Extraction of bioactive compounds from buriti (Mauritia flexuosa L.) fruit by eco-friendly solvents: Chemical and functional characterization

Buriti (Mauritia flexuosa L.) is a palm tree found in several regions of Latin America. Buriti fruit is a rich source of bioactive compounds such as carotenoids and phenolic compounds. Thus, the aim of this study was to extract bioactive compounds from buriti fruit by ethanol and a supramolecular solvent system (SUPRAS) formed by octanoic acid aggregates. The extracts were evaluated for total carotenoids, β-carotene, phenolic compounds and antioxidant capacity. Additionally, SUPRAS extracts were characterized for antibacterial activity and modulating effect. The extraction of β-carotene with SUPRAS showed a yield of 5.82 ± 0.05 mg/g for the peel and 26.7 ± 0.02 mg/g for the pulp. In relation to total phenolic compounds, the yields were 32.1 ± 1.2 μg GAE/g for the peel and 24.53 ± 4.9 μg GAE/g for the pulp. The presence of gallic acid, quercetin and catechin stand out regarding the phenolics identified. The extracts showed antioxidant activity, with an emphasis on the extracts obtained by SUPRAS, which presented EC₅₀ (concentration required to obtain a 50% antioxidant effect) for the ABTS radical sequestration of 3.00 μg/mL for the peel and 0.84 μg/mL for the pulp. When combined with norfloxacin and gentamicin antibiotics, the extracts also showed a synergistic action against multi-resistant strains of Staphylococcus aureus, Pseudomonas aeruginosa and Escherichia coli. Thus, the extraction of bioactive compounds from buriti fruit using a safe, biocompatible, biodegradable and environmentally friendly solvent such as SUPRAS represents potential for developing new pharmaceuticals, cosmetics and functional foods.     

Green approach to extract bioactive compounds from orange peel employing hydrophilic and hydrophobic deep eutectic solvents

Consumer interest in natural products with advantageous biological impacts on their health has increased in recent years. Therefore, academic and industrial communities have concentrated their research on developing sustainable techniques for extracting bioactive compounds from natural resources. In the present study, extracts rich in bioactive compounds from orange peel were obtained using novel hydrophilic and hydrophobic deep eutectic solvents (DESs). Bioactive compounds such as carotenoids and polyphenols, their stability, antioxidant capacity, permeability, and biological activity were determined to consider their inclusion in food formulations. The results demonstrated that the highest total carotenoid values were obtained with hydrophobic DESs using DL-Menthol: camphor (163.5 ± 1.1 mg/100g_fw), DL-Menthol: Eucalyptol (168.7 ± 1.7mg/100g_fw), and lauric acid: octanoic acid (153.1 ± 7.1 mg/100g_fw). Total polyphenols were higher in hydrophilic DESs such as proline: malic acid (282.8 ± 7.3 mg/100g_fw). The antioxidant values showed that hydrophobic extracts have higher antioxidant activity than traditional solvents. Carotenoid stability was also improved using DL-Menthol: camphor, while lactic acid: glucose and proline: malic acid showed a better capacity to stabilize polyphenols. To simulate carotenoid and polyphenol permeation, the Parallel Artificial Membrane Permeability Assay (PAMPA) was used and demonstrated that DESs can enhance the permeability of these bioactive compounds. Biological tests were also performed, and the antiproliferative effect in HeLa cells showed only 26.70% cell viability in DL-Menthol: camphor extracts. Based on the presented results, DESs can be used to extract hydrophilic and hydrophobic compounds from orange peels, and the obtained extracts could be included in food formulations, avoiding the solvent elimination process.     

