Valorization of pomelo ( Citrus grandis Osbeck) peel: A review of current utilization, phytochemistry, bioactivities, and mechanisms of action

Metabolomic profiles and differential metabolites of volatile components in Citrus aurantium Changshan-huyou pericarp during different growth and development stages

Citrus fruits possess a distinctive aroma and flavor, with Citrus aurantium Changshan-huyou (CACH) standing out due to their considerable edible and medicinal value. However, the volatile components (VOCs) in the CACH pericarp (CP) remain underexplored. In this study, gas chromatography-mass spectrometry (GC-MS) was utilized to qualitatively analyze VOCs in 27 CP samples across different growth stages. A total of 544 VOCs were identified, including 91 terpenoids. The types, quantities and distributions of VOCs were conducted. Detailed discussions on the major terpenoids in CP were also presented. A metabolomics approach combining multivariate statistical analysis with univariate analysis was employed for screening the differential metabolites. The study provides comprehensive insights into the VOCs in CP and citrus plants. Moreover, it delivers the first in-depth analysis of differential metabolites in CP throughout the entire CACH growth and development process, laying a foundation for ongoing research and development of the VOCs in CP.

Analysis of the Pomelo Peel Essential Oils at Different Storage Durations Using a Visible and Near-Infrared Spectroscopic on Intact Fruit

Pomelo fruit pulp mainly is consumed fresh and with very little processing, and its peels are discarded as biological waste, which can cause the environmental problems. The peels contain several bioactive chemical compounds, especially essential oils (EOs). The content of a specific EO is important for the extraction process in industry and in research units such as breeding research. The explanation of the biosynthesis pathway for EO generation and change was included. The chemical bond vibration affected the prediction of EO constituents was comprehensively explained by regression coefficient plots and x-loading plots. Visible and near-infrared spectroscopy (VIS/NIRS) is a prominent rapid technique used for fruit quality assessment. This research work was focused on evaluating the use of VIS/NIRS to predict the composition of EOs found in the peel of the pomelo fruit (Citrus maxima (J. Burm.) Merr. cv Kao Nam Pueng) following storage. The composition of the peel oil was analyzed by gas chromatography-mass spectrometry (GC-MS) at storage durations of 0, 15, 30, 45, 60, 75, 90, 105 and 120 days (at 10 °C and 70% relative humidity). The relationship between the NIR spectral data and the major EO components found in the peel, including nootkatone, geranial, β-phellandrene and limonene, were established using the raw spectral data in conjunction with partial least squares (PLS) regression. Preprocessing of the raw spectra was performed using multiplicative scatter correction (MSC) or second derivative preprocessing. The PLS model of nootkatone with full MSC had the highest correlation coefficient between the predicted and reference values (r = 0.82), with a standard error of prediction (SEP) of 0.11% and bias of 0.01%, while the models of geranial, β-phellandrene and limonene provided too low r values of 0.75, 0.75 and 0.67, respectively. The nootkatone model is only appropriate for use in screening and some other approximate calibrations, though this is the first report of the use of NIR spectroscopy on intact fruit measurement for its peel EO constituents during cold storage.

Valorization of Food Waste: Utilizing Natural Porous Materials Derived from Pomelo-Peel Biomass to Develop Triboelectric Nanogenerators for Energy Harvesting and Self-Powered Sensing

Food waste is an enormous challenge, with implications for the environment, society, and economy. Every year around the world, 1.3 billion tons of food are wasted or lost, and food waste-associated costs are around $2.6 trillion. Waste upcycling has been shown to mitigate these negative impacts. This study's optimized pomelo-peel biomass-derived porous material-based triboelectric nanogenerator (PP-TENG) had an open circuit voltage of 58 V and a peak power density of 254.8 mW/m2. As porous structures enable such triboelectric devices to respond sensitively to external mechanical stimuli, we tested our optimized PP-TENG's ability to serve as a self-powered sensor of biomechanical motions. As well as successfully harvesting sufficient mechanical energy to power light-emitting diodes and portable electronics, our PP-TENGs successfully monitored joint motions, neck movements, and gait patterns, suggesting their strong potential for use in healthcare monitoring and physical rehabilitation, among other applications. As such, the present work opens up various new possibilities for transforming a prolific type of food waste into value-added products and thus could enhance long-term sustainability while reducing such waste.

Discovery of pharmacological effects and targets of Citri Grandis Exocarpium based on SYSTCM and virtual screening

Citri Grandis Exocarpium (Huajuhong, CGE) is the peel of the unripe fruits of Citrus grandis 'Tomentosa' and Citrus grandis (L.) Osbeck, which is commonly used in the clinic for the treatment of cough and indigestion. The pharmacological mechanism of CGE is unclear. In this study, the pharmacological effect of CGE was predicted by System Traditional Chinese Medicine (SYSTCM), which integrated the pharmacological effect prediction approach by artificial intelligence into the systemic traditional Chinese medicine (TCM) platform. The main pharmacological effect of CGE was antiallergy, promoting bile, blood lipid regulation, cardiotonics, diuresis, and antiarrhythmia by prediction of SYSTCM. In vitro cell experiments were carried out to identify the antiallergic effect of CGE. Extracts of Citri Grandis Exocarpium (ECGE) inhibited lipopolysaccharide-induced cell injury and nitric oxide release in RAW264.7 cells. ECGE and naringin-inhibited immunoglobulin E-induced cell degranulation in RBL-2H3 cells. Target profiling, protein interaction network, and molecular docking of compounds from CGE indicated that mitogen-activated protein kinase 14 (MAPK14) and matrix metalloprotease 9 (MMP9) were key potential targets of CGE with antiallergic activity. This study identified and validated the antiallergic effect of CGE by combining SYSTCM, cell experiments, and virtual screening, which provided a new paradigm and approach for studying the pharmacological effect and mechanism of TCM.

Protective Effects of Tunisian Orange Co-Product Extract and Oleuropein-Hesperidin Combination on Bleomycin-Induced Pulmonary Fibrosis in Rats

Idiopathic pulmonary fibrosis (IPF) is a chronic interstitial pneumonia that leads to acute lung damage, deterioration of lung function, and increased mortality risk. In this study, we investigated the effects of the orange coproduct extract (OCE) and the combination of pure hesperidin and oleuropein (HO) on an experimental model of pulmonary fibrosis induced by bleomycin (BLM) in Wistar rats. Rats were divided into six groups: the control group (G1), the BLM group (G2), three groups (G3, G4, G5) receiving a single dose of BLM combined with OCE extract at 100, 200, and 300 mg/kg, and group 6 (G6) receiving a single dose of BLM combined with HO: both pure major phenolic compounds of OCE (hesperidin at 50 mg/kg) and olive leaves (oleuropein at 2.5 mg/kg). Oxidative stress in lung tissues was investigated using catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidase (GPX) assays and the measurement of malondialdehyde (MDA) and lactate dehydrogenase (LDH) levels. Treatment with OCE and HO normalized the disturbance in oxidative markers' levels and showed a significant reduction in fibrosis score with no renal or hepatic toxic effects. In conclusion, OCE and HO exhibit antifibrotic effects on a rat model of pulmonary fibrosis.

