Optimization of Ultrasound-Assisted Extraction of Flavonoids from Olive (Olea europaea) Leaves, and Evaluation of Their Antioxidant and Anticancer Activities

Guide for Optimization of Olive Leaf Extraction and Silver Nanoparticles Biosynthesis as an Initial Step for Pilot Plant Design

This account presents the results of two successful optimization processes. First, a polyphenol-rich aqueous olive extract was obtained and then silver nanoparticles (AgNPs) synthesized with high efficiency. Selected parameters for both processes were optimized based on the procedure of the Box-Behnken multifactorial design. The independent variables in the extraction process were the biomass/water ratio, temperature, and time. For AgNPs synthesis, the independent variables were the volume of olive extract, temperature, and process duration. The relationship between the process parameters was visualized graphically by using the response surface methodology. A high fit of the experimental data with the predicted models was shown. The regression coefficients were high, 0.9936 for extraction and 0.9757 for AgNPs biosynthesis. The extraction efficiency under its optimal conditions was as follows: biomass/solvent ratio 0.016, temperature 80 °C for 80 min, and yield 160.67 [μg GAE (gallic acid equivalent)/mL]. The highest yield of AgNPs synthesis, equal to 1.955, was obtained when it was carried out for 50 min at 75 °C with the application of 11 mL of extract. Studies on the AgNPs suspension's stability depending on the extract amount were demonstrated. A physicochemical analysis using dynamic light scattering, transmission electron microscopy images, and Fourier transform infrared spectroscopy for AgNPs obtained under optimal conditions was shown. Finally, a pilot-scale biosynthesis of AgNPs was designed.

Comprehensive Review of Olea europaea: A Holistic Exploration into Its Botanical Marvels, Phytochemical Riches, Therapeutic Potentials, and Safety Profile

Human health is now inextricably linked to lifestyle choices, which can either protect or predispose people to serious illnesses. The Mediterranean diet, characterized by the consumption of various medicinal plants and their byproducts, plays a significant role in protecting against ailments such as oxidative stress, cancer, and diabetes. To uncover the secrets of this natural treasure, this review seeks to consolidate diverse data concerning the pharmacology, toxicology, phytochemistry, and botany of Olea europaea L. (O. europaea). Its aim is to explore the potential therapeutic applications and propose avenues for future research. Through web literature searches (using Google Scholar, PubMed, Web of Science, and Scopus), all information currently available on O. europaea was acquired. Worldwide, ethnomedical usage of O. europaea has been reported, indicating its effectiveness in treating a range of illnesses. Phytochemical studies have identified a range of compounds, including flavanones, iridoids, secoiridoids, flavonoids, triterpenes, biophenols, benzoic acid derivatives, among others. These components exhibit diverse pharmacological activities both in vitro and in vivo, such as antidiabetic, antibacterial, antifungal, antioxidant, anticancer, and wound-healing properties. O. europaea serves as a valuable source of conventional medicine for treating various conditions. The findings from pharmacological and phytochemical investigations presented in this review enhance our understanding of its therapeutic potential and support its potential future use in modern medicine.

Ultrasonic-assisted extraction to enhance the recovery of bioactive phenolic compounds from Commiphora gileadensis leaves

The "ultrasonic-assisted extraction (UAE)" method was utilized in this work to assess how different process parameters affected the yield and recovery of phenolic compounds from the leaf of Commiphora gileadensis, which is one of the medicinal plants with a variety of biological functions. Its leaf is used for a various of therapeutic applications, such as the treatment of bacterial infections, inflammation, and wound healing. The "One-Factor-At-a-Time (OFAT)" approach was employed to examine the impacts of various UAE process parameters on the process of extraction, which include time of extraction, sample/solvent ratio, ultrasonic frequency, and solvent (ethanol) concentration. The extracts were then investigated for the presence of several phytochemicals using analytical techniques such as "Gas Chromatography-Mass Spectroscopy (GC-MS)" and "Fourier Transform Infrared Spectroscopy (FTIR)" studies. The findings showed that the maximum extraction yield, the total phenolic content (TPC), and the total flavonoids content (TFC) of the ethanolic extract of the leaves of C. gileadensis using the UAE method were at 31.80 ± 0.41 %, 96.55 ± 2.81 mg GAE/g d.w. and 31.66 ± 2.01 mg QE/g d.w. accordingly under a procedure duration of 15 min, ultrasonic frequency of 20 kHz, solvent/sample ratio of 1:20 g/mL, and solvent concentration of 40 % v/v. The leaves extract of C. gileadensis included 25 phenolic compounds that were previously unreported, and GC-MS analysis confirmed their presence. Hence, it follows that the UAE technique can successfully extract the phytochemicals from C. gileadensis for a variety of therapeutic uses.