Microwave-assisted hydrodistillation extraction based on microwave-assisted preparation of deep eutectic solvents coupled with GC-MS for analysis of essential oils from clove buds

In recent years, deep eutectic solvents (DESs) as green and sustainable solvents have been widely used in the effective extraction of natural products. Usually, DESs are synthesized by heating and stirring method which takes a long time and energy. In this case, a microwave assisted preparation technique was used to form DESs for saving time and energy. And the DESs as pretreatment solvents were combined with microwave-assisted hydrodistillation (MAHD) for the extraction of essential oils (EOs) from the clove buds in this work. The maximum essential oils yield of 4.60% was obtained with the microwave power of 600 W, the pretreatment time of 5 min and the hydrodistillation time of 40 min using a deep eutectic solvent composed of choline chloride and lactic acid (molar ratio with 1:2). In addition, the essential oil was analyzed by gas chromatography-mass spectrometry (GC-MS), a total of 40 compounds were identified. Compared with MAHD, water-based MAHD and traditional hydrodistillation (HD), the content and composition of essential oil extracted by DES-based MAHD were higher. Thus, the combination of deep eutectic solvents with a microwave-assisted technique in this study provided an eco-friendly way of extracting essential oils.     

Effect of deep eutectic solvents on the biocatalytic properties of β-glucosidase@ZnOFe nano-biocatalyst

In this work, we investigate the use of aqueous deep eutectic solvents (DESs) consisting of different hydrogen bond acceptors (choline chloride, ammonium salts or betaine) and hydrogen bond donors (amines, sugars and alcohols), as co-solvents in biocatalytic reactions catalyzed by a nano-biocatalyst with β-glucosidase (BGL) activity. For this purpose, β-glucosidase from Thermotoga maritima was immobilized on the surface of green zinc oxide-iron oxide nanoparticles (BGL@ZnOFe) derived from an aqueous olive leaf extract. The covalent bonding of β-glucosidase on the surface of nanoparticles was demonstrated by X-ray photoelectron spectroscopy. The effect of a wide range of DES solutions on the biocatalytic features of BGL@ZnOFe was thoroughly investigated. The concentration of DES as well as the specific combination of hydrogen bond acceptors and hydrogen bond donors had a significant impact on the hydrolytic activity of immobilized β-glucosidase. Most choline chloride and betaine-based DESs enhanced the enzymatic activity and thermal stability of BGL@ZnOFe up to 50%. The enzymatic activity of the nano-biocatalyst towards the hydrolysis of bioactive phenolic compounds depends on the nature of the DES used. Choline chloride:butylene glycol-based medium had beneficial effect on a transglycosylation reaction, such as the synthesis of salidroside, increasing the total turnover number of the biocatalytic process by 55%. This work indicates that the use of several choline chloride and betaine-based DESs can be successfully employed as green co-solvents in various hydrolytic and synthetic biocatalytic processes.     

The influence of extraction methods on rutin yield of cassava leaves (Manihot esculenta Crantz)

Rutin, a well-known bioflavonoid, was found abundantly in cassava leaves. In the present study, extraction techniques including maceration, boiling, reflux, ultrasound-assisted extraction (UAE), and microwave-assisted extraction (MAE) were optimised to increase the yield of rutin. Extraction parameters such as solvents, solid-liquid ratio, temperature, and time were optimised to give better extraction yields for each method. HPLC analysis showed a high content of rutin which is up to 2.4% per dry weight of cassava leaves. The extraction yields under optimised condition were found to be 16.00 ± 0.21, 20.38 ± 0.66, 22.33 ± 2.3, 24.49 ± 0.41, and 23.37 ± 1.00 g rutin per kg dry weight for maceration, boiling, reflux, UAE and MAE methods, respectively. Specifically, UAE reduced the extraction time to 90 min, using only 40–60% of aqueous ethanol. Meanwhile, MAE completed the extraction under 5 min and no significant differences in output was observed between the use of water and aqueous ethanol. Accordingly, with the extraction efficiency of up to 99 and 94%, respectively, both processes provided better results. The subsequent green purification using chilling method produced a typical cassava bioflavonoid containing 82% of rutin and 17% of nicotiflorin. This study informs a new abundant source of rutin and provides the optimum condition of extraction methods for high yield of rutin from cassava leaves.     