Unveiling the Chemistry of Citrus Peel: Insights into Nutraceutical Potential and Therapeutic Applications

The recent millennium has witnessed a notable shift in consumer focus towards natural products for addressing lifestyle-related disorders, driven by their safety and cost-effectiveness. Nutraceuticals and functional foods play an imperative role by meeting nutritional needs and offering medicinal benefits. With increased scientific knowledge and awareness, the significance of a healthy lifestyle, including diet, in reducing disease risk is widely acknowledged, facilitating access to a diverse and safer diet for longevity. Plant-based foods rich in phytochemicals are increasingly popular and effectively utilized in disease management. Agricultural waste from plant-based foods is being recognized as a valuable source of nutraceuticals for dietary interventions. Citrus peels, known for their diverse flavonoids, are emerging as a promising health-promoting ingredient. Globally, citrus production yields approximately 15 million tons of by-products annually, highlighting the substantial potential for utilizing citrus waste in phyto-therapeutic and nutraceutical applications. Citrus peels are a rich source of flavonoids, with concentrations ranging from 2.5 to 5.5 g/100 g dry weight, depending on the citrus variety. The most abundant flavonoids in citrus peel include hesperidin and naringin, as well as essential oils rich in monoterpenes like limonene. The peel extracts exhibit high antioxidant capacity, with DPPH radical scavenging activities ranging from 70 to 90%, comparable to synthetic antioxidants like BHA and BHT. Additionally, the flavonoids present in citrus peel have been found to have antioxidant properties, which can help reduce oxidative stress by 30% and cardiovascular disease by 25%. Potent anti-inflammatory effects have also been demonstrated, reducing inflammatory markers such as IL-6 and TNF-α by up to 40% in cell culture studies. These findings highlight the potential of citrus peel as a valuable source of nutraceuticals in diet-based therapies.

Laboratory evaluation of a bio-insecticide candidate from tangerine peel extracts against Trialeurodes vaporariorum (Homoptera: Aleyrodidae)

Background

The excessive use of synthetic insecticides in modern agriculture has led to environmental contamination and the development of insect resistance. Also, the prolonged use of chemical insecticides in producing flowers and tomatoes in greenhouses has caused health problems for workers and their offspring. In this study, we analyzed the efficacy of mandarin peel (Citrus reticulata L.) essential oil (EO) as a natural insecticide against greenhouse whitefly (Trieurodes vaporariorum W., Homoptera: Aleyrodidae), a common pest in greenhouse production of different crops.

Methods

Petroleum ether (PET) and n-hexane (HEX) were used as solvents to extract essential oil (EO) from tangerine peels.

Results

The yield of EO was 1.59% and 2.00% (m/m) for PET and HEX, respectively. Additionally, the insect-killing power of EO was tested by checking how many greenhouse whiteflies died at different times. The results showed that PET and HEX extracts of tangerine EO effectively controlled greenhouse whiteflies. Furthermore, with both solvents, a 12.5% (v/v) application was as practical as the commercial insecticide imidacloprid. Further characterization tests with the polarimeter, FTIR, HPLC-RP, and GC-MS showed that the essential oil (EO) contained about 41% (v/v) of d-limonene and that this compound may be responsible for the observed insecticidal properties.

Conclusion

Therefore, tangerine peel essential oil is an excellent botanical insecticide candidate for controlling greenhouse whiteflies.

Emulsification Characteristics of Insoluble Dietary Fibers from Pomelo Peel: Effects of Acetylation, Enzymatic Hydrolysis, and Wet Ball Milling

To improve the application potential of pomelo peel insoluble dietary fiber (PIDF) in emulsion systems, acetylation (PIDF-A), cellulase hydrolysis (PIDF-E), and wet ball milling (PIDF-M) were investigated in this paper as methods to change the emulsification properties of PIDF. The impact of the methods on PIDF composition, structure, and physicochemical properties was also assessed. The results demonstrated that both acetylation modification and cellulase hydrolysis could significantly improve the emulsification properties of PIDF. The emulsions stabilized with PIDF-A and PIDF-E could be stably stored at 25 °C for 30 d without phase separation at particle concentrations above 0.8% (w/v) and had higher storage stability: The D4,3 increments of PIDF-A- and PIDF-E-stabilized emulsions were 0.98 μm and 0.49 μm, respectively, at particle concentrations of 1.2% (w/v), while the storage stability of PIDF-M-stabilized emulsion (5.29 μm) significantly decreased compared with that of PIDF (4.00 μm). Moreover, PIDF-A showed the highest water retention capacity (21.84 g/g), water swelling capacity (15.40 mL/g), oil retention capacity (4.67 g/g), and zeta potential absolute (29.0 mV) among the PIDFs. In conclusion, acetylation modification was a promising method to improve the emulsifying properties of insoluble polysaccharides.

Copper ion/gallic acid MOFs-laden adhesive pomelo peel sponge effectively treats biofilm-infected skin wounds and improves healing quality

Bacterial infection and scar formation remain primary challenges in wound healing. To address these issues, we developed a decellularized pomelo peel (DPP) functionalized with an adhesive PVA-TSPBA hydrogel and antibacterial gallic acid/copper MOFs. The hybrid wound dressing demonstrates favorable biocompatibility. It does not impede the proliferation of fibroblasts or immune cells and can stimulate fibroblast migration, endothelial angiogenesis, and M2 macrophage polarization. Additionally, the dressing can scavenge reactive oxygen species (ROS) and provide antioxidant effects. Furthermore, DPP + MOF@Gel effectively inhibits the viability of S. aureus and E. coli in vitro and in vivo. The histological observations revealed enhanced granulation tissue formation, re-epithelialization, and angiogenesis in the DPP + MOF@Gel group compared to other groups. The local immune response also shifted from a pro-inflammatory to a pro-regenerative status with DPP + MOF@Gel treatment. The skin incision stitching experiment further exhibits DPP + MOF@Gel could reduce scar formation during wound healing. Taken together, the hybrid DPP + MOF@Gel holds great promise for treating bacteria-infected skin wounds and inhibiting scar formation during wound healing.

Enhancement of anti-diabetic activity of pomelo peel by the fermentation of Aspergillus oryzae CGMCC23295: In vitro and in silico docking studies

In this work, pomelo peel was fermented by Aspergillus oryzae CGMCC23295 to enhance its anti-diabetic properties. Results showed the total phenolic and flavonoids contents, ferric reducing antioxidant power (FRAP), scavenging capacities against 2,2'-azinobis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), 1,1-diphenyl-2-picrylhydrazyl (DPPH) and hydroxyl radicals, as well as inhibitory abilities against α-amylase and α-glucosidase of pomelo peel were increased and fermentation for 8 days was the best. Additionally, the fermented sample could also enhance the glucose consumption and glycogen of HepG2 cell. Based on UPLC-MS/MS analysis, binding energy calculation, concentration determination and IC50 measurement, purpurin, apigenin, genistein, and paxilline could be concluded to be the main compounds to enhance the inhibition activities of fermented sample against α-amylase and α-glucosidase. Furthermore, computational studies were performed to reveal the the binding site and molecular interactions between paxilline and α-amylase, as well as purpurin and α-glucosidase. These findings provide a base for the utilization and valorization of pomelo peels as functional food additives by fermentation.

