Valorization of olive mill leaves through ultrasound-assisted extraction

An Eco-Friendly Supercritical CO2 Recovery of Value-Added Extracts from Olea europaea Leaves

An eco-friendly approach towards the recovery of value-added extracts from olive tree leaves with the aid of supercritical CO2 at 30 MPa was carried out. The impact of extraction temperature (35-90 °C) and presence of co-solvents (ethanol, water, and aqueous ethanol) on the total phenolic, flavonoid, and pigment content, as well as oleuropein, hydroxytyrosol, tyrosol, and α-tocopherol content was determined. In addition, the antioxidant activity of extracts from tree leaves using DPPH, ABTS, and CUPRAC assays was investigated. The results of the study showed that the most effective supercritical CO2 extraction was at 90 °C with an addition of ethanol, which enabled the separation of extract with the highest content of tested compounds. Some of the highest recorded values were for oleuropein 1.9 mg/g, for carotenoids 5.3 mg/g, and for α-tocopherol 2.0 mg/g. Our results are expected to contribute to the efforts towards the valorization of olive leaves as a sustainable source of valuable compounds, and boost local economies as well as the interest of pharmaceutical, food, and cosmetic industries for novel food by-product applications.

Microwave and ultrasound extraction of antioxidant phenolic compounds from Lantana camara Linn. leaves: Optimization, comparative study, and FT-Orbitrap MS analysis

INTRODUCTION

The species Lantana camara is used in folk medicine. The biological activities of this medicinal plant are attributable to the presence of various derivatives of triterpenoids and phenolic compounds present in its preparations, indicating excellent economic potential.

OBJECTIVE

In this study, the operational conditions of ultrasound-assisted extraction (UAE) and microwave-assisted extraction (MAE) were optimized using Box-Behnken design to improve the total phenolic content (TPC) recovered in hydroethanolic extracts of L. camara leaves.

MATERIAL AND METHODS

The TPC, total flavonoid content (TFC), and antioxidant activities of the hydroalcoholic extracts of L. camara, prepared by UAE and MAE under the optimized extraction conditions, were compared with those of the extracts obtained by conventional extraction methods.

RESULTS

Under the optimal conditions, the extracts obtained by UAE (35% ethanol, 25 min, and a solvent-to-solid ratio of 60:1 mL/g) and by MAE (53% ethanol, 15 min, and 300 W) provided high yields of 32.50% and 38.61% and TPC values of 102.89 and 109.83 mg GAE/g DW, respectively. The MAE extract showed the best results with respect to TPC, TFC, and antioxidant activities, followed by extracts obtained by UAE, Soxhlet extraction, decoction, maceration, and infusion, in that order.

CONCLUSION

The results obtained indicate that L. camara may be used as an important source of antioxidant phenolic compounds to obtain products with high biological and economic potential, especially when the extraction process is performed under appropriate conditions using MAE and/or UAE, employing environmentally friendly solvents such as water and ethanol.

Development and cross-validation of simple HPLC-fluorescence and UPLC-MS-UV methods for rapid determination of oleuropein in olive leaves

INTRODUCTION

Olive leaves, abundant by-products of the olive oil industry, are a rich source of oleuropein, an important polyphenol in olive leaves. So far, no published methods have been validated using matrix standards for oleuropein quantification in olive leaves.

OBJECTIVES

The study aimed to develop an HPLC method for oleuropein determination in olive leaves using spiked matrix standards prepared from a blank olive leaf matrix, to validate the method with respect to aqueous standards, and cross-validate the HPLC method with UPLC-MS and UPLC-UV techniques.

METHODOLOGY

Oleuropein was extracted into methanol and analysed by HPLC with fluorescence detection (FLD; excitation and emission wavelengths 281 and 316 nm, respectively) and by UPLC-MS-UV. For validation, calibration curves of spiked matrix standards (0.4 to 4.8 mg/g) were analysed by the three methods over several days. Oleuropein was then analysed in French olive varieties.

RESULTS

For the HPLC-FLD method, repeatability and intermediate precision were less than 5% RSD and linearity was demonstrated by the Fischer test. Differences in results of the spiked placebos by the three methods were non-significant, as confirmed by ANOVA. Extraction recovery was >90%, and there was a strong linear relationship between authentic and spiked matrix standards. The determination of oleuropein in French olive varieties is reported, including analysis in "Olivière" cultivar for the first time, leaves of which contained twice the amount of oleuropein compared with "Picholine".

CONCLUSION

Accurate quantification of oleuropein is possible using aqueous standards. Cross-validation indicates that selective analysis can equally be carried out by HPLC or by UPLC-MS techniques.

Recovery of Oleuropein from Olive Leaf Extract Using Zinc Oxide Coated by Polyaniline Nanoparticle Mixed Matrix Membranes

This study explores the integration of zinc oxide coated with polyaniline (ZnO-PANI) nanoparticles into a poly(ether sulfone) (PES) matrix to concurrently enhance permeate flux and oleuropein (OLP) rejection during the filtration of olive leaf extract (OLE). The effect of ZnO-PANI content on porosity, pore size, surface hydrophilicity, and pure water flux (PWF) was studied. The results indicate that an increase in ZnO-PANI content (0-0.2%) leads to a 3-fold increase in mean pore size, permeability (1.29-7.18 L/m2 h bar), porosity (72.2-77.8%), and improved surface hydrophilicity of the prepared membranes. Membrane performance was tested for OLE permeate flux of the OLE and total phenolic compounds (TPC) rejection at various pressures (10-30 bar), the performance of the OLP rejection at 30 bar, and fouling resistance. The 0.2 wt % ZnO-PANI membrane exhibits the highest permeate flux, while the 0.4 wt % ZnO-PANI membrane offers the highest rejection values (90-97% for TPC and 100% for OLP). Bare PES demonstrated the best fouling resistance. Strategic ZnO-PANI incorporation achieves a balance, enhancing both the flux and rejection efficiency. The 0.2 wt % ZnO-PANI membrane emerges as particularly favorable, striking a beneficial equilibrium between permeate flux and OLP rejection. Intriguingly, the use of these membranes for OLE filtration, postpretreatment with ultrafiltration (UF), results in a remarkable 100% rejection of OLP. This discovery underscores the significant and specific separation of OLP from OLE facilitated by a ZnO-PANI-based mixed matrix membrane (MMM). The study contributes valuable insights into the development of advanced membranes with enhanced filtration capabilities for high-added value phenolic compound separation.

