

CONCLUSION

In our study differences in the extraction methods of C. aurantium peel oils resulted in differences in the oils' chemical composition. Citrus essential oils and their components showed potential antioxidant, anticholinesterase, antimelanogenesis, and antidiabetic activities. The presence of linalool and α-terpineol acetate may explain the superior activity observed for the oil isolated by HD in both radical scavenging and AChE inhibition assays, as well as in the enzyme inhibition assays.

Chemometric discrimination of eight citrus plants utilizing chromatographic and spectroscopic techniques and insights into their biological potentials

Citrus sinensis balady orange, C. sinensis navel orange, C. paradisi, C. limon, C. sinensis bloody orange, C. sinensis sweet orange, C. aurantium var. amara and C. reticulata were successfully discriminated using chromatographic and spectroscopic techniques coupled with chemometrics. Ultraviolet spectroscopy (UV), and nuclear magnetic resonance spectroscopy (NMR) managed to discriminate the alcohol extract samples to six and five clusters respectively on exposing the obtained data to Principle component analysis (PCA). High performance liquid chromatography (HPLC) was utilized for differentiating the different samples based upon their rutin content where C. aurantium demonstrated the highest rutin content (0.795 mg/mL). LC-ESI-MS led to the identification of 35 compounds belonging mainly to flavonoids and limonoids. In vitro biological investigations including DDPH, ABTS, FRAP and enzyme inhibitory activities revealed the promising antioxidant, neuroprotective, anti-hyperglycaemic and skin-lightning potentials of citrus samples that were correlated with the total phenol and flavonoid contents. In silico ADME/TOPKAT reflected the acceptable pharmacokinetic, pharmacodynamic and toxicity properties of the identified secondary metabolites.

Enhancement of hepatoprotective activity of limonin from citrus seeds against acetaminophen-induced liver injury by HSCCC purification and liposomal encapsulation

Limonin is a natural tetracyclic triterpenoid compound in citrus seeds that presents hepatoprotective effects but is often discarded as agricultural waste because of its low content and low solubility. Herein, limonin with high purity (98.11%) from citrus seeds was obtained via purification by high-speed counter-current chromatography (HSCCC) and recrystallization. Limonin-loaded liposomes (Lip-LM) prepared by thin film hydration and high pressure homogenization method to enhance its solubility and hepatoprotective effect on APAP-induced liver injury (AILI). Lip-LM appeared as lipid nanoparticles under a transmission electron microscope, and showed well dispersed nano-scale size (69.04 ± 0.42 nm), high encapsulation efficiency (93.67% ± 2.51%), sustained release, fine stability. Lip-LM also exhibited significantly better hepatoprotective activity on AILI than free limonin in vivo. In summary, Lip-LM might be used as a potential hepatoprotective agent in the form of dietary supplement and provide an effective strategy to improve the potential value of citrus seeds.

Identifying citrus limonoids as a potential fusion inhibitor of DENV-2 virus through its in silico study and FTIR analysis

Dengue virus type 2 (DENV-2) is an arthropod-borne deadly RNA human pathogen transmitted through the mosquito Aedes. The DENV-2 roots viral infection by facilitating entry with its envelope glycoprotein to the receptor protein Dendritic-cell-specific ICAM3-grabbing non-integrin (DC-SIGN) through membrane fusion. Here, an organizational path is reported for inhibiting the transition due to fusion activation and by blocking the residues of the DC-SIGN-E-Glyco protein complex through citrus limonoids with its antiviral effect. Based on lower binding affinity obtained with E-glycoprotein, and based on ADMET and drug-likeness study, limonin was selected as having effective interaction with DC-SIGN-E-glycoprotein complex in comparison to other citrus limonoids. The FTIR spectra performed with the limonin-E-glycoprotein sample provide evidence of hydrogen bond formation that indicates the formation of a strong limonin-E-glycoprotein conjugate. Further, the strong physical interaction between DC-SIGN and small limonin molecules in comparison to that of E-glyco with DC-SIGN assures the development of immunity against DENV-2.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40203-024-00207-2.

Computational Binding Study Hints at Ecdysone 20-Mono-Oxygenase as the Hitherto Unknown Target for Ring C-Seco Limonoid-Type Insecticides

The insecticidal property of ring C-seco limonoids has been discovered empirically and the target protein identified, but, to date, the molecular mechanism of action has not been described at the atomic scale. We elucidate on computational grounds whether nine C-seco limonoids present sufficiently high affinity to bind specifically with the putative target enzyme of the insects (ecdysone 20-monooxygenase). To this end, 3D models of ligands and the receptor target were generated and their interaction energies estimated by docking simulations. As a proof of concept, the tetrahydro-isoquinolinyl propenamide derivative QHC is the reference ligand bound to aldosterone synthase in the complex with PDB entry 4ZGX. It served as the 3D template for target modeling via homology. QHC was successfully docked back to its crystal pose in a one-digit nanomolar range. The reported experimental binding affinities span over the nanomolar to lower micromolar range. All nine limonoids were found with strong affinities in the range of -9 < ΔG < -13 kcal/mol. The molt hormone ecdysone showed a comparable ΔG energy of -12 kcal/mol, whereas -11 kcal/mol was the back docking result for the liganded crystal 4ZGX. In conclusion, the nine C-seco limonoids were strong binders on theoretical grounds in an activity range between a ten-fold lower to a ten-fold higher concentration level than insecticide ecdysone with its known target receptor. The comparable or even stronger binding hints at ecdysone 20-monooxygenase as their target biomolecule. Our assumption, however, is in need of future experimental confirmation before conclusions with certainty can be drawn about the true molecular mechanism of action for the C-seco limonoids under scrutiny.

Insights into the Mechanism of Action of the Degraded Limonoid Prieurianin

Limonoids are extremely diversified in plants, with many categories of products bearing an intact, rearranged or fragmented oxygenated scaffold. A specific subgroup of fragmented or degraded limonoids derives from the tetranortriterpenoid prieurianin, initially isolated from the tree Trichilia prieuriana but also found in other plants of the Meliaceae family, including the more abundant species Aphanamixis polystachya. Prieurianin-type limonoids include about seventy compounds, among which are dregeanin and rohitukin. Prieurianin and analogs exhibit insecticidal, antimicrobial, antiadipogenic and/or antiparasitic properties but their mechanism of action remains ill-defined at present. Previous studies have shown that prieurianin, initially known as endosidin 1, stabilizes the actin cytoskeleton in plant and mammalian cells via the modulation of the architecture and dynamic of the actin network, most likely via interference with actin-binding proteins. A new mechanistic hypothesis is advanced here based on the recent discovery of the targeting of the chaperone protein Hsp47 by the fragmented limonoid fraxinellone. Molecular modeling suggested that prieurianin and, to a lesser extent dregeanin, can form very stable complexes with Hsp47 at the protein-collagen interface. Hsp-binding may account for the insecticidal action of the product. The present review draws up a new mechanistic portrait of prieurianin and provides an overview of the pharmacological properties of this atypical limonoid and its chemical family.

