Valorisation of the green waste parts from turnip, radish and wild cardoon: Nutritional value, phenolic profile and bioactivity evaluation

Consistency of Phenolic Compounds in Plant Residues Parts: A Review of Primary Sources, Key Compounds, and Extraction Trends

A significant challenge in valorizing food waste is the accurate extraction and identification of metabolites, as the composition of phenolic compounds varies by plant species, part, growth conditions, and processing. This review examined phenolic compounds in plant residue groups (leaves/stalks, peels/husks, pulp/pomace, and seeds) to verify the predominance of specific compounds in the same plant groups, establishing a comprehensive database. This database may be helpful for future studies that seek sources of a given compound or develop solvents to extract phenolic compounds from a specific material. Moreover, the primary plant residues and trends in extracting and analyzing these compounds were reviewed. The predominance of specific compounds within these groups, such as luteolin in plant leaves and stalks, was observed. Most studies focus on extracts with the highest total phenolic content (TPC), limiting insights into how extraction variables affect the target compounds. Chromatographic methods vary according to sample type, column, and conditions, shifting toward reducing acetone/methanol use, shortening the analysis time, and integrating inline UV-vis detection. This perspective highlights plant residue parts rich in specific phenolics, contributing to more targeted, selective, and sustainable extraction methodologies.

A systematic review on Cynara cardunculus L.: bioactive compounds, nutritional properties and food-industry applications of a sustainable food

The cardoon (Cynara cardunculus L.), is a perennial plant belonging to the Asteraceae family, and its cultivated species are widely used in the Mediterranean diet. This review provides an overview of cardoons' chemical composition, bioactive properties and multiple industrial and food applications. Thanks to its nutritional composition, the use of cardoon has increased in food, cosmetic and industrial sectors, such as the energy industry or in the production of paper pulp or bio-packaging. An application in the food industry has involved using of cardoon as a vegetable coagulant for gourmet cheeses-making, as the flowers are rich in aspartic proteases. Cardoon by-products are also rich in bioactive compounds with important health benefits. Most of these nutritional activities are due to the presence of phenolic compounds, minerals, inulin, fibre and sesquiterpene lactones with interesting antioxidant and antimicrobial, anti-inflammatory, anti-tumour, lipid-lowering, cytotoxic and anti-diabetic activities.

Insights into the phenolic composition and in vitro bioactivity of cardoon capitulum: A nutraceutical-oriented valorization study

The capitulum constituents (stigma, corolla, bracts, pappus, and receptacle) of seven cardoon cultivars were studied for their polyphenolic composition and bioactive properties. Fifteen phenolic compounds were identified, secoiridoid, secoxyloganin, and apigenin-O-hexuronoside in higher concentrations. The bracts had the highest concentration of phenolic compounds, and the corolla had the greatest variety. The corolla of F4-1-4 and F1-34-1 cultivars, and bracts of F1-1-1, F1-19-4, and F4-37-1 cultivars revealed the greatest capacity to inhibit the thiobarbituric acid reactive substances formation (IC50 of 38 and 40.4 µg/mL, respectively). The corolla of F1-34-1 cultivar showed higher antihaemolytic activity than the positive control Trolox (IC50 5.5 vs. 20 µg/mL). Bracts of the F4-25-2 cultivar showed higher cytotoxic activity. No hepatotoxicity or anti-inflammatory effects were presented by the studied samples. These bioactivities exhibit a significative correlation with phenolic compounds, in particular flavonoids. Antimicrobial capacity was also observed, with all samples presenting higher antifungal potential than positive controls.

Chemical Profile of Turnip According to the Plant Part and the Cultivar: A Multivariate Approach

Turnip (Brassica rapa subsp. rapa) is a cruciferous plant cultivated worldwide that serves as a source of nutrients and bioactive compounds. Most turnip studies have focused on a few compounds or on part of the plant. The establishment of a complete chemical profile of different plant parts would facilitate its use for nutritional and medicinal purposes. In the current study, mineral elements, soluble sugars, free amino acids (FAA), total phenols (TP), total flavonoids (TF), and glucosinolates (GS) were quantified in the leaves, stems, and roots. Results were compared for 20 strains of turnip. The outcomes showed significant differences between parts of the plant and strains. The leaves exhibited the highest TF, TP, indispensable FAA, and microelement levels, and they showed a higher GS. Moreover, the stems had a high content of GS and macroelements. Furthermore, the roots showed high levels of free sugars and total FAA. The findings of this work provide the basis for utilizing each part of the turnip plant based on its chemical composition.