Compositional Changes during Storage of Industrially Produced Olive Oils Co-Milled with Olive Leaves

The possibility of enriching the oil produced from Leccino cultivar olive fruits with phenolic and volatile compounds by adding olive leaves (2.5%) during industrial-scale production were investigated. Furthermore, the influence of the addition of leaves on the oil quality, composition, and oxidative stability during storage for 6 and 12 months was studied. A slight negative impact on the oil quality after processing with leaves was determined. The addition of leaves had no influence on the total saturated, monounsaturated, and polyunsaturated fatty acids in oils, while it influenced increases in total phenolic compounds (+29.55%), total secoiridoids (+29.43%), chlorophylls (+47.59%), and the oil stability index (+18.70%), and their higher values were also determined in the stored oils. The addition of leaves increased C5 volatiles (+10.50%) but decreased C6 volatiles (-10.48%). The intensity of most of the positive sensory characteristics increased in fresh oils obtained with leaves, and the established improvements were also maintained in the stored oils. The extractability of olive paste was positively affected by the addition of olive leaves, which increased the oil yield (+27.17%). The obtained results significantly contribute to the knowledge about the possibilities of enriching olive oils with bioactive compounds.

Exploring the Bioactive Content of Liquid Waste and Byproducts Produced by Two-Phase Olive Mills in Laconia (Greece): Is There a Prospect for Added-Value Applications?

The use of a two-phase decanter (TwPD) for olive-oil extraction produces wastes and byproducts (a small volume of water from oil washing, olive leaves from the defoliator, and a high moisture pomace which can be destoned) that contain valuable bioactive compounds, such as phenolics and/or triterpenic acids. So far, there is no (water) or limited information (leaves and the destoned pomace fraction) on their content of bioactives, especially triterpenic acids. To contribute to the characterization of such streams from cultivars of international interest, in the present study, samples obtained from five mills from the region of Laconia (from one or two harvests) in Greece, where Koroneiki cv dominates, were screened for phenols and/or triterpenic acids. The leaves and pomace were dried at two temperatures (70 °C and/or 140 °C), and the pomace was also destoned before analysis. The liquid wastes contained low amounts of total (TPC) phenols (<140 mg gallic acid/L), hydroxytyrosol (<44 mg/L), and tyrosol (<33 mg/L). The olive leaves varied widely in TPC (12.8-57.4 mg gallic acid/g dry leaf) and oleuropein (0.4-56.8 mg/g dry leaf) but contained an appreciable amount of triterpenic acids, mainly oleanolic acid (~12.5-31 mg/g dry leaf, respectively). A higher drying temperature (140 vs. 70 °C) affected rather positively the TPC/oleuropein content, whereas triterpenic acids were unaffected. The destoned pomace TPC was 15.5-22.0 mg gallic acid/g dw, hydroxytyrosol 3.9-5.6 mg/g dw, and maslinic 5.5-19.3 mg/g dw. Drying at 140 °C preserved better its bioactive phenols, whereas triterpenic acids were not influenced. The present findings indicate that TwPD streams may have a prospect as a source of bioactives for added-value applications. Material handling, including drying conditions, may be critical but only for phenols.

Antioxidant Capacity of Free and Bound Phenolics from Olive Leaves: In Vitro and In Vivo Responses

Olive leaves are rich in phenolic compounds. This study explored the chemical profiles and contents of free phenolics (FPs) and bound phenolics (BPs) in olive leaves, and further investigated and compared the antioxidant properties of FPs and BPs using chemical assays, cellular antioxidant evaluation systems, and in vivo mouse models. The results showed that FPs and BPs have different phenolic profiles; 24 free and 14 bound phenolics were identified in FPs and BPs, respectively. Higher levels of phenolic acid (i.e., sinapinic acid, 4-coumaric acid, ferulic acid, and caffeic acid) and hydroxytyrosol were detected in the BPs, while flavonoids, triterpenoid acids, and iridoids were more concentrated in the free form. FPs showed a significantly higher total flavonoid content (TFC), total phenolic content (TPC), and chemical antioxidant properties than those of BPs (p < 0.05). Within the range of doses (20-250 μg/mL), both FPs and BPs protected HepG2 cells from H2O2-induced oxidative stress injury, and there was no significant difference in cellular antioxidant activity between FPs and BPs. The in vivo experiments suggested that FP and BP treatment inhibited malondialdehyde (MDA) levels in a D-galactose-induced oxidation model in mice, and significantly increased antioxidant enzyme activity of superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), catalase (CAT), and the total antioxidant capacity (T-AOC). Mechanistically, FPs and BPs exert their antioxidant activity in distinct ways; FPs ameliorated D-galactose-induced oxidative stress injury partly via the activation of nuclear factor erythroid-2-related factor 2 (Nrf2) signaling pathway, while the BP mechanisms need further study.