Limonin inhibits the stemness of cancer stem-like cells derived from colorectal carcinoma cells potentially via blocking STAT3 signaling

BACKGROUND

Limonin is one of the most abundant active ingredients of Tetradium ruticarpum. It exerts antitumor effects on several kinds of cancer cells. However, whether limonin exerts antitumor effects on colorectal cancer (CRC) cells and cancer stem-like cells (CSCs), a subpopulation responsible for a poor prognosis, is unclear.

AIM

To evaluate the effects of limonin on CSCs derived from CRC cells.

METHODS

CSCs were collected by culturing CRC cells in serum-free medium. The cytotoxicity of limonin against CSCs and parental cells (PCs) was determined by cholecystokinin octapeptide-8 assay. The effects of limonin on stemness were detected by measuring stemness hallmarks and sphere formation ability.

RESULTS

As expected, limonin exerted inhibitory effects on CRC cell behaviors, including cell proliferation, migration, invasion, colony formation and tumor formation in soft agar. A relatively low concentration of limonin decreased the expression stemness hallmarks, including Nanog and β-catenin, the proportion of aldehyde dehydrogenase 1-positive CSCs, and the sphere formation rate, indicating that limonin inhibits stemness without presenting cytotoxicity. Additionally, limonin treatment inhibited invasion and tumor formation in soft agar and in nude mice. Moreover, limonin treatment significantly inhibited the phosphorylation of STAT3 at Y705 but not S727 and did not affect total STAT3 expression. Inhibition of Nanog and β-catenin expression and sphere formation by limonin was obviously reversed by pretreatment with 2 μmol/L colievlin.

CONCLUSION

Taken together, these results indicate that limonin is a promising compound that targets CSCs and could be used to combat CRC recurrence and metastasis.

Exploration of limonoids for their broad spectrum antiviral potential via DFT, molecular docking and molecular dynamics simulation approach

Limonoids serve as vital secondary metabolites. Citrus limonoids show a wide range of pharmacological potential. As a result of which limonoids from citrus are of considerable research interest. Identification of new therapeutic molecules from natural origins has been widely adopted as a successful strategy in drug discovery. This work mainly focused on the high-throughput computational exploration of the antiviral potential of three vital limonoids, i.e. Obacunone, Limonin and Nomilin against spike proteins of SARS CoV-2 (PDB:6LZG), Zika virus NS3 helicase (PDB:5JMT), Serotype 2 RNA dependent RNA polymerase of dengue virus (PDB:5K5M). Herein we report the molecular docking, MD simulation studies of nine docked complexes, and density functional theory (DFT) of selected limonoids. The results of this study indicated that all three limonoids have good molecular features but out of these three obacunone exerted satisfactory results for DFT, docking and MD simulation study.

Citrus clementine Peel Essential Oil Ameliorates Potassium Dichromate-Induced Lung Injury: Insights into the PI3K/AKT Pathway

Acute Lung Injury (ALI) is a life-threatening syndrome that has been identified as a potential complication of COVID-19. There is a critical need to shed light on the underlying mechanistic pathways and explore novel therapeutic strategies. This study aimed to examine the potential therapeutic effects of Citrus clementine essential oil (CCEO) in treating potassium dichromate (PDC)-induced ALI. The chemical profile of CCEO was created through GC-MS analysis. An in vivo study in rats was conducted to evaluate the effect of CCEO administrated via two different delivery systems (oral/inhalation) in mitigating acute lung injury (ALI) induced by intranasal instillation of PDC. Eight volatile compounds were identified, with monoterpene hydrocarbons accounting for 97.03% of the identified constituents, including 88.84% of D-limonene. CCEO at doses of 100 and 200 mg/kg bw exhibited antioxidant and anti-inflammatory properties. These significant antioxidant properties were revealed through the reduction of malondialdehyde (MDA) and the restoration of reduced glutathione (GSH). In addition, inflammation reduction was observed by decreasing levels of cytokines tumor necrosis factor-α and tumor growth factor-β (TNF-α and TGF-β), along with an increase in phosphatidylinositide-3-kinase (PI3K) and Akt overexpression in lung tissue homogenate, in both oral and inhalation routes, compared to the PDC-induced group. These results were supported by histopathological studies and immunohistochemical assessment of TGF-β levels in lung tissues. These findings revealed that CCEO plays an integral role in relieving ALI induced by intranasal PDC and suggests it as a promising remedy.

Chemical profile of persian lime seeds (Citrus Limettioides T.): Focus on limonoids and polyphenols

Citrus fruit industrial processing generates tons of waste composed of peels, seeds and pulp. Incorrect disposal of these residues may harm the environment. The extraction of oil and bioactive compounds from citrus fruit seeds may be considered a sustainable alternative to the disposal of waste by the citrus agroindustry. In order to provide safe disposal of citrus waste an evaluation of its composition is necessary. Here we report the results of the application of a methodology to evaluate the composition the seeds of Citrus limettioides. In the first step, extraction with supercritical carbon dioxide was used. This work allowed the isolation and identification of four aglycone-type limonoids by High Performance Liquid Chromatography and Nuclear Magnetic Resonance, identified as limonin, nomilin, deacetylnomilin, and obacunone. In addition, six other polar limonoids and two glycosyl flavonoids were identified by HPLC-ESI/MS/MS.

An overview of limonoid synthetic derivatives as promising bioactive molecules

Limonoids, a class of abundant natural tetracyclic triterpenoids, present diverse biological activity and provide a versatile platform amenable by chemical modifications for clinical use. Among all of the limonoids isolated from natural sources, obacunone, nomilin, and limonin are the primary hub of limonoid-based chemical modification research. To date, more than 800 limonoids analogs have been synthesized, some of which possess promising biological activities. This review not only discusses the synthesis of limonoid derivatives as promising therapeutic candidates and details the pharmacological studies of their underlying mechanisms from 2002 to 2022, but also proposes a preliminary limonoid synthetic structure-activity relationship (SAR) and provides future direction of limonoid derivatization research.

Natural compounds as lactate dehydrogenase inhibitors: potential therapeutics for lactate dehydrogenase inhibitors-related diseases

Lactate dehydrogenase (LDH) is a crucial enzyme involved in energy metabolism and present in various cells throughout the body. Its diverse physiological functions encompass glycolysis, and its abnormal activity is associated with numerous diseases. Targeting LDH has emerged as a vital approach in drug discovery, leading to the identification of LDH inhibitors among natural compounds, such as polyphenols, alkaloids, and terpenoids. These compounds demonstrate therapeutic potential against LDH-related diseases, including anti-cancer effects. However, challenges concerning limited bioavailability, poor solubility, and potential toxicity must be addressed. Combining natural compounds with LDH inhibitors has led to promising outcomes in preclinical studies. This review highlights the promise of natural compounds as LDH inhibitors for treating cancer, cardiovascular, and neurodegenerative diseases.