Differential analysis of phytochemistry and antioxidant activity in five citrus by-products based on chromatography, mass spectrometry, and spectrum-effect relationships

The unripe fruit or peel of Citrus aurantium L., Citrus sinensis Osbeck, and Citrus reticulata Blanco are often disregarded due to perceptions of their marginal value. The present study was undertaken to explore the differences in phytochemical composition and bioactive properties of five citrus by-products in China and demonstrate their potential value. 214 compounds were systematically identified using LC-Orbitrap-MS analysis. Among them, narirutin, naringin, hesperidin, and neohesperidin were established as essential compounds for the discrimination and authentication of the five by-products via a combination of LC-MS, HPLC, and TLC techniques. Variations in the antioxidant activity of the by-products were observed, which correlated with their maturity and were attributable to differences in their active ingredients. Moreover, spectrum-effect relationship analysis revealed that the four previously identified differential markers, along with nobiletin and tangeretin, significantly contributed to the differences in antioxidant activity. The results highlight the potential for citrus by-product enhancement and utilization.

Efficient removal of purine compounds from solutions via biomass carbons derived from pomelo peel

The high purine diet could result in the increase of the level of blood uric acid, causing serious health problems such as hyperuricemia, gout, nephropathy and cardiovascular diseases. To find out a safe, cheap and super adsorption material for removing purines in stomach or pretreating high-purine beverages, we used different tissues of pomelo peel to prepare biomass carbon by drying, chemical modification and carbonization and then applied it to remove purine compounds in strong acidic solution, beer and soybean milk. The characteristic analysis of pomelo-peel-derived carbons (PPCs) indicated that the preparation methods significantly affected the structures and adsorption capacities of PPCs. Compared with the biomass carbon derived from bamboo, PPCs exhibited higher adsorption capabilities for purine compounds in strong acidic solution (adsorption rates > 99% in 15 min) and soybean milk (adsorption rates > 56% in 30 min) but slightly lower adsorption capabilities in beer (adsorption rates > 52% in 30 min). In addition, the adsorption capabilities of PPCs for purine compounds in beer and soybean milk were not obviously affected by temperatures. Therefore, PPCs are promising absorbents for applications in removing purine compounds from beverages to produce low-purine, healthier products for treating hyperuricemia. The strong adsorption capabilities of PPCs on purine compounds in strong acidic environment also provides a possibility of using the PPCs as food additives for removing purines in stomach for healthcare applications such as gout prevention after confirming their biosafety.

Numerical optimization of hydrothermal liquefaction process for the production of bio-oil and bio-char from Citrus maxima peel waste and product characterization

This research study aims to potential utilization of Citrus maxima peel waste and optimize the hydrothermal liquefaction process for the production of bio-oil (BO) and bio-char (BC). The effect of several HTL processing variables on BO yield (%) and BC yield (%), including temperature, retention period, and slurry concentration, has been examined using central composite design (CCD) (a three-level three-factor design). The optimized values of HTL process variables were found to be 240 °C (temperature), 52 min (retention time), and 7% (slurry concentration) and the corresponding responses were 5.794% (BO yield) and 29.450% (BC yield). The values obtained from the RSM-CCD model as the predicted values agreed with the experimental values (5.93% and 30.14%). Further the BO and BC obtained under optimized conditions and CPP were analyzed to identify the variations by 1H-NMR, GC-MS, FT-IR, and CHNO-S.

Antioxidants from different citrus peels provide protection against cancer

Cancer is one of the leading causes of death. Despite significant advancements in the discovery of medications for the treatment of cancer, these drugs are hindered by applicability and efficacy issues and frequently exhibit major side effects that can further impair patients 'quality of life. Therefore, the development of therapeutically sound anti-cancer medicines derived from natural products has gained prominence in the field of functional foods. Some of these compounds have shown efficacy in the prevention and treatment of cancer as well as low toxicity. Additionally, many recent studies have explored the recycling of agro-industrial waste to create bioactive chemicals. Citrus peels are produced in vast quantities in the food processing sector; due to their abundance of flavonoids, they may be inexpensive sources of protection against several cancers. Citrus is a common type of fruit that contains a variety of nutrients. In particular, the antioxidant chemicals found in citrus peel have been identified as potential cancer-fighting agents. Antioxidant substances such as flavonoids prevent the development of cancer by inhibiting the metastatic cascade, decreasing the mobility of cancer cells in the circulatory system, promoting apoptosis, and suppressing angiogenesis. To explore the most effective uses of citrus peel-derived antioxidants, this review presents background information, an overview of the role of citrus antioxidants in cancer therapy, and a discussion of the key underlying molecular mechanisms.

Green removal of unpleasant volatiles from soapberry (Sapindus mukorossi) extracts by two-phase microbial fermentation fortified with pomelo peel waste

Soapberry (Sapindus mukorossi Gaertn) is a popular woody plant in Vietnam, often used as a cleaning product due to its ability to wash, foam and emulsify due to high saponin content. In this study, the performance of fermentation by two microbial strains, namely Saccharomyces cerevisiae active dry yeast (ADY) and Levilactobacillus brevis lactic acid bacteria (LB) along with the addition of pomelo peel (flavedo) was evaluated during 15 days in terms of sugar removal, antioxidant and antibacterial activities, foaming power, volatile composition, and sensory acceptability. The results showed that the soluble solid content of original extracts experienced a significant decrease from 14.5% to a stable range of 9.4-11.0% until day 15 for all fermented samples, which correlated with a reduction by approximately 60% in reducing sugars (from 12.52 g L-1 to 4.77-6.56 g L-1). In addition, the saponin content of fermented extracts was in the range of 118.2-145.0 mg L-1 while antioxidant activities were extremely reduced after 15 days of fermentation. Increases in pomelo peel imparted fermented extracts with greater antibacterial activity against Staphylococcus aureus ATCC 6538, Proteus mirabilis ATCC 25933, and Candida albicans ATCC 10231, and LB had higher activity than ADY overall. Regarding the volatile profiles, two main compounds in the original extracts, including trilaurin (75.02%) and 1-dodecanoyl-3-myristoyl glycerol (24.85%), were completely removed and replaced by new alkanes, alkenes, alcohols, esters, and organic acids, and particularly d-limonene (86.34-95.31%) upon pomelo addition. Additionally, the foaming ability and stability of fermented extracts were also enhanced and there was clear distinction between fermented and unfermented samples using principal component analysis based on sensory liking data which showed consumers' preference towards fermented samples with a high percentage of pomelo peel.

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.

