Anti-Inflammatory and Neuroprotective Constituents from the Peels of Citrus grandis

Rhoifolin: A promising flavonoid with potent cytotoxic and anticancer properties: molecular mechanisms and therapeutic potential

Rhoifolin is a flavonoid found in various plant species, especially within the Rutaceae family, and is considered a dietary component due to its presence in edible plants. Its bioactive properties, such as cytotoxic and anticancer activities, have gained significant attention. This review aims to highlight the general properties and diverse bioactivities of rhoifolin, with a particular focus on its cytotoxic and anticancer effects. This is based on a comprehensive literature search, focusing on the presence of rhoifolin in different plant species and its biological activities, particularly its anticancer properties. Rhoifolin is widely distributed in the plant kingdom, especially in Citrus species. It exhibits a variety of bioactivities, including strong cytotoxic and anticancer effects. Recent studies have shown that rhoifolin can induce apoptosis and inhibit cancer cell proliferation, making it a promising candidate for anticancer therapies. Rhoifolin's diverse bioactivities, particularly its cytotoxic and anticancer properties, position it as a potential therapeutic agent. Further detailed investigations into its molecular mechanisms and well-designed clinical studies are needed to fully understand and utilize its therapeutic potential. See also the graphical abstract(Fig. 1).

Rhoifolin, baicalein 5,6-dimethyl ether and agathisflavone prevent amnesia induced in scopolamine zebrafish (Danio rerio) model by increasing the mRNA expression of bdnf, npy, egr-1, nfr2α, and creb1 genes

The increasing attention towards age-related diseases has generated significant interest in the concept of cognitive dysfunction associated with Alzheimer's disease (AD). Certain limitations are associated with the current therapies, and flavonoids have been reported to exhibit multiple biological activities and anti-AD effects in several AD models owing to their antioxidative, anti-inflammatory, and anti-amyloidogenic properties. In this study, we performed an initial in silico predictions of the pharmacokinetic properties of three flavonoids (rhoifolin, baicalein 5,6-dimethyl ether and agathisflavone). Subsequently, we evaluated the antiamnesic and antioxidant potential of flavonoids in concentrations of 1, 3, and 5 μg/L in scopolamine (100 μM)-induced amnesic zebrafish (Danio rerio) model. Zebrafish behavior was analyzed by novel tank diving test (NTT), Y-maze, and novel object recognition test (NOR). Acetylcholinesterase (AChE) activity, brain antioxidant status and the expression of bdnf, npy, egr1, nrf2α, creb1 genes, and CREB-1 protein level was measured to elucidate the underlying mechanism of action. Our flavonoids improved memory and decreased anxiety-like behavior of scopolamine-induced amnesia in zebrafish. Also, the studied flavonoids reduced AChE activity and brain oxidative stress and upregulated the gene expression, collectively contributing to neuroprotective properties. The results of our study add new perspectives on the properties of flavonoids to regulate the evolution of neurodegenerative diseases, especially AD, by modulating the expression of genes involved in the regulation of synaptic plasticity, axonal growth, and guidance, sympathetic and vagal transmission, the antioxidant response and cell proliferation and growth.

Qualitative and quantitative analysis of chemical constituents in goupi plaster prepared by various extraction methods using UPLC-Q-Exactive-MS and UPLC-MS/MS

Goupi plaster, a representative preparation of black plaster, has demonstrated promising effects in treating knee osteoarthritis. However, high temperature used in traditional frying extraction may cause decomposition of its effective components, thus limiting the efficacy. This study aimed to explore the scientific nature of the traditional preparation technology of Goupi plaster, and to compare the effects of different extraction methods on the types of chemical components and the content of index components. The UPLC-Q-Exactive-MS and UPLC-MS/MS technologies which have high efficiency, sensitivity and accuracy, were used to qualitatively and quantitatively analyze the chemical components of Goupi plaster under different preparation processes. The results show that the extraction solvent approach is different from the traditional frying extraction method, and has a positive effect. However, the mechanism of action of Goupi plaster is complex and its pharmacological effects are diverse. Future studies should explore whether it necessary to change the frying extraction method. This experiment provides a theoretical basis that will guide further scientific discussion and research into the frying extraction of Goupi plaster.

Bergaptol, a Major Furocoumarin in Citrus: Pharmacological Properties and Toxicity

Bergaptol (5-hydroxypsoralen or 5-hydroxyfuranocoumarin) is a naturally occurring furanocoumarin widely found in citrus fruits, which has multiple health benefits. Nonetheless, no specific review articles on bergaptol have been published. Compiling updated information on bergaptol is crucial in guiding future research direction and application. The present review focuses on the research evidence related to the pharmacological properties and toxicity of bergaptol. Bergaptol has anti-inflammatory, antioxidant, anti-cancer, anti-osteoporosis, anti-microbial, and anti-lipidemic effects. It can inhibit the activities of cytochrome P450s (CYP), especially CYP2C9 and CYP3A4, thereby affecting the metabolism and concentrations of some drugs and toxins. Compared with other coumarins, bergaptol has the least potency to inhibit CYP3A4 in cancer cells. Instead, it can suppress drug efflux transporters, such as P-glycoprotein, thereby overcoming chemotherapeutic drug resistance. Furthermore, bergaptol has antimicrobial effects with a high potential for inhibition of quorum sensing. In vivo, bergaptol can be retained in plasma for longer than other coumarins. Nevertheless, its toxicity has not been clearly reported. In vitro study suggests that, unlike most furocoumarins, bergaptol is not phototoxic or photomutagenic. Existing research on bergaptol has mostly been conducted in vitro. Further in vivo and clinical studies are warranted to identify the safe and effective doses of bergaptol for its multimodal application.