Comparative study on secondary metabolites from different citrus varieties in the production area of Zhejiang

To investigate the distribution pattern of bioactive components and their correlations between citrus varieties, we thoroughly analyzed secondary metabolites (including flavonoids, phenolic acids, carotenoids, and limonoids) in the peel and pulp of 11 citrus varieties from the production area of Zhejiang. Citrus peels accumulated metabolites far more than the pulp, and the accumulation varied significantly between species. Flavonoids were the most abundant compounds, followed by phenolic acids, with carotenoids and limonoids being far less abundant than the first two, but limonoids were more abundant than carotenoids. Hesperidin was the main flavonoid in most varieties, but cocktail grapefruit and Changshanhuyou contained naringin, with Ponkan having the most abundant polymethoxylated flavones (PMFs). The major components of phenolic acids, carotenoids, and limonoids were ferulic acid, β-cryptoxanthin, and limonin, respectively. Principal component analysis (PCA) and hierarchical cluster analysis (HCA) indicated that these components were mostly correlated with each other, and these citrus varieties could be categorized into four groups by pulp and three groups by peel. The obtained results filled the data gap for secondary metabolites from local citrus and could provide data references for citrus resource utilization, selection and breeding of superior varieties, and other research.

Evolution-guided multiomics provide insights into the strengthening of bioactive flavone biosynthesis in medicinal pummelo

Pummelo (Citrus maxima or Citrus grandis) is a basic species and an important type for breeding in Citrus. Pummelo is used not only for fresh consumption but also for medicinal purposes. However, the molecular basis of medicinal traits is unclear. Here, compared with wild citrus species/Citrus-related genera, the content of 43 bioactive metabolites and their derivatives increased in the pummelo. Furthermore, we assembled the genome sequence of a variety for medicinal purposes with a long history, Citrus maxima 'Huazhouyou-tomentosa' (HZY-T), at the chromosome level with a genome size of 349.07 Mb. Comparative genomics showed that the expanded gene family in the pummelo genome was enriched in flavonoids-, terpenoid-, and phenylpropanoid biosynthesis. Using the metabolome and transcriptome of six developmental stages of HZY-T and Citrus maxima 'Huazhouyou-smooth' (HZY-S) fruit peel, we generated the regulatory networks of bioactive metabolites and their derivatives. We identified a novel MYB transcription factor, CmtMYB108, as an important regulator of flavone pathways. Both mutations and expression of CmtMYB108, which targets the genes PAL (phenylalanine ammonia-lyase) and FNS (flavone synthase), displayed differential expression between Citrus-related genera, wild citrus species and pummelo species. This study provides insights into the evolution-associated changes in bioactive metabolism during the origin process of pummelo.

Himalayan Citrus jambhiri juice reduced renal crystallization in nephrolithiasis by possible inhibition of glycolate oxidase and matrix metalloproteinases

ETHNOPHARMACOLOGICAL RELEVANCE

Citrus fruits are a very rich source of electrolytes and citric acid. They have been used traditionally for treating urinary ailments and renal stones. Citrus jambhiri is indigenously used as a diuretic.

AIM OF THE STUDY

Present study aimed at establishing the antiurolithiatic potential of the juice of Citrus jambhiri fruits along with the elucidation of the mechanism involved in the urolithiasis disease defying activity.

METHODS

The antiurolithiatic activity was established by means of nucleation, growth and aggregation assay in the in vitro settings and by means of ethylene glycol mediated calcium oxalate urolithiasis in the male Wistar rats. Docking studies were performed in an attempt to determine the mechanism of the antiurolithiatic action.

RESULTS

Present study revealed the role of C. jambhiri fruit juice in reducing nucleation, growth and aggregation of calcium oxalate crystals by possible reduction in the urinary supersaturation relative to calcium oxalate and raising the zeta potential of the calcium oxalate crystals. C. jambhiri fruit juice treatment in experimental rats produced significant amelioration of hypercalciuria, hyperoxaluria, hyperphosphaturia, hyperproteinuria, hyperuricosuria, hypocitraturia and hypomagnesiuria and ion activity product of calcium oxalate. It exhibited nephroprotection against calcium oxalate crystals induced renal tubular dilation and renal tissue deterioration. Docking studies further revealed high binding potential of the phytoconstituents of C. jambhiri viz. narirutin, neohesperidin, hesperidin, rutin and citric acid with glycolate oxidase and matrix metalloproteinase-9.

CONCLUSION

C. jambhiri fruit juice possesses excellent antiurolithiatic activity. The study reveals antiurolithiatic mechanism that involves restoration of equilibrium between the promoters and inhibitors of stone formation; and inhibition of matrix metalloproteinases and glycolate oxidase.

A review of citrus plants as functional foods and dietary supplements for human health, with an emphasis on meta-analyses, clinical trials, and their chemical composition

Fruits, flowers, leaves, essential oils, hydrosols, and juices of citrus spp. Are utilized to prepare various forms of food products. Along with their nutritional values, in the health industry, different parts of the plants of the citrus genus have been used as supplements or remedies to prevent or control diseases. This review focused on reported meta-analyses and clinical trials on the health benefits of citrus plants as functional foods. Also, chemical compounds of various citrus species were reviewed. The following information sources were used for data collection: Google Scholar, the Web of Science, Scopus, and PubMed. Various keywords, including "citrus AND chemical compounds," "citrus AND phytochemicals," "citrus species," "citrus AND meta-analysis," "nutritional and therapeutical values of citrus spp.," "clinical trials AND citrus," "clinical trials AND Rutaceae," "health benefits of citrus spp.," "citrus edible or non-edible applications," and scientific names of the citrus plants were utilized to collect data for the review. The scientific name and common name of all twenty-eight citrus species, along with any of the above keywords, were also searched in the mentioned databases. Scientific papers and data sources were sought to review and discuss the citrus plant's nutritional and therapeutic importance. Several meta-analyses and clinical trials have reported beneficial effects of citrus spices on a variety of cancer risks, cardiovascular risk factors, neurologic disorders, urinary tract conditions, and gastrointestinal tract conditions. They have shown anxiolytic, antimicrobial, and pain-alleviating effects. Some of them can be helpful in managing obesity and cardiovascular risk factors.

LC-MS and GC-MS Data Fusion Metabolomics Profiling Coupled with Multivariate Analysis for the Discrimination of Different Parts of Faustrime Fruit and Evaluation of Their Antioxidant Activity

The comparative chemical composition of different part of Faustrime fruits (peels, pulp, albedo, and seeds) extracted with different solvents was determined by GC-MS and UHPLC-HRMS QTof. The obtained data were also combined for their in vitro antioxidant activity by multivariate analysis to define a complex fingerprint of the fruit. The principal component analysis model showed the significative occurrence of volatile organic compounds as α-bisabolol and α-trans-bergamotol in the pulp and albedo, hexanoic acid in the seeds, and several coumarins and phenolics in the peels. The higher radical scavenging activity of the pulp was related to the incidence of citric acid in partial least square regression.