Optimization of ultrasound-assisted extraction of bioactive chemicals from Hemidesmus indicus (L.) R.Br. using response surface methodology and adaptive neuro-fuzzy inference system

This study was designed to optimize the ultrasound-assisted extraction (UAE) of bioactive chemicals from Hemidesmus indicus (L.) R.Br. through RSM (response surface methodology) and ANFIS (adaptive neuro-fuzzy inference system). The effect of four independent parameters, methanol concentration (X1: 55-65%), temperature (X2: 30-40 °C), time (X3: 15-20 min) and particle size (X4: 0.5-1.00 mm) at five levels (- 2 ,- 1, 0, + 1, + 2) with respect to dependent parameters, total polyphenols content (TP) (y1), total flavonoids content (TF) (y2), %DPPHsc (y3), %ABTSsc (y4) and %H2O2sc (y5) were selected. The optimal extraction condition was observed at X1 = 65%, X2 = 40 °C, X3 = 20 min and X4 = 0.5 mm; under this circumstance, y1 = 352.85 mg gallic acid equivalents (GA)/g, y2 = 300.204 mg rutin equivalents (RU)/g and their antioxidant potentials (y3 = 81.33%, y4 = 65.04%, and y5 = 71.01%) has been attained. ANFIS was used to compare and confirm the optimized extraction parameter values. Further, GC-MS and LC-MS were performed to investigate the bioactive chemicals present in the optimized extract.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10068-023-01351-9.

Synergistic antileishmanial activity of erythrodiol, uvaol, and oleanolic acid isolated from olive leaves of cv. Chemlali

This study aimed to assess the antileishmanial activity of biomolecules obtained from Olea europaea L. leaves and twigs recovered from eight Tunisian cultivars. The extraction was first carried out with 80% methanol, and then the obtained extract was fractionated using three solvents of increasing polarity: cyclohexane (CHX), dichloromethane (DCM) and ethyl acetate (EtOAc). The antileishmanial activity was determined against leishmanial strains responsible for cutaneous, visceral, and mucocutaneous leishmaniasis. The cyclohexane fraction of the leaves of cv. Chemlali from the region of Sidi-Bouzid exhibited the strongest leishmanicidal activity against all the tested leishmanial strains. The inhibition concentrations (IC50) were 16.5, 14.5, and 7.4 μg mL-1 for Leishmania mexicana (cutaneous), Leishmania braziliensis (mucocutaneous), and Leishmania donovani (visceral), respectively. Interestingly, low cytotoxicity was observed on THP-1 cells with selective indexes (SI) ranging from 22.8 to 50.5. HPLC-HRMS and full-house NMR analysis allowed the identification of three triterpenic compounds, oleanolic acid (IC50 = 64.1 μg mL-1), erythrodiol (IC50 = 52.0 µg mL-1), and uvaol (IC50 = 53.8 μg mL-1). Antileishmanial activity of uvaol and oleanolic acid has been previously reported. However, this work constitutes the first report of the antileishmanial activity of erythrodiol which showed combinatorial interaction with uvaol (IC50 = 26.1 μg mL-1) against Leishmania tropica. The mixture of the three compounds, as major ones, exhibited an enhanced activity against Leishmania tropica (IC50 = 16.3 µg mL-1) compared to erythrodiol alone or the combination of uvaol and erythrodiol. This finding is of great importance and needs further investigation.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-023-03825-3.

Plackett-Burman design in the biosynthesis of silver nanoparticles with Mutisia acuminatta (Chinchircoma) and preliminary evaluation of its antibacterial activity

Background: The aim of this study was to synthesize silver nanoparticles (AgNPs) using the methanolic fraction of Mutisia acuminatta leaves using Plackett-Burman design to optimize process parameters and to evaluate its antibacterial effect. Methods: For the separation of Mutisia acuminatta phytoconstituents, chromatographic techniques were used. For characterization and identification, UV - VIS spectrophotometry, FTIR spectrophotometry, Dynamic Light Scattering (DLS) and transmission electron microscopy (TEM) were used. The Plackett-Burman design used polynomial regression statistical analysis to determine the most influential variables. Results: UV-VIS spectroscopy reported an absorbance concerning surface plasmon resonance between 410-420 nm wavelength for the AgNPs. FTIR spectrophotometry reported characteristic peaks in the biosynthesized AgNPs, observing the disappearance of spectral peaks between 1000-1500 cm -1. By UHPLC-MS, caffeic acid derivatives, coumarins, flavonoids, lignans, disaccharide and a complex formed between silver and the solvent (AgCH3CN+) were identified. Using DLS, the AgNPs presented an average hydrodynamic size of 45.91 nm. TEM determined the spherical shape of the AgNPs, presenting diameters in the range of 30 to 60 nm. The biosynthesized AgNPs showed higher antibacterial activity against Escherichia coli and Staphylococcus aureus than the total extract, the methanolic fraction and pure methanol. The polynomial model in the biosynthesis was validated with an adequate fitting representing the experimental data of the process. The most significant variables for the model obtained were the reaction pH (X 2) and the concentration of the precursor salt AgNO 3 (X 6). Conclusions: The synthesized AgNPs offer a viable option for further development due to the presence of bioactive compounds, adequate characterization and antibacterial activity.