A Review of the Ethnobotanical Use, Chemistry and Pharmacological Activities of Constituents Derived from the Plant Genus Geijera (Rutaceae)

Geijera Schott is a plant genus of the Rutaceae Juss. (rue and citrus) family, comprising six species which are all native to Oceania. Of the plants belonging to this genus, the most significant species that has a customary use is Geijera parviflora, which was used by Indigenous Australians, primarily as a pain reliever. Herein, a comprehensive review of the literature published on the genus Geijera from 1930 to 2023 was conducted. This is the first review for this plant genus, and it highlights the chemical constituents reported to date, together with the range of pharmacological properties described from the various species and different parts of the plant. These properties include anti-inflammatory, anti-microbial, anti-parasitic, insect repellent, analgesic, neuroactive, and anti-cancer activities. Finally, a reflection on some of the important areas for future focused studies of this plant genus is provided.

Neurotrophic Natural Products

Neurotrophins (NGF, BDNF, NT3, NT4) can decrease cell death, induce differentiation, as well as sustain the structure and function of neurons, which make them promising therapeutic agents for the treatment of neurodegenerative disorders. However, neurotrophins have not been very effective in clinical trials mostly because they cannot pass through the blood-brain barrier owing to being high-molecular-weight proteins. Thus, neurotrophin-mimic small molecules, which stimulate the synthesis of endogenous neurotrophins or enhance neurotrophic actions, may serve as promising alternatives to neurotrophins. Small-molecular-weight natural products, which have been used in dietary functional foods or in traditional medicines over the course of human history, have a great potential for the development of new therapeutic agents against neurodegenerative diseases such as Alzheimer's disease. In this contribution, a variety of natural products possessing neurotrophic properties such as neurogenesis, neurite outgrowth promotion (neuritogenesis), and neuroprotection are described, and a focus is made on the chemistry and biology of several neurotrophic natural products.

Mitigative potential of rhoifolin against cisplatin prompted testicular toxicity: biochemical, spermatogenic and histological based analysis

Rhoifolin (ROF) is a naturally occurring flavonoid compound with diverse pharmacological and therapeutic benefits. The current investigation was designed to evaluate the curative potential of Rhoifolin (ROF) against Cisplatin (CP) induced testicular damage. Mature male albino rats (n = 48) were randomly distributed into 4 equal groups: control, CP (10 mg/kg), CP + ROF (10 mg/kg + 20 mg/kg) and ROF (20 mg/kg) supplemented group. Following 56 days of the trial, biochemical, inflammatory markers, spermatogenic, steroidogenic, hormonal, apoptotic, anti-apoptotic, and histopathological parameters were evaluated. The exposure to CP markedly (p < 0.05) lowered the activities of anti-oxidant enzymes, glutathione reductase (GSR), catalase (CAT), and glutathione peroxidase (GPx) as well as superoxide dismutase (SOD) in testicular tissues of male albino rats. Besides the levels of reactive oxygen species (ROS) and thiobarbituric acid reactive substances (TBARS) were considerably augmented in CP exposed rats. The administration of CP also increased the level of inflammatory cytokines i.e. IL-6, TNF-α, 1L-1β and NF-κβ as well as COX-2 activity. Additionally, a notable (p < 0.05) upsurge was observed in dead sperms count, abnormality in the tail, midpiece as well as head of sperms along with a notable decline in sperm motility in CP treated rats. Moreover, the expressions of steroidogenic enzymes were also lowered in CP administered group. The levels of follicle stimulating hormone (FSH) and plasma testosterone as well as luteinizing hormone (LH) were decreased in CP treated group. Moreover, the expression of Bax as well as Caspase-3 (apoptotic markers) were increased. On the other hand, Bcl-2 expression (anti-apoptotic marker) was reduced. Furthermore, the histopathological analysis showed that CP considerably (p < 0.05) damaged the testicular tissues. However, the administration of ROF significantly reduced the damaging effects of CP in testicular tissues. The results of our study suggested that ROF can potentially alleviate CP-induced testicular damages due to its androgenic, anti-oxidant and anti-inflammatory as well as anti-apoptotic nature.

Qualitative and Quantitative Analyses of the Chemical Components of Peels from Different Pomelo Cultivars (Citrus grandis [L.] Osbeck) Based on Gas Chromatography-Mass Spectrometry, Ultraperformance Liquid Chromatography-Q-Exactive Orbitrap-MS, and High-Performance Liquid Chromatography-Photodiode Array Detection

The volatile and nonvolatile phytochemicals in peels of 5 major pomelo cultivars (including Citrus grandis cv. Yuhuanyou, C. grandis cv. Liangpingyou, C. grandis cv. Guanximiyou, C. grandis cv. Duweiwendanyou, and C. grandis cv. Shatianyou) from 11 places in China were characterized. First, 194 volatile compounds in pomelo peels were identified by gas chromatography-mass spectrometry (GC-MS). Of these, 20 major volatile compounds were subjected to cluster analysis. The heatmap indicated that the volatile compounds in peels of C. grandis cv. Shatianyou and C. grandis cv. Liangpingyou were different from those in other varieties, while there was no difference among C. grandis cv. Guanximiyou, C. grandis cv. Yuhuanyou, and C. grandis cv. Duweiwendanyou from different origins. Second, 53 nonvolatile compounds were identified in pomelo peels by ultraperformance liquid chromatography-Q-exactive orbitrap tandem MS (UPLC-Q-exactive orbitrap-MS), of which 11 components were detected for the first time. Third, six major nonvolatile compounds were quantitatively analyzed with high-performance LC-photodiode array detection (HPLC-PDA). Combining the results of HPLC-PDA and the heatmap, 6 nonvolatile compounds in 12 batches of pomelo peel were well separated among varieties. Comprehensive analysis and identification of chemical components in pomelo peels are of great significance for their further development and utilization.