Bioactive Usual and Unusual Triterpenoids Derived from Natural Sources Used in Traditional Medicine

Triterpenoids are accessible in several terrestrial plants as well as marine organisms, including sponges, algae, fungi, and sea cucumbers are examples of marine creatures. So far, more than 20,000 natural triterpenoids have exhibited several varied bioactivities, including anticancer, antimalarial, anti-HIV, inhibit HIF-1 activation, antibacterial, chemopreventive, anti-inflammatory, antioxidant, cardioprotective, antiviral, neuroprotective, hepatoprotective, insecticidal, antidiabetic, cytotoxic. Several plants are used in folklore medicine to treat numerous ailments, and the preparation or uses of traditional practices have been scientifically validated. Although various structural diversity has been observed in the triterpenoids, this review presents the sources and uses of those triterpenoids that showed significant biological activities which could be accessible and promoted to familiar people in the form of traditional medicine or for industrial, or pharmaceutical applications.

Comparative Untargeted Metabolic Profiling of Different Parts of Citrus sinensis Fruits via Liquid Chromatography-Mass Spectrometry Coupled with Multivariate Data Analyses to Unravel Authenticity

Differences between seven authentic samples of Citrus sinensis var. Valencia peel (albedo and flavedo) and juices from Spain and Uruguay, in addition to a concentrate obtained from Brazil, were investigated by untargeted metabolic profiling. Sixty-six metabolites were detected by nano-liquid chromatography coupled to a high-resolution electrospray-ionization quadrupole time-of-flight mass spectrometer (nLC-ESI-qTOF-MS) belonging to phenolic acids, coumarins, flavonoid glycosides, limonoids, terpenes, and fatty acids. Eleven metabolites were detected for the first time in Citrus sinensis and identified as citroside A, sinapic acid pentoside, apigenin-C-hexosyl-O-pentoside, chrysoeriol-C-hexoside, di-hexosyl-diosmetin, perilloside A, gingerol, ionone epoxide hydroxy-sphingenine, xanthomicrol, and coumaryl alcohol-O-hexoside. Some flavonoids were completely absent from the juice, while present most prominently in the Citrus peel, conveying more industrial and economic prospects to the latter. Multivariate data analyses clarified that the differences among orange parts overweighed the geographical source. PCA analysis of ESI-(-)-mode data revealed for hydroxylinoleic acid abundance in flavedo peel from Uruguay the most distant cluster from all others. The PCA analysis of ESI-(+)-mode data provided a clear segregation of the different Citrus sinensis parts primarily due to the large diversity of flavonoids and coumarins among the studied samples.

New Insight on Phenolic Composition and Evaluation of the Vitamin C and Nutritional Value of Smoothies Sold on the Spanish Market

Fruits and vegetables are a source of a wide range of nutrients, including bioactive compounds. These compounds have great biological activity and have been linked to the prevention of chronic non-communicable diseases. Currently, the food industry is developing new products to introduce these compounds, whereby smoothies are becoming more popular among consumers. The aim of this study was to evaluate the nutritional quality and the polyphenol and vitamin C content of smoothies available on the Spanish market. An evaluation of the nutritional information and ingredients was carried out. The phenolic compounds were determined by HPLC-ESI-TOF-MS; the vitamin C content was quantified using HPLC-UV/VIS; and the antioxidant activity was analyzed by DPPH and FRAP. Among all of the ingredients of the smoothies, coconut and banana have shown a negative impact on the polyphenol content of the smoothies. In contrast, ingredients such as orange, mango, and passion fruit had a positive correlation with the vitamin C content. Moreover, apple and red fruits showed the highest positive correlations with most of the phenolic acids, flavonoids, total phenolic compounds, and antioxidant activities. In addition, a clustering analysis was performed, and four groups were clearly defined according to the bioactive composition determined here. This research is a precious step for the formulation of new smoothies and to increase their polyphenol quality.

Concise Chemoenzymatic Synthesis of Gedunin

The limonoids have attracted significant attention from the synthetic community owing to their striking structural complexity and medicinal potential. Recent efforts notwithstanding, synthetic access to many intact or ring D-seco limonoids still remains elusive. Here, we report the first de novo synthesis of gedunin, a ring D-seco limonoid with HSP90 inhibitory activity, that proceeds in 13 steps. Two enabling features in our strategy are the application of modern catalytic transformations to set the key quaternary centers in the carbocyclic core and the use of biocatalytic oxidation at C3 to establish a chemical handle to access the A-ring enone motif. The strategy presented herein may provide an entry point to a wider range of oxidized limonoids.

Citrus aurantium ‘Changshan-huyou’—An ethnopharmacological and phytochemical review

Citrus fruits are composed of oil cells layer, white membrane layer, pulp and seeds. The cultivar Citrus aurantium ‘Changshan-huyou’ (CACH) is a hybridization of Citrus grandis Osbeck and C. sinensis Osbeck. It is a rutaceae plant, and mainly grows in Changshan, Zhejiang, China. With the exploration of its high traditional values, it has been paid more and more attention by the scientific community in recent years. At present, one hundred and two chemical constituents have been identified from the pulp and peel of CACH, including volatile oils, terpenoids, phenols, limonins, sugars, etc., As the representative active component of CACH, phenols have been widely investigated. Studies have shown that CACH shows a variety of significant pharmacological activities, such as anti-inflammatory, antioxidant, hepatoprotective activity, respiratory system protection and intestinal regulation activity. This review mainly introduces the chemical constituents and pharmacological activities of CACH, and discusses its future research and development directions. It will provide theoretical basis for further research of its pharmacodynamic substances, functional mechanism and rational utilization.

A cream containing the sap of oat plantlets and mandarin extract soothes the symptoms of rosacea and improves the quality of life of patients

BACKGROUND

Rosacea is a chronic inflammatory disease of the facial skin that affects all skin types and occurs mostly in adults. The main clinical sign of rosacea is a characteristic and persistent form of centro-facial erythema that is prone to exacerbation and can impair quality of life (QoL). The current therapeutic approach for rosacea is to combine various treatments, use appropriate skincare products and avoid flare-up triggers.

OBJECTIVE

To evaluate the use of a facial skincare product containing protein-free sap extruded from Rhealba® oat plantlets and mandarin extract in subjects with rosacea.

METHODS

Three clinical studies were conducted in adult subjects with various rosacea phenotypes (erythematotelangiectatic or papulopustular) and treatment histories to assess the dermatological and ophthalmological tolerance of the study product, as well as its clinical effectiveness, after a twice-daily application on the whole face and neck for up to 4 weeks.

RESULTS

Tolerance of the product was rated as good to very good by dermatologists across the three studies, which involved a total of 105 evaluable subjects. Subjects with untreated erythematotelangiectatic rosacea reported fewer functional signs and symptoms of the disease and an improved QoL. The evaluation of skin biometric parameters revealed a reduction in transepidermal water loss, indicating that the study product helped to restore skin barrier integrity after 4 weeks, and a higher skin pH, indicating that the cutaneous microbiote was respected. Most subjects (93%) who had either undergone a superficial dermatological procedure for erythematotelangiectatic rosacea or were taking oral/topical treatments for papulopustular rosacea, rated the study product as very good (8/10) and felt it further relieved their symptoms.