Physicochemical and Biological Characterization of Encapsulated Olive Leaf Extracts for Food Preservation

Phenolic compounds in olive leaves have an excellent antioxidant activity and good antimicrobial properties. These bioactive molecules have beneficial properties for health, arousing great scientific and commercial interest. This study reports lyophilized olive leaf extracts (OLE) encapsulated by spray-drying using maltodextrins, maltodextrins-pectin and maltodextrins-gum Arabic as encapsulating agents. Lyophilized OLE were collected from two varieties cultivated in a harsh pedo-climatic conditions of the arid region of Tunisia. The effects of the genetic factor and the different encapsulating agents on the physicochemical properties of microcapsules and their behavior during storage, as well as their antimicrobial activities, were studied. Microcapsules successfully passed heat treatment and storage conditions and their antimicrobial activities were preserved. The encapsulating agent combination improved the encapsulation efficiency and the product yield in Zarrazi variety compared to Dhokar one. In addition, Dhokar variety microparticles showed the best heat stability at 4 and 25 °C after 90 days of storage and the higher inhibition percent against bacteria. The results of the present study evidenced that the best conditions for OLE encapsulation were obtained when the maltodextrins-pectin and maltodextrins-gum Arabic were combined to form a hybrid coating material.

Nocellara Del Belice (Olea europaea L. Cultivar): Leaf Extract Concentrated in Phenolic Compounds and Its Anti-Inflammatory and Radical Scavenging Activity

Olea europaea L. is a plant belonging to the Oleaceae family, widely grown around the Mediterranean Basin and its leaves are a source of phenolic compounds with antioxidant and anti-inflammatory capacity. Among these, oleuropein and luteolin-7-O-glucoside represent two major polyphenolic compounds in olive-leaf extract. Herein, a polystyrene resin was used to recover the polyphenolic fraction from the acetone-water leaf extract from Nocellara del Belice cultivar, which showed the higher level of analysed bioactive compounds, compared to Carolea cultivar. The antioxidant activity of the extract concentrated in phenolic compounds (OLECp) was evaluated through a classical assay and electron paramagnetic resonance (EPR) for DPPH and hydroxyl radicals scavenging. Thus, the anti-inflammatory activity and the potential beneficial effects in reducing lipid accumulation in an in vitro model of NAFLD using McA-RH7777 cells exposed to oleic acid (OA) were evaluated. Nile Red and Oil Red O have been used to stain the lipid accumulation, while the inflammatory status was assessed by Cytokines Bioplex Assay. OLECp (TPC: 92.93 ± 9.35 mg GAE/g, TFC: 728.12 ± 16.04 mg RE/g; 1 g of extract contains 315.250 mg of oleuropein and 17.44 mg of luteolin-7-O-glucoside) exerted a good radical scavenging capability (IC₅₀: 2.30 ± 0.18 mg/mL) with a neutralizing power against DPPH and hydroxyl radicals, as confirmed by the decreased signal area of the EPR spectra. Moreover, OLECp at concentration of 25, 50 and 100 μg/mL counteracted the intracellular inflammatory status, as result of decreased intracellular lipid content. Our results highlighted the multiple properties and applications of an O. europaea extract concentrated in polyphenols, and the possibility to formulate novel nutraceuticals with antioxidant properties, destined to ameliorate human health.

Valorizing the usage of olive leaves, bioactive compounds, biological activities, and food applications: A comprehensive review

Olive oil production is a significant source of economic profit for Mediterranean nations, accounting for around 98 percent of global output. Olive oil usage has increased dramatically in recent years, owing to its organoleptic characteristics and rising knowledge of its health advantages. The culture of olive trees and the manufacture of industrial and table olive oil produces enormous volumes of solid waste and dark liquid effluents, involving olive leaves, pomace, and olive oil mill wastewaters. These by-products cause an economic issue for manufacturers and pose major environmental concerns. As a result, partial reuse, like other agronomical production wastes, is a goal to be achieved. Because these by-products are high in bioactive chemicals, which, if isolated, might denote components with significant added value for the food, cosmetic, and nutraceutical sectors, indeed, they include significant amounts of beneficial organic acids, carbohydrates, proteins, fibers, and phenolic materials, which are distributed differently between the various wastes depending on the olive oil production method and table olive agronomical techniques. However, the extraction and recovery of bioactive materials from chosen by-products is a significant problem of their reasonable value, and rigorous detection and quantification are required. The primary aims of this review in this context are to outline the vital bioactive chemicals in olive by-products, evaluate the main developments in extraction, purification, and identification, and study their uses in food packaging systems and safety problems.