Intensifying Effect of Instant Controlled Pressure Drop (DIC) Pre-Treatment on Hesperidin Recovery from Orange Byproducts: In Vitro Antioxidant and Antidiabetic Activities of the Extracts

The orange byproduct is a widely accessible and valuable source of functional phenolic compounds, particularly hesperidin. Hesperidin extraction remains a challenging phase in its valorization chain due to its low solubility and limited extractability in solvents. This work aims to examine the effect of conventional solvent extraction (CSE) compared to emerging and innovative extraction methods: accelerated solvent extraction (ASE) and ultrasound-assisted extraction (UAE) when applied with or without a pretreatment process of instant controlled pressure drop (DIC) to intensify extraction, antioxidant, and antidiabetic activities. The total phenols, flavonoids, hesperidin contents, radical scavenging activities, iron chelating activity, and in vitro α-amylase inhibition of the extracts were determined for CSE (80%, 70 °C), UAE (ethanol 80%, 70 °C, 200 W), and ASE (ethanol 60%, 100 °C, 100 bars) with or without DIC pretreatment (pressure = 0.4 MPa, total thermal time = 30 s). The hesperidin amounts obtained were 0.771 ± 0.008 g/100 g DM, 0.823 ± 0.054 g/100 g DM, and 1.368 ± 0.058 g/100 g DM, for CSE, UAE, and ASE, respectively. DIC pretreatment of orange byproducts increased hesperidin recovery by 67%, 25.6%, and 141% for DIC-CSE, DIC-UAE, and DIC-ASE, respectively. The DPPH and ABTS radical scavenging and iron chelating activities of extracts were also significantly enhanced, and the in vitro antidiabetic activity of extracts was preserved.

The Chemical Variability, Nutraceutical Value, and Food-Industry and Cosmetic Applications of Citrus Plants: A Critical Review

Citrus fruits occupy an important position in the context of the fruit trade, considering that both fresh fruits and processed products are produced on a large scale. Citrus fruits are recognized as an essential component of the human diet, thanks to their high content of beneficial nutrients such as vitamins, minerals, terpenes, flavonoids, coumarins and dietary fibers. Among these, a wide range of positive biological activities are attributed to terpenes and flavonoids derivatives. In this review, a list of bibliographic reports (from 2015 onwards) on the phytochemical composition, beneficial effects and potential applications of citrus fruits and their by-products is systematically summarized. In detail, information regarding the nutraceutical and medicinal value closely linked to the presence of numerous bioactive metabolites and their growing use in the food industry and food packaging, also considering any technological strategies such as encapsulation to guarantee their stability over time, were evaluated. In addition, since citrus fruit, as well as its by-products, are interesting alternatives for the reformulation of natural cosmetic products, the sector of the cosmetic industry is also explored. More in-depth knowledge of the latest information in this field will contribute to future conscious use of citrus fruits.

Effect of Dietary Pomelo Peel Powder on Growth Performance, Diarrhea, Immune Function, Antioxidant Function, Ileum Morphology, and Colonic Microflora of Weaned Piglets

This trial evaluated how dietary-accommodated pomelo peel powder (PPP) affected average daily feed intake (ADFI) and average daily gain (ADG), diarrhea, antioxidation, and colonic microbial in weaned piglets. Thirty piglets weaned at 28 d were divided into three groups: a basal diet (CON); a CON containing 75 mg/kg chlortetracycline (CTC); and a CON containing 8 g/kg (PPP). This trial had a period of 28 days. Piglets supplemented with PPP had higher ADFI and ADG than piglets in CTC and CON (p < 0.05). The diarrhea rate in PPP and CTC was lower than in CON in the 3rd and 4th weeks (p < 0.05). Serum superoxide dismutase and glutathione peroxidase enzyme activities, and total antioxidant capacity in PPP were higher than those in CON (p < 0.05). Serum interleukin (IL)-4, insulin-like growth factor-I, immunoglobulin (Ig)A, and IgG concentrations in the PPP and CTC groups were higher than those in the CON group (p < 0.05). Serum IL-1β, IL-8, IL-17, and interferon (IFN)-γ concentrations and the cecal pH in PPP were lower than those in CON (p < 0.05). Serum IL-1β, IFN-γ, and IgA concentrations of piglets in PPP were lower than in CTC (p < 0.05). The villus height and villus height/crypt depth of the ileum of piglets in PPP and CTC were higher than those in CON (p < 0.05), but there was no difference between PPP and CTC (p > 0.05). The Firmicutes and Cyanobacteria relative abundances in PPP and CTC (p < 0.05) were lower than those in CON, whereas the Bacteroidetes relative abundances in PPP and CTC were higher than those in CON. The Prevotellaceae relative abundance in CTC was higher than in CON (p < 0.05), whereas the Lactobacillaceae relative abundance in CTC was lower than in CON (p < 0.05). The Ruminococcaceae relative abundance in PPP was higher than in CON (p < 0.05), whereas the Veillonellaceae relative abundance in PPP was lower than in CON (p < 0.05). PPP can improve ADFI and ADG, relieve diarrhea, and enhance the colonic microflora of weaned piglets. Therefore, PPP is expected to replace CTC as a feed additive to alleviate weaning stress and ensure normal growth and development of piglets.

[Solid phase microextraction of benzenes in river water by pomelo peel biochar]

苯、甲苯、乙苯和二甲苯(邻二甲苯、间二甲苯、对二甲苯)组成的苯系物(BTEX)是炼油厂和石化厂等工业园区普遍制造和排放的碳氢化合物,具有一定的毒性和致癌作用,对生态环境和人类健康造成极大威胁。研究以低成本、绿色且富含木质素和含氧官能团的柚子皮作为植物原料,在有限氧条件下采用程序升温热解法制备了柚子皮生物炭质吸附剂,通过N₂吸附-脱附等温线和孔径分布图对不同热解温度下制备的柚子皮生物炭质吸附剂的孔隙结构进行了考察。结果表明:在1000 ℃热解温度下制得的柚子皮生物炭质具有更高的比表面积(749.9 m²/g)、更大的孔体积(0.42 cm³/g)、更集中的孔径分布(2~3 nm)。将吸附剂通过溶胶-凝胶法(sol-gel)涂覆在铁丝上制成固相微萃取纤维,与气相色谱-火焰离子化检测器(GC-FID)相结合,对影响萃取和分离BTEX的条件进行优化,建立了用于BTEX检测的高灵敏度分析方法。方法具有检出限低(0.004~0.032 μg/L)、线性范围宽(1~100 μg/L)、线性关系好、萃取效率高(约为商品化涂层聚二甲基硅氧烷(7 μm)的2.9~18.3倍)等优势。此外,应用该方法已成功在河水样本中检测出了乙基苯(4.80 μg/L),邻二甲苯(3.00 μg/L)和对二甲苯、间二甲苯(2.46 μg/L)。最后将该方法应用于河水样本的加标试验中,得到了满意的回收率(75.7%~117.6%)。实验结果表明所建立的分析方法可实现对环境水样(河水)中BTEX的低成本、高灵敏度检测。

Recovery of Antioxidants from Tomato Seed Industrial Wastes by Microwave-Assisted and Ultrasound-Assisted Extraction