Study of Comparative Morphology of Eight Cultivated Genotypes of Olea europaea L

The current study was designed to assess the comparative morphology of eight olive cultivars with different geographical origins and diverse genetic backgrounds, introduced to a new climatic zone. The morphological parameters of eight (five exotic and three domestic) olive cultivars (Bari Zaitoon-1, Bari Zaitoon-2, Favolosa (FS-17), Koroneiki, Balkasar, Ottobratica, Leccino, and Arbequina) were compared at the experimental area of the Department of Botany, The Islamia University of Bahawalpur, Pakistan (29°24′0″ North, 71°41′0″ East, 401–421 feet above sea level). Plant height, number of leaves/15 cm shoot, leaf size characteristics (leaf length, leaf width, leaf area, and length/width ratio), leaf shape characteristics (margin, leaf axil, base, and apex angles), leaf pigments (Chlorophyll a, Chlorophyll b, total chlorophyll contents, and carotenoids), phyllotaxy, and leaf color and venation were recorded. The highest plant height (28 cm) was obtained by Bari Zaitoon-2 followed by Bari Zaitoon-1 (24 cm), both of which are domestic cultivar of Pakistan, while the shortest height (5 cm) was obtained by Koroneiki. Leccino displayed the highest average number of leaves (17.8) on main shoot, followed by BARI-2 (16.4) and the lowest score was from Balkasar (10.4). Leaf area ranged from 5.66 cm2 (Bari Zaitoon-1) to 3.08 cm2 (Koroneiki). The longest leaf length (5.74 cm) was found in Bari Zaitoon-1 and the shortest (4.04 cm) in Koroneiki, while the broadest leaves were found in Leccino (1.54 cm) and the narrowest (1.12 cm) in Koroneiki. Bari Zaitoon-2 led in leaf length to width ratio (4.058) followed by Bari Zaitoon-1 (3.772) with small lanceolate leaves hardly reaching the value of 4, with the lowest value illustrated by Leccino. The total chloroplast pigments were highest in FS-17 followed by Bari Zaitoon-1 and Bari Zaitoon-2, while the lowest was in Arbequina. Chlorophyll a was highest in Bari Zaitoon-1 followed by FS-17 and Balkasar, with the lowest rate in Arbequina. Chlorophyll b content of FS-17 was the highest whereas the Chlorophyll b and total chlorophyll contents in Arbequina were the lowest of all the cultivars. The highest value of total carotenoids was found in Balkasar followed by FS-17 with the lowest value in Arbequina. The phyllotaxy was categorized into three types, i.e., alternate, opposite, and whorled. The combination of two or more types was usually observed on the same branch. The whorl of four leaves was also present in rare cases. Leaf venation was both pinnate and reticulate. The leaf base of most (four) of the olive cultivars, i.e., Arbequina, Balkasar, Leccino and FS-17, were cuneate having acute, rounded, apiculate, and cuspidate leaf tips, respectively. The findings revealed remarkable variations in olive morphology, especially in the leaves and a successful record of the preliminary data of olive cultivars from the study area was made. The present research demonstrated that local olive cultivars have unique characteristics that differentiate them from imported cultivars. Thus, local cultivars provide novel genetic resources that should be conserved.

Ultrasound-assisted extraction of tamarind xyloglucan: an effective approach to reduce the viscosity and improve the α-amylase inhibition of xyloglucan

BACKGROUND

Water extraction (WE) is the classical extraction method for tamarind xyloglucan (XyG), but its low yield, high viscosity and poor dispersion in aqueous solution are not conducive to the industrial applications. To promote the industrial application of tamarind XyG, an ultrasonic-assisted extraction (UAE) method for extracting low-viscosity XyG from tamarind kernel powder was proposed.

RESULTS

The yield of UAE-XyG was higher (502.33 ± 0.036 g kg^-1 ) than that of WE-XyG (163.43 ± 0.085 g kg^-1 ). UAE reduced the molecular weight, monosaccharide content and apparent viscosity of XyG. The hypoglycemic experiment in vitro showed that UAE-XyG had a stronger inhibitory effect on α-amylase activity than WE-XyG, but its glucose dialysis retardation index was lower.

CONCLUSION

In sum, UAE is a type of extraction method that could effectively improve the yield of XyG and reduce its viscosity to expand its application without reducing its physiological activity. UAE exhibits an excellent potential in the extraction of XyG. © 2022 Society of Chemical Industry.

Extraction Systems and Analytical Techniques for Food Phenolic Compounds: A Review

Phenolic compounds are highly valuable food components due to their potential utilisation as natural bioactive and antioxidant molecules for the food, cosmetic, chemical, and pharmaceutical industries. For this purpose, the development and optimisation of efficient extraction methods is crucial to obtain phenolic-rich extracts and, for some applications, free of interfering compounds. It should be accompanied with robust analytical tools that enable the standardisation of phenolic-rich extracts for industrial applications. New methodologies based on both novel extraction and/or analysis are also implemented to characterise and elucidate novel chemical structures and to face safety, pharmacology, and toxicity issues related to phenolic compounds at the molecular level. Moreover, in combination with multivariate analysis, the extraction and analysis of phenolic compounds offer tools for plant chemotyping, food traceability and marker selection in omics studies. Therefore, this study reviews extraction techniques applied to recover phenolic compounds from foods and agri-food by-products, including liquid-liquid extraction, solid-liquid extraction assisted by intensification technologies, solid-phase extraction, and combined methods. It also provides an overview of the characterisation techniques, including UV-Vis, infra-red, nuclear magnetic resonance, mass spectrometry and others used in minor applications such as Raman spectroscopy and ion mobility spectrometry, coupled or not to chromatography. Overall, a wide range of methodologies are now available, which can be applied individually and combined to provide complementary results in the roadmap around the study of phenolic compounds.

