Impact of different solvents on the recovery of bioactive compounds and antioxidant properties from lemon (Citrus limon L.) pomace waste

The effects of different solvents on the recovery of (i) extractable solids (ES), (ii) total phenolic compounds (TPC), (iii) total flavonoid content (TFC), (iv) vitamin C, and (v) antioxidant activity from lemon pomace waste were investigated. The results revealed that solvents significantly affected the recovery of ES, TPC, TFC, and antioxidant properties. Absolute methanol and 50% acetone resulted in the highest extraction yields of TPC, whereas absolute methanol resulted in the highest extraction of TFC, and water had the highest recovery of vitamin C. 50% ethanol, and 50% acetone had higher extraction yields for TPC, and TFC, as well as higher antioxidant activity compared with their absolute solvents and water. TPC and TFC were shown to be the major components contributing to the antioxidant activity of lemon pomace.

Optimization of microwave-assisted extration of phenolic compounds from tomao by full factorial design coupled with response surface methodology

Tomato (Lycopersicon esculentum Mill.), apart from being a functional food rich in carotenoids, vitamins and minerals, is also an important source of phenolic compounds [1 ,2]. As antioxidants, these functional molecules play an important role in the prevention of human pathologies and have many applications in nutraceutical, pharmaceutical and cosmeceutical industries. Therefore, the recovery of added-value phenolic compounds from natural sources, such as tomato surplus or industrial by-products, is highly desirable. Herein, the microwave-assisted extraction of the main phenolic acids and flavonoids from tomato was optimized. A S-Ieve! full factorial Box-Behnken design was implemented and response surface methodology used for analysis. The extraction time (0-20 min), temperature (60-180 "C), ethanol percentage (0-100%), solidlliquid ratio (5-45 g/L) and microwave power (0-400 W) were studied as independent variables. The phenolic profile of the studied tomato variety was initially characterized by HPLC-DAD-ESIIMS [2]. Then, the effect of the different extraction conditions, as defined by the used experimental design, on the target compounds was monitored by HPLC-DAD, using their UV spectra and retention time for identification and a series of calibrations based on external standards for quantification. The proposed model was successfully implemented and statistically validated. The microwave power had no effect on the extraction process. Comparing with the optimal extraction conditions for flavonoids, which demanded a short processing time (2 min), a low temperature (60 "C) and solidlliquid ratio (5 g/L), and pure ethanol, phenolic acids required a longer processing time ( 4.38 min), a higher temperature (145.6 •c) and solidlliquid ratio (45 g/L), and water as extraction solvent. Additionally, the studied tomato variety was highlighted as a source of added-value phenolic acids and flavonoids.

Contribution of plant-derived phenolic compounds to combat Candida species biofilms

Opportunistic fungal infections, namely involving Candida species, constitute a hot topic for scientific researchers. The present wor1( aims to access antifungal potential of plant-derived phenolic extrac:ls against planktonic cells and biofilms of Candida species. Eucalyptvs globulus Labill. (blue gum), Glycyrrhiza glabra L. (licorice), Juglans regia L. (walnut) and Salvia officina/is L. (sage) evidenced to be the most effective Candida growth inhibitors, using disc diffusion assay. Minmal inhibitory (MIC) and minimal fungicidal (MFC) concentrations, and chemical composition of extracts by using HPLC-DAO-ESVMS were also determined. Blue gum and walnut mainly exerted fungistatic potential, while sage exerted an interesting anti-Candida potential. However, the most prominent candidacidal potential was observed to licorice extract, being achieved the lowest MIC and MFC values. The candidacidal potential of these phenolic extracts was mainly attributed to their high abundance in flavonoids, mainly flavones: luteolin (sage) and apigen~ derivatives (licorice), and flavanones: liQuiritin derivatives (licorice). In order to deepen the knowledge on the most effective extract. its abiity to inhibit biofilm formation was evaluated. Overall, a double concentration of MFC value was necessary to achieve similar results in biofims. Row cytometry assays were also carried out, and the obtained results revealed that primary lesion of cellular membrane appear to be most relevant mode of action. Thus, plant derived phenolic compounds evidence a promising potential to combat Candida species biofilms, both individually or combined with conventional therapy.