In-Silico Analysis of Phytocompounds of Olea europaea as Potential Anti-Cancer Agents to Target PKM2 Protein

Globally, cancer is the second leading cause of mortality and morbidity. The growth and development of cancer are extremely complex. It is caused by a variety of pathways and involves various types of enzymes. Pyruvate kinase M2 (PKM2) is an isoform of pyruvate kinase, that catalyses the last steps of glycolysis to produce energy. PKM2 is relatively more expressed in tumour cells where it tends to exist in a dimer form. Various medicinal plants are available that contain a variety of micronutrients to combat against different cancers. The phytocompounds of the olive tree (Olea europaea) leaves play an important role in inhibiting the proliferation of several cancers. In this study, the phytocompounds of olive leaf extract (OLE) were studied using various in silico tools, such as pkCSM software to predict ADMET properties and PASS Online software to predict anticancer activity. However, the molecular docking study provided the binding energies and inhibition constant and confirmed the interaction between PKM2 and the ligands. The dynamic behaviour, conformational changes, and stability between PKM2 and the top three hit compounds (Verbascoside (Ver), Rutin (Rut), and Luteolin_7_O_glucoside (Lut)) are studied by MD simulations.

Prospects of ultrasonically extracted food bioactives in the field of non-invasive biomedical applications - A review

Foods incorporated with bioactive compounds, called nutraceuticals, can fight or prevent or alleviate diseases. The contribution of nutraceuticals or phytochemicals to non-invasive biomedical applications is increasing. Although there are many traditional methods for extracting bioactive compounds or secondary metabolites, these processes come with many disadvantages like lower yield, longer process time, high energy consumption, more usage of solvent, yielding low active principles with low efficacy against diseases, poor quality, poor mass transfer, higher extraction temperature, etc. However, nullifying all these disadvantages of a non-thermal technology, ultrasound has played a significant role in delivering them with higher yield and improved bio-efficacy. The physical and chemical effects of acoustic cavitation are the crux of the output. This review paper primarily discusses the ultrasound-assisted extraction (USAE) of bioactives in providing non-invasive prevention and cure to diseases and bodily dysfunctions in human and animal models. The outputs of non-invasive bioactive components in terms of yield and the clinical efficacy in either in vitro or in vitro conditions are discussed in detail. The non-invasive biomedical applications of USAE bioactives providing anticancer, antioxidant, cardiovascular health, antidiabetic, and antimicrobial benefits are analyzed in-depth and appraised. This review additionally highlights the improved performance of USAE compounds against conventionally extracted compounds. In addition, an exhaustive analysis is performed on the role and application of the food bioactives in vivo and in vitro systems, mainly for promoting these efficient USAE bioactives in non-invasive biomedical applications. Also, the review explores the recovery of bioactives from the less explored food sources like cactus pear fruit, ash gourd, sweet granadilla, basil, kokum, baobab, and the food processing industrial wastes like peel, pomace, propolis, wine residues, bran, etc., which is rare in literature.

Exploitation of Olive (Olea europaea L.) Seed Proteins as Upgraded Source of Bioactive Peptides with Multifunctional Properties: Focus on Antioxidant and Dipeptidyl-Dipeptidase—IV Inhibitory Activities, and Glucagon-like Peptide 1 Improved Modulation

Agri-food industry wastes and by-products include highly valuable components that can upgraded, providing low-cost bioactives or used as an alternative protein source. In this context, by-products from olive production and olive oil extraction process, i.e., seeds, can be fostered. In particular, this work was aimed at extracting and characterizing proteins for Olea europaea L. seeds and at producing two protein hydrolysates using alcalase and papain, respectively. Peptidomic analysis were performed, allowing to determine both medium- and short-sized peptides and to identify their potential biological activities. Moreover, an extensive characterization of the antioxidant properties of Olea europaea L. seed hydrolysates was carried out both in vitro by 2,2-diphenyl-1-picrylhydrazyl (DPPH), by ferric reducing antioxidant power (FRAP), and by 2,2′-Azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS) assays, respectively, and at cellular level by measuring the ability of these hydrolysates to significant reduce the H₂O₂-induced reactive oxygen species (ROS) and lipid peroxidation levels in human intestinal Caco-2 cells. The results of the both hydrolysates showed significant antioxidant properties by reducing the free radical scavenging activities up to 65.0 ± 0.1% for the sample hydrolyzed with alcalase and up to 75.7 ± 0.4% for the papain hydrolysates tested at 5 mg/mL, respectively. Moreover, similar values were obtained by the ABTS assays, whereas the FRAP increased up to 13,025.0 ± 241.5% for the alcalase hydrolysates and up to 12,462.5 ± 311.9% for the papain hydrolysates, both tested at 1 mg/mL. According to the in vitro results, both papain and alcalase hydrolysates restore the cellular ROS levels up 130.4 ± 4.24% and 128.5 ± 3.60%, respectively, at 0.1 mg/mL and reduce the lipid peroxidation levels up to 109.2 ± 7.95% and 73.0 ± 7.64%, respectively, at 1.0 mg/mL. In addition, results underlined that the same hydrolysates reduced the activity of dipeptidyl peptidase-IV (DPP-IV) in vitro and at cellular levels up to 42.9 ± 6.5% and 38.7 ± 7.2% at 5.0 mg/mL for alcalase and papain hydrolysates, respectively. Interestingly, they stimulate the release and stability of glucagon-like peptide 1 (GLP-1) hormone through an increase of its levels up to 660.7 ± 21.9 pM and 613.4 ± 39.1 pM for alcalase and papain hydrolysates, respectively. Based on these results, olive seed hydrolysates may represent new ingredients with antioxidant and anti-diabetic properties for the development of nutraceuticals and functional foods for the prevention of metabolic syndrome onset.