Antioxidant and Antimicrobial Activity of Hydroethanolic Leaf Extracts from Six Mediterranean Olive Cultivars

Phenolic profiles, antioxidant, and antimicrobial activities of hydroethanolic olive leaf extracts from six Mediterranean olive cultivars (Croatian: Lastovka, Levantinka, Oblica; Italian: Moraiolo, Frantoio, Nostrana di Brisighella) were investigated. As expected, various distributions of phenolic levels were observed for each cultivar and the total phenolic content showed high variability (ranging from 4 to 22 mg GAE/g of dry extract), with the highest amount of phenolics found in the Oblica sample, which also provided the highest antiradical (ORAC) and reducing activity (FRAP). The screening of individual compounds was performed by HPLC-PDA-ESI-QTOF-MS and the main detected compounds were oleuropein, hydroxytyrosol, oleoside/secologanoside, verbascoside, rutin, luteolin glucoside, hydroxyoleuropein, and ligstroside. While the antioxidant activity of the samples was relatively high, they showed no bactericidal and bacteriostatic activity against E. coli and S. Typhimurium; weak activity against Staphylococcus aureus, Bacillus cereus, and Listeria innocua; and inhibitory effects against Campylobacter jejuni at 0.5 mg dry extract/mL. The obtained results support the fact that olive leaf extracts, and especially those from the Oblica cultivar, could potentially be applied in various industries as natural preservatives and effective and inexpensive sources of valuable antioxidants.

Oleuropein-Enriched Extract From Olive Mill Leaves by Homogenizer-Assisted Extraction and Its Antioxidant and Antiglycating Activities

Olive oil consumption has increased in the last two decades and consequently, its wastes have increased, which generates a tremendous environmental impact. Among the by-products are the olive mill leaves, which are easier and inexpensive to treat than other olive by-products. However, little research has been done on their chemical composition and potential bioactivity. Hence, in this study, olive mill leaves were used to obtain Oleuropein-Enriched Extracts (OLEU-EE) using Conventional Extraction, Ultrasound-Assisted Extraction, and Homogenization-Assisted Extraction. These three techniques were evaluated using a Factorial Design to determine the parameters to obtain an OLEU-EE with high contents of Total Phenolic Compounds (TPC), Antioxidant Activity (AA), and Oleuropein concentration (OLEU). From the results, the Homogenizer-Assisted Extraction (HAE) technique was selected at 18,000 rpm, solid:liquid ratio 1:10, and 30 s of homogenization with 70% ethanol, due to its high TPC (5,196 mg GA/100 g), AA (57,867 μmol of TE/100 g), and OLEU (4,345 mg of OLEU/100 g). In addition, the antiglycating effect of OLEU-EE on the levels of (1) fluorescent Advanced Glycation End Products (AGEs) were IC50 of 0.1899 and 0.1697 mg/mL for 1λEXC 325/λEM 440 and 2λEXC 389/λEM 443, respectively; (2) protein oxidative damage markers such as dityrosine (DiTyr), N-formylkynurenine (N-formyl Kyn), and kynurenine (Kyn) were IC50 of 0.1852, 0.2044, and 0.1720 mg/mL, respectively. In conclusion, OLEU-EE from olive mill leaves has different capacities to inhibit AGEs evidenced by the IC50 of fluorescent AGEs and protein oxidation products, together with the scavenging free radical evidenced by the concentration of Trolox Equivalent. Therefore, OLEU-EE could be potential functional ingredients that prevent oxidative damage caused by free radicals and AGEs accumulation.

Changes in Phytochemical Profiles and Biological Activity of Olive Leaves Treated by Two Drying Methods

Olive leaves, which are the most abundant byproducts of the olive industry, offer multiple health benefits. The investigation of the phytochemical profiles and relevant biological activities is an essential step toward transforming these low-value byproducts into value-added ones. This study systematically investigated the phytochemical profiles, antioxidant capacity, and inhibition rates of olive leaves from four cultivars on the α-glucosidase, α-amylase, and angiotensin-converting enzyme (ACE). The leaves were prepared using two common drying methods, namely, hot air-drying and freeze-drying. A total of 33 bioactive compounds were identified in the olive leaves, namely, 19 flavonoids, 2 phenylethanoids, 2 coumarins, 2 hydroxycinnamic acids, 2 iridoids, and 6 triterpenic acids. Quantification of the bioactive compounds revealed high amounts of polyphenols, especially flavonoids [2,027–8,055 mg/kg dry weight (DW)], iridoids (566–22,096 mg/kg DW), and triterpenic acids (13,824–19,056 mg/kg DW) in the olive leaves. The hot air-dried leaves showed significantly (P < 0.05) higher iridoid (oleuropein and secoxyloganin) content than the fresh leaves, while freeze-drying resulted in significantly (P < 0.05) higher flavonoid aglycone and hydroxytyrosol content. Additionally, freeze-drying led to samples with the highest radical scavenging, α-amylase, α-glucosidase, and ACE inhibition abilities. The flavonoid (e.g., quercetin, luteolin, eriodictyol, kaempferol-7-O-glucoside, and luteolin-7-O-glucoside), hydroxytyrosol, and oleanolic acid contents in the olive leaves were positively correlated (P < 0.05) with their bioactive potentials.