Phenolic compounds in Coleostephus myconis (L.) Rchb.f.: characterization by HPLC-DAD-ESI/MS and phenology effects

The Asteraceae family is spread worldwide. In Portugal, there are more than 300 species, standing out as one of the botanical families with largest representation in the Portuguese flora. Coleostephus myconis (L.) Rchb.f. is a scarcely studied Asteraceae species, characterized as having ruderal growth and persistence in abandoned soils (an expanding problem due to the desertification phenomena in rural areas). In this work, the flowers of C. myconis were collected in three different flowering stages (i: flower bud; ii: flower in anthesis; iii: senescent flower) from the Northwestern area of the Portuguese territory. Powdered samples (1 g) were extracted twice with ethanol:water 50:50 (v/v). After removing solvents, the combined extracts were re-dissolved, filtered through 0.22-μm disposable LC filter disks and analyzed by high performance liquid chromatography coupled to a diode array detector and electrospray ionization-mass spectrometry (HPLC-DAD/ESI-MS). The phenolic compounds were characterized according to their UV and mass spectra, and retention times. For the quantitative analysis, calibration curves of standard compounds were used. According to the UV spectra (λmax = 314-330 nm) and pseudomolecular ions ([M-H]-) at m/z 353 and 515, all producing an m/z 191 ion, four compounds derived from quinic acid were detected: 3-O-caffeoylquinic acid (Figure 1A), 5-O-caffeoylquinic acid (Figure 1B), 3,5-O-dicaffeoylquinic acid (Figure 1C) and 4,5-O-dicaffeoylquinic acid (Figure 1D), as also supported by the literature [1,2]. A fifth phenolic acid was identified as protocatechuic acid. The detected flavonoid were quercetin-O-glucuronide, quercetin-3-Oglucoside, myricetin-O-methyl-hexoside and a second glycosylated myricetin (not possible to identify completely). Some statistically significant changes were detected among the different assayed flowering stages; nevertheless, 3,5-O-dicaffeoylquinic acid was the major compound, independently of the phenologic stage. According to the previous results, C. myconis might be considered as a potential natural source of these valuable bioactive compounds, especially considering the high botanical representativeness of this plant and its inexpensiveness.

HPLC-DAD-ESI/MS analysis of phenolic compounds in four tomato varieties and evaluation of the antioxidant capacity

Tomato (Lycopersicon esculentum L.) is the second most important vegetable crop worldwide and a key component in the so-called “Mediterranean diet”. In the Northeastern region of Portugal, local populations still prefer to consume traditional tomato varieties which they find very tasty and healthy, as they are grown using extensive farming techniques. A previous study of our research team described the nutritional value of the round (batateiro), long (comprido), heart (coração) and yellow (amarelo) tomato varieties [1], but the phenolic profile was unknown until now. Thus, the objective of this study was to characterize the phenolic profiles of these four tomato farmers’ varieties by using HPLC-DAD-ESI/MS and evaluate its antioxidant capacity through four in vitro assays based on different reaction mechanisms. A cis p-coumaric acid derivative was the most abundant compound in yellow and round tomato varieties, while 4-O-caffeolyquinic acid was the most abundant in long and heart varieties. The most abundant flavonoid was quercetin pentosylrutinoside in the four tomato varieties. Yellow tomato presented the highest levels of phenolic compounds, including phenolic acids and flavonoids, but the lowest antioxidant activity. In turn, the round tomato gave the best results in all the antioxidant activity assays. This study demonstrated that these tomato farmers’ varieties are a source of phenolic compounds, mainly phenolic acid derivatives [2], and possess high antioxidant capacity [1]; being thus key elements in the diet to prevent chronic degenerative diseases associated to oxidative stress, such as cancer and coronary artery disease.