Valorization of Fruit Waste for Bioactive Compounds and Their Applications in the Food Industry

The fruit production and processing sectors produce tremendous amounts of by-products and waste that cause significant economic losses and an undesirable impact on the environment. The effective utilization of these fruit wastes can help to reduce the carbon footprint and greenhouse gas emissions, thereby achieving sustainable development goals. These by-products contain a variety of bioactive compounds, such as dietary fiber, flavonoids, phenolic compounds, antioxidants, polysaccharides, and several other health-promoting nutrients and phytochemicals. These bioactive compounds can be extracted and used as value-added products in different industrial applications. The bioactive components extracted can be used in developing nutraceutical products, functional foods, or food additives. This review provides a comprehensive review of the recent developments in fruit waste valorization techniques and their application in food industries. The various extraction techniques, including conventional and emerging methods, have been discussed. The antioxidant and antimicrobial activities of the active compounds extracted and isolated from fruit waste have been described. The most important food industrial application of bioactive compounds extracted from fruit waste (FW) has been provided. Finally, challenges, future direction, and concluding remarks on the topic are summarized.

Recent developments in citrus bioflavonoid encapsulation to reinforce controlled antioxidant delivery and generate therapeutic uses: Review

Citrus fruits contain numerous antioxidative biomolecules including phenolic acids, flavonols, flavanones, polymethoxyflavones (PMFs), and their derivatives. Previous in vitro and in vivo studies thoroughly investigated the antioxidant and therapeutic potential of bioflavonoids extracted from different citrus varieties and fruit fractions. Major bioflavonoids such as hesperidin, naringin, naringenin, and PMFs, had restricted their incorporation into food and health products due to their poor solubility, chemical stability and bioavailability. Considering these limitations, modern encapsulation methodologies such as hydrogelation, liposomal interactions, emulsifications, and nanoparticles have been designed to shield bioflavonoids with improved target distribution for therapeutic enhancements. The size, durability, and binding efficiency of bioflavonoid-loaded encapsulates were acquired by the optimized chemical and instrumental parameters such as solubility, gelation, dispersion, extrusion, and drying. Bioflavonoid-enriched encapsulates have been also proven to be effective against cancer, inflammation, neurodegeneration, and various other illnesses. However, in the future, newer natural binding agents with higher binding capacity might accelerate the encapsulating potential, controlled release, and enhanced bioavailability of citrus bioflavonoids. Overall, these modern encapsulation systems are currently leading to a new era of diet-based medicine, as demand for citrus fruit-based nutritional supplements and edibles grows.

Metabolic Profiling and Transcriptional Analysis of Carotenoid Accumulation in a Red-Fleshed Mutant of Pummelo (Citrus grandis)

Citrus grandis ‘Tomentosa’, commonly known as ‘Huajuhong’ pummelo (HJH), is used in traditional Chinese medicine and can moisten the lungs, resolve phlegm, and relieve coughs. A spontaneous bud mutant, named R-HJH, had a visually attractive phenotype with red albedo tissue and red juice sacs. In this study, the content and composition of carotenoids were investigated and compared between R-HJH and wild-type HJH using HPLC–MS analysis. The total carotenoids in the albedo tissue and juice sacs of R-HJH were 4.03- and 2.89-fold greater than those in HJH, respectively. The massive accumulation of carotenoids, including lycopene, β-carotene and phytoene, led to the attractive red color of R-HJH. However, the contents of flavones, coumarins and most volatile components (mainly D-limonene and γ-terpinene) were clearly reduced in R-HJH compared with wild-type HJH. To identify the molecular basis of carotenoid accumulation in R-HJH, RNA-Seq transcriptome sequencing was performed. Among 3948 differentially expressed genes (DEGs), the increased upstream synthesis genes (phytoene synthase gene, PSY) and decreased downstream genes (β-carotene hydroxylase gene, CHYB and carotenoid cleavage dioxygenase gene, CCD7) might be the key factors that account for the high level of carotenoids in R-HJH. These results will be beneficial for determining the molecular mechanism of carotenoid accumulation and metabolism in pummelo.

Utilization of Pomelo (Citrus maxima) Peel Waste into Bioactive Essential Oils: Chemical Composition and Insecticidal Properties

Simple Summary

The disposal of agricultural waste products is an emerging concern and an alternative to this is the development of value-added products from these wastes. Here we extracted the essential oil from Citrus maxima (CMEO) and examined its larvicidal and pest control potentials. Results pointed out that CMEO can be effective biopesticides against two major insect pests of stored grains. Furthermore, CMEO had a significant larvicidal action against different mosquito species. This study provided useful information on the compositional aspects and insecticidal properties of CMEO.