Application of levulinic acid-based natural deep eutectic solvents for extraction and determination of deltamethrin in food samples

In the study, a fast and green natural deep eutectic solvent based ultrasound-assisted liquid liquid microextraction (NDES-UALLME) were proposed for the determination and extraction of deltamethrin in food samples using UV/Vis spectrophotometry. The extraction step was based on ion-pair formation between deltamethrin and levulinic acid-tetraethylammonium bromide (as extraction solvent) at pH 5.5, and then extraction of deltamethrin into micro-drops of extraction solvent by using tetrahydrofuran. Levulinic acid-based natural deep eutectic solvents composed of natural, green compounds, i.e., choline acetyl chloride, tetrabutylammonium bromide, tetraethylammonium chloride and tetraethylammonium bromide were used for the first time as extraction solvents for extraction of deltamethrin. The NDES-UALLME procedure allowed to exclude matrixes effects and increase enrichment factor (283) of deltamethrin. Several key factors, including the type and the volume of extraction solvent, the pH of sample solution, ultrasound time, extraction temperature, ionic strength and sample volume were optimized in detail. At optimized conditions, the NDES-UALLME procedure was characterized by low limit of detection (2.4 ng mL^?1), a wide linear dynamic range (8–950 ng mL^?1), quantitative recoveries (93 ± 4%-103 ± 2%) and acceptable relative standard deviations (2.9%≤). The validation of NDES-UALLME procedure was carried out using recovery tests, intraday and intraday studies. The applicability of NDES-UALLME procedure was confirmed by the assay of deltamethrin in real food samples.     

Green extraction of Buchanania siamensis and water-based formulations

Buchanania siamensis is a local plant in eastern and north-eastern Thailand belonging to the Anacardiaceae family. The plant provides shading and is a good source of food and medicine since its fruits possess antioxidant and anti-cancer effects. The green, environmental-friendly, extraction of B. siamensis, under ultrasound- and microwave-assisted extraction, using solvents consisting of a variation of tween 80, propylene glycol (PG), and ethanol concentrations were investigated. Extraction by aqueous PG under ultrasound-assisted extraction (UAE) conditions yielded the highest total phenolic (TPC) and total flavonoid contents (TFC). The optimum condition, which was using a 40 mL/g ratio, 50% PG at 60°C for 20 min, yielded the extract with TPC at 49.12 ± 0.51 mgGAE/g DW and TFC at 14.18 ± 0.48 mgQE/g DW. The extract exhibited antioxidant activity at IC₅₀ 2.49 ± 0.03 mg/mL. Water-based formulations (solution and hydrogel) of this extract were successfully fabricated. The formulations demonstrated stable properties, TPC, myriscitrin, quercetrin content, and antioxidant properties after the heating and cooling test (6 cycles). Consequently, the B. siamensis extract, rich in antioxidative agents, was proper for incorporation into water-based cosmeceutical products.     

Extraction of flavonoid compounds from bark using sustainable deep eutectic solvents

The use of green solvents in extraction processes, especially for applications of lignocellulosic biomass, has been extensively studied over the last years. Among the range of different green solvents, deep eutectic solvents (DES) show promising results for extraction processes. Therefore, the aim of this work was the use of DES as additives in aqueous mixtures for the selective extraction of flavonoid compounds from the bark of Larix decidua. For this purpose, bark has been treated using different solvent ratios consisting of a DES/H₂O mixture (0, 25, 50 and 75 wt%). Two DES were studied, choline chloride:urea and choline chloride:1,4-butanediol. In order to study the success of the extractions, the extracts and the remaining solid fraction were characterised. From the results, it was concluded that the choline chloride:1,4-butanediol (75 wt%) gave the best results, obtaining the richest extracts in flavonoids (383 mg CE/g dried bark extract), as well as those with the highest antioxidant capacity. These good results confirm the capacity of this DES to obtain active biomolecules for further application.     