Tomato seed (TS) wastes are obtained in large amounts from the tomato processing industry. In this work, microwave-assisted extraction (MAE) and ultrasound-assisted extraction (UAE) of antioxidant compounds from TS were optimized by using response surface methodology. The effect of MAE and UAE main extraction parameters was studied on total phenolic content (TPC) and antioxidant activity (DPPH) responses. Antioxidant, structural, morphological, and thermal properties of MAE and UAE extracts were evaluated. A great influence of ethanol concentration was observed in both extraction methods. Optimal MAE conditions were determined as 15 min, 80 °C, 63% ethanol and 80 mL, with a desirability value of 0.914, whereas 15 min, 61% ethanol and 85% amplitude (desirability = 0.952) were found as optimal conditions for UAE. MAE extracts exhibited higher TPC and antioxidant activity values compared to UAE (1.72 ± 0.04 and 1.61 ± 0.03 mg GAE g TS⁻¹ for MAE and UAE, respectively). Thermogravimetric analysis (TGA) results suggested the presence of some high molecular weight compounds in UAE extracts. Chlorogenic acid, rutin and naringenin were identified and quantified by HPLC-DAD-MS as the main polyphenols found by MAE and UAE, showing MAE extracts higher individual phenolics content (1.11–2.99 mg 100 g TS⁻¹). MAE and UAE have shown as effective green techniques for extracting bioactive molecules with high antioxidant activity from TS with high potential to be scaled-up for valorizing of TS industrial wastes.

The flavonoid profiles in the pulp of different pomelo (Citrus grandis L. Osbeck) and grapefruit (Citrus paradisi Mcfad) cultivars and their in vitro bioactivity

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Fourteen flavonoid compounds were detected in pomelo and grapefruit pulp.

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The flavonoid profiles in pomelo and grapefruit pulp had varietal difference.

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Flavonoids of pomelo and grapefruit showed strong cellular antioxidant activity.

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Flavonoids of pomelo and grapefruit are good inhibitors of pancreatic lipase.

Previous results indicated that the flavonoid profiles might have varietal differences in pomelo, but detailed information is unknown. We previously isolated 4 new flavonoids, cigranoside C, D, E, F, in Citrus grandis Shatianyu pulp. However, their distribution in different pomelo cultivars remains to be explored. Therefore, the flavonoid profiles and in vitro bioactivity of the pulp from 5 pomelo and 1 grapefruit cultivars commonly consumed in China were investigated. Fourteen flavonoids were identified, cigranoside C, D, E were detected in these pomelo and grapefruit. Naringin and cigranoside C were the major flavonoids in grapefruit, Guanximiyu-W, Guanximiyu-R and Liangpingyu, while melitidin and rhoifolin was the predominant flavonoid in Shatianyu and Yuhuanyu, respectively. Pomelo and grapefruit showed strong antioxidant activity, and were potent inhibitors of pancreatic lipase with IC₅₀ values of 11.4–72.6 mg fruit/mL except Shatianyu. Thus, pomelo and grapefruit are natural antioxidants and possess anti-obesity potential.

Impact of Storage Condition on Chemical Composition and Antifungal Activity of Pomelo Extract against Colletotrichum gloeosporioides and Anthracnose in Post-harvest Mango

Anthracnose caused by Colletotrichum leads to a tremendous post-harvest mango loss. While chemical fungicides are applied to control anthracnose, natural alternatives are preferred due to food safety and environmental concerns. Pomelo extract (PE) exhibits a broad spectrum of antimicrobial activities; however, its effect against anthracnose is unknown. Here we investigated the chemical profile of PE using GC-MS and the anti-anthracnose activity of PE using in vitro and in vivo assays. We also evaluated the impact of storage temperature (0°, 5°, 10°, 20°, -20°, and -80 °C) and light conditions on the composition and antifungal activity of PE. We found that PE inhibited C. gloeosporioides in vitro with an IC₅₀ of 3.2 mL L^-1. Applying chitosan-based coating incorporated with 20 mL L^-1 PE significantly suppressed anthracnose in post-harvest 'Keitt' mango. A storage temperature below 5 °C substantially preserved major compounds and the antifungal activity of PE after 6 m of storage. Finally, we showed that applying d-limonene, the key constituent of PE, inhibited C. gloeosporioides in vitro (IC₅₀: 10.9 mM) and suppressed anthracnose in vivo. In conclusion, we demonstrated that the application of PE and d-limonene are sustainable methods for anthracnose control in post-harvest crops and established the preservation protocol for PE.

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.

Review of phytochemical and nutritional characteristics and food applications of Citrus L. fruits

Since the dietary regimen rich in fruits is being widely recognized and encouraged, Citrus L. fruits have been growing in popularity worldwide due to their high amounts of health-promoting phytonutrients and bioactive compounds, such as flavonoids, phenolic acids, vitamins, carotenoids, pectins, and fatty acids. The diverse physicochemical properties and multiple utilization of citrus fruits in food industry are associated with their unique chemical compositions. Throughout the world, citrus has been used for producing various value-added and nutritionally enhanced products, including juices, wines, jams, canned citrus, and dried citrus. However, the current studies regarding the phytochemical and nutritional characteristics and food applications of citrus are scattered. This review systematically summarizes the existing bibliography on the chemical characteristics, functional and nutraceutical benefits, processing, and potential applications of citrus. A thorough understanding of this information may provide scientific guidance for better utilizing citrus as a functional fruit and benefit the extension of citrus value chain.

Green production of a yellow laccase by Coriolopsis gallica for phenolic pollutants removal

As a group of green biocatalysts, fungal laccases have aroused great interest in diverse biotechnological fields. Therein, yellow laccase has advantages over blue laccase in catalytic performance, but it is not common in the reported fungal laccases. Here, we report a yellow laccase from white-rot fungus Coriolopsis gallica NCULAC F1 about its production, purification, characterization, and application. Laccase production in the co-fermentation of pomelo peel and wheat bran reached the enzyme activity by 10,690 U/L after 5 days with a 13.58-time increase. After three steps of purification, laccase increased the specific activity from 30.78 to 188.79 U/mg protein with an activity recovery of 45.64%. The purified C. gallica laccase (CGLac) showed a molecular mass of about 57 kDa. CGLac had a yellow color and no absorption peaks at 610 nm and 330 nm, suggesting that it’s a yellow laccase. CGLac exhibited stability towards temperature (40–60 °C) and neutral pH (6.0–8.0). Fe³⁺ and Mn²⁺ strongly stimulated CGLac activity by 162.56% and 226.05%, respectively. CGLac remained high activities when exposed to organic reagents and putative inhibitors. Additionally, CGLac contributed to 90.78%, 93.26%, and 99.66% removal of phenol, p-chlorophenol and bisphenol A after 120 min, respectively. In conclusion, a green efficient production strategy was introduced for fungal laccase, and the obtained CGLac presented great enzymatic properties and catalytic potential in the removal of phenolic pollutants.

Pomelo peels and wheat bran are great nutritional sources and laccase inducers.

CGLac showed the spectral characteristic of yellow laccase.

CGLac had great stability and catalytic ability for phenolic pollutants removal.