CONCLUSION

Overall, the study product was very well tolerated and may be beneficial for subjects with rosacea as an adjunct to superficial dermatological procedures or oral/topical therapies, in line with the current recommendations for rosacea management.

Limonin stabilises SIRT6 by activating USP10 in cardiac hypertrophy

BACKGROUND AND PURPOSE

Limonin, a natural tetracyclic triterpenoid extract, exerts extensive pharmacological effects; however, its role in cardiac hypertrophy remains to be elucidated. We investigated the beneficial effects of limonin on cardiac hypertrophy and explored the potential mechanisms.

EXPERIMENTAL APPROACH

C57/BL6 male mice were subjected to aortic banding (AB) surgery and neonatal rat cardiac myocytes (NRCMs) were stimulated with phenylephrine (PE) to evaluate the effects of limonin on cardiac hypertrophy.

KEY RESULTS

Limonin markedly improved the cardiac function and heart weight in AB operation mice. In addition, limonin-treated mice and NRCMs produced fewer cardiac hypertrophy markers than those treated with the vehicle in hypertrophic groups. Sustained AB- or PE-stimulation impaired cardiac sirtuin 6 (SIRT6) protein levels, which were partially rescued by limonin and subsequently enhanced the activity of PPARα, and Sirt6 siRNA inhibited the anti-hypertrophic effects of limonin in vitro. Interestingly, limonin did not influence Sirt6 mRNA levels, but controlled its ubiquitin levels. Thus, the protein biosynthesis inhibitor, cycloheximide (CHX), and proteasome inhibitor, MG-132, were used to determine SIRT6 protein expression levels. Under PE stimulation, limonin increased SIRT6 protein levels in the presence of CHX, but it didn't influence SIRT6 expression in the presence of MG-132, suggesting that limonin promotes SIRT6 abundance by inhibiting its ubiquitination degradation. Furthermore, limonin inhibited the degradation of SIRT6 by activating ubiquitin-specific peptidase (Cuspidi et al.)-10, while USP10 siRNA abrogated the beneficial effects of limonin.

CONCLUSION AND IMPLICATIONS

Limonin mediates the ubiquitination and degradation of SIRT6 by activating USP10, providing an attractive therapeutic target for cardiac hypertrophy.

The Antimicrobial Potential of the Neem Tree Azadirachta indica

Azadirachta indica (A. Juss), also known as the neem tree, has been used for millennia as a traditional remedy for a multitude of human ailments. Also recognized around the world as a broad-spectrum pesticide and fertilizer, neem has applications in agriculture and beyond. Currently, the extensive antimicrobial activities of A. indica are being explored through research in the fields of dentistry, food safety, bacteriology, mycology, virology, and parasitology. Herein, some of the most recent studies that demonstrate the potential of neem as a previously untapped source of novel therapeutics are summarized as they relate to the aforementioned research topics. Additionally, the capacity of neem extracts and compounds to act against drug-resistant and biofilm-forming organisms, both of which represent large groups of pathogens for which there are limited treatment options, are highlighted. Updated information on the phytochemistry and safety of neem-derived products are discussed as well. Although there is a growing body of exciting evidence that supports the use of A. indica as an antimicrobial, additional studies are clearly needed to determine the specific mechanisms of action, clinical efficacy, and in vivo safety of neem as a treatment for human pathogens of interest. Moreover, the various ongoing studies and the diverse properties of neem discussed herein may serve as a guide for the discovery of new antimicrobials that may exist in other herbal panaceas across the globe.

Citrus maxima (Brum.) Merr. (Rutaceae): Bioactive Chemical Constituents and Pharmacological Activities

Citrus maxima (Burm). Merr. (family Rutaceae), commonly known as Pomelo, is an ethnomedicinally, pharmacologically, and phytochemically valued species. Various ethnomedicinal reports have revealed the use of C. maxima for cough, fever, asthma, diarrhea, ulcer, and diabetes and as a sedative. Numerous phytochemicals have been reported from C. maxima such as polyphenols, terpenoids, sterols, carotenoids, vitamins, and amino acids. The plant possesses significant bioactivities like antioxidant, antimicrobial, anti-inflammatory, analgesic, anticancer, antidiabetic, anti-Alzheimer's disease, insecticidal, anxiolytic, hepatoprotective, antimalarial, and antiobesity. Extensive research is necessary to explore the detailed mechanism of action of extracts and compounds to design effective medicines, herbal products, and functional foods.

Phytochemical Characterization of Citrus-Based Products Supporting Their Antioxidant Effect and Sensory Quality

The increasing attention on the impact of food on human and environmental health has led to a greater awareness about nutrition, food processing, and food waste. In this perspective, the present work deals with the investigation of the chemical non-volatile and volatile profiles of two Citrus-based products, produced through a conscious process, using Citrus peels as natural gelling agents. Moreover, the total polyphenol content (TPC) and the antioxidant properties were evaluated, as well as their sensorial properties. Chemical and antioxidant results were compared with those of Citrus fresh fruits (C. reticulata, C. sinensis, and C. limon). Concerning the non-volatile fingerprint, the two samples showed a very similar composition, characterized by flavanones (naringenin, hesperetin, and eriodyctiol O-glycosides), flavones (diosmetin and apigenin C-glucosides), and limonoids (limonin, nomilinic acid, and its glucoside). The amount of both flavonoids and limonoids was higher in the Lemon product than in the Mixed Citrus one, as well as the TPC and the antioxidant activity. The aroma composition of the two samples was characterized by monoterpene hydrocarbons as the main chemical class, mainly represented by limonene. The sensorial analysis, finally, evidenced a good quality of both the products. These results showed that the most representative components of Citrus fruits persist even after the transformation process, and the aroma and sensorial properties endow an added value to Citrus preparations.

A Targeted Metabolomics Approach to Study Secondary Metabolites and Antioxidant Activity in 'Kinnow Mandarin' during Advanced Fruit Maturity

In this study, we investigated the impact of harvest maturity stages and contrasting growing climates on secondary metabolites in Kinnow mandarin. Fruit samples were harvested at six harvest maturity stages (M1−M6) from two distinct growing locations falling under subtropical−arid (STA) and subtropical−humid (STH) climates. A high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) technique was employed to identify and quantify secondary metabolites in the fruit juice. A total of 31 polyphenolics and 4 limonoids, with significant differences (p < 0.05) in their concentration, were determined. With advancing maturity, phenolic acids and antioxidant activity were found to increase, whereas flavonoids and limonoids decreased in concentration. There was a transient increase in the concentration of some polyphenolics such as hesperidin, naringin, narirutin, naringenin, neoeriocitrin, rutin, nobiletin and tangeretin, and limonoid aglycones such as limonin and nomilin at mid-maturity stage (M3) which coincided with prevailing low temperature and frost events at growing locations. A higher concentration of limonin and polyphenolics was observed for fruit grown under STH climates in comparison to those grown under STA climates. The data indicate that fruit metabolism during advanced stages of maturation under distinct climatic conditions is fundamental to the flavor, nutrition and processing quality of Kinnow mandarin. This information can help in understanding the optimum maturity stage and preferable climate to source fruits with maximum functional compounds, less bitterness and high consumer acceptability.

