Efficient extraction of proanthocyanidin from Ginkgo biloba leaves employing rationally designed deep eutectic solvent-water mixture and evaluation of the antioxidant activity

A preclinical randomized controlled study of ischemia treated with Ginkgo biloba extracts: Are complex components beneficial for treating acute stroke?

The rigorous design of preclinical experimental studies of candidate neuroprotectants for the treatment of acute ischemic stroke is crucial for the success of subsequent randomized clinical trials. The efficacy of Ginkgo biloba extracts (GBEs) in complex mixtures for the treatment of acute ischemic stroke remains unclear. In this preclinical randomized controlled trail (pRCT), the effects of a novel (n)GBE containing pinitol versus traditional (t)GBE without pinitol were evaluated on the mouse models of acute transient and permanent stroke, separately. The sample size, an important aspect of study design, was calculated based on our experimental data. Mice with ischemia that were induced by transient middle cerebral artery occlusion (tMCAO) or permanent distal middle cerebral artery occlusion (pdMCAO), were treated with vehicle, nGBE, tGBE, or pinitol alone by tail-vein injection. Our results showed that nGBE significantly reduced infarct size in mice with tMCAO compared with vehicle-treated control mice. Both nGBE and tGBE significantly reduced infarct size in mice with pdMCAO compared with the vehicle-treated controls. None of the three treatments rescued weight loss or prevented the neurological deficits in either the tMCAO- or pdMCAO-model mice. These findings suggest that nGBE, which includes all of the components of tGBE and pinitol, is neuroprotective in two ischemic stroke models. Additional studies of complex GBE mixtures for stroke treatment compared to single component medications are undergoing evaluation.

Impact of Deep Eutectic Solvents on Extraction of Polyphenols from Grape Seeds and Skin

In the past few years, research efforts have focused on plant exploitation for deriving some valuable compounds. Extraction has been usually performed using petrochemical and volatile organic solvents, but nowadays, increased recognition of environmental pollution has prompted the utilization of green solvents as alternatives. Therefore, the aim of the present study was to exploit deep eutectic solvents (DES) (choline chloride: citric acid and choline chloride: glucose) as solvents for extracting valuable phenolic antioxidants from grapes. Investigation was conducted on ten grape varieties, observing seeds and skin as different matrix. Total polyphenol content (TPC) was determined by Folin-Ciocalteu spectrophotometric microassay. Antioxidant activity was investigated using four different tests and results were combined in a unique Antioxidant Composite Index (ACI) to reveal comprehensive information about this biological activity. Polyphenol compounds were identified and quantified with the aim of HPLC-diode array detector (DAD). Overall results support that DES (particularly choline chloride: citric acid) were comparable to conventional solvent, and in most cases even outperformed acidified aqueous ethanol (concerning extraction efficiency and antioxidant activity). Regardless of varietal distinctions, grape seeds have higher antioxidant capacity compared to grape skin, and such findings are according to their phenol compound concentrations.

Bioactive Phenolic Compounds From Agri-Food Wastes: An Update on Green and Sustainable Extraction Methodologies

Phenolic compounds are broadly represented in plant kingdom, and their occurrence in easily accessible low-cost sources like wastes from agri-food processing have led in the last decade to an increase of interest in their recovery and further exploitation. Indeed, most of these compounds are endowed with beneficial properties to human health (e.g., in the prevention of cancer and cardiovascular diseases), that may be largely ascribed to their potent antioxidant and scavenging activity against reactive oxygen species generated in settings of oxidative stress and responsible for the onset of several inflammatory and degenerative diseases. Apart from their use as food supplements or as additives in functional foods, natural phenolic compounds have become increasingly attractive also from a technological point of view, due to their possible exploitation in materials science. Several extraction methodologies have been reported for the recovery of phenolic compounds from agri-food wastes mostly based on the use of organic solvents such as methanol, ethanol, or acetone. However, there is an increasing need for green and sustainable approaches leading to phenolic-rich extracts with low environmental impact. This review addresses the most promising and innovative methodologies for the recovery of functional phenolic compounds from waste materials that have appeared in the recent literature. In particular, extraction procedures based on the use of green technologies (supercritical fluid, microwaves, ultrasounds) as well as of green solvents such as deep eutectic solvents (DES) are surveyed.

Efficient extraction and determination of prenylflavonol glycosides in Epimedium pubescens Maxim. using deep eutectic solvents

INTRODUCTION

The Epimedium herb, Yinyanghuo in Chinese, is a famous Chinese herbal medicine. In this study, an efficient extraction method was developed for the extraction of major bioactive constituent epimedin A, epimedin B, epimedin C and icariin from E. pubescens Maxim. using deep eutectic solvents (DESs).

METHODOLOGY

A series of choline chloride-based DESs were synthesised for the extraction of four target compounds. DES composed of lactic acid and choline chloride with the ratio of 2:1 was selected as the most promising. Three vital factors affecting the extraction yields including water content, volume of DES aqueous solution and extraction time were optimised systematically by Box-Behnken experimental design in combination with response surface methodology. A high-performance liquid chromatography ultraviolet (HPLC-UV) method was developed for the sensitive and accurate quantification.