Fruit and Vegetable Peel-Enriched Functional Foods: Potential Avenues and Health Perspectives

Fresh fruit and vegetables are highly utilized commodities by health-conscious consumers and represent a prominent segment in the functional and nutritional food sector. However, food processing is causing significant loss of nutritional components, and the generation of waste is creating serious economic and environmental problems. Fruit and vegetables encompass husk, peels, pods, pomace, seeds, and stems, which are usually discarded, despite being known to contain potentially beneficial compounds, such as carotenoids, dietary fibers, enzymes, and polyphenols. The emerging interest in the food industry in the nutritional and biofunctional constituents of polyphenols has prompted the utilization of fruit and vegetable waste for developing enriched and functional foods, with applications in the pharmaceutical industry. Moreover, the utilization of waste for developing diverse and crucial bioactive commodities is a fundamental step in sustainable development. Furthermore, it provides evidence regarding the applicability of fruit and vegetable waste in different food formulations especially bakery, jam, and meat based products.

Volatiles Accumulation during Young Pomelo (Citrus maxima (Burm.) Merr.) Fruits Development

As widely planted fruits with high nutritional and medical values, pomelos are managed systematically to achieve the largest economic benefits. But the annual shedding of young pomelos, which could be applied as feedstocks for essential oil extraction with their abundant volatiles, leads to a waste of source. The present study selected two commonly planted pomelo (Citrus maxima (Burm.) Merr.) varieties in Southern China, to investigate the volatile profiles during young pomelo fruits development. Combing transcriptomic analysis, this study aimed at identifying the prominent volatile components in young pomelo fruits in order to preferably extract profitable volatiles, as well, increasing the knowledge concerning regulatory roles of transcription factors (TFs) on volatiles accumulation in young pomelos. Totally 29 volatiles were identified, including 14 monoterpenoids and 13 sesquiterpenoids. Diprene was the principal component with the highest amount. Volatiles were generally decreased during fruits development but preferable stages were figured out for volatile collections. 12 and 17 TFs were related to developing time while ERF003 and MYC2 were highly correlated to monoterpenoids. These findings put forward the comprehensive usages of young pomelos and enriched the regulatory roles of TFs on both fruit development and volatiles metabolism.

Facile Preparation of Porous Carbon Derived from Pomelo Peel for Efficient Adsorption of Methylene Blue

Pomelo peel waste-derived porous carbon (PPPC) was prepared by a facile one-step ZnCl₂ activation method. The preparation parameters of PPPC were the mass ratio of ZnCl₂ to pomelo peel of 2:1, carbonization temperature of 500 °C, and carbonization time of 1 h. This obtained PPPC possessed abundant macro-,meso-, and micro-porous structures, and a large specific surface area of 939.4 m² g^-1. Surprisingly, it had excellent adsorption ability for methylene blue, including a high adsorption capacity of 602.4 mg g^-1 and good reusability. The adsorption isotherm and kinetic fitted with Langmuir and pseudo-second order kinetic models. This work provides a novel strategy for pomelo peel waste utilization and a potential adsorbent for treating dye wastewater.

Comparative Analysis of the Chalcone-Flavanone Isomerase Genes in Six Citrus Species and Their Expression Analysis in Sweet Orange (Citrus sinensis)

Citrus fruit contains rich nutrients which is edible and of officinal value. Citrus flavanones are widely used in the treatment of cardiovascular and other diseases, and they are a foundational material of Chinese medicine. The chalcone-flavanone isomerase (CHI) plays a key role in flavanone synthesis. Therefore, we comprehensively analyzed CHI genes in Citrus species. Here, thirty CHI genes were identified for the first time in six Citrus species, which were divided into CHI and FAP groups. Evolutionary analysis showed that CHI gene members were highly conserved and were an ancient family. All CsCHI genes showed the highest expression level after the second physiological fruit-falling period in C. sinensis. CsCHI1 and CsCHI3 were highly expressed at 50 days after the flowering (DAF) stage in albedo. The expression of CsFAP2 and CsCHI3 genes at the 50 DAF stage was 16.5 and 24.3 times higher than that at the 220 DAF stage, respectively. The expression of CsCHI1, CsCHI3, and CsFAP2 genes in the peel was higher than that in the pulp, especially in common sweet orange. The CsCHI3 gene maintained a high expression level in the epicarp and juice sac at all periods. The members of CHIs interacted with chalcone synthase (CHS), flavonol synthase/flavanone 3-hydroxylase (FLS) and naringenin, and 2-oxoglutarate 3-dioxygenase (F3H) to form heterodimers, which might together play a regulatory role and participate in the flavonoid pathway. This study will provide the basis for the selection of flavonoids in plant tissues and periods and fundamental information for further functional studies.

Polysaccharide derived from pomelo seed coat ameliorates APAP-induced liver injury in hybrid grouper (<i>Epinephelus lanceolatus</i>♂ × <i>Epinephelus fuscoguttatus</i>♀)

Ever-increasingly Citrus wastes have been generating during the industrial processing, which is troublesome to dispose them for the considerations of economic feasibility and environmental protection. Meanwhile, liver disease, which causes liver damage, is the one of the major threats for the further development of aquaculture, especially in marine fish. The present study explored the hepatoprotective effect of PSCP, a polysaccharide extracted from the pomelo seed coat, in the primary hepatocytes of hybrid grouper (<i>Epinephelus fuscoguttatus</i>♂ × <i>Epinephelus lanceolatus</i>♀). PSCP displayed considerably scavenging effect to the free radicals and strong inhibitive effect to the erythrocyte hemolysis. In vitro, we added PSCP (0, 100, 200 and 400 μg/mL) to the primary hepatocytes before incubation with Acetaminophen (APAP) (12 mM). The CKK-8 experiment displayed the administration of PSCP (100 and 200 μg/mL) substantially mitigated the reduction of hepatocyte viability inflicted by APAP. Moreover, we found that PSCP effectively alleviated APAP-induced oxidative stress, as shown by the significantly reduced level of reactive oxygen species and the elevated enzymatic activities of superoxide dismutase, catalase, and glutathione peroxidase, which indicated its anti-liver injury effect (P<0.05). The more direct signs associating with the hepatoprotection of PSCP are reflected in the results of hematoxylin and eosin staining, as evident by the morphological recovery following the addition of PSCP. In brief, these findings showed that the therapeutic potential of PSCP on APAP-induced fish liver injury, which not only provided a now prospect in treating the liver impairment in aquatic animals, but to also improve the utilization of pomelo fruitlets.

A simple, environmental-friendly and reliable d-SPE method using amino-containing metal-organic framework MIL-125-NH2 to determine pesticide residues in pomelo samples from different localities

A simple, environmentally-friendly and reliable method was developed to simultaneously monitor the residue of methyl 1-naphthalene acetate, parathion-methyl, fenitrothion, bromophos and phenthoate in pomelo by using dispersive solid-phase extraction technique (d-SPE). In this method, these target analytes were captured by MIL-125-NH₂ and detected by GC-MS/MS. The key parameters of d-SPE were optimized by the single factor experiment. Under the optimized conditions, a good determination coefficient (R² > 0.9922) and extraction recoveries (64.7-116.8%) are obtained. The limit of detections (0.03-1.07 ng/g) is lower than the MRLs in citrus fruits established by EU (10-15000 ng/g) and China (10-10000 ng/g). The precisions of intra-day and inter-day are 1.3-8.9% and 3.8-14.9%, respectively. In addition, the sorbent MIL-125-NH₂ is stable and can be reused at least eight times. These results prove the established method is efficient and reliable to detect the pesticide residues in pomelo.