Phytochemical profile of Tibetan native fruit "Medog lemon" and its comparison with other cultivated species in China

Tibet's native fruit resources have not been explored and remain underutilized due to geographical isolation. "Medog lemon" (ML), an ethno-species of wild citron, is an important functional food and dietary resource for the local people in southeastern Tibet. Herein comprehensive characterization of components of ML were firstly performed with an integrated strategy based on UHPLC-QE Orbitrap MS. A total of 196 components were characterized, among which 33 were detected from Citrus genus for the first time, and 55 were identified as potential new phytochemicals. The chemical comparison of ML with cultivated citron and fingered citron based on partial least squares-discriminant analysis model and univariate analysis revealed the distinct chemical composition of ML and in which more than 30 differentiated components were identified. The distinct morphological and chemical characters, as well as its good antioxidant properties, indicated ML as a potential new food resource that can be beneficial for human health.

General Enantioselective and Stereochemically Divergent Four-Stage Approach to Fused Tetracyclic Terpenoid Systems

Tetracyclic terpenoid-derived natural products are a broad class of medically relevant agents that include well-known steroid hormones and related structures, as well as more synthetically challenging congeners such as limonoids, cardenolides, lanostanes, and cucurbitanes, among others. These structurally related compound classes present synthetically disparate challenges based, in part, on the position and stereochemistry of the numerous quaternary carbon centers that are common to their tetracyclic skeletons. While de novo syntheses of such targets have been a topic of great interest for over 50 years, semisynthesis is often how synthetic variants of these natural products are explored as biologically relevant materials and how such agents are further matured as therapeutics. Here, focus was directed at establishing an efficient, stereoselective, and molecularly flexible de novo synthetic approach that could offer what semisynthetic approaches do not. In short, a unified strategy to access common molecular features of these natural product families is described that proceeds in four stages: (1) conversion of epichlorohydrin to stereodefined enynes, (2) metallacycle-mediated annulative cross-coupling to generate highly substituted hydrindanes, (3) tetracycle formation by stereoselective forging of the C9-C10 bond, and (4) group-selective oxidative rearrangement that repositions a quaternary center from C9 to C10. These studies have defined the structural features required for highly stereoselective C9-C10 bond formation and document the generality of this four-stage synthetic strategy to access a range of unique stereodefined systems, many of which bear stereochemistry/substitution/functionality not readily accessible from semisynthesis.

Chemical Variation of Chenpi (Citrus Peels) and Corresponding Correlated Bioactive Compounds by LC-MS Metabolomics and Multibioassay Analysis

The peel of Citrus reticulata “Chachi” (CP) possesses various health-promoting benefits and is not only one of the most famous Chinese herbal medicine, but also an ingredient in fermented foods. In the present study, the effects of storage years (1-, 3-, 4-, 5-, 6-, and 11-years) on the chemical profiling and potential bioactive compounds of CP were compared by metabolomics and in vitro bioactivity analysis. With the increase of storage time, the content of hesperidin significantly decreased, but nobiletin, 3,5,6,7,8,3′,4′-heptamethoxyflavone, and tangeretin were increased. Meanwhile, the antioxidant activity of CP was enhanced. Phenolic acids, flavonol glycosides, fatty acids, and alkyl glycosides were marker compounds that were responsible for distinguishing the storage time of CP. Correlation analysis suggested that some polyphenols including quercetin-glucoside, quinic acid, trihydroxydimethoxyflavone, and rutin were potential antioxidant compounds in CP. The dichloromethane and n-butanol fractions showed the better antioxidant capacity and inhibitory effects on glucose-hydrolysis enzymes. They mainly contained ferulic acid, nobiletin, 3,5,6,7,8,3′,4′-heptamethoxyflavone, kaempferol, and hesperidin.

Ultrasound-Assisted Extraction, Chemical Characterization, and Impact on Cell Viability of Food Wastes Derived from Southern Italy Autochthonous Citrus Fruits

Citrus fruits are one of the principal fruits used to produce juices. Over the years, these fruits have been recognized as new health-promoting agents. In this work, food wastes derived from autochthonous citrus fruits of Southern Italy, named Limone di Rocca Imperiale, Arancia Rossa Moro, and Arancia Bionda Tardivo from Trebisacce, were analyzed. After fresh-squeezing juice, peel and pomace were employed to obtain six different extracts using an ultrasound-assisted method in a hydroalcoholic solvent. The extracts were analyzed in terms of qualitative composition, antioxidant properties, and antiproliferative activity on MCF-7, MDA-MB-231, and BJ-hTERT cell lines. GC-MS and LC-ESI-MS analyses showed different compounds: of note, limonin-hexoside, neodiosmin, obacunone glucoside, and diacetyl nomilinic acid glucoside have been identified as limonoid structures present in all the samples, in addition to different polyphenols including naringenin-glucoside, hesperetin-O-hexoside-O-rhamnoside-O-glucoside, diferuloyl-glucaric acid ester, chlorogenic acid, and the presence of fatty acids such as palmitic, myristic, and linoleic acids. These extracts were able to exert antioxidant activity as demonstrated by DPPH and ABTS assays and, although at higher doses, to reduce the cell viability of different solid tumor cell lines, as shown in MTT assays.

A Green Extraction Method to Achieve the Highest Yield of Limonin and Hesperidin from Lime Peel Powder (Citrus aurantifolia)

Green extraction is aimed at reducing energy consumption by using renewable plant sources and environmentally friendly bio-solvents. Lime (Citrus aurantifolia) is a rich source of flavonoids (e.g., hesperidin) and limonoids (e.g., limonin). Manufacturing of lime products (e.g., lime juice) yields a considerable amount of lime peel as food waste that should be comprehensively exploited. The aim of this study was to develop a green and simple extraction method to acquire the highest yield of both limonin and hesperidin from the lime peel. The study method included ethanolic-aqueous extraction and variable factors, i.e., ethanol concentrations, pH values of solvent, and extraction temperature. The response surface methodology was used to optimize extraction conditions. The concentrations of limonin and hesperidin were determined by using UHPLC-MS/MS. Results showed that the yields of limonin and hesperidin significantly depended on ethanol concentrations and extraction temperature, while pH value had the least effect. The optimal extraction condition with the highest amounts of limonin and hesperidin was 80% ethanol at pH 7, 50 °C, which yields 2.072 and 3.353 mg/g of limonin and hesperidin, respectively. This study illustrates a green extraction process using food waste, e.g., lime peel, as an energy-saving source and ethanol as a bio-solvent to achieve the highest amount of double bioactive compounds.