A novel strategy to improve the recovery of phenolic compounds from Pistacia lentiscus L. fruits using design-based statistical modeling for ultrasound-deep eutectic solvents extraction and the evaluation of their antioxidant potential

Recently, there has been increasing interest in using alternative green technologies for the isolation of bioactive metabolites from medicinal plants. This study was designed to select the optimal solvent for phenolic compounds (TPC) extraction from Pistacia lentiscus L. black fruits (PBF) and the development of an experimental model by response surface methodology using ultrasound-assisted deep eutectic solvents (UAE-DES). The characterization and the antioxidant capacity of PBF phytochemicals using a multi-test system in-vitro were investigated. The highest amount of phenolic compounds (TPC: 183.95 ± 0.01 mg GAE/Gdw) was obtained using choline chloride-acetic acid solvent DES, under the optimum extraction conditions: 28.3% of water percentage, 40 °C of extraction temperature, and 18 min of extraction time. Moreover, DES extract had a more important antioxidant capacity with no significant difference compared to the control (Ascorbic acid). Furthermore, HPLC-DAD and TLC analysis indicated the presence of rutin and Cyanidin-3-glycoside in fraction number 4 after fractionation using the HP-20 diaion resin column. This extraction media has proved to be an alternative approach for the extraction of bioactive compounds as a sustainable and safe extraction media for pharmaceutical and industrial applications.     

Flavonoid compositions and antioxidant activity of calamondin extracts prepared using different solvents

Calamondin has been demonstrated to exhibit antioxidant function and tyrosinase inhibitory activity, which might be attributed to its flavonoid compounds. To improve their application, the flavonoid compositions and antioxidant activity of calamondin extracts, prepared by different solvents, were investigated. The results showed that total phenolic and flavonoid contents of extracts from peel of calamondin were higher than that from pulp, except the flavonoid content in hot water extract. The flavonoids found in extracts of calamondin were 3′,5′-di-C-β-glucopyranosylphloretin (DGPP), naringin, hesperidin, nobiletin, tangeretin, and diosmin. DGPP exhibited the highest quantity, while naringin and hesperidin were the other two major flavonoids. The content of DGPP in hot water extract of peel was higher than in extracts of organic solvents, however, the contents of nobiletin and tangeretin were found only in extracts of organic solvents. The highest levels of total flavonoids and DGPP were obtained in hot water extract from peel at 90°C. The extracts of hot water and ethyl acetate showed higher 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging potency than that of ethanol and methanol. A positive relationship existed between total phenolic contents and DPPH scavenging potency (p < 0.01), while total flavonoid compositions also showed correlation (p < 0.05). Thus, DGPP, naringin, and hesperidin might contribute to antioxidant activity. Collectively, the hot water extract of calamondin peel might have potential for health food and cosmetic applications due to its good antioxidant activity and high level of DGPP.     

Ultrasound-assisted extraction of antioxidant phenolic compounds from Lavandula angustifolia flowers using natural deep eutectic solvents: An experimental design approach

In this study, the green extraction of antioxidant phenolic compounds from Lavandula angustifolia was investigated using ultrasound-assisted extraction coupled with natural deep eutectic solvents (NADESs). One variable at a time, fractional factorial design, steepest ascent/descent method, and central composite design were used to optimize the extraction conditions. Eighteen NADESs based on choline chloride, organic acids, and sugars were tested by one variable at a time approach. The NADES composed of choline chloride and glycerol with a molar ratio of 1:2 showed higher extraction performance than other NADESs and benchmark solvents (70 % ethanol and 80 % methanol). After solvent selection, other extraction parameters including ultrasound amplitude (20–100 %), temperature (40–70 °C), time (5–30 min), liquid to solid ratio (10–50 mL/g), and water content in NADES (10–50 %) were screened using fractional factorial design. Subsequently, the steepest ascent/descent method was applied to approach the suitable level of the selected parameters. Finally, response surface methodology was used to determine the optimal extraction conditions. The optimum conditions were ultrasound amplitude of 60 %, temperature of 60 °C, time of 17.5 min, liquid to solid ratio of 31.7 mL/g, and water content in NADES of 33.5 % with the predicted phenolic content of 50.50 mg gallic acid equivalent/g, flavonoid content of 35.79 mg catechin equivalent/g, antioxidant capacity (AC)_DPPH of 41.60 mg Trolox equivalent (TE)/g, AC_ABTS of 77.13 mg TE/g, and AC_CUPRAC of 163.33 mg TE/g. Phenolics and volatiles were analyzed by HPLC and GC-MS, respectively. The results showed a sustainable, green, and effective extraction of antioxidant phenolic compounds from L. angustifolia.     