Characterization and Influence of Static In Vitro Digestion on Bioaccessibility of Bioactive Polyphenols from an Olive Leaf Extract

Olive leaves, one of the most abundant olive production by-products, have shown incredible potential for their characteristic bioactive compound composition, with unique compounds such as the polyphenol oleuropein. In order to evaluate the bioaccessibility of bioactive compounds present in an olive leaf extract, samples were submitted to an in vitro digestion process following INFOGEST protocol, and qualitative and quantitative characterization of the original extract and digestive samples at different times were carried out using HPLC-ESI-TOF-MS. The analyzed extract presented an abundance of phenolic compounds, such as secoiridoids, with oleuropein being the main identified compound. The in vitro digestion process showed an effect on the phenolic profile of the extract, with a lower recovery in the gastric phase and an increase at the beginning of the intestinal phase. Most of the studied compounds showed high bioaccessibility at the end of the digestion, with oleuropein, ligstroside, and quercetin-3-O-galactoside being among the ones with higher value. These findings show the potential for future use of olive leaf polyphenols. However, further research is needed in order to evaluate the absorption, delivery, and interaction of these compounds with the colon.

Comparative Evaluation of the Phytochemical Profiles and Antioxidant Potentials of Olive Leaves from 32 Cultivars Grown in China

Olives (Olea europaea L.) are a significant part of the agroindustry in China. Olive leaves, the most abundant by-products of the olive and olive oil industry, contain bioactive compounds that are beneficial to human health. The purpose of this study was to evaluate the phytochemical profiles and antioxidant capacities of olive leaves from 32 cultivars grown in China. A total of 32 phytochemical compounds were identified using high-performance liquid chromatography–electrospray ionization–tandem mass spectrometry, including 17 flavonoids, five iridoids, two hydroxycinnamic acids, six triterpenic acids, one simple phenol, and one coumarin. Specifically, olive leaves were found to be excellent sources of flavonoids (4.92–18.29 mg/g dw), iridoids (5.75–33.73 mg/g dw), and triterpenic acids (15.72–35.75 mg/g dw), and considerable variations in phytochemical content were detected among the different cultivars. All tested cultivars were classified into three categories according to their oil contents for further comparative phytochemicals assessment. Principal component analysis indicated that the investigated olive cultivars could be distinguished based upon their phytochemical profiles and antioxidant capacities. The olive leaves obtained from the low-oil-content (<16%) cultivars exhibited higher levels of glycosylated flavonoids and iridoids, while those obtained from high-oil-content (>20%) cultivars contained mainly triterpenic acids in their compositions. Correspondingly, the low-oil-content cultivars (OL3, Frantoio selection and OL14, Huaou 5) exhibited the highest ABTS antioxidant activities (758.01 ± 16.54 and 710.64 ± 14.58 mg TE/g dw, respectively), and OL9 (Olea europaea subsp. Cuspidata isolate Yunnan) and OL3 exhibited the highest ferric reducing/antioxidant power assay values (1228.29 ± 23.95 mg TE/g dw and 1099.99 ± 14.30 mg TE/g dw, respectively). The results from this study may be beneficial to the comprehensive evaluation and utilization of bioactive compounds in olive leaves.

Control of the Verticillium Wilt on Tomato Plants by Means of Olive Leaf Extracts Loaded on Chitosan Nanoparticles

In this research, a new ecofriendly and sustainable fungicide agent, with the ability to control Verticillium wilt, was developed. To this purpose, a green extract of olive leaf (OLE) was prepared by ultrasound-assisted extraction (UAE) and characterized in terms of polyphenol content and antioxidant activity. Then, OLE was loaded in chitosan nanoparticles (CTNPs) to combine the antifungal activity of CTNPs and phenolic compounds to obtain an important synergic effect. Nanoparticles were synthetized using the ionic gelation technique and characterized in terms of sizes, polydispersity index, Z-potential, encapsulation efficiency, and release profile. Qualitative and quantitative analyses of OLE were performed by the HPLC method. OLE-loaded CTNPs exhibited good physicochemical properties, such as a small size and positive surface charge that significantly contributed to a high antifungal efficacy against Verticillum dahliae. Therefore, their antifungal activity was evaluated in vitro, using the minimal inhibition concentration (MIC) assay in a concentration range between 0.071 and 1.41 mg/mL. Free OLE, blank CTNPs, and OLE-loaded CTNPs possessed MIC values of 0.35, 0.71, and 0.14 mg/mL, respectively. These results suggest an important synergic effect when OLE was loaded in CTNPs. Thereafter, we tested the two higher concentrations on tomato plants inoculated with V. dahliae, where no fungal growth was observed in the in vitro experiment, 0.71 and 1.41 mg/mL. Interestingly, OLE-loaded CTNPs at the higher concentration used, diminished the symptoms of Verticillium wilt in tomato plants inoculated with V. dahliae and significantly enhanced plant growth. This research offers promising results and opens the possibility to use OLE-loaded CTNPs as safe fungicides in the control strategies of Verticillium wilt at open field.

Innovative Extraction Technologies for Development of Functional Ingredients Based on Polyphenols from Olive Leaves

Olive tree (Olea europea L.) leaves represent around 10% of the total weight of olives arriving at any given mill, which are generally discarded, causing economic and environmental issues. However, these are rich sources of natural bioactive compounds (i.e., polyphenols), which have health-promoting potential. Thus, the valorization of olive leaves by recovering and reusing their components should be a must for food sustainability and circular economy. This review provides an insight into the principal polyphenols present in olive leaves, together with agronomic variables influencing their content. It also summarizes the recent advances in the application of novel extraction technologies that have shown promising extraction efficacy, reducing the volume of extraction solvent and saving time and cost. Moreover, potential industrial uses and international patents filed in the pharmaceutic, food, and cosmetic sectors are discussed.