Abstract

The wastes generated during the post-harvest handling of various agricultural commodities is rather under-utlilized. The peels of citrus fruits are often discarded as waste. Citrus peels are rich in essential oils and exhibit toxicity towards various insect species. The essential oils are also an eco-friendly option for insect pest management. The Citrus maxima peel essential oil (CMEO), a waste product, characterized it, and evaluated its potential for insect pest management. The major terpenoids present in CMEO are Limonene and α-Pinene. The CMEO displayed potentials in controlling the insect pests via contact and fumigant toxicity. Moreover, CMEO showed significant larvicidal activities against Culex tritaeniorhynchus and Aedes aegypti species of mosquitoes; however, Armigeres subalbatus was more resistant. The biological safety of the essential oil was also tested against the stored seeds, where no significant inhibition of seed germination was noticed compared to the control. Utilizing a waste product such as citrus peel for pest management can achieve the dual objective of waste utilization and eco-friendly pest management. Overall, the CMEO is therefore found to be a bioactive essential oil extracted from the wastes of pomelo (C. maxima).

Fruit Peels: Food Waste as a Valuable Source of Bioactive Natural Products for Drug Discovery

Fruits along with vegetables are crucial for a balanced diet. These not only have delicious flavors but are also reported to decrease the risk of contracting various chronic diseases. Fruit by-products are produced in huge quantity during industrial processing and constitute a serious issue because they may pose a harmful risk to the environment. The proposal of employing fruit by-products, particularly fruit peels, has gradually attained popularity because scientists found that in many instances peels displayed better biological and pharmacological applications than other sections of the fruit. The aim of this review is to highlight the importance of fruit peel extracts and natural products obtained in food industries along with their other potential biological applications.

Flavonoids as inhibitors of human neutrophil elastase

Elastase is a proteolytic enzyme belonging to the family of hydrolases produced by human neutrophils, monocytes, macrophages, and endothelial cells. Human neutrophil elastase is known to play multiple roles in the human body, but an increase in its activity may cause a variety of diseases. Elastase inhibitors may prevent the development of psoriasis, chronic kidney disease, respiratory disorders (including COVID-19), immune disorders, and even cancers. Among polyphenolic compounds, some flavonoids and their derivatives, which are mostly found in herbal plants, have been revealed to influence elastase release and its action on human cells. This review focuses on elastase inhibitors that have been discovered from natural sources and are biochemically characterised as flavonoids. The inhibitory activity on elastase is a characteristic of flavonoid aglycones and their glycoside and methylated, acetylated and hydroxylated derivatives. The presented analysis of structure-activity relationship (SAR) enables the determination of the chemical groups responsible for evoking an inhibitory effect on elastase. Further study especially of the in vivo efficacy and safety of the described natural compounds is of interest in order to gain better understanding of their health-promoting potential.

Structurally diverse biflavonoids from the fruits of Citrus medica L. var. sarcodactylis Swingle and their hypolipidemic and immunosuppressive activities

The fruit of Citrus medica L. var. sarcodactylis Swingle is not only used as a traditional medicinal plant, but also served as a delicious food. Six new (3'→7″)-biflavonoids (1-6), and twelve known biflavonoid derivatives (7-18) were isolated and characterized from the fruits of C. medica L. var. sarcodactylis Swingle for the first time. Their structures were determined by extensive and comprehensive analyzing NMR, HR-ESI-MS, UV, and IR spectral data coupled with the data described in the literature. Compounds (1-18) were evaluated for their hypolipidemic activities with Orlistat as the positive control, and assayed for their immunosuppressive activities with Dexamethasone as the positive control, respectively. Among them, compounds (1-3) exhibited moderate inhibition of pancreatic lipase activity by inhibiting 68.56 ± 1.40%, 56.18 ± 1.57%, 53.51 ± 1.59% of pancreatic lipase activities at the concentration of 100 μM, respectively. Compounds (4-6) and 8 showed potent immunosuppressive activities with the IC₅₀ values from 16.83 ± 1.32 to 50.90 ± 1.79 μM. The plausible biogenetic pathway and preliminary structure activity relationship of the selected compounds were scientifically summarized and discussed in this study.

Rhoifolin Alleviates Inflammation of Acute Inflammation Animal Models and LPS-Induced RAW264.7 Cells via IKKβ/NF-κB Signaling Pathway

Rhoifolin (ROF) is a main effective component in Citrus grandis 'Tomentosa'. ROF has a potential anti-inflammatory activity, but its specific effects and mechanisms have not been studied. This study investigated the anti-inflammatory activity of ROF and searched for its possible molecular mechanisms. A mouse model of acute inflammation was induced by lipopolysaccharide, and the effects of ROF on pathological damages of the lung and liver were observed. Carrageenan-induced paw edema rat model was used to evaluate the effect of ROF on the volume of swelling paw. In LPS-induced RAW264.7 macrophages, the expression levels of pro-inflammatory cytokines IL-1β, IL-6, and TNF-α were measured using ELISA. Real-time PCR was used to measure the mRNA levels of iNOS and CCL2. Western blot was used to detect the activation of IκBα and IKKβ in NF-κB signaling pathways. The results showed that ROF accelerated the recoveries of liver and lung tissue damages in acute inflammation mice and inhibited carrageenan-induced paw edema in rats; in addition, ROF significantly suppressed the secretion of TNF-α, IL-1β, and IL-6 in the serum of rats and mouse model. In LPS-induced RAW264.7 cells, 100 μmol/L ROF enhanced cell viability and suppressed the production of TNF-α, IL-6, and IL-1β significantly. ROF also decreased the mRNA expression of iNOS and CCL2 and inhibited IκBα and IKKβ phosphorylation. In summary, ROF had a potential therapeutic value for inflammation. Our research provided experimental basis for the further development of ROF as an anti-inflammatory drug and for clarifying the anti-inflammatory substance basis of Citrus grandis 'Tomentosa'. Graphical Abstract.