Extraction and quantification of polyphenols from kinnow (Citrus reticulate L.) peel using ultrasound and maceration techniques

An investigation was carried out to extract polyphenols from the peel of kinnow (Citrus reticulate L.) by maceration and ultrasound-assisted extraction (UAE) techniques. The antioxidant potential of these polyphenols was evaluated using ferric reducing antioxidant power (FRAP), 2,2-diphenyl-1-picrylhydrazyl (DPPH), and superoxide radical scavenging assays; and their antimicrobial activity was assessed against bacterial strains Staphyloccoccus aureus, Bacillus cereus, and Salmonella typhimurium. The highest extraction yield was obtained through the solvent ethanol at 80% concentration level, whereas UAE was a more efficient technique and yielded comparatively higher polyphenol contents than maceration. Maximum polyphenols were extracted with 80% methanol [32.48 mg gallic acid equivalent (GAE)/g extract] using UAE, whereas minimum phenolics (8.64 mg GAE/g extract) were obtained with 80% ethyl acetate through the maceration technique. Elevated antioxidant activity of kinnow peel extracts was exhibited in three antioxidant assays, where 80% methanolic extracts showed the highest antioxidant activity (27.67 ± 1.11mM/100 g for FRAP) and the highest scavenging activity, 72.83 ± 0.65% and 64.80 ± 0.91% for DPPH and superoxide anion radical assays, respectively. Strong correlations between total polyphenols and antioxidant activity were recorded. Eleven phenolic compounds—including five phenolic acids and six flavonoids—were identified and quantified by high performance liquid chromatography. Ferulic acid and hesperidin were the most abundant compounds whereas caffeic acid was the least abundant phenolic compound in kinnow peel extracts. Maximum inhibition zone was recorded against S. aureus (16.00 ± 0.58 mm) whereas minimum inhibition zone was noted against S. typhimurium (9.00 ± 1.16 mm). It was concluded that kinnow mandarin peels, being a potential source of phenolic compounds with antioxidant and antimicrobial properties, may be used as an ingredient for the preparation of functional foods.     

Carotenoid composition of Rosa canina fruits determined by thin-layer chromatography and high-performance liquid chromatography

The carotenoid composition of fruits of Rosa canina (Rosaceae) was determined comparatively by thin-layer chromatography (TLC) and high-performance liquid chromatography (HPLC) in total extracts and in three different fractions derived from previous separation of the total fruit extract on alumina columns. Both chromatographic analyses revealed as major carotenoids: β-carotene, lycopene, β-chryptoxanthin, rubixanthin, zeaxanthin and lutein. The distribution of these compounds was reproducible by TLC and by HPLC. The I—III fractions eluted successively from alumina columns by increasing the polarity of the solvents were analysed also by TLC and HPLC. In all situations, carotenoids were better separated and identified by gradient HPLC systems than by isocratic HPLC or TLC.     

超临界CO_2萃取桔梗总皂苷的工艺研究

采用正交试验优化桔梗总皂苷的超临界CO_2萃取工艺,探讨了表面活性剂对萃取的影响.所得优化工艺为萃取温度40℃、萃取压力35 MPa、萃取时间2 h,夹带剂为95%乙醇,与药材投料量比例为1:1(v/w).在95%乙醇中加入表面活性剂吐温-80或司盘-80可提高桔梗总皂苷的得率.     