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.

Ultrasound-Assisted "Green" Extraction (UAE) of Antioxidant Compounds (Betalains and Phenolics) from Opuntia stricta var. Dilenii's Fruits: Optimization and Biological Activities

Opuntia stricta var. Dillenii’s prickly pears are an underutilized fruit with a high content of betalains and phenolic compounds that could bring potential health benefits for humans. The aim of this study is the optimization of the “green” extraction of betalains and phenolic compounds from Opuntia stricta var. Dillenii’s whole fruits by ultrasound-assisted extraction (UAE), using a response surface methodology (RSM) by a central composite design (CCD) in order to obtain extracts rich in betalains and phenolic compounds with proven biological activities. For UAE optimization, the extraction temperature (20–50 °C), the amplitude (20–50%) and the ethanol volume in extraction solvent (15–80%, v/v) were selected as independent variables. All combinations were conducted at 2, 5, 10, 20 and 30 min to determinate the time effect. The betalain and phenolic compound content in Opuntia stricta var. Dillenii’s whole fruits and UAE extracts were identified by HPLC-DAD-ESI/MS and HPLC-DAD-MS/QTOF and the antioxidant (ORAC method) and the anti-inflammatory (hyaluronidase inhibition method) in vitro biological activities also were determined. The most efficient extraction time was 5 min and the best UAE parameter combination was 50% amplitude, 15% ethanol in solvent (ethanol/water, 15/85, v/v) and 20 °C temperature, obtaining 10.06 ± 0.10 mg of total major betalains/g dry weight, 2.32 ± 0.08 mg of piscidic acid/g dry weight and 0.38 ± 0.00 mg of total major flavonoids/g dry weight. All applied UAE combinations significantly improved the in vitro bioactive activities (antioxidant and anti-inflammatory) of the Opuntia stricta var. Dillenii’s extracts compared to the bioactivities of the extracts obtained by standard homogenization processes.

Olive Fruit and Leaf Wastes as Bioactive Ingredients for Cosmetics-A Preliminary Study

Olea europaea cultivar, native in the Mediterranean basin, has expanded worldwide, mainly due to the olive oil industry. This expansion is attributed to the benefits of olive oil consumption, since this product is rich in nutritional and bioactive compounds. However, the olive industry generates high amounts of wastes, which could be related to polluting effects on soil and water. To minimize the environmental impact, different strategies of revalorization have been proposed. In this sense, the aim of this work was to develop high cosmetic value added oleuropein-enriched extracts (O20 and O30), a bioactive compound from olive byproducts, performing a comprehensive characterization using high performance liquid chromatography coupled to mass spectrometry and evaluate their bioactivity by in vitro assays. A total of 49 compounds were detected, with oleuropein and its derivatives widely found in O30 extract, whereas iridoids were mainly detected in O20 extract. Moreover, 10 compounds were detected for the first time in olive leaves. Both extracts demonstrated strong antioxidant and antiradical activities, although O30 showed higher values. In addition, radical oxygen and nitrogen species scavenging and enzyme inhibition values were higher in O30, with the exception of HOCl and hyaluronidase inhibition assays. Regarding cell viability, olive byproduct extracts did not lead to a decrease in keratinocytes viability until 100 µg/mL. All data reported by the present study reflect the potential of industrial byproducts as cosmetic ingredients.

Flavonoids ameliorate aluminum chloride-induced learning and memory impairments via suppression of apoptosis and oxidative stress in rats