Valorization of Citrus Co-Products: Recovery of Bioactive Compounds and Application in Meat and Meat Products

Citrus fruits (orange, lemon, mandarin, and grapefruit) are one of the most extensively cultivated crops. Actually, fresh consumption far exceeds the demand and, subsequently, a great volume of the production is destined for the citrus-processing industries, which produce a huge quantity of co-products. These co-products, without proper treatment and disposal, might cause severe environmental problems. The co-products obtained from the citrus industry may be considered a very important source of high-added-value bioactive compounds that could be used in the pharmaceutical, cosmetic, and dietetic industries, and mainly in the food industry. Due to consumer demands, the food industry is exploring a new and economical source of bioactive compounds to develop novel foods with healthy properties. Thus, the aim of this review is to describe the possible benefits of citrus co-products as a source of bioactive compounds and their applications in the development of healthier meat and meat products.

Isolation and characterization of neolignan derivatives with hepatoprotective and neuroprotective activities from the fruits of Citrus medica L. var. Sarcodactylis Swingle

The fruit of Citrus medica L. var. sarcodactylis Swingle is a functional food with rich nutrients and medicinal values because of its content of bioactive compounds. A bioactivity-guided chemical investigation from the fruits of C. medica L. var. sarcodactylis Swingle afforded three new benzodioxane neolignans (1-3), three new phenanthrofuran neolignan glycosides (4-6), two new biphenyl-ketone neolignans (7-8), two new 1',7'-bilignan neolignans (9-10), as well as fourteen known neolignan derivatives (11-24), which were isolated and characterized from the fruits of C. medica L. var. sarcodactylis Swingle for the first time. These neolignan derivatives were determined by extensive and comprehensive analyzing NMR, HR-ESI-MS, UV, IR spectral data and compared with the data described in the literature. Among them, compounds 1-3 and 12-13 exhibited moderate hepatoprotective activities to improve the survival rates of HepG2 cells from 46.26 ± 1.90% (APAP, 10 mM) to 67.23 ± 4.25%, 62.87 ± 4.43%, 60.06 ± 6.34%, 56.75 ± 2.30%, 58.35 ± 6.14%, respectively. Additionally, compounds 7-8 and 21-22 displayed moderate neuroprotective activities to raise the survival rates of PC12 cells from 55.30 ± 2.25% to 66.94 ± 3.37%, 70.98 ± 5.05%, 64.64 ± 1.93%, and 62.81 ± 4.11% at 10 μM, respectively. The plausible biogenetic pathway and preliminary structure-activity relationship of the selected compounds were scientifically summarized and discussed in this paper.

Isolation and Characterization of Neuroprotective Components from Citrus Peel and Their Application as Functional Food

The elderly experience numerous physiological alterations. In the brain, aging causes degeneration or loss of distinct populations of neurons, resulting in declining cognitive function, locomotor capability, etc. The pathogenic factors of such neurodegeneration are oxidative stress, mitochondrial dysfunction, inflammation, reduced energy homeostatis, decreased levels of neurotrophic factor, etc. On the other hand, numerous studies have investigated various biologically active substances in fruit and vegetables. We focused on the peel of citrus fruit to search for neuroprotective components and found that: 1) 3,5,6,7,8,3',4'-heptamethoxyflavone (HMF) and auraptene (AUR) in the peel of Kawachi Bankan (Citrus kawachiensis) exert neuroprotective effects; 2) both HMF and AUR can pass through the blood-brain barrier, suggesting that they act directly in the brain; 3) the content of AUR in the peel of K. Bankan was exceptionally high, and consequently the oral administration of the dried peel powder of K. Bankan exerts neuroprotective effects; and 4) intake of K. Bankan juice, which was enriched in AUR by adding peel paste to the raw juice, contributed to the prevention of cognitive dysfunction in aged healthy volunteers. This review summarizes our studies in terms of the isolation/characterization of HMF and AUR in K. Bankan peel, analysis of their actions in the brain, mechanisms of their actions, and trials to develop food that retains their functions.

Neuroprotective and Neurorestorative Effects of Holothuria scabra Extract in the MPTP/MPP+-Induced Mouse and Cellular Models of Parkinson's Disease

Extracts from Holothuria scabra (HS) have been shown to possess anti-inflammation, anti-oxidant and anti-cancer activities. More recently, it was shown to have neuroprotective potential in Caenorhabditis elegans PD model. Here, we assessed whether HS has neuroprotective and neurorestorative effects on dopaminergic neurons in both mouse and cellular models of PD. We found that both pre-treatment and post-treatment with HS improved motor deficits in PD mouse model induced with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) as determined by grid walk test. This was likely mediated by HS protective and restorative effects on maintaining the numbers of dopaminergic neurons and fibers in both substantia nigra pars compacta (SNpc) and striatum. In a cellular model of PD, HS significantly attenuated 1-methyl-4-phenylpyridinium (MPP⁺)-induced apoptosis of DAergic-like neurons differentiated from SH-SY5Y cells by enhancing the expression of Bcl-2, suppressing the expression of cleaved Caspase 3 and preventing depolarization of mitochondrial membrane. In addition, HS could stimulate the expression of tyrosine hydroxylase (TH) and suppressed the formation of α-synuclein protein. Taken together, our in vivo and in vitro findings suggested that HS is an attractive candidate for the neuroprotection rather than neurorestoration in PD.