RESULTS

The optimal extraction conditions were obtained as follows: water content of 17.5% (v/v), volume of DES aqueous solution 3.14 ml, and extraction time of 21 min. Under the optimal extraction conditions, the developed DES method could supply almost the same extraction yield as 50% ethanol, which were 98%, 99%, 97%, 96% for epimedin A, epimedin B, epimedin C and icariin, respectively.

CONCLUSION

The present study exhibited high efficiency in extraction of prenylflavonol glycosides in E. pubescens Maxim. Thus, DESs could be used as an alternative for efficient extraction and quantification of biologically active components from natural medical plants.

Ultrasound-assisted extraction of bioactive alkaloids from Phellodendri amurensis cortex using deep eutectic solvent aqueous solutions

ChCl/citric acid-based DESs are demonstrated to be effective green solvents for the ultrasound-assisted extraction of bioactive alkaloids from herbs.

Deep Eutectic Solvents for Pretreatment, Extraction, and Catalysis of Biomass and Food Waste

Valorization of lignocellulosic biomass and food residues to obtain valuable chemicals is essential to the establishment of a sustainable and biobased economy in the modern world. The latest and greenest generation of ionic liquids (ILs) are deep eutectic solvents (DESs) and natural deep eutectic solvents (NADESs); these have shown great promise for various applications and have attracted considerable attention from researchers who seek versatile solvents with pretreatment, extraction, and catalysis capabilities in biomass- and biowaste-to-bioenergy conversion processes. The present work aimed to review the use of DESs and NADESs in the valorization of biomass and biowaste as pretreatment or extraction solvents or catalysis agents.

Improvement of the Quality of Ginkgo biloba Leaves Fermented by Eurotium cristatum as High Value-Added Feed

Ginkgo biloba leaves are well known for their high content of nutrients and bioactive substances. However, unpleasant smell and a small number of ginkgolic acids greatly reduce the utilization of the leaves. In this work, solid-state fermentation of G. biloba leaves using Eurotium cristatum was studied by investigation of the nutrient changes and its feasibility as a functional feed. E. cristatum could grow on pure G. biloba leaves and the addition of excipients could significantly improve the growth of E. cristatum. The optimal medium was with 10% (w/w) of whole G. biloba seeds and the optimized water content, pH, inoculum size and fermentation time were 45% (w/w), 4.5, 4.76 × 107 CFU/100 g wet medium, and eight days, respectively. Under the optimal conditions, the spore number increased by about 40 times. The content of flavonoids was greatly increased by 118.6%, and the protein and polyprenyl acetates (PPAs) were increased by 64.9% and 10.6%, respectively. The ginkgolic acids, lignin, and cellulose were decreased by 52.4%, 38.5%, and 20.1% than before, respectively. Furthermore, the fermented G. biloba leaves showed higher antioxidant activity and held more aroma substances. Thus, G. biloba leaves fermented by E. cristatum have potential as s high value-added feed. This is the first investigation of E. cristatum fermentation on ginkgo leaves, which will facilitate the use of ginkgo leaves in the feed industry.

Deep eutectic solvents-derived carbon dots for detection of mercury (II), photocatalytic antifungal activity and fluorescent labeling for C. albicans

A novel nitrogen and chloride co-doped carbon dots (N/Cl-CDs) based choline chloride-urea deep eutectic solvents (DESs) were synthesized by one-step hydrothermal method with high quantum yield of 37% and excellent photoluminescent properties. This N/Cl-CDs fluorescent probe had been successfully applied to sensitively and selectively detect the concentration of Hg²⁺ with a linear range of 0.2-40 μM and a detection limit of 0.05 μM. Moreover, the N/Cl-CDs displayed a strong photocatalytic antifungal activity against C. albicans and their photoinduced antifungal functions were evaluated under conditions of varying other experimental parameters. The antifungal efficiency of N/Cl-CDs (7 mg/mL) against C. albicans is upon 100% when extending the visible light irradiation time to 80 min. In addition, the excellent luminescence properties of N/Cl-CDs can also label C. albicans and displayed multicolour fluorescence imaging at different excitation wavelengths. Based on their functions of fluorescence probe, antifungal and fluorescence imaging, N/Cl-CDs would provide potentials for a wide range of applications in the detection and microbe in the near future.