Bioactive Compounds from Leaf Vegetables as Preservatives

Trends toward a healthier diet are increasing attention to clean-label products. This has led to the search for new ingredients that avoid the use of chemical additives. Food industries are responding to these demands by incorporating natural preservatives into their products, which consumers perceive as healthy. Leafy vegetables would fit this strategy since they are common components of the diet and are associated with beneficial health effects. The objective of this chapter is to offer an overview of the large number of bioactive compounds (phenolic acids, flavonoids, anthocyanins, glucosinolates, and sulfur compounds) present in these plants, which would be responsible for their activity as potential preservatives. Its incorporation into food would improve the quality and extend the shelf life by reducing oxidative processes and inhibiting or retarding the microbial growth that occurs during processing and storage without reducing the organoleptic characteristics of the product.

Evaluation of the Efficacy of Antioxidant Extract from Lemon By-Products on Preservation of Quality Attributes of Minimally Processed Radish (Raphanus sativus L.)

The aim of this work was to enhance the use of a food-grade antioxidant extract obtained from lemon processing byproducts (peel, pulp and seeds) to extend the shelf life of minimally processed radishes. The extract (LPE) was previously characterized in terms of total phenolic (6.75 ± 0.34 mg GAE g-1 d.w.) and flavonoid content (2.04 ± 0.09 mg CE g-1 d.w.) and antioxidant activity, and eriocitrin and hesperidin were identified as the most prevalent phenolic compounds by a UHPLC system. The effects of different dipping aqueous solutions (UCR, DRa, DRb) and alginate-based edible coating formulations (CRc, CRd) with and without the antioxidant extract were studied on the quality parameters of minimally processed radishes, characterized regarding their microbiological and physicochemical characteristics for up to 14 days at 3 °C. The coating formulated with LPE delayed the radish respiration process, as well as resulting in less color variation (ΔE < 3) and reduced mesophilic aerobic count values (4.49 ± 1.43 log CFU g-1), proving the effectiveness of LPE as a value-added ingredient in developing post-harvest strategies to prolong the shelf life of minimally processed vegetables. Indeed, coated samples without the extract showed a clear development of rotting, which led to the end of their shelf life on their 7th day of storage.

Metabolic diversity in a collection of wild and cultivated Brassica rapa subspecies

Brassica rapa (B. rapa) and its subspecies contain many bioactive metabolites that are important for plant defense and human health. This study aimed at investigating the metabolite composition and variation among a large collection of B. rapa genotypes, including subspecies and their accessions. Metabolite profiling of leaves of 102 B. rapa genotypes was performed using ultra-performance liquid chromatography coupled with a photodiode array detector and quadrupole time-of-flight mass spectrometry (UPLC-PDA-QTOF-MS/MS). In total, 346 metabolites belonging to different chemical classes were tentatively identified; 36 out of them were assigned with high confidence using authentic standards and 184 were those reported in B. rapa leaves for the first time. The accumulation and variation of metabolites among genotypes were characterized and compared to their phylogenetic distance. We found 47 metabolites, mostly representing anthocyanins, flavonols, and hydroxycinnamic acid derivatives that displayed a significant correlation to the phylogenetic relatedness and determined four major phylometabolic branches; 1) Chinese cabbage, 2) yellow sarson and rapid cycling, 3) the mizuna-komatsuna-turnip-caitai; and 4) a mixed cluster. These metabolites denote the selective pressure on the metabolic network during B. rapa breeding. We present a unique study that combines metabolite profiling data with phylogenetic analysis in a large collection of B. rapa subspecies. We showed how selective breeding utilizes the biochemical potential of wild B. rapa leading to highly diverse metabolic phenotypes. Our work provides the basis for further studies on B. rapa metabolism and nutritional traits improvement.

Kaempferol rhamnoside catabolism in rosette leaves of senescing Arabidopsis and postharvest stored radish