Neuroprotective potential of Myrica esulenta in Haloperidol induced Parkinson's disease

BACKGROUND

Myrica esculenta is a notable therapeutic plant widely utilized in Indian system of medicine. Ayurvedic literature reported fruit and bark of this plant is used in gulma, jvara, arsa, grahani, pandu roga, hrillasa, mukha roga, kasa, svasa, agnimandhya, aruchi, meha, and kantharoga.

OBJECTIVE

The present study aimed to investigate the neuroprotective potential of "Himalayan Bayberry" (Myrica esculenta Buch.-Ham. ex D. Don) leaves methanol extract in Parkinson's disease induced by haloperidol.

MATERIALS AND METHODS

The present investigation was completed in wistar rats, in which Parkinson's disease (PD) was induced with haloperidol 1 mg/kg, intraperitoneally. The rats were randomly divided into six gatherings and the test animals received the methanolic extract of M. esculenta (MEME) at a dose of 50, 100 and 200 mg/kg, orally for one week. Various behavioural, biochemical and histopathological parameters were estimated in haloperidol exposed rats.

RESULTS

MEME demonstrated significant and dose-dependent increment in behavioural activity and improved muscle coordination. The significant diminution in malonaldehyde level while improved the level of antioxidant enzymes like catalase, superoxide dismutase and reduced glutathione in extract treated group were observed as compared to the control group. Histopathological changes revealed MEME significantly reduced haloperidol-induced damage in the substantia nigra and there was very little neuronal atrophy.

CONCLUSION

The outcomes showed the defensive role of M. esculenta against PD. The mechanism of protection may be due to an escalation of cellular antioxidants.

Ameliorative Effects of Rhoifolin in Scopolamine-Induced Amnesic Zebrafish (Danio rerio) Model

Rhoifolin (Rho) exerts many biological activities such as anticancer, antidiabetic, hepatoprotective, antirheumatic, antibacterial, and antiviral properties. The neuroprotective action of this compound has not been studied. The goal of this study was to investigate the improvement impact of Rho on scopolamine (Sco)-induced zebrafish anxiety, amnesia, and brain oxidative stress and to elucidate the underlying mechanisms involved. Zebrafish were treated with Rho (1, 3, and 5 μg/L) for nine consecutive days and were subsequently subjected to Sco (100 μM) 30 min before behavioral tests (novel tank diving test, Y-maze, and novel object recognition tests). Rho was isolated from Chorisia crispiflora (Malvaceae) leaves and identified by different spectroscopic techniques. To further assess the possible mechanisms of Rho in enhancing the memory capacities in zebrafish, the in vivo antioxidant status and acetylcholinesterase (AChE) activity was also evaluated. Rho from Chorisia crispiflora leaves was identified. Rho could alleviate anxiety, memory deficits, and brain oxidative stress in Sco-treated zebrafish and could regulate the cholinergic function by inhibiting the AChE activity. Our results demonstrated that Rho could be a promising candidate compound against anxiety and amnesia by restoring the cholinergic activity and the amelioration of brain oxidative stress.

Integrated anti-hyperlipidemic bioactivity of whole Citrus grandis [L.] osbeck fruits-multi-action mechanism evidenced using animal and cell models

Changes in human life style have increased the incidence of obesity which has become a risk factor to human health. In Taiwan, the annual production of Citrus grandis [L.] reaches 75 000 tons, while the amount of waste fruits could reach 5%. We propose that abundant phytochemicals present in the wastes can be beneficial to attenuate obesity with hyperlipidemia. An animal Wistar rat model showed that pomelo flesh, peels, carpel (the segmental membrane), as well as the essential oil attenuated obesity as well as hyperlipidemia, and the AMPK-SREBP-PPARS pathway was involved. To further verify the mechanism, a HepG2 cell model was used to test some representative pomelo phytonutrients including limonene (Ln), γ-terpinene (γT), p-synephrine (SP), β-sitosterol (βS), and hesperidin (Hn). Data interestingly revealed it to be a multiple mechanism of anti-lipogenic bioactivity via downregulating the enzymes involved in both the cholesterol and triacylglyceride de novo biosynthesis (in the order of decreasing bioactivity): acetyl CoA carboxylase (Hn, SP, βS, Ln = γT), fatty acid synthase (Ln, γT, SP, βS, Hn), HMG-CoA synthase (Ln, Hn, SP, βS, γT), and HMG-CoA reductase (Hn, Ln, βS, γT, SP), and via upregulation of cholesterol-7α-monooxygenase (CYP7A1) (Hn, βS). In addition, all pomelo fruit parts enhanced the fecal crude lipid and sterol excretion capability. Thus, fruits of C. grandis can serve as a rather promising integrative antihyperlipidemic agent.

Low-Molecular Weight Metabolites from Polyphenols as Effectors for Attenuating Neuroinflammation

Age-associated pathophysiological changes such as neurodegenerative diseases are multifactorial conditions with increasing incidence and no existing cure. The possibility of altering the progression and development of these multifactorial diseases through diet is an attractive approach with increasing supporting data. Epidemiological and clinical studies have highlighted the health potential of diets rich in fruits and vegetables. Such food sources are rich in (poly)phenols, natural compounds increasingly associated with health benefits, having the potential to prevent or retard the development of various diseases. However, absorption and the blood concentration of (poly)phenols is very low when compared with their corresponding (poly)phenolic metabolites. Therefore, these serum-bioavailable metabolites are much more promising candidates to overcome cellular barriers and reach target tissues, such as the brain. Bearing this in mind, it will be reviewed that the molecular mechanisms underlying (poly)phenolic metabolites effects, range from 0.1 to <50 μM and their role on neuroinflammation, a central hallmark in neurodegenerative diseases.