Economic pre-feasibility of supercritical fluid extraction of antioxidants from fruit residues

During the different stages of the supply chain, large amounts of waste are generated, being mostly disposed of in landfills. Most of these residues have a high content of valuable compounds with a high antioxidant capacity. These compounds have a high potential for use in different industries, such as the pharmaceutical and food industries. Supercritical fluid extraction is one of the technologies available for extracting effectively these components from wastes. Several studies have focused on this technology to show its advantages. This work aims evaluates the production of bioactive compound from different fruit residues to analyze their economic pre-feasibility using supercritical fluid extraction. Five fruit wastes were used for the analysis: mango peel, yellow passion fruit seed, raspberry seeds, mandarin peel, and açaí berry exhausted pulp. As results there was found that the use of a co-solvent increases production costs. Another influencing factor was the extraction yield related to the raw material used. The appropriate selection of these variables makes it possible to obtain economically viable processes. The yellow passion fruit presents the better economic indicators for obtaining an oil extract mainly composed of palmitic acid. With the raw material flow of 100 kg/h, a profit margin of 86.94% was obtained, which was the higher than for other raw materials. Additionally, the minimum flow of yellow passion fruit is 5.13 kg/h to obtain an NPV of zero at ten years.     

Characterization of bioactive compounds from raw and ripe Mangifera indica L. peel extracts

Mango is one of the important tropical fruits in the world. As it is a seasonal fruit, it is processed for various products. During its processing, peel is one of the major byproducts, which is being wasted. Bioactive conserves were extracted using 80% acetone from peels of raw and ripe mango fruits and subjected to acid hydrolysis. The prominent phenolic compounds identified by HPLC were protocatechuic acid, gentisic acid and gallic acid. The phenolic acid derivatives present in acetone extracts of raw and ripe peels were tentatively identified by LC–MS. Gallic acid, syringic acid, mangiferin, ellagic acid, gentisyl-protocatechuic acid, quercetin were the phenolic compounds identified in both raw and ripe peels, while raw peel showed the presence of glycosylated iriflophenone and maclurin derivatives also. β-Carotene was the major carotenoid followed by violaxanthin and lutein. Thus, both raw and ripe mango peel extracts have different phenolic compounds and carotenoids, which will have various pharmaceutical applications.     

Recovery of phenolic compounds from spent coffee grounds through optimized extraction processes

The aim of the present study was to compare novel methods and technologies of phenolics extraction from spent coffee grounds, as “green” alternative techniques of the conventional ethanol extraction. Three extraction techniques, ultrasound- and microwave-assisted extraction, along with the use of β-cyclodextrin as a solvent have been studied and optimized as the eco-friendly solutions for the efficient extraction of phenolic compounds from Spent Coffee Grounds (SCG). The investigated factors were temperature (20–60 °C), solvent concentration (0–100% v/v water ethanol, EtOH), amplitude (20–60%), and liquid/solid ratio (5–60 mL/g) for ultrasound-assisted extraction (UAE). In the case of microwave extraction (MAE), the effects of solvent concentration (0–100% v/v), liquid/solid ratio (5–60 mL/g), and power (100–600 Watt) were studied. Ethanol (0–100% v/v) and β-cyclodextrin (β-CD, 1–18.5 mg/mL) were also compared as solvents, under the same range of liquid/solid ratio (5–60 mL/g) and temperatures (20–60 °C). In addition, the effect of the drying method (oven drying and freeze-drying), as well as a defatting pretreatment of SCG, were studied under the optimum conditions of each extraction method. The optimum extraction yield (31.79 ± 0.25 mg GAE/g SCG) was achieved using MAE with a liquid/solid ratio of 60 mL/g, a power level 600 W, and a solvent concentration of 68% v/v EtOH. While the maximum yield (34.43 mg GAE/g SCG) was also obtained by the same method from the freeze-dried sample.     

Extraction of protein with protease inhibitor activity from Brazilwood (Caesalpinia echinata LAM.) seeds using choline-based ionic liquids