Total Phenolic, Anthocyanin, Catechins, DPPH Radical Scavenging Activity, and Toxicity of Lepisanthes alata (Blume) Leenh

Anthocyanins and catechin are natural antioxidants presented in many plants. Lepisanthes alata (Blume) Leenh is a plant with fruit that ripens to an intense red. This coloring suggests a high polyphenol content. However, limited information is available regarding the polyphenol or other antioxidant content in this fruit or its suitability as a food additive. The purpose of this research was to determine the total phenolic, total monomeric anthocyanin, catechin, epicatechin and epigallocatechin gallate content, DPPH radical scavenging activity, and toxicity in rind, flesh, seed, and whole fruit of L. alata. This research was conducted using an exploratory method with four analyses; samples from six parts of the plant were analyzed for polyphenols (rind, fruit pulp, seeds, whole fruit, bark, and leaves), four for anthocyanins (rind, fruit pulp, seeds, and whole fruit), and six parts of the plant for DPPH radical scavenging activity in water, methanol, and ethanol (rind, fruit pulp, seeds, whole fruit, bark, and leaves) and toxicity. This plant was found to contain high levels of polyphenol; the lowest level was measured in the flesh (0.64 mg GAE/g of DW) and the highest in the whole fruit (2.87 mg GAE/g of DW). The lowest anthocyanin content is found in the flesh and the highest in the rind with the respective average values of 672.27 mg/100 g FW and 1462.82 mg/100 g FW. Epicatechin is the major catechin in whole fruit and bark of L. alata. L. alata DPPH radical scavenging activity was in the range of 21.23 to 92.5% depending on the solvent, and the highest activity was recorded in bark in ethanol extract. No toxins were found in any part of the plant indicating that an extract from it could be safely used as a natural antioxidant supplement in processed foods to protect against free radicals.

Ionic deep eutectic solvents for the extraction and separation of natural products

Room ionic liquids (ILs) used as green solvents have received considerable attention and wide application in different research and industrial fields, such as chemistry, biology, catalysis, energy, and even environmental sciences. Recently, a new class of sustainable solvents named deep eutectic solvents (DESs) have been developed, which share the promising solvent characteristics of ILs, such as thermal and chemical stability, low vapor pressure and design ability. In addition, the major advantages of DESs over ILs are their lower prices and easier preparation. Therefore, DESs have been considered to be a potential alternative to replace conventional organic solvents and ILs. Currently, the developed DESs may be classified into ionic and nonionic liquids. Typically, choline chloride (ChCl)/urea (1:2) is an ionic DES, while glucose/sucrose (1:1) is a nonionic DES. Although several reviews have covered advancements in DESs, in this review, we aim to provide a general insight into DESs, particularly ionic DESs, like choline-based DES, in terms of their preparation and application in the extraction of natural products (NPs) mainly from traditional Chinese medicines and the recovery of extracted compounds from their extracts. Additionally, various factors affecting the extraction efficiency of DESs are discussed.

Deep Eutectic Solvent-Based Ultrahigh Pressure Extraction of Baicalin from Scutellaria baicalensis Georgi

Deep eutectic solvents (DESs), promising green solvents, and ultrahigh pressure extraction (UPE) as an effective auxiliary extraction method, have attracted wide attention. In this study, DES was coupled with UPE to efficiently extract baicalin from Scutellaria baicalensis Georgi. First, choline chloride: lactic acid (ChCl-LA, molar ratio 1:1) was selected as the most appropriate DES by comparing the extraction yield of different DESs. Second, the extraction protocol was optimized by response surface methodology (RSM) considering the impacts of ChCl-LA concentration, extraction pressure, extraction time and liquid-solid ratio on the extraction yield. Under the optimal condition (40 vol% water content, extraction pressure of 400 MPa, extraction time of 4 min and a liquid-solid ratio of 110 mL/g), a maximum yield of 116.8 mg/g was achieved, higher than that obtained by the traditional extraction method. The microstructure of the raw and extracted Scutellaria baicalensis Georgi samples according to scanning electron microscope (SEM) images revealed that the dissolution of chemical components was enhanced from the disrupted root tissues after DESs-UPE. DESs coupled with UPE could effectively extract the baicalin from Scutellaria baicalensis Georgi as a rapid and efficient extraction method.

Natural deep eutectic solvents-mediated extractions: The way forward for sustainable analytical developments

The concept of sustainable development has impacted in analytical chemistry changing the way of thinking processes and methods. It is important for analytical chemists to consider how sample preparation can integrate the basic concepts of Green Chemistry. In this sense, the replacement of traditional organic solvents is of utmost importance. Natural Deep Eutectic Solvents (NADES) have come to light as a green alternative. In the last few years, a growing number of contributions have applied these natural solvents proving their efficiency in terms of extraction ability, analyte stabilization capacity and detection compatibility. However, the arising question that has to be answered is: the use of NADES is enough to green an extraction process? This review presents an overview of knowledge regarding sustainability of NADES-based extraction procedures, focused on reported literature within the timeframe spanning from 2011 up to date. The contributions were analyzed from a green perspective in terms of energy, time, sample and solvent consumption. Moreover, we include a critical analysis to clarify whether the use of NADES as extraction media is enough for greening an analytical methodology; strategies to make them even greener are also presented. Finally, recent trends and future perspectives on how NADES-based extraction approaches in combination with computational methodologies can contribute are discussed.