The study was to investigate the effects of flavonoids (rutin, puerarin, and silymarin) on learning and memory function in rats exposed to aluminum chloride (AlCl₃). Wistar rats were administered flavonoids at a dose of 100 mg/(kg·bw)/day or 200 mg/(kg·bw)/day after exposed to 281.40 mg/(kg·bw)/day AlCl₃·6H₂O. The results of Morris water maze suggested that rutin and puerarin increased the frequency of crossing the platform and swimming time spent in the target quadrant of AlCl₃-induced rats significantly. Terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) assay indicated that three flavonoids could alleviate apoptosis of hippocampal neurons induced by AlCl₃. Real time-PCR and western blot suggested that rutin, puerarin and 100 mg/(kg·bw)/day silymarin could decrease the AlCl₃-induced high expression of Bcl-2 associated X protein (Bax) mRNA and protein in hippocampus, but the expression of B cell lymphoma/leukemia-2 (Bcl-2) mRNA and protein was not significantly different among groups. Flavonoids could up regulate the low expression of autophagy related proteins (Beclin 1 (Bcl-2-interacting protein with a coiled-coil domain 1) and LC3 (microtubule-associated protein 1 light chain 3)) caused by AlCl₃ exposure. Flavonoids could also adjust the change in adenosine triphosphatase, superoxide dismutase, glutathione peroxidase and malondialdehyde induced by intake of AlCl₃. The results of inductively coupled plasma atomic emission spectroscopy (ICP-AES) suggested that flavonoids could effectively reduce the high Al level in brain and serum of AlCl₃ exposed rats. In conclusion, three flavonoids may improve learning and memory function by inhibiting excessive apoptosis and oxidative stress in AlCl₃ exposed rats.

Environmentally Friendly Methods for Flavonoid Extraction from Plant Material: Impact of Their Operating Conditions on Yield and Antioxidant Properties

The flavonoids are compounds synthesized by plants, and they have properties such as antioxidant, anticancer, anti-inflammatory, and antibacterial, among others. One of the most important bioactive properties of flavonoids is their antioxidant effect. Synthetic antioxidants have side toxic effects whilst natural antioxidants, such as flavonoids from natural sources, have relatively low toxicity. Therefore, it is important to incorporate flavonoids derived from natural sources in several products such as foods, cosmetics, and drugs. For this reason, there is currently a need to extract flavonoids from plant resources. In this review are described the most important parameters involved in the extraction of flavonoids by unconventional methods such as ultrasound, pressurized liquid extraction, mechanochemical, high hydrostatic pressure, supercritical fluid, negative pressure cavitation, intensification of vaporization by decompression to the vacuum, microwave, infrared, pulsed electric field, high-voltage electrical discharges, and enzyme-assisted extraction. There are no unified operation conditions to achieve high yields and purity. Notwithstanding, progress has been achieved in the development of more advanced and environmentally friendly methods of extraction. Although in literature are found important advances, a complete understanding of the extraction process in each of the unconventional techniques is needed to determine the thermodynamic and kinetic mechanisms that govern each of the techniques.

Antioxidant activities of anastatin A & B derivatives and compound 38c's protective effect in a mouse model of CCl4-induced acute liver injury

Anastatins A and B, two flavonoid compounds isolated from desert plant Anastatica hierochuntica, have protective activities for primary rat hepatocytes. Anastatins A and B, and their derivatives, were synthesized by our group previously. In this study, the antioxidant activity and cytotoxicity of these compounds were studied using chemical assessment methods, cell proliferation inhibition experiments, and cell oxidative damage models. The best compound, 38c, was used to study the hepatoprotection activity and mechanism by using a CCl4-induced liver injury model in mice. The results show that most of these flavonoid compounds have good antioxidant activity and low cytotoxicity in vitro. Among them, the most potent compound was 38c, which exhibited a protective effect on CCl4-induced hepatic injury by suppressing the amount of CYP2E1. These findings indicate that anastatin flavonoid derivatives have potential therapeutic utility against oxidative hepatic injury.

Optimization of Ultrasound-Assisted Extraction of Flavonoids from Celastrus hindsii Leaves Using Response Surface Methodology and Evaluation of Their Antioxidant and Antitumor Activities

Celastrus hindsii is a potential source of flavonoids with biological activities. This study aimed to develop an ultrasound-assisted technique for extracting flavonoids from leaves of C. hindsii. Response surface methodology was employed to optimize the extraction conditions for maximizing the total flavonoid content (TFC). A maximum TFC of 23.6 mg QE/g was obtained under the extraction conditions of ultrasonic power of 130 W, extraction temperature of 40°C, extraction time of 29 min, and ethanol concentration of 65%. The flavonoid-rich extracts were then studied for their antioxidant and anticancer activities. The results showed that the C. hindsii leaf extract exhibited potent radical scavenging activities against DPPH (IC₅₀ of 164.85 μg/mL) and ABTS (IC₅₀ of 89.05 μg/mL). The extract also significantly inhibited the growth of 3 cancer cell lines MCF7, A549, and HeLa with the IC₅₀ values of 88.1 μg/mL, 120.4 μg/mL, and 118.4 μg/mL, respectively. Notably, the extract had no cytotoxicity effect on HK2 normal kidney cell line. This study suggests that flavonoid-rich extract is a promising antioxidant and anticancer agent and that ultrasound-assisted extraction is an efficient method for extracting flavonoids from C. hindsii leaves.