Flavonol rhamnosides including kaempferitrin (i.e., kaempferol 3-O-α-rhamnoside-7-O-α-rhamnoside) occur throughout the plant kingdom. Mechanisms governing flavonol rhamnoside biosynthesis are established, whereas degradative processes occurring in plants are relatively unknown. Here, we investigated the catabolic events affecting kaempferitrin status in the rosette leaves of Arabidopsis thaliana L. Heynh. (Arabidopsis) and Raphanus sativus L. (radish), respectively, in response to developmental senescence and postharvest handling. On a per plant basis, losses of several kaempferol rhamnosides including kaempferitrin were apparent in senescing leaves of Arabidopsis during development and postharvest radish stored at 5 °C. Conversely, small pools of kaempferol 7-O-α-rhamnoside (K7R), kaempferol 3-O-α-rhamnoside (K3R), and kaempferol built up in senescing leaves of both species. Evidence is provided for ⍺-rhamnosidase activities targeting the 7-O-α-rhamnoside of kaempferitrin and K7R in rosette leaves of both species. An HPLC analysis of in vitro assays of clarified leaf extracts prepared from developing Arabidopsis and postharvest radish determined that these metabolic shifts were coincident with respective 237% and 645% increases in kaempferitrin 7-O-⍺-rhamnosidase activity. Lower activity rates were apparent when these ⍺-rhamnosidase assays were performed with K7R. A radish ⍺-rhamnosidase containing peak eluting from a DEAE-Sepharose Fast Flow column hydrolyzed various 7-O-rhamnosylated flavonols, as well as kaempferol 3-O-β-glucoside. Together it is apparent that the catabolism of 7-O-α-rhamnosylated kaempferol metabolites in senescing plant leaves is associated with a flavonol 7-O-α-rhamnoside-utilizing α-rhamnosidase.

Phenolic Composition and Antioxidant, Anti-Inflammatory, Cytotoxic, and Antimicrobial Activities of Cardoon Blades at Different Growth Stages

Simple Summary

The rapid increase of the world population has promoted a more sustainable and efficient use of natural resources. To achieve complete and proper upcycling of plant crops, it is important to know their potential for industrial exploitation. Cardoon (Cynara cardunculus L.) is a species native to the Mediterranean basin widely used in different sectors, including food and pharmaceuticals. Despite their multiple industrial applications, not all plant tissues have been incorporated into the value chain. Therefore, this work aimed to characterize the phenolic composition and bioactive properties of cardoon blades throughout the phenological growth cycle. In addition to the structural variety of phytochemicals detected in the blade extracts, their antioxidant, anti-inflammatory, anti-proliferative, and antimicrobial properties were also highlighted. While immature material showed higher levels of phenolic compounds and greater potential to inhibit lipid peroxidation, samples at higher development stages had greater anti-proliferative, anti-inflammatory, and antimicrobial potential. These results demonstrate that the growth cycle influences the bioactive potential of cardoon blades and will be useful to establish suitable industrial applications, such as the development of ingredients for functional foods and nutraceuticals, among other products.

Abstract

Cardoon (Cynara cardunculus var. altilis) blades were collected at sixteen sampling dates (B1–B16) to study the influence of the phenological growth stage on the phenolic composition and biological properties. Twenty phenolic compounds were identified, among which trans 3,4-O-dicaffeoylquinic acid, 5-O-caffeoylquinic acid, and luteolin-O-hexoside (39.6, 42.6, and 101.0 mg/g extract, respectively) were the main compounds. Immature blades (B3) had a higher content of phenolic compounds (178 mg/g extract) and a greater ability to inhibit the formation of thiobarbituric acid reactive substances (IC₅₀ of 1.61 µg/mL). Samples at more advanced growth stages revealed a greater capacity to inhibit oxidative hemolysis (B8, IC₅₀ of 25 and 47.4 µg/mL for Δt of 60 and 120 min, respectively) and higher cytotoxic (B8–B13, GI₅₀ between 7.1 and 17 µg/mL), anti-inflammatory (B13, IC₅₀ of 10 µg/mL), and antibacterial activities. In turn, the antifungal activity varied depending on the tested fungi. All these results suggest that maturity influences the phenolic composition and bioactive properties of cardoon blades, which reveal great potential for the development of bioactive ingredients for food and pharmaceutical applications, among others.

Chemical composition and biological activity of cardoon (Cynara cardunculus L. var. altilis) seeds harvested at different maturity stages

Cardoon seeds collected in Greece at four different maturity stages (samples S1 to S4) were analysed in terms of chemical composition and in vitro bioactivities. The content of phenolic compounds (six compounds in total) increased with increasing maturity, and 3,5-O-dicaffeyolquinic (14.8-33.8 mg/g extract) acid was the compound detected in higher abundance. Mature seeds (sample S4) also revealed the highest content in lipids (23 g/100 g extract) and tocopherols (29.62 mg/100 g dw) and demonstrated the highest cytotoxic (GI₅₀ of 97-216 µg/mL) and anti-inflammatory (IC₅₀ = 148 µg/mL) activities, and capacity to inhibit the formation of thiobarbituric acid reactive substances (TBARS) (IC₅₀ = 5 µg/mL). Cardoon seed hydroethanolic extracts also revealed high antibacterial and antifungal potential, particularly samples S3 and S1, respectively. This study proved the multifaceted potential associated with valorisation of cardoon seeds, while their biological and chemical composition can be influenced by the maturity stage.