Exploring plant tissue culture to improve the production of phenolic compounds: A review

Plant tissue and organ culture has been extensively used from the beginning of the XX century for the study and comprehension of some primary biological mechanisms such as morphogenesis. However, with the increasing demand of the market for novel products derived from plants, in vitro culture became a reliable technique for the mass production of plant material. Moreover, the potential to use this technique for the production of some bioactive compounds, such as phenolic compounds, is immense since it allows the manipulation of the biosynthetic routes to increase the production and accumulation of specific compounds. This work intends to make a brief historical review of in vitro culture, highlighting its use for the production of bioactive compounds. Also, emphasizes the importance of phenolic compounds for the consumer as well reviews the metabolic pathways involved in its production in plant cells. Furthermore, it was carried out a comprehensive study on the work developed for the production of plant phenolic compounds in in vitro cultures, as well as on the type of elicitors used to increase of the same production; also a brief highlighting of the phenolic compounds which serve as elicitors. There are numerous reports directed to the production of phenolic extracts in in vitro plant cultures, however there is a lack in the production of individual phenolic compounds mainly due to the complexity of the biosynthetic routes and extraction procedures. Elicitation procedures are often used to increase the production of phenolics, archieving in most cases higher yields than in non-elicitated cultures. The increasing production of bioactive phenolic extracts/compounds allows for their further applicability, namely in the industry of functional foods or in pharmaceutical/medical fields.

Wild Roman chamomile extracts and phenolic compounds: enzymatic assays and molecular modelling studies with VEGFR-2 tyrosine kinase

Angiogenesis is a process by which new blood vessels are formed from the pre-existing vasculature, and it is a key process that leads to tumour development. Some studies have recognized phenolic compounds as chemopreventive agents; flavonoids, in particular, seem to suppress the growth of tumor cells modifying the cell cycle. Herein, the antiangiogenic activity of Roman chamomile (Chamaemelum nobile L.) extracts (methanolic extract and infusion) and the main phenolic compounds present (apigenin, apigenin-7-O-glucoside, caffeic acid, chlorogenic acid, luteolin, and luteolin-7-O-glucoside) was evaluated through enzymatic assays using the tyrosine kinase intracellular domain of the Vascular Endothelium Growth Factor Receptor-2 (VEGFR-2), which is a transmembrane receptor expressed fundamentally in endothelial cells involved in angiogenesis, and molecular modelling studies. The methanolic extract showed a lower IC50 value (concentration that provided 50% of VEGFR-2 inhibition) than the infusion, 269 and 301 μg mL(-1), respectively. Regarding phenolic compounds, luteolin and apigenin showed the highest capacity to inhibit the phosphorylation of VEGFR-2, leading us to believe that these compounds are involved in the activity revealed by the methanolic extract.

In vivo antioxidant activity of phenolic compounds: facts and gaps

Numerous diseases have been related with free radicals overproduction and oxidative stress. Botanical preparations possess a multitude of bioactive properties, including antioxidant potential, which has been mainly related with the presence of phenolic compounds. However, the mechanisms of action of these phytochemicals, in vivo effects, bioavailability and bio-efficacy still need research. Scope and Approach: The present report aims to provide a critical review on the aspects related with the in vivo antioxidant activity of phenolic extracts and compounds from plant origin. Key findings: Biological functions beyond the human metabolism were discussed, comparing in vivo vs. in vitro studies, as also focusing the conditioning factors for phenolic compounds bioavailability and bio-efficacy. Furthermore, an upcoming perspective about the use of phytochemicals as life expectancy promoters and anti-aging factors in human individuals was provided. Conclusions: Overall, and despite all of those advances, the study of the biological potential of numerous natural matrices still remains a hot topic among the scientific community. In fact, the available knowledge about the responsible phytochemicals for the biological potential, their mechanisms of action, the establishment of therapeutic and prophylactic doses, and even the occurrence of biochemical inter-relations, is considerable scarce.