Nobiletin suppresses IL-21/IL-21 receptor-mediated inflammatory response in MH7A fibroblast-like synoviocytes (FLS): An implication in rheumatoid arthritis

The mechanisms driving the development and progression of Rheumatoid arthritis (RA) are complex, novel targeted therapies are gaining traction as potential methods to prevent or slow the progression of RA. Nobiletin is a derivative of citrus fruit that has been shown to attenuate the development of osteoarthritis and inhibit the expression of proinflammatory cytokines. However, the exact mechanisms by which nobiletin exerts these chondroprotective effects remain poorly understood. In the present study, we investigated the impact of nobiletin in mediating the effects of interleukin-21 (IL-21) in MH7A fibroblast-like synoviocytes (FLS), the main cell type found in the articular synovium. Firstly, we demonstrate that nobiletin (25 μM and 50 μM) reduced the expression of the IL-21 receptor by 29% and 51%, respectively, in FLS. Additionally, our findings demonstrate that nobiletin potently ameliorated IL-21-induced increased production of reactive oxygen species and 4-hydroxynonenal, increased expression of interleukin 6 (IL-6), tumor necrosis factor-α (TNF-α), and high-mobility group box 1 (HMGB1), and decreased mitochondrial membrane potential. We also demonstrate the ability of nobiletin to attenuate IL-21-induced expression of matrix metalloproteinases 3 and 13 (MMP-3, MMP-13), key degradative enzymes involved in RA-associated cartilage destruction. Finally, we show that the effects of nobiletin are mediated through the JAK1/STAT3 pathway, as nobiletin significantly reduced the phosphorylation of both JAK1 and STAT3. Taken together, our findings indicate that nobiletin may offer a safe and effective treatment against the development and progression of RA induced by the expression of IL-21 and its receptor.

Prenylated benzenepropanoic acid analogues from the Citrus grandis (L.) Osbeck and their anti-neuroinflammatory activity

Phytochemical studies of the air-dried pericarp of Citrus grandis led to the isolation of four new compounds including three prenylated benzenepropanoic acids (2, 3 and 5) and one alkamidic glycoside (6), together with ten known compounds (1, 4 and 7-14). The structures of these compounds were determined by the NMR spectroscopy, optical rotation data and modified Mosher's method. Meanwhile, the anti-neuroinflammatory activities of all isolated compounds were evaluated by detecting the production of nitric oxide (NO) in LPS-stimulated BV2 cells. The results showed that compounds 1, 2, 5 and 13 exhibited strong inhibition effects on NO production in LPS-stimulated BV2 cells. Mechanistically, compounds 1, 2 and 5 could suppress the expressions of iNOS. In addition, compounds 1, 2 and 5 also showed obvious inhibition effects on COX-2 expression, another vital enzyme in the inflammation process, in LPS-treated BV2 cells. These findings shed light on the potent anti-neuroinflammatory effects of Citrus grandis.

Modern Extraction and Purification Techniques for Obtaining High Purity Food-Grade Bioactive Compounds and Value-Added Co-Products from Citrus Wastes

Citrus contains a range of highly beneficial bioactive compounds, such as polyphenols, carotenoids, and vitamins that show antimicrobial and antioxidant properties and help in building the body's immune system. On consumption or processing, approximately 50% of the fruit remains as inedible waste, which includes peels, seeds, pulp, and segment residues. This waste still consists of substantial quantities of bioactive compounds that cause environmental pollution and are harmful to the ecosystem because of their high biological oxygen demand. In recent years, citrus cultivation and the production of processed foods have become a major agricultural industry. In addition to being a substantial source of economy, it is an ideal and sustainable and renewable resource for obtaining bioactive compounds and co-products for food and pharmaceutical industries. In the present article, the various methods of extraction, conventional and modern, as well as separation and isolation of individual bioactive compounds from the extraction mixture and their determination have been reviewed. This article presents both aspects of extraction methods, i.e., on a small laboratory scale and on an industrial mass scale. These methods and techniques have been extensively and critically reviewed with anticipated future perspectives towards the maximum utilization of the citrus waste.

Anti-inflammatory Effect of Pomelo Peel and Its Bioactive Coumarins

Citrus grandis (L.) Osbeck is a popular fruit cultivated around the world, and its peels are sometimes used for the treatment of cough, abdominal pain, and indigestion in China. However, the peel is discarded after fruit consumption in most cases, and its chemical constituents and biological activities have not been validated before. The present study focused on evaluation of the chemical and pharmacological profile of coumarins from peels of C. grandis against inflammation. The extracts and phytochemicals from peels of C. grandis were prepared, and anti-inflammatory activities were carried out in vivo and in vitro, including inhibiting xylene-induced ear edema and carrageenan-induced paw edema in mice and the production of inflammatory cytokines (interleukin 1β, prostaglandin 2, and tumor-necrosis factor α) in lipopolysaccharide (LPS)-induced RAW 264.7 cells. Results indicated that methanolic extract, ethyl acetate fraction, and four major coumarins (compounds 7, 8, 13, and 16) inhibited swelling induced by xylene and carrageenan, separately, in vivo. Furthermore, 18 coumarins inhibited inflammatory factor secretion in macrophages primed by LPS, in which compounds 4, 6, 7, 10, 17 showed the most pronounced change, which were comparable to dexamethasone. In summary, peel of C. grandis showed an anti-inflammatory effect and coumarin compounds were responsible for regulating inflammatory mediators and cytokines, which might provide a novel nutritional strategy for inflammatory diseases.