Seasonal Variations in the Chemical Composition of Liangshan Olive Leaves and Their Antioxidant and Anticancer Activities

The seasonal changes in the chemical composition of Olea europaea leaves from January to December at Liangshan (China) have been investigated. The highest total phenolic content (TPC), total flavonoid content (TFC), and free amino acid content (FAAC) levels were found in May and December, while the lowest levels were detected in April and September. The soluble protein content (SPC) and the soluble sugar content (SSC) were highest in spring but lowest in summer and winter. The levels of major phenolic compounds, including oleuropein, and luteolin-4’-O-glucoside, followed by apigenin-7-O-glucoside, quercetin, rutin, luteolin, and apigenin, increased during spring and winter but decreased during summer and autumn. In addition, phenolic extracts (PEs) showed dose-dependent antioxidant activity using 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical and superoxide radical scavenging activity assays; the reducing power was tested. The anticancer activities of PE at various concentrations were assessed by a cell counting kit-8 (CCK-8), and the IC₅₀ (50% effective concentration) to HEK293, HeLa, and S180 cells were 841.48, 7139, and 457.69 μg/mL, respectively. PE-treated S180 cells inhibited proliferation through activation of caspase-3/9 and disruption of the mitochondrial membrane potential. Thus, PE in Liangshan olive leaves possessed strong antioxidant and anticancer potential, and spring and winter were determined as optimal harvesting seasons.

Strategic enhancement of genetic gain for nutraceutical development in buckwheat: A genomics-driven perspective

Buckwheat (Fagopyrum spp.) under the family Polygonaceae is an ancient pseudocereal with stupendous but less studied nutraceutical properties. The gluten free nature of protein, balanced amino acid profile and health promoting bioactive flavonoids make it a golden crop of future. Besides a scanty basic research, not much attention has been paid to the improvement of plant type and breeding of nutraceutical traits. Scanning of scientific literature indicates that adequate genetic variation exists for agronomic and nutritional traits in mainstream and wild gene pool of buckwheat. However, the currently employed conventional approaches together with poorly understood genetic mechanisms restrict effective utilization of the existing genetic variation in nutraceutical breeding of buckwheat. The latest trends in buckwheat genomics, particularly avalilabity of draft genome sequences for both the cultivated species (F. esculentum and F.tataricum) hold immense potential to overcome these limitations. Utilizing the transgenic hairy rot cultures, role of various transcription factors and gene families have been deduced in production and biosynthesis of bioactive flavonoids. Further, the acquisition of high-density genomics data coupled with the next-generation phenotyping will certainly improve our understanding of underlying genetic regulation of nutraceutical traits. The present paper highlights the application of multilayered omics interventions for tailoring a nutrient rich buckwheat cultivar and nutraceutical product development.

Ultrasound-Assisted Extraction of Total Flavonoids from Pteris cretica L.: Process Optimization, HPLC Analysis, and Evaluation of Antioxidant Activity

In the present work, the ultrasonic-assisted extraction (UAE) of total flavonoids (TF) from Pteris cretica L. was optimized by response surface methodology (RSM) on the basis of a single-factor experiment. The optimized UAE parameters were as follows: Ethanol concentration 56.74%, extraction time 45.94 min, extraction temperature 74.27 °C, and liquid/solid ratio 33.69 mL/g. Under the optimized conditions, the total flavonoids yield (TFY) was 4.71 ± 0.04%, which was higher than that obtained by heat reflux extraction (HRE). The extracts were further analyzed by HPLC, and five major flavonoids, including rutin, quercitrin, luteolin, apigenin, and luteolin-7-O-glucoside, were identified and quantified. Furthermore, the results of the antioxidant test showed that the TF extract obtained under optimized UAE conditions exhibited good 2,2-diphenyl-1-picrylhydrazyl radical (DPPH•) and 2,2-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) radical (ABTS⁺•), nitric oxide radical (NO•) scavenging activities, and ferrous ion (Fe²⁺) chelating capacity, with IC₅₀ values of 74.49, 82.92, 89.12, and 713.41 µg/mL, respectively. Results indicated that the UAE technique developed in this work was an efficient, rapid, and simple approach for the extraction of flavonoids with antioxidant activity from P. cretica.

Simultaneous Optimization of Ultrasound-Assisted Extraction for Flavonoids and Antioxidant Activity of Angelica keiskei Using Response Surface Methodology (RSM)

Angelica keiskei Koidzumi (A. keiskei), as a Japanese edible herbal plant, enjoys a variety of biological activities due to the presence of numerous active compounds, especially flavonoids. This study aims for the optimization of ultrasound-assisted extraction (UAE) for flavonoids in A. keiskei and their antioxidant activity by using the response surface methodology (RSM). Single-factor experiments and a four-factor three-level Box-Behnken design (BBD) were performed to explore the effects of the following parameters on flavonoid extraction and antioxidant activity evaluation: ultrasonic temperature (X1), ultrasonic time (X2), ethanol concentration (X3) and liquid-solid ratio (X4). The optimum conditions of the combination of total flavonoid content (TFC), 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging capacity (DPPH-RSC) and ferric-reducing antioxidant power (FRAP) were as follows: X1 = 80 °C, X2 = 4 min, X3 = 78%, X4 = 35 mL/g, respectively. The experimental results provide a theoretical basis for the extensive utilization of A. keiskei and flavonoids extraction from A. keiskei as a potential source of antioxidants.