Limonin, an AMPK Activator, Inhibits Hepatic Lipid Accumulation in High Fat Diet Fed Mice

NAFLD is the most prevalent liver disease in human history. The treatment is still limited yet. In the current study, we reported that limonin inhibited hepatic lipid accumulation and fatty acid synthesis in HFD fed mice. Using AMPK inhibitor and AMPK deficient C. elegans, we revealed the effect was dependent on the activation of AMPK. We found that limonin activated AMPK through inhibition of cellular energy metabolism and increasing ADP:ATP ratio. Furthermore, the treatment of limonin induced AMPK mediated suppression of the transcriptional activity of SREBP1/2. Our study suggests that limonin may a promising therapeutic agent for the treatment of NAFLD.

Limonin Alleviates Non-alcoholic Fatty Liver Disease by Reducing Lipid Accumulation, Suppressing Inflammation and Oxidative Stress

Non-alcoholic fatty liver disease (NAFLD) is the most common cause of chronic liver disease and continues to rise in the worldwide. Limonin is a triterpenoid compound widely found in the fruits of citrus plants with a wide range of pharmacological effects, including anti-cancer, anti-inflammation, anti-viral, anti-oxidation and liver protection properties. However, the potential molecular mechanism of limonin on NAFLD in zebrafish remains unknown. In this study, zebrafish larvae were exposed to thioacetamide to establish an NAFLD model and the larvae were treated with limonin for 72 h simultaneously. The human liver cell line was stimulated with lipid mixture and meanwhile incubated with limonin for 24 h. The results showed that Limonin significantly reduced the accumulation of lipid droplets in the liver and down-regulated the levels of lipogenic transcription factors FASN and SREBP1 in NAFLD. Limonin suppressed macrophages infiltration and the down-regulated the relative expression levels of the pro-inflammatory factors IL-6, IL-1β and TNF-α secreted by macrophages. Besides, limonin could reversed the reduction of glutathione and the accumulation of reactive oxygen species through up-regulating NRF2/HO-1 signaling pathway in the liver. In conclusion, this study revealed that limonin has a protective effect on NAFLD due to its resistance to lipid deposition as well as antioxidant and anti-inflammatory actions.

Neutral loss scan in complement with high-resolution MS/MS: Combination of detection methods for flavonoid and limonoid glycosides analysis

In this study, neutral loss scan and high-resolution MS/MS were used in combination to detect and tentatively identify various flavonoid and limonoid glycosides in navel orange albedo, juice, peel and pulp. These compound classes are of research interest due to their flavour and bioactive properties, and although flavonoid glycosides have been previously studied in other food matrices, to the best of our knowledge, neutral loss scans have not been used for the elucidation of limonoid glycosides. Neutral loss masses of 120, 162 and 308 Da were selected for the detection of hexose, rutinose and neohesperidose-substituted flavonoids, whereas 197 Da was explored for limonoid glycosides due to their tendency to form ammonium adducts. Fragmentation patterns obtained from targeted MS/MS were then used to differentiate rutinose and neohesperidose substituents as well as flavonoid subclasses of flavones, flavanones and flavonols. Additionally, high-resolution MS/MS was also used for the identification of aglycones by accurate mass (to four decimal places), allowing for the differentiation of aglycones with similar unit masses but different chemical formulas. In total, 19 flavonoid glycosides and six limonoid glycosides were detected. This workflow allows for a rapid screening of flavonoid and limonoid glycosides in citrus, which can be further extended to other food products such as tea.

Integrated Strategy From In Vitro, In Situ, In Vivo to In Silico for Predicting Active Constituents and Exploring Molecular Mechanisms of Tongfengding Capsule for Treating Gout by Inhibiting Inflammatory Responses

The study of screening active constituents from traditional Chinese medicine (TCM) is important for explicating the mechanism of action of TCM and further evaluating the safety and efficacy effectively. However, detecting and identifying the active constituents from complicated biological samples still remain a challenge. Here, a practical, quick, and novel integrated strategy from in vitro, in situ, in vivo to in silico for rapidly screening the active constituents was developed. Firstly, the chemical profile of TCM in vitro was identified using UPLC-Q Exactive-Orbitrap HRMS. Secondly, the in situ intestinal perfusion with venous sampling (IPVS) method was used to investigate the intestinal absorption components. Thirdly, after intragastric administration of the TCM extract, the in vivo absorbed prototype components were detected and identified. Finally, the target network pharmacology approach was applied to explore the potential targets and possible mechanisms of the absorbed components from TCM. The reliability and availability of this approach was demonstrated using Tongfengding capsule (TFDC) as an example of herbal medicine. A total of 141 compounds were detected and identified in TFDC, and among them, 64 components were absorbed into the plasma. Then, a total of 35 absorbed bioactive components and 50 related targets shared commonly by compounds and gout were integrated via target network pharmacology analysis. Ultimately, the effects of the absorbed components on metabolism pathways were verified by experiments. These results demonstrated that this original method may provide a practical tool for screening bioactive compounds from TCM treating particular diseases. Furthermore, it also can clarify the potential mechanism of action of TCM and rationalize the application of TFDC as an effective herbal therapy for gout.

Pharmacognostic approach to evaluate the micromorphological, phytochemical and biological features of Citrus lumia seeds

This study evaluated the micro-morphology as well as the chemical and biological features of Citrus lumia seeds. The cream-colored pyriform seed showed a woody coat covered by a thick layer of mucilage and an embryo with two large cotyledons rich in oil bodies. Hydroxycinnamic acid glycosides and flavonoids are the most abundant compounds in methanol and ethyl acetate extracts (ME and EAE), respectively. Conversely, fatty acids and α-tocopherol represent the main bioactive compounds in the hexane extract (HE). ME showed the most promising antioxidant and anti-inflammatory activities already in cell-free assays. These results were confirmed by experiments carried out on human primary cells. Indeed, ME showed the best inhibitory activity against heat-induced haemolysis and ROS formation in erythrocytes. Moreover, the same order of potency (ME > EAE > HE) was observed also on peripheral blood mononuclear cells, in which the seed extracts were able to decrease TNF-α and IL-6 release after LPS-induced inflammation.

New treatment options for acute rhinosinusitis according to EPOS 2020

Acute rhinosinusitis (ARS) is a very common condition and mostly of viral origin. About 0.5–2% of the viral ARS are complicated by a bacterial infection. Due to viral etiology and inflammatory mechanisms of rhinitis and rhinosinusitis, symptomatic treatment including phytotherapy have been used for their treatment for decades. Scientific societies and expert groups recommend the use of herbal medicines in acute viral and acute post-viral rhinosinusitis. In 2021, Polish patients gained access to a new therapeutic option for acute sinusitis in the form of a drug containing a distillate of a mixture of rectified essential oils of eucalyptus, sweet orange, myrtle and lemon common.