Coumarin Analogues from the Citrus grandis (L.) Osbeck and Their Hepatoprotective Activity

Seven new coumarin analogues (1, 2, and 4-8), together with ten known analogues (3, 9-17), were isolated from the air-dried pericarp of Citrus grandis. The structures of these compounds were determined by HR-ESI-MS, UV/vis, and 1D- and 2D-NMR spectra. Meanwhile, the hepatoprotective activities of all these coumarins were evaluated by MTT assays using the d-galactosamine-induced LO2 cell injury model. The results show that compounds 3 and 4 exhibited the strongest hepatoprotective activities. Moreover, compounds 3 and 4 suppressed increases in the levels of alanine transaminase (ALT) and aspartate transaminase (AST) in d-galactosamine-treated LO2 cells, further confirming the hepatoprotective effects of these compounds. Mechanistically, compounds 3 and 4 increased the activities of antioxidant enzymes such as superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) and decreased the level of malondialdehyde (MDA) in injured LO2 cells induced by d-galactosamine. These findings shed light on a better understanding of the hepatoprotective effect of Citrus grandis, providing novel insights into the development of coumarin-based hepatoprotective drugs in the future.

Bioactivity-Guided Separation of Potential D₂ Dopamine Receptor Antagonists from Aurantii Fructus based on Molecular Docking Combined with High-Speed Counter-Current Chromatography

The typical compounds of Aurantii fructus (AF) reported in previous research were screened for their high antagonistic ability on the D₂ dopamine receptor (D₂R) in silico, and then bioactivity-guided separation was undertaken on the potential D₂R antagonists from AF using high-speed counter-current chromatography (HSCCC). Three flavanones, two polymethoxyflavonoids, and three coumarins were effectively isolated from ethanol extracts of Aurantii fructus (AF) by the use of a two-step HSCCC method, and their chemical structures were identified by mass spectrometry, ¹H-NMR, and ¹³C-NMR and compared with published data. Firstly, crude extract of 70% ethanol eluent (150 mg) was isolated by HSCCC using an n-hexane−ethyl acetate−n-butanol−methanol−0.05% acetic acid (1:3:1.8:1:5, v/v/v/v/v) solvent system, and compounds 1 (naringin, 28 mg), 2 (neohesperidin, 13 mg), 3 (meranzin, 5 mg) and 4 (poncirin, 3 mg) were successfully isolated with 98.5%, 95.1%, 97.7%, and 92.4% purity, respectively. Then, the crude extract of 95% ethanol eluent (120 mg) was isolated by n-hexane−n-butanol−ethanol (methanol)−0.05% acetic acid (2:0.6:1:3, v/v/v/v) solvent system and compounds 3 (meranzin, 3 mg), 5 (meranzin hydrate, 4 mg), 6 (isomeranzin, 6 mg), 7 (nobiletin, 10 mg), and 8 (tangeretin, 7 mg) were successfully isolated with 95.8%, 98.5%, 95.1%, 92.4%, and 97.7% purity, respectively. Naringenin, a parent structure of naringin with the excellent binding score of −9.3 kcal/mol, was completely in conjunction with the active site of D₂R, indicating that it is critical for the treatment of gastrointestinal dysfunction. The results indicated that the bioactivity-guided method is practical for the effective separation of active compounds from natural resources.

Neuroprotective effect of Citrus kawachiensis (Kawachi Bankan) peels, a rich source of naringin, against global cerebral ischemia/reperfusion injury in mice

Cerebral ischemia/reperfusion is known to induce the generation of reactive oxygen species and inflammatory responses. Numerous studies have demonstrated that naringin (NGIN) has anti-oxidant and anti-inflammatory properties. We previously reported that Citrus kawachiensis contains a large quantity of NGIN in its peel. In the present study, we orally (p.o.) administered dried peel powder of C. kawachiensis to mice of a transient global ischemia model and found in the hippocampus region that it 1) suppressed neuronal cell death, 2) reversed the reduction in the level of phosphorylated calcium-calmodulin-dependent protein kinase II, 3) had the tendency to reverse the reduction in the level of glutathione, and 4) blocked excessive activation of microglia and astrocytes. These results suggested that the dried peel powder of C. kawachiensis had a neuroprotective effect against ischemic brain via anti-oxidative and anti-inflammatory effects. We also showed that these effects of the dried peel powder were more powerful than those obtained with a comparable amount of NGIN alone.

Study on Chemical Profile and Neuroprotective Activity of Myrica rubra Leaf Extract

The chemical profile of Myrica rubra (a native species in China) leaf extract was investigated by UPLC-PDA-HRMS, and the neuroprotective activity of two characteristic constituents, myricanol and myricetrin, was evaluated with N2a cells using H₂O₂-inducedoxidative challenge through a series of methods, e.g., MTT assay, ROS assay and [Ca2+]i assay. Among the 188 constituents detected in the extract of Myrica rubra leaf, 116 were identified definitely or tentatively by the comprehensive utilization of precise molecular weight and abundant multistage fragmentation information obtained by quadrupole orbitrap mass spectrometry. In addition, 14 potential new compounds were reported for the first time. This work established an example for the research of microconstituents in a complex analyte and revealed that suppression of H₂O₂-induced cytotoxicity in N2a cells was achieved by the pretreatment with myricanol. The evidence suggested myricanol may potentially serve as a remedy for prevention and therapy of neurodegenerative diseases induced by oxidative stress.