Rhodium(III)-catalyzed one-pot synthesis of flavonoids from salicylaldehydes and sulfoxonium ylides

Rh(III)-catalyzed C–H activation of salicylaldehyde followed by an insertion reaction with sulfoxonium ylides and cyclization is applied to the synthesis of flavonoids. This one-pot strategy exhibits good functional group tolerance and gives flavones in moderate-to-good yields.

Optimization of Oleuropein and Luteolin-7-O-Glucoside Extraction from Olive Leaves by Ultrasound-Assisted Technology

The olive orchard cultivation in Mediterranean countries results in huge amounts of lignocellulosic biomass residues. One of the main residues are olive leaves. Olive leaves contain high concentrations of bioactive antioxidant compounds like oleuropein and luteolin-7-glucoside. The production of biactive compounds from olive leaves requires treatments capable of breaking the lignocellulosic structure. Current research focuses on use of inexpensive, quick, and not harmful to the environment treatments, searching a more simplified large-scale operation approach. Recently, advances in applied chemistry have led to possible new emerging industrial techniques like ultrasound-assisted extraction (UAE). This technology is a promising candidate as a green treatment solution for olive leaves utilization in a biorefinery. However, this application goes through prior optimization of technique and operating conditions. The goal of this study was to optimize the extraction of oleuropein and luteolin-7-glucoside from olive leaves through an investigation of the influence of key factors of ultrasound-assisted extraction using an experimental central composite design, in comparison with conventional Soxhlet extraction. The highest extraction efficiency and antioxidant capacity were obtained under optimal increment of temperature and amplitude conditions (40 °C and 30%, respectively). Values for oleuropein, luteolin-7-glucoside were 69.91 g/kg and 1.82 g/kg, respectively.

Assessment of Ultrasound Assisted Extraction as an Alternative Method for the Extraction of Anthocyanins and Total Phenolic Compounds from Maqui Berries (Aristotelia chilensis (Mol.) Stuntz)

Research interest regarding maqui (Aristotelia chilensis) has increased over the last years due to its potential health benefits as one of the most antioxidant-rich berries. Ultrasound-assisted extraction (UAE) is an advanced green, fast, and ecological extraction technique for the production of high quality extracts from natural products, so it has been proposed in this work as an ideal alternative extraction technique for obtaining extracts of high bioactivity from maqui berries. In order to determine the optimal conditions, the extraction variables (percentage of methanol, pH, temperature, ratio “sample mass/volume of solvent”, amplitude, and cycle) were analyzed by a Box-Behnken design, in conjunction with the response surface method. The statistical analysis revealed that the temperature and the percentage of methanol were the most influential variables on the extraction of the total phenolic compounds and total anthocyanins, respectively. The optimal extraction time was determined at 15 min for total phenolic compounds, while it was only 5 min for anthocyanins. The developed methods showed a high precision level with a coefficient of variation of less than 5%. Finally, the new methods were successfully applied to several real samples. Subsequently, the results were compared to those that were obtained in previous experiments by means of microwave assisted extraction (MAE). Similar extraction yields were obtained for phenolic compounds under optimized conditions. However, UAE proved to be slightly more efficient than MAE in the extraction of anthocyanins.

In Vivo and In Vitro Antioxidant Activities of Methanol Extracts from Olive Leaves on Caenorhabditis elegans

The aim of this study was to evaluate the antioxidant activities of extracts from olive leaves (EOL). The main contents of EOL were determined by colorimetric methods. The antioxidant activities were assessed by measuring the scavenging free radicals in vitro. To investigate the antioxidant activity in vivo, we detected the survival of Caenorhabditis elegans, under thermal stress. Subsequently the reactive oxygen species (ROS) level, activities of antioxidant enzymes, the expression of HSP-16.2 and the translocation of daf-16 were measured. The results showed that, polyphenols was the main component. EOL could well scavenge DPPH and superoxide anion radicals in vitro. Compared to the control group, the survival rate of C. elegans treated with EOL was extended by 10.43%, under heat stress. The ROS level was reduced, while the expression of hsp-16.2 was increased to protect the organism against the increasing ROS. The level of malondialdehyde (MDA) also decreased sharply. The activities of inner antioxidant enzymes, such as catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidase (GSH-PX) were potentiated, which might have had a correlation with the DAF-16 transcription factor that was induced-turned into the nuclear. Therefore, EOL showed a strong antioxidant ability in vitro and in vivo. Hence, it could be a potential candidate when it came to medicinal and edible plants.