Phenolic Composition and Biological Properties of Cynara cardunculus L. var. altilis Petioles: Influence of the Maturity Stage

Hydroethanolic extracts of cardoon petioles collected at sixteen growth stages (P1-P16) were characterized in terms of their phenolic composition and bioactive potential (antioxidant, cytotoxic, anti-inflammatory, and antimicrobial activities). Fifteen phenolic compounds were tentatively identified (i.e., ten phenolic acids and five flavonoid glycosides); the main compounds were 5-O-caffeoylquinic and 1,5-di-O-caffeoylquinic acids. Samples collected at early maturity (P1-P4) presented a weak positive correlation between the higher content in polyphenols (P3: 101-mg/g extract) and better inhibition capacity against thiobarbituric acid reactive substance formation (TBARS; P3: IC₅₀ = 5.0 µg/mL). Samples at intermediate maturation stages (P9) presented higher cytotoxic and anti-inflammatory potential. Moreover, immature petioles showed greater antihemolytic (OxHLIA; P4: IC₅₀ = 65 and 180 µg/mL for Δt of 60 and 120 min, respectively) and antibacterial activity. The antifungal activity varied depending on the maturation stage and the fungi strain. In conclusion, the maturation stage may greatly affect the polyphenols composition and content and the bioactive potential of cardoon petioles.

Vitamin E as an essential micronutrient for human health: Common, novel, and unexplored dietary sources

Vitamin E comprises a group of vitamers that includes tocopherols and tocotrienols. They occur in four homologues according to the number and position of methyl groups attached to the chromanol ring. Vitamin E, a liposoluble antioxidant, may participate as an adjuvant in the prevention and treatment of cardiovascular, neurological, and aging-related diseases. Furthermore, vitamin E has applications in the food industry as a natural additive. In this contribution, the most recent information on the dietary sources of vitamin E, including common, novel, and unexplored sources, is presented. Common edible oils, such as those of corn, olive, palm, rice bran, and peanut, represent the most prominent sources of vitamin E. However, specialty and underutilized oils such as those obtained from tree nuts, fruit seeds, and by-products, emerge as novel sources of this important micronutrient. Complementary studies should examine the tocotrienol content of vitamin E dietary sources to better understand the different biological functions of these vitamers.

Changes in Fatty Acid, Tocopherol and Sterol Contents of Oils Extracted from Several Vegetable Seeds

Oil contents of seeds changed between 15.89 g/100 g (purslane) and 38.97 g/100 g (black radish). Palmitic acid contents of oil samples were found between 2.2 g/100 g (turnip) and 15.0 g/100 g (purslane). While oleic acid contents of oil samples change between 12.1% (turnip) and 69.8% (purple carrot), linoleic acid contents of oils were determined between 8.9% (black radish) and 57.0% (onion). The highest linolenic acid was found in purslane oil (26.7%). While α-tocopherol contents of oil samples range from 2.01 mg/kg (purple carrot) to 903.01 mg/kg (onion), γ-tocopherol contents of vegetable seed oils changed between 1.14 mg/kg (curly lettuce) and 557.22 mg/kg (purslane). While campesterin contents of seed oils change between 203.2 mg/kg (purple carrot) and 2808.5 mg/kg (cabbage Yalova), stosterin contents of oil samples varied from 981.5 (curly lettuce) to 4843.3 mg/kg (purslane). The highest brassicasterin and δ5-avenasterin were found in red cabbage oil (894.5 mg/kg) and purslane seed oils (971.3 mg/kg), respectively. Total sterol contents of seed oils changed between 2960.4 mg/kg (purple carrot) and 9185.1 mg/kg (purslane). According to the results, vegetable seeds have different bioactive compound such as fatty acid, tocopherol and phytosterol.

Bioactive Compounds from Agricultural Residues, Their Obtaining Techniques, and the Antimicrobial Effect as Postharvest Additives

Agricultural vegetable products always seek to meet the growing demands of the population; however, today, there are great losses in supply chains and in the sales stage. Looking for a longer shelf life of fruits and vegetables, postharvest technologies have been developed that allow an adequate transfer from the field to the point of sale and a longer shelf life. One of the most attractive methods to improve quality and nutritional content and extend shelf life of fruits and vegetables is the incorporation of bioactive compounds with postharvest technologies. These compounds are substances that can prevent food spoilage and the proliferation of harmful microorganisms and, in some cases, act as a dietary supplement or provide health benefits. This review presents an updated overview of the knowledge about bioactive compounds derived from plant residues, the techniques most used for obtaining them, their incorporation in edible films and coatings, and the methods of microbial inhibition.