Extraction, identification, fractionation and isolation of phenolic compounds in plants with hepatoprotective effects

The liver is one of the most important organs of human body, being involved in several vital functions and regulation of physiological processes. Given its pivotal role in the excretion of waste metabolites and drugs detoxification, the liver is often subjected to oxidative stress that leads to lipid peroxidation and severe cellular damage. The conventional treatments of liver diseases such as cirrhosis, fatty liver and chronic hepatitis are frequently inadequate due to side effects caused by hepatotoxic chemical drugs. To overcome this problematic paradox, medicinal plants, owing to their natural richness in phenolic compounds, have been intensively exploited concerning their extracts and fraction composition in order to find bioactive compounds that could be isolated and applied in the treatment of liver ailments. The present review aimed to collect the main results of recent studies carried out in this field and systematize the information for a better understanding of the hepatoprotective capacity of medicinal plants in in vitro and in vivo systems. Generally, the assessed plant extracts revealed good hepatoprotective properties, justifying the fractionation and further isolation of phenolic compounds from different parts of the plant. Twenty-five phenolic compounds, including flavonoids, lignan compounds, phenolic acids and other phenolic compounds, have been isolated and identified, and proved to be effective in the prevention and/or treatment of chemically induced liver damage. In this perspective, the use of medicinal plant extracts, fractions and phenolic compounds seems to be a promising strategy to avoid side effects caused by hepatotoxic chemicals.

Ceratonia siliqua L. hydroethanolic extract obtained by ultrasonication: antioxidant activity, phenolic compounds profile and effects in yogurts functionalized with their free and microencapsulated forms

Bioactive extracts were obtained from powdered carob pulp through an ultrasound extraction process and then evaluated in terms of antioxidant activity. Ten minutes of ultrasonication at 375 Hz were the optimal conditions leading to an extract with the highest antioxidant effects. After its chemical characterization, which revealed the preponderance of gallotannins, the extract (free and microencapsulated) was incorporated in yogurts. The microspheres were prepared using an extract/sodium alginate ratio of 100/400 (mg mg(-1)) selected after testing different ratios. The yogurts with the free extract exhibited higher antioxidant activity than the samples added with the encapsulated extracts, showing the preserving role of alginate as a coating material. None of the forms significantly altered the yogurt's nutritional value. This study confirmed the efficiency of microencapsulation to stabilize functional ingredients in food matrices maintaining almost the structural integrity of polyphenols extracted from carob pulp and furthermore improving the antioxidant potency of the final product.

Preconcentration of polar phenolic compounds from water samples and soil extract by liquid-phase microextraction and determination via liquid chromatography with ultraviolet detection.

2016

Study of extraction conditions for phenolic compounds from Strawberry fruits

Strawberries are an important source of phytochemicals, namely vitamins and phenolic compounds such as anthocyanins and tannins with antioxidant properties [1]. The yield and phenolic content of natural extracts are dependent on the conditions used for extraction [2]. In the present work three different types of extracting solutions (methanol, ethanol:water and aceton:water), two times of extraction (15 and 60 min) and three ratios of solid/solvent (5/25, 5/50 and 5/100 g/mL) were tested in order to evaluate the efficiency of the extraction of phenolic compounds. Phenolic compounds were determined by Folin-Ciocalteu method [3]. Each assay was performed in triplicate. Regarding the extraction solution, it was possible to observe a slight tendency towards a higher efficiency of acetone:water (AcO:H2O, 60:40), but the differences mioght not be statistically significant. A longer time of contact, 60 min as opposed to 15 min, did not show advantages in the yield of extraction. Considering the factors under study, the results obtained showed that volume of extraction solution was the parameter that most influenced the values obtained. Using a higher volume lead to an increase in the amount of phenolic compounds extracted, in a more pronounced way for 15 min of extraction. For a volume of 25 mL the amount of phenolic compounds quantified ranged from 2.13-2.41 mg GAE/g, and increased 30-68% when it was used 50 mL of solution. Using 100 mL of solution, it was extracted twice as double of phenolic compounds. In case of 60 min, the amount of phenolic compounds quantified in samples obtained with 25 mL of solution ranged from 2.32-2.97 mg GAE/g, and increased for 2.43-4.27 mg GAE/g and 3.98-4.68 mg GAE/g when was used 50 and 100 mL, respectively.