Edible pectin film added with peptides from jackfruit leaves obtained by high-hydrostatic pressure and pepsin hydrolysis

Jackfruit (Artocarpus heterophyllus Lam.) is an evergreen tree that produces a high waste of leaves. This study evaluated the obtention of peptides from jackfruit leaves using pancreatin and pepsin, their antifungal activity, and their effect on pectin films. The protein content was 7.64 ± 0.12 g/100 g of jackfruit fresh leaves. Pancreatin produced a higher yield than pepsin in the obtention of peptides (p ≤ 0.05). However, peptides obtained after 2 h by pepsin hydrolysis (Pep-P) had six essential amino acids and inhibited > 99% of mycelial growth and spore germination of Colletotrichum gloeosporioides. Pectin films with Pep-P showed a slight brown color, lower thickness, water vapor permeability, and moisture content, as well as higher thermal stability and better inhibition properties against C. gloeosporioides than pectin films without Pep-P (p ≤ 0.05). Pectin films added with Pep-P from jackfruit leaf could be a green alternative to anthracnose control in tropical fruits.

Optimum Conditions and LC-ESI-MS Analysis of Phenolic Rich Extract from Eucalyptus marginata L. under Maceration and Ultrasound-Assisted Extraction Methods Using Response Surface Methodology

Eucalyptus marginata L. has a significant value in traditional medicine and recently has been shown to possess many pharmacological properties in vitro. The main goal of the present study was to optimize the extraction parameters of phenolic compounds from Eucalyptus marginata L. leaves using the extraction technique assisted by ultrasound in comparison with maceration using response surface methodology as a predicted tool. Therefore, total phenolic and flavonoid contents have been optimized, taking into account four variables: extraction time, temperature, liquid-to-solid ratio, and ethanol concentration. The optimum ultrasound-assisted extraction method for total phenolic and total flavonoid contents was obtained by ensuring the following parameters: t = 49.9 min, T = 74.9°C, liquid-to-solid ratio = 39.5 ml/g, and ethanol = 58.48%. The optimum extract has been subjected to LC-ESI-MS analysis. This technique allowed us to identify ten phenolic compounds: four phenolic acids mainly gallic acid (27.77 ± 0.06 µg/g DW) and protocatechuic acid (37.66 ± 0.04 µg/g DW) and six flavonoid compounds such as quercetrin (150.78 ± 0.02 µg/g DW) and hyperoside (39.19 ± 0.03 µg/g DW). These green and efficient procedures should be a promising option to guide industrial design for the production of phenolic-rich plant extracts.

Sonication, a Potential Technique for Extraction of Phytoconstituents: A Systematic Review

Traditional extraction techniques have lost their optimum performance because of rising consumer demand and novel technologies. In this regard, several techniques were developed by humans for the extraction of plant materials from various indigenous sources, which are no longer in use. Many of the techniques are not efficient enough to extract maximum plant material. By this time, evolution in extraction has led to development of various techniques including microfiltration, pulsed electric fields, high pressure, microwave assistance, enzyme assistance, supercritical fluid, subcritical fluid and ultrasonication. These innovations in food processing/extraction are known as “Green Food Processing”. These technologies were basically developed by focusing on three universal parameters: simplicity, energy efficiency and economy. These green technologies are practical in a number of different food sectors, mostly for preservation, inhibition of microorganisms, inactivation of enzymes and extraction of plant material. Like the others, ultrasonication could also be used for the said purposes. The primary objective of this review is to confine the potential use of ultrasonication for extraction of oils, pectin and phytochemicals by reviewing the literature systematically.

Ultrasound extraction optimization for bioactive molecules from Eucalyptus globulus leaves through antioxidant activity

Antioxidant products present a very high added value and are demanded in the market. The optimization of their extraction is a high-stakes matter for both economic and environmental points of view. Ultrasound extraction has been considered one of the most promising methods, so the relative importance of key parameters may have decisive economic significance. For this reason, different parameters that have influence on the extraction capacity such as ultrasound power, time, temperature, pH and % ethanol in water have been studied to know the relationships between the independent parameters and their influence on the extraction from Eucalyptus globulus leaves. An experimental Box-Behnken factorial design and subsequent analysis by neural networks have been used. The relative influence of each parameter varies according to the nature of the extracted compound. In this regard, the higher capacity of extraction of the selected antioxidant compounds by means of the variation of the operation conditions can be facilitated. For all the studied compounds, temperature has been the most important parameter for their extraction. The relative content (%) of bioactive compounds (terpenes) in the optimized Eucalyptus globulus extract has been performed by GC-MS analysis.

Use of Polyphenols as Modulators of Food Allergies. From Chemistry to Biological Implications

The multifactorial process of aging predisposes humans to infections and inflammatory disorders, thus affecting their quality of life and longevity. Given this reality, the need to increase the consumption of bioactive compounds, like dietary polyphenols emerges in our daily basis mostly due to their health related effects in slowing-down the incidence of chronic and degenerative diseases and even food allergy, which has been growing rapidly in prevalence currently affecting 5% of adults and 8% of children. Polyphenols embrace a large family of secondary metabolites from plant-derived foods and food wastes and are considerable of interest since they have attracted special attention over the years because of their reported anti-inflammatory and antimicrobial properties along with their high antioxidant capacity. These compounds are claimed as nutraceuticals with protective effect in offsetting oxidant species over-genesis in normal cells, and with the potential ability to stop or reverse oxidative stress-related diseases. Plant-derived foods represent a substantive portion of human diet containing a significant amount of structurally diverse polyphenols. There is a need to understand the polyphenolic composition of plant-derived foods mainly because of its chemistry, which discloses the bioactivity of a plant extract. However, the lack of standardized methods for analysis and other difficulties associated to the nature and distribution of plant polyphenols leads to a high variability of available data. Furthermore, there is still a gap in the understanding of polyphenols bioavailability and pharmacokinetics, which clearly difficult the settlement of the intake needed to observe health outcomes. Many efforts have been made to provide highly sensitive and selective analytical methods for the extraction (liquid-liquid; solid-liquid; supercritical-fluid), separation (spectrophotometric methods) and structural identification (chromatographic techniques, NMR spectroscopy, MS spectrometry) of phenolic and polyphenolic compounds present in these extracts. Liquid chromatography coupled to mass spectrometry (LC-MS) has been a fundamental technique in this area of research, not only for the determination of this family of compounds in food matrices, but also for the characterization and identification of new polyphenols classified with nutraceutical interest. This review summarizes the nature, distribution and main sources of polyphenols, analytical methods from extraction to characterization to further evaluate the health effects toward immune reactions to food.