Phenolic-Rich Plant Extracts With Antimicrobial Activity: An Alternative to Food Preservatives and Biocides?

In recent years, the search for natural plant-based antimicrobial compounds as alternatives to some synthetic food preservatives or biocides has been stimulated by sanitary, environmental, regulatory, and marketing concerns. In this context, besides their established antioxidant activity, the antimicrobial activity of many plant phenolics deserved increased attention. Indeed, industries processing agricultural plants generate considerable quantities of phenolic-rich products and by-products, which could be valuable natural sources of natural antimicrobial molecules. Plant extracts containing volatile (e.g., essential oils) and non-volatile antimicrobial molecules can be distinguished. Plant essential oils are outside the scope of this review. This review will thus provide an overview of current knowledge regarding the promises and the limits of phenolic-rich plant extracts for food preservation and biofilm control on food-contacting surfaces. After a presentation of the major groups of antimicrobial plant phenolics, of their antimicrobial activity spectrum, and of the diversity of their mechanisms of action, their most promising sources will be reviewed. Since antimicrobial activity reduction often observed when comparing in vitro and in situ activities of plant phenolics has often been reported as a limit for their application, the effects of the composition and the microstructure of the matrices in which unwanted microorganisms are present (e.g., food and/or microbial biofilms) on their activity will be discussed. Then, the different strategies of delivery of antimicrobial phenolics to promote their activity in such matrices, such as their encapsulation or their association with edible coatings or food packaging materials are presented. The possibilities offered by encapsulation or association with polymers of packaging materials or coatings to increase the stability and ease of use of plant phenolics before their application, as well as to get systems for their controlled release are presented and discussed. Finally, the necessity to consider phenolic-rich antimicrobial plant extracts in combination with other factors consistently with hurdle technology principles will be discussed. For instance, several authors recently suggested that natural phenolic-rich extracts could not only extend the shelf-life of foods by controlling bacterial contamination, but could also coexist with probiotic lactic acid bacteria in food systems to provide enhanced health benefits to human.

High Value-Added Application of Natural Products in Crop Protection: Semisynthesis and Acaricidal Activity of Limonoid-Type Derivatives and Investigation of Their Biocompatible O/W Nanoemulsions as Agronanopesticide Candidates

The increasingly serious resistance of Tetranychus cinnabarinus Boisduval to a wide range of insecticides/acaricides poses a major challenge to their control. The citrus processing industry generates a huge quantity of various wastes that contain many limonoids. To effectively utilize these byproducts and discover more potent green acaricidal molecules as sustainable alternatives for traditional resistant pesticides, various limonoid-type derivatives (halogenated/seven-membered lactam derivatives of obacunone and halogenated/oxime esters/oxime ethers/seven-membered lactam derivatives of limonin) were synthesized based on a diversity-oriented synthetic strategy. The key steric configurations of 10 derivatives were further confirmed by X-ray crystallography. Compound 9m, which displayed greater than 9.7-fold potent acaricidal activity of limonin, was of preeminence. In addition, some interesting structure-activity relationships were observed. Moreover, a biocompatible O/W nanoemulsion delivery system was used to prepare the limonin-based agronanoacaricide, which exhibited pronounced control efficiency against T. cinnabarinus Boisduval in the greenhouse. This systematic investigation will provide valuable information and guidance for future value-added applications of novel eco-friendly natural product-based nanopesticides.

The Regulatory Effects of Citrus Peel Powder on Liver Metabolites and Gut Flora in Mice with Non-Alcoholic Fatty Liver Disease (NAFLD)

Gannan navel orange and Jinggang pomelo, belonging to the genus Citrus, are good sources of phenolic compounds, which are mainly concentrated in the peel. These phenolic compounds are considered promising in the prevention and treatment of non-alcoholic fatty liver disease (NAFLD). In order to maximize nutrients retention and bioactivity in the peel, pomelo peel and orange peel were processed using freeze-drying technology and mixed in the ratio (pomelo peel powder 50% and orange peel powder 50%) to make citrus peel powder (CPP). The purpose of this study was to explore new strategies and mechanisms associated with the consumption of CPP to alleviate nonalcoholic fatty liver injury, lipid metabolism disorders, and gut microbiota dysbiosis in obese mice induced by high-fat diet (HFD). The results showed that after 12 weeks of CPP administration, CPP supplementation had a strong inhibitory effect on HFD-induced weight gain, hepatic fat accumulation, dyslipidemia, and the release of pro-inflammatory cytokines. In particular, CPP modulates the composition of the intestinal flora, such as increasing the relative abundance of phylum Firmicutes, genus Faecalibaculum, genus Lactobacillus, genus Dubosiella, and genus Lachnospiraceae_NK4A136_ group and decreasing the relative abundance of phylum Bacteroidota, genus Helicobacter, and genus Bacteroides. These results suggest that CPP has a preventive effect on NAFLD, which can be related to the regulation of intestinal flora.

Phytochemical and Therapeutic Potential of Citrus grandis (L.) Osbeck: A Review

Citrus grandis or Citrus maxima, widely recognized as Pomelo is widely cultivated in many countries because of their large amounts of functional, nutraceutical and biological activities. In traditional medicine, various parts of this plant including leaf, pulp and peel are used for generations as they are scientifically proven to have therapeutic potentials and safe for human use. The main objective of this study was to review the different therapeutic applications of Citrus grandis and the phytochemicals associated with its medicinal values. In this article different pharmacological properties like antimicrobial, antitumor, antioxidant, anti-inflammatory, anticancer, antiepileptic, stomach tonic, cardiac stimulant, cytotoxic, hepatoprotective, nephroprotective, and anti-diabetic activities of the plant are highlighted. The enrichment of the fruit with flavonoids, polyphenols, coumarins, limonoids, acridone alkaloids, essential oils and vitamins mainly helps in exhibiting the pharmacological activities within the body. The vitamins enriched fruit is rich in nutritional value and also has minerals like calcium, phosphorous, sodium and potassium, which helps in maintaining the proper health and growth of the bones as well as the electrolyte balance of the body. To conclude, various potential therapeutic effects of Citrus grandis have been demonstrated in recent literature. Further studies on various parts of fruit, including pulp, peel, leaf, seed and it essential oil could unveil additional pharmacological activities which can be beneficial to the mankind.