The Ethnobotany and Chemistry of South African Meliaceae: A Review

Meliaceae are widely distributed across the world in tropical or subtropical climates and are of considerable ethnobotanical importance as sources of traditional medicine and cosmetics. This comprehensive review summarizes the ethnobotanical uses and chemistry of 12 South African species, belonging to six genera: Ekebergia, Nymania, Entandrophragma, Pseudobersama, Trichilia, and Turraea. Eight of the species have ethnomedicinal records, classified into 17 major disease categories. The ethnomedicinal uses comprise 85 ailments dominated by gastrointestinal complaints, followed by gynaecological and obstetrics related problems. Chemical records were found for 10 species, which describe nine classes of compounds. In nearly all South African Meliaceae, limonoids are the predominant constituents while triterpenes, sterols, and coumarins are also common. The widest range of use-records and medicinal applications are found with the two most chemically diverse species, Ekebergiacapensis and Trichiliaemetica. Of the chemical compounds identified in the various plant organs of the 10 species of South African Meliaceae for which data are available, 42% was found in bark and 17% in seeds. Roots represent 35% and bark 33% of the organs that are used medicinally, and they are typically prepared as decoctions or infusions. Root and bark harvesting are destructive so that it may be important to examine the chemistry of plant parts such as wild-crafted leaves and fruits.

Interaction of selected terpenoids with two SARS-CoV-2 key therapeutic targets: An in silico study through molecular docking and dynamics simulations

The outbreak of COVID-19 disease caused by SARS-CoV-2, along with the lack of targeted medicaments, forced the scientific world to search for new antiviral formulations. In the current emergent situation, drug repurposing of well-known traditional and/or approved drugs could be the most effective strategy. Herein, through computational approaches, we aimed to screen 14 natural compounds from limonoids and terpenoids class for their ability to inhibit the key therapeutic target proteins of SARS-CoV-2. Among these, some limonoids, namely deacetylnomilin, ichangin and nomilin, and the terpenoid β-amyrin provided good interaction energies with SARS-CoV-2 3CL hydrolase (Mpro) in molecular dynamic simulation. Interestingly, deacetylnomilin and ichangin showed direct interaction with the catalytic dyad of the enzyme so supporting their potential role in preventing SARS-CoV-2 replication and growth. On the contrary, despite the good affinity with the spike protein RBD site, all the selected phytochemicals lose contact with the amino acid residues over the course of 120ns-long molecular dynamics simulations therefore suggesting they scarcely can interfere in SARS-CoV-2 binding to the ACE2 receptor. The in silico analyses of docking score and binding energies, along with predicted pharmacokinetic profiles, indicate that these triterpenoids might have potential as inhibitors of SARS-CoV-2 Mpro, recommending further in vitro and in vivo investigations for a complete understanding and confirmation of their inhibitory potential.

Multifunctional inhibitors of SARS-CoV-2 by MM/PBSA, essential dynamics, and molecular dynamic investigations

The ongoing COVID-19 pandemic demands a novel approach to combat and identify potential therapeutic targets. The SARS-CoV-2 infection causes a hyperimmune response followed by a spectrum of diseases. Limonoids are a class of triterpenoids known to prevent the release of IL-6, IL-15, IL-1α, IL-1β via TNF and are also known to modulate PI3K/Akt/GSK-3β, JNK1/2, MAPKp38, ERK1/2, and PI3K/Akt/mTOR signaling pathways and could help to avoid viral infection, persistence, and pathogenesis. The present study employs a computational approach of virtual screening and molecular dynamic (MD) simulations of such compounds against RNA-dependent RNA polymerase (RdRp), Main protease (Mpro), and Papain-like protease (PLpro) of SARS-CoV-2. MD simulation, Molecular Mechanics Poisson-Boltzmann Surface Area (MM/PBSA), and Essential dynamics revealed that the macromolecule-ligand complexes are stable with very low free energy of binding. Such compounds that could modulate both host responses and inhibit viral machinery could be beneficial in effectively controlling the global pandemic.

In silico analysis of selected components of grapefruit seed extract against SARS-CoV-2 main protease

At the end of December 2019, first identified cases of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) started emerging. Ever since the emergence of the first case of infection with SARS-CoV-2 or COVID-19, it became the hottest research topic of numerous studies, in which scientists are trying to understand the path of infection, transmission, replication and viral action, all in order of finding a potential cure or vaccine applying various fundamental principles and methodologies. Using in silico method via AutoDock Vina 1.1.2., we analysed the binding affinity of six selected compounds from grapefruit seed extract (GSE) (narirutin, naringin, naringenin, limonin, ascorbic acid and citric acid) to SARS-CoV-2 main protease Mpro (PDB ID: 6Y84), using acetoside, remdesivir and gallic acid as a positive controls of binding affinity. Results showed highest affinity (rmsd l.b. 0.000; rmsd u.b. 0.000) for narirutin (-10.5), then for naringin (-10.1), acetoside (-10.0), limonin (-9.9), remdesivir (-9.6), naringenin (-8.2), ascorbic acid (-6.7), citric acid (-6.4) and gallic acid (-6.4), all expressed in kcal/mol. Our findings suggest that selected compounds from grapefruit seed extract represent potential inhibitors of SARS-CoV-2 Mpro, but further research is needed as well as preclinical and clinical trials for final confirmation of inhibitory functionality of these compounds.

Optimization of Ultrasound-Assisted Extraction via Sonotrode of Phenolic Compounds from Orange By-Products

Orange peel is the main by-product from orange juice industry. It is a known source of bioactive compounds, mostly phenolic compounds, and it has been widely studied for its healthy activities. Thus, this research focuses on the establishment of ultrasound-assisted extraction of phenolic compounds in orange peel using a sonotrode. For this purpose, a Box–Behnken design of 27 experiments was carried out with four independent factors—ratio ethanol/water (v/v), time (min), amplitude (%), and pulse (%). Quantitative analyses of phenolic compounds were performed and the antioxidant activity was measured by ABTS and DPPH methods. The validity of the experimental design was confirmed by ANOVA and the optimal sonotrode extraction conditions were obtained by response surface methodology (RSM). The extracts obtained in the established conditions were analyzed by High Performance Liquid Chromatography (HPLC) coupled to mass spectrometer detector and 74 polar compounds were identified. The highest phenolic content and antioxidant activity were obtained using 45/55 ethanol/water (v/v), 35 min, amplitude 90% (110 W), and pulse 100%. The established method allows an increment of phenolics recovery up to 60% higher than a conventional extraction. Moreover, the effect of drying on phenolic content was also evaluated.

Valorization of Bio-Residues from the Processing of Main Portuguese Fruit Crops: From Discarded Waste to Health Promoting Compounds

Food processing generates a large amount of bio-residues, which have become the focus of different studies aimed at valorizing this low-cost source of bioactive compounds. High fruit consumption is associated with beneficial health effects and, therefore, bio-waste and its constituents arouse therapeutic interest. The present work focuses on the main Portuguese fruit crops and revises (i) the chemical constituents of apple, orange, and pear pomace as potential sources of functional/bioactive compounds; (ii) the bioactive evidence and potential therapeutic use of bio-waste generated in the processing of the main Portuguese fruit crops; and (iii) potential applications in the food, nutraceutical, pharmaceutical, and cosmetics industries. The current evidence of the effect of these bio-residues as antioxidant, anti-inflammatory, and antimicrobial agents is also summarized. Conclusions of the revised data are that these bio-wastes hold great potential to be employed in specific nutritional and pharmaceutical applications.