Green and Non-conventional Extraction of Bioactive Compounds from Olive Leaves: Screening of Novel Natural Deep Eutectic Solvents and Investigation of Process Parameters

ABSTRACT

Olive leaf as an agricultural waste contains valuable bioactive compounds that are mainly used for pharmaceutical and cosmetic industries. Lately the major component, oleuropein, has gained extra attention due to the anti-viral activity against SARS-CoV-2 that causes Coronavirus disease (Covid-19). In this study, extraction of the bioactive compounds from olive leaves was conducted using a non-conventional and green method. New generation green solvents, natural deep eutectic solvents (NADES) were used in combination with ultrasound assisted extraction. Screening of NADES type, temperature, and particle size were investigated using one-pot-at-a-time method while, NADES amount and liquid-to-solid ratio were optimized using experimental design. The results were evaluated in terms of total polyphenol yield (Y_TP), total flavonoid yield (Y_TF) and antiradical activity (A_AR). At the optimized conditions, the highest total polyphenol yield and the highest total flavonoid yield were achieved with choline chloride-fructose-water (CFW) (5:2:5) as 187.31 ± 10.3 mg gallic acid equivalent g^-1 dw and 12.75 ± 0.6 mg apigenin equivalent g^-1 dw, respectively. The extracts were also analyzed for oleuropein, caffeic acid and luteolin contents. The highest amount of oleuropein and caffeic acid were extracted by glucose-fructose-water (GFW) (1:1:11) as 1630.80 mg kg^-1 dw and 112.77 mg kg^-1 dw, respectively.

SUPPLEMENTARY INFORMATION

The online version of this article (10.1007/s12649-021-01411-3) contains supplementary material, which is available to authorized users.

Olive Pomace-Derived Biomasses Fractionation through a Two-Step Extraction Based on the Use of Ultrasounds: Chemical Characteristics

Olive-derived biomass is not only a renewable bioenergy resource but also it can be a source of bioproducts, including antioxidants. In this study, the antioxidant composition of extracted olive pomace (EOP) and a new byproduct, the residual fraction from olive pit cleaning (RFOPC or residual pulp) was characterized and compared to olive leafy biomass, which have been extensively studied as a source of antioxidants and other bioactive compounds with pharmacological properties. The chemical characterization showed that these byproducts contain a high amount of extractives; in the case of EOP, it was even higher (52.9%) than in olive leaves (OL) and olive mill leaves (OML) (35.8–45.1%). Then, ultrasound-assisted extraction (UAE) was applied to recover antioxidants from the extractive fraction of these biomasses. The solubilization of antioxidants was much higher for EOP, correlating well with the extractives content and the total extraction yield. Accordingly, this also affected the phenolic richness of the extracts and the differences between all biomasses were diminished. In any case, the phenolic profile and the hydroxytyrosol cluster were different. While OL, OML, and EOP contained mainly hydroxytyrosol derivatives and flavones, RFOPC presented novel trilignols. Other compounds were also characterized, including secoiridoids, hydroxylated fatty acids, triterpenoids, among others, depending on the bioresource. Moreover, after the UAE extraction step, alkaline extraction was applied recovering a liquid and a solid fraction. While the solid fraction could of interest for further valorization as a biofuel, the liquid fraction contained proteins, sugars, and soluble lignin, which conferred antioxidant properties to these extracts, and whose content depended on the biomass and conditions applied.

Metabolic profile of olive leaves of different cultivars and collection times

Due to the appreciable amounts of bioactive compounds in olive leaves and the effect of abiotic stresses on their synthesis, this study evaluated the metabolic profile of leaves of olive cultivars (Arbequina, Manzanilla and Picual) collected in four periods of the year (autumn, winter, spring and summer). The determination of the profile of bioactive compounds (phenolic compounds, flavonoids, tannins, carotenoids and chlorophylls) by spectrophotometry and the individual compounds by liquid chromatography coupled to mass spectrum, as well as antioxidant potential tests were performed. As results it was possible to observe that the leaves of the cultivar Manzanilla presented the highest levels of phenolic compounds and that the leaves collected in the summer presented a number of compounds much more relevant than the others. Thus, it was possible to conclude that the cultivar and the collection season significantly affect the bioactive content and the antioxidant potential of olive leaves.

Avocado-Derived Biomass as a Source of Bioenergy and Bioproducts

The avocado (Persea americana Mill.) is a tree native to Mexico and Guatemala. Avocado consumption, fresh or in the form of processed products, is growing everywhere and it has caused a large number of countries to invest heavily in avocado production. The industrialization of avocado gives as a result a huge amount of waste, not only the peel and stone but also that waste generated by the pruning practices and oil extraction. These biomasses could be converted into raw materials to obtain different types of co-products, but this implies changes in the use of these resources, the design of efficient production systems, and integration to take full advantage of them, e.g., by developing biorefinery models. Therefore, this review firstly gives a snapshot of those residues generated in the avocado industry and provides their chemical composition. Secondly, this review presents updated information about the valorization ways of avocado-derived biomass to obtain bioenergy, biofuels, and other marketable products (starch, protein, phenolic compounds, and biosorbents, among others) using a single process or integrated processes within a biorefinery context. Green technologies to obtain these products are also covered, e.g., based on the application of microwaves, ultrasound, supercritical fluids, etc. As a conclusion, there is a variety of ways to valorize avocado waste in single processes, but it would be promising to develop biorefinery schemes. This would enable the avocado sector to move towards the zero-waste principle.