Evaluation of Pomelo Seed Extracts as Natural Antioxidant, Antibacterial, Herbicidal Agents, and Their Functional Components

Pomelo seeds (PS) are important by-product of pomelo fruits (Citrus grandis Osbeck). The value-added utilization of PS remains highly challenged. This study aimed to investigate the utilization potential of PS as natural antioxidant, antibacterial, herbicidal agents, and their functional components. The ethanolic extract (EE) of PS and its four fractions as PEE (petroleum ether extract), AcOEtE (ethyl acetate extract), BTE (butanol extract), and WE (water extract), were prepared and biologically evaluated. BTE exhibited the best antioxidant activity among all these extracts, in both ABTS (2,2-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt) and FRAP (ferric reducing antioxidant power) assays. AcOEtE was superior to other extracts in herbicidal assay against both Festuca elata Keng (IC₅₀ of 0.48 mg mL^-1 ) and Amaranthus retroflexus L. (IC₅₀ of 0.94 mg mL^-1 ). Meanwhile, both AcOEtE and BTE demonstrated inhibitory effects against Bacillus subtilis, Escherichia coli, and Xanthomonas citri subsp. citri, with MIC ranging 2.5-5.0 mg mL^-1 . Furthermore, the primary chemical components involving naringin, deacetylnomilin, limonin, nomilin, and obacunone, were quantified in all these extracts. PCA (principal component analysis) suggested that naringin might highly contribute to the antioxidant activity of PS, and the herbicidal activity should be ascribed to limonoids. This study successfully identified AcOEtE and BTE as naturally occurring antioxidant, antibacterial, and herbicidal agents, showing application potential in food and cosmetics industries, and organic farming agriculture.

Nutrients and bioactives in citrus fruits: Different citrus varieties, fruit parts, and growth stages

Citrus fruits are consumed in large quantities worldwide due to their attractive aromas and taste, as well as their high nutritional values and various health-promoting effects, which are due to their abundance of nutrients and bioactives. In addition to water, carbohydrates, vitamins, minerals, and dietary fibers are important nutrients in citrus, providing them with high nutritional values. Citrus fruits are also rich in various bioactives such as flavonoids, essential oils, carotenoids, limonoids, and synephrines, which protect from various ailments, including cancer and inflammatory, digestive, and cardiovascular diseases. The composition and content of nutrients and bioactives differ significantly among citrus varieties, fruit parts, and growth stages. To better understand the nutrient and bioactive profiles of citrus fruits and provide guidance for the utilization of high-value citrus resources, this review systematically summarizes the nutrients and bioactives in citrus fruit, including their contents, structural characteristics, and potential health benefits. We also explore the composition variation in different citrus varieties, fruits parts, and growth stages, as well as their health-promoting effects and applications.

The Second Life of Citrus Fruit Waste: A Valuable Source of Bioactive Compounds

Citrus fruits (CF) are among the most widely cultivated fruit crops throughout the world and their production is constantly increasing along with consumers' demand. Therefore, huge amounts of waste are annually generated through CF processing, causing high costs for their disposal, as well as environmental and human health damage, if inappropriately performed. According to the most recent indications of an economic, environmental and pharmaceutical nature, CF processing residues must be transformed from a waste to be disposed to a valuable resource to be reused. Based on a circular economy model, CF residues (i.e., seeds, exhausted peel, pressed pulp, secondary juice and leaves) have increasingly been re-evaluated to also obtain, but not limited to, valuable compounds to be employed in the food, packaging, cosmetic and pharmaceutical industries. However, the use of CF by-products is still limited because of their underestimated nutritional and economic value, hence more awareness and knowledge are needed to overcome traditional approaches for their disposal. This review summarizes recent evidence on the pharmacological potential of CF waste to support the switch towards a more environmentally sustainable society.

Variation in Phytochemical, Antioxidant and Volatile Composition of Pomelo Fruit (Citrus grandis (L.) Osbeck) during Seasonal Growth and Development

Citrus fruits exhibit a high level of different phytoconstituents, of which the changes in the different parts of the fruit during ripening have not been thoroughly studied yet. Thus, in this study, we have investigated how different parts of pomelo fruit (Citrus grandis L.) are modified throughout the development of two consecutive growing seasons. In detail, the main phytochemical compounds, such as total phenolic content, total flavonoid content, antioxidant capacity, DPPH free radical scavenging activity, Ferric reducing antioxidant power (FRAP), and naringin and tannin content, were analyzed. A systematic metabolism of these compounds was found during the development of the fruit, but some pomelo tissues showed a fluctuating trend, suggesting a dependence on the different growing season. Focusing on the tissue distribution of these compounds, the fruit membrane contained the highest level of total phenolic and flavonoid content; fruit flavedo displayed the highest antioxidant capacities and FRAP activities, whereas maximum accumulation of naringin was noticed in fruit albedo. Instead, the highest DPPH free radical scavenging activity and tannin contents were found in the pomelo juice. Regarding the distribution of compounds, a possible bias pattern for the accumulation of those compounds has been noticed throughout the fruit development. From the GC-MS analysis, a total of 111 compounds were identified, where 91 compounds were common in both seasons. Overall, these results could be useful for the food processing industry as guidelines for excellent quality foods and for introducing health-beneficial products and components into our daily diets.

Evaluation of Carotenoids Accumulation and Biosynthesis in Two Genotypes of Pomelo (Citrus maxima) during Early Fruit Development

Pomelo is rich in bioactive compounds (carotenoids, phenolics and essential oil) in the early stage of fruit development, but it is often wasted in the cultivation and management process. To gain an insight into the carotenoid metabolism pathway in pomelo, the carotenoid profiles and the expression patterns of carotenogenic genes were investigated in two genotypes of pomelo during early fruit development. The results showed that a higher carotenoid content was observed in honey pomelo as compared with golden pomelo, which may be related to different gene regulation mechanisms. Lutein, α-carotene, and β-carotene were the main carotenoids in pomelo young fruit, and lutein was the highest one. The accumulation of carotenoids during fruit early development in honey pomelo is related to the transcriptional regulation of ZISO and LUT5. In golden pomelo, the rate-limiting gene for carotenoids is PDS and ZDS. In addition, the expression of seven genes except CRTISO in honey pomelo was higher than that in golden pomelo. The results are helpful to further clarify the regulatory mechanism of carotenoid accumulation during early fruit development and provide a direction for the high-value utilization of young fruits in pomelo.

Comparison of the Physico-Mechanical and Weathering Properties of Wood-Plastic Composites Made of Wood Fibers from Discarded Parts of Pomelo Trees and Polypropylene

The purpose of this study is to compare the characteristics of wood–plastic composites (WPCs) made of polypropylene (PP) and wood fibers (WFs) from discarded stems, branches, and roots of pomelo trees. The results show that the WPCs made of 30–60 mesh WFs from stems have better physical, flexural, and tensile properties than other WPCs. However, the flexural strengths of all WPCs are not only comparable to those of commercial wood–PP composites but also meet the strength requirements of the Chinese National Standard for exterior WPCs. In addition, the color change of WPCs that contained branch WFs was lower than that of WPCs that contained stem or root WFs during the initial stage of the accelerated weathering test, but the surface color parameters of all WPCs were very similar after 500 h of xenon arc accelerated weathering. Scanning electron microscope (SEM) micrographs showed many cracks on the surfaces of WPCs after accelerated weathering for 500 h, but their flexural modulus of rupture (MOR) and modulus of elasticity (MOE) values did not differ significantly during weathering. Thus, all the discarded parts of pomelo trees can be used to manufacture WPCs, and there were no significant differences in their weathering properties during 500 h of xenon arc accelerated weathering.