Proteolytic inhibitors are low molecular weight proteins that prevent protein hydrolysis and are used against moderate to high severity diseases. Some plants can produce these protease inhibitors, such as Brazilwood seeds (Caesalpinia echinata LAM.). This work aimed to optimise the extraction of proteins from Brazilwood seeds with proteolytic inhibitory activity, using choline-based ionic liquid. The seeds were characterised in terms of their dimensions (15 mm in length, 11 mm in width and 4.8 mm in thickness), centesimal composition (moisture - 9.21%, ash - 3.37%, lipids - 32.6%, total fibre - 0.80%, crude proteins - 17.2%, carbohydrates - 36.8%), energy (510 Kcal.100 g^-1) and major fatty acid (linoleic acid - 43%). Protein extraction was performed by maceration of the Brazilwood seeds using ionic liquids (choline bitartrate, choline chloride and choline dihydrogen citrate) and optimised using a factorial design of experiments, whose variables were the temperature and solvent concentration, with the total protein content as the response variable. The best extraction conditions were 25.42 °C, 5.42% (m/v) choline bitartrate, solid-liquid ratio 1:5, 500 rpm and pH 7.0 (1.74 mg mL^?1 theoretical and 1.88 mg mL^?1 experimental). The kinetic model best fitted to the experimental data was Peleg's, and the best extraction time was 15 min. Under optimised conditions, the protein extract of Brazilwood seeds provided a 60.8% inhibition of trypsin. According to the molecular docking results, the inhibition of bovine trypsin is driven by Caesalpinia echinata kallikrein inhibitor (CeKI) and the selected ionic liquid (choline bitartrate), promoting a synergistic inhibition effect.     

Exploring the potential of novel R. kratochvilovae red yeasts towards the sustainable synthesis of natural carotenoids

The development of microbial cell factories is nowadays a main route for the production of safe and environmentally friendly bioactive compounds. Rhodosporidium kratochvilovae yeasts constitute an unexplored source for the production of natural carotenoids, thus further insights on their metabolism and fermentative behavior would contribute towards the sustainable synthesis of bioactive compounds. The aim of this study was to investigate the ability of two R. kratochvilovae isolates (FMCC Y-42 and Y-43) to produce carotenoids under different experimental conditions. Cell growth, carotenoid synthesis and lipid accumulation were evaluated using synthetic media containing either glucose or mixtures of glucose:galactose (1:1), under different carbon-to-nitrogen (C/N) ratios. Carotenogenesis was highly affected by C/N ratio in both strains, while a competitive trend with lipid accumulation was also observed. Yeast strain Y-42 reached the highest concentration of total carotenoids (2.59 mg/L) when grown on glucose-based medium at a C/N ratio of 80 after 39 h of fermentation. Likewise, the strain Y-43 produced approximately 2 mg/L of total carotenoids from both glucose (C/N of 80) and its mixture with galactose (C/N 80 and 120), with similar biomass concentration (9.3, 10.3 and 10.9 g/L, respectively). HPLC-DAD analysis of carotenoid extracts indicated that the main carotenoid was β-carotene (60–75%) followed by γ-carotene (9–18%), torulene (6–13%) and torularhodin (5–17%), regardless the fermentation conditions or the strain-employed. This is the first study to reveal γ-carotene synthesis by R. kratochvilovae strains. The obtained results provided new knowledge on the production of natural carotenoids by novel red yeast strains and could pave the way towards their application in sustainable functional food products and nutraceuticals.     

Pterocarpus santalinoides leaves extract as a sustainable and potent inhibitor for low carbon steel in a simulated pickling medium

The crude extract of Pterocarpus santalinoides leaves (PSLE) extracted using water, ethanol, and methanol as the extraction solvent has been studied as inhibitor for low carbon steel in 1 moL/dm³ HCl solution using electrochemical approaches at 25 °C and 60 °C. The results obtained reveal that, PSLE extract has the capacity to effectively suppress the dissolution of the studied substrate. The inhibition performance of PSLE is a function of concentration, temperature, and extraction solvent. Corrosion inhibition is in the order: ethanolic extract > methanolic extract > aqueous extract. With 0.7 g/L PSLE, inhibition efficiency of >90% has been obtained at 60 °C. Based on calculated values of adsorption parameters and UV–vis results, it is proposed that PSLE molecules chemically interacted with the substrate surface. PSLE extract suppressed both the rate of cathodic and anodic reactions according to the PDP results. However, aqueous PSLE extract inhibited anodic corrosion reactions predominantly while ethanolic and methanolic extracts mainly inhibited the cathodic corrosion reactions. Surface characterization studies via SEM, EDAX, and AFM provide experimental evidence to the claim of interaction and presence of PSLE molecules on the studied substrate surface.