Valorisation of Exhausted Olive Pomace by an Eco-Friendly Solvent Extraction Process of Natural Antioxidants

Exhausted olive pomace (EOP) is the waste generated from the drying and subsequent extraction of residual oil from the olive pomace. In this work, the effect of different aqueous solvents on the recovery of antioxidant compounds from this lignocellulosic biomass was assessed. Water extraction was selected as the best option for recovering bioactive compounds from EOP, and the influence of the main operational parameters involved in the extraction was evaluated by response surface methodology. Aqueous extraction of EOP under optimised conditions (10% solids, 85 °C, and 90 min) yielded an extract with concentrations (per g EOP) of phenolic compounds and flavonoids of 44.5 mg gallic acid equivalent and 114.9 mg rutin equivalent, respectively. Hydroxytyrosol was identified as the major phenolic compound in EOP aqueous extracts. Moreover, these extracts showed high antioxidant activity, as well as moderate bactericidal action against some food-borne pathogens. In general, these results indicate the great potential of EOP as a source of bioactive compounds, with potential uses in several industrial applications.

Valorization of by-products from olive oil industry and added-value applications for innovative functional foods

BACKGROUND

In the last years, the consumption of olive oil has experienced a sharp rise due to its organoleptic and healthy properties and with this the wastes and by-products derived from the olive production and the olive oil industry have also increased causing important environmental and economic issues. However, the high content in bioactive compounds of these wastes and by-products makes that its recovery is both a great challenge and an excellent opportunity for the olive oil sector.

AIM OF THE REVIEW

This review encompasses the more outstanding aspects related to the advances achieved until date in the olive oil by-products valorisation and added-value applications for innovative functional foods.

CONCLUSION

Taking into account the information reported in this manuscript, the development of a multiproduct biorefinery in cascade using eco-friendly technologies interchangable seems a suitable stratety to obtaining high added value compounds from olive oil by-products with applications in the field of innovative functional foods. In addition, this would allow an integral valorization of these residues enhancing the profitability of the olive oil industry. On the other hand, the biocompounds fom olive oil by-products have been described by their interesting bioactivities with beneficial properties for the consumers' health; therefore, their incorporation into the formulation of functional foods opens new possibilities in the field of innovative foods. Future perspective: Despite the studies descibed in the literature, more research on the healthy properties of the recovered compounds and their interactions with food components is key to allow their reintegration in the food chain and therefore, the removal of the olive oil by-products.

Green and Sustainable Valorization of Bioactive Phenolic Compounds from Pinus By-Products

In Europe, pine forests are one of the most extended forests formations, making pine residues and by-products an important source of compounds with high industrial interest as well as for bioenergy production. Moreover, the valorization of lumber industry residues is desirable from a circular economy perspective. Different extraction methods and solvents have been used, resulting in extracts with different constituents and consequently with different bioactivities. Recently, emerging and green technologies as ultrasounds, microwaves, supercritical fluids, pressurized liquids, and electric fields have appeared as promising tools for bioactive compounds extraction in alignment with the Green Chemistry principles. Pine extracts have attracted the researchers’ attention because of the positive bioproperties, such as anti-inflammatory, antimicrobial, anti-neurodegenerative, antitumoral, cardioprotective, etc., and potential industrial applications as functional foods, food additives as preservatives, nutraceuticals, pharmaceuticals, and cosmetics. Phenolic compounds are responsible for many of these bioactivities. However, there is not much information in the literature about the individual phenolic compounds of extracts from the pine species. The present review is about the reutilization of residues and by-products from the pine species, using ecofriendly technologies to obtain added-value bioactive compounds for industrial applications.

Ultrasound assisted maceration for improving the aromatization of extra-virgin olive oil with rosemary and basil

Aromatization of extra-virgin olive oil (EVOO) with aromatic plants is commonly used to enrich the oil with aromatic and antioxidant compounds. Ultrasound can be an alternative to accelerate this process. The objective of this work was to determine if ultrasound is able to accelerate EVOO aromatization with rosemary and basil and how it affects the migration of volatile and other compounds, the oxidative stability and the antioxidant capacity of the aromatized products. Ultrasound parameters (amplitude, time, and temperature of extraction) were optimized for each herb with central composite designs. Free fatty acid, peroxide value, K₂₃₂, K₂₇₀, ΔK, fatty acid profile, total phenolics, antioxidant capacity, polar compounds, oxidative stability and volatile compounds profile were evaluated in all samples. Physical effects of ultrasound on the herbs were observed by scanning electron microscopy. In the optimization, variables related to the oxidative processes were minimized and compounds migration and oxidative stability were maximized. Results were 70.09% amplitude, 36.6 min and 35 °C for rosemary and 95.98% amplitude, 9.9 min and 30 °C for basil. These conditions were compared to 7 and 15 days of conventional maceration (CM). Aromatization of EVOO with rosemary, both by ultrasound assisted maceration (UAM) or CM, improved total phenolics, terpenes, esters, ketones, stability and induction times, as well as decreased the values for the quality parameters. The use of UAM accelerated the process to 37 min. However, aromatization with basil by CM increased the values for the quality parameters and reduced the total phenolics, the antioxidant capacity and the induction and stability times. UAM with basil reached better results than those observed for CM, in only 10 min. In conclusion, rosemary is more appropriate than basil for EVOO aromatization, and UAM was the best choice to accelerate the processes when compared to CM.