The Effects of Turnip (Brassica rapa) Extract on the Growth Performance and Health of Broilers

Simple Summary

Antibiotics are commonly added to the diet of chickens grown for meat to reduce bacterial contamination of their gastrointestinal tract. The bacteria reduce the efficiency of feed utilization and, hence, growth. However, there are concerns about the inclusion of antibiotics in the feed of chickens grown for meat, because of the development of resistance in the bacteria. As a result, scientists are searching for alternative feed additives. Turnip extract is known to have antibacterial properties but has not been tested in the diet of broiler chickens. We tested several levels of turnip extract in the water for chickens and compared their growth and the level of bacterial contamination of their gut with that of chickens given a standard antibiotic. Although chickens with the highest level of turnip extract initially had slow growth, those given a medium level of turnip extract had faster growth overall, better feed conversion, fewer Gram-negative lactose bacteria in their cecum and fewer antibodies in their blood, compared with those fed the antibiotic. This suggests that inclusion of turnip extract in the diet of chickens could provide an alternative to conventional antibiotics.

Abstract

There are concerns about inclusion of antibiotics in the feed of broiler chickens, because of the development of antibiotic resistance, leading to a search for alternative feed additives. Turnip extract is known to have antibacterial properties but has not been tested in the diet of broiler chickens. We allocated 200 broiler chicks to receive one of four levels of turnip extract in their water, 0, 150, 300 or 450 ppm, or a standard antibiotic, Virginiamycin, over a 42-day growing period. Although initially there were detrimental effects of providing 450 ppm, overall the 150 ppm level of supplementation increased weight gain, compared with birds given Virginiamycin, and decreased gizzard weight. Birds given 150 ppm or Virginiamycin had increased low-density lipoproteins (LDLs) and reduced very low-density lipoproteins (VLDLs) in their blood serum and reduced antibody responses to sheep red blood cells, compared to birds in the 450 ppm treatment. Birds given turnip extract at 450 ppm had fewer Gram-negative lactose and coliform bacteria than those provided with no turnip extract, and those provided with 150–300 ppm had the same as those provided with Virginiamycin. Turnip extract could potentially replace antibiotics included in the feed of broiler chickens for growth promotion and the control of bacterial infection of the gastrointestinal tract.

Seasonal variation in bioactive properties and phenolic composition of cardoon (Cynara cardunculus var. altilis) bracts

Cardoon (Cynara cardunculus L.) bracts were collected at different maturation stages to investigate seasonal changes in the phenolic compounds profile and in vitro bioactivities. Among the 12 phenolic compounds tentatively identified, 3,5-O-dicaffeoylquinic acid (21.83 mg/g extract) and apigenin-7-O-glucuronide (10.6 mg/g extract) were the most abundant. Immature bracts (C1: principal growth stage (PGS) 5) had the highest phenolic compounds content, and anti-inflammatory (IC₅₀ = 72 µg/mL) and cytotoxic (GI₅₀ of 30-79 µg/mL) activities. Moreover, extract C1 inhibited efficiently the formation of thiobarbituric acid reactive substances (TBARS; IC₅₀ = 26.8 µg/mL), while extract C8 (PGS 8/9) was more effective against oxidative haemolysis (IC₅₀ 38 and 75 µg/mL). The highest antibacterial and antifungal activities were attributed to samples C1 and C6 (PGS 7/8) and samples C2 (PGS 5/6) and C4 (PGS 6/7), respectively. Overall, the obtained results suggest the seasonal changes of polyphenolic composition and bioactivity of cardoon bracts of variable maturity.

A New Insight on Cardoon: Exploring New Uses besides Cheese Making with a View to Zero Waste

Cardoon, Cynara cardunculus L., is a perennial plant whose flowers are used as vegetal rennet in cheese making. Cardoon is native from the Mediterranean area and is commonly used in the preparation of salads and soup dishes. Nowadays, cardoon is also being exploited for the production of energy, generating large amount of wastes, mainly leaves. These wastes are rich in bioactive compounds with important health benefits. The aim of this review is to highlight the main properties of cardoon leaves according to the current research and to explore its potential uses in different sectors, namely the food industry. Cardoon leaves are recognized to have potential health benefits. In fact, some studies indicated that cardoon leaves could have diuretic, hepato-protective, choleretic, hypocholesterolemic, anti-carcinogenic, and antibacterial properties. Most of these properties are due to excellent polyphenol profiles, with interesting antioxidant and antimicrobial activities. These findings indicate that cardoon leaves can have new potential uses in different sectors, such as cosmetics and the food industry; in particular, they can be used for the preparation of extracts to incorporate into active food packaging. In the future, these new uses of cardoon leaves will allow for zero waste of this crop.