Antioxidant properties of kilned and roasted malts

Compounds possessing antioxidant activity play a crucial role in delaying or preventing lipid oxidation in foods and beverages during processing and storage. Such reactions lead to loss of product quality, especially as a consequence of off-flavor formation. The aim of this study was to determine the antioxidant activity of kilned (standard) and roasted (speciality) malts in relation to phenolic compounds, sugars, amino acids, and color [assessed as European Brewing Convention units (degrees EBC) and absorbance at 420 nm]. The concentrations of sugars and amino acids decreased with the intensity of the applied heat treatment, and this was attributed to the extent of the Maillard reaction, as well as sugar caramelization, in the highly roasted malts. Proline, followed by glutamine, was the most abundant free amino/imino acid in the malt samples, except those that were highly roasted, and maltose was the most abundant sugar in all malts. Levels of total phenolic compounds decreased with heat treatment. Catechin and ferulic acid were the most abundant phenolic compounds in the majority of the malts, and amounts were highest in the kilned samples. In highly roasted malts, degradation products of ferulic acid were identified. Antioxidant activity increased with the intensity of heating, in parallel with color formation, and was significantly higher for roasted malts compared to kilned malts. In kilned malts, phenolic compounds were the main identified contributors to antioxidant activity, with Maillard reaction products also playing a role. In roasted malts, Maillard reaction products were responsible for the majority of the antioxidant activity.

Antioxidant properties of kilned and roasted malts

Compounds possessing antioxidant activity play a crucial role in delaying or preventing lipid oxidation in foods and beverages during processing and storage. Such reactions lead to loss of product quality, especially as a consequence of off-flavor formation. The aim of this study was to determine the antioxidant activity of kilned (standard) and roasted (speciality) malts in relation to phenolic compounds, sugars, amino acids, and color [assessed as European Brewing Convention units (degrees EBC) and absorbance at 420 nm]. The concentrations of sugars and amino acids decreased with the intensity of the applied heat treatment, and this was attributed to the extent of the Maillard reaction, as well as sugar caramelization, in the highly roasted malts. Proline, followed by glutamine, was the most abundant free amino/imino acid in the malt samples, except those that were highly roasted, and maltose was the most abundant sugar in all malts. Levels of total phenolic compounds decreased with heat treatment. Catechin and ferulic acid were the most abundant phenolic compounds in the majority of the malts, and amounts were highest in the kilned samples. In highly roasted malts, degradation products of ferulic acid were identified. Antioxidant activity increased with the intensity of heating, in parallel with color formation, and was significantly higher for roasted malts compared to kilned malts. In kilned malts, phenolic compounds were the main identified contributors to antioxidant activity, with Maillard reaction products also playing a role. In roasted malts, Maillard reaction products were responsible for the majority of the antioxidant activity.

Antioxidant activity of selected phenols and herbs used in diets for medical conditions.

The antioxidant capacity of some herbs used in dietology practice was determined by the DPPH free radical method, which was calibrated with ascorbic acid. Partially hydrophilic phenolic compounds are the most active compounds in plants, and therefore water was used as the extraction agent. Besides antioxidant capacity, the content of total phenolic compounds was also measured and a strong correlation between these two variables was found. The extracts of lemon balm (Melissa officinalis L.), peppermint (Mentha x piperita L.), oregano (Origanum vulgare L.), Greek oregano (Origanum heracleoticum L.), sage (Salvia officinalis L.) and winter savory (Satureja montana L.) showed very significant activity. It was comparable with the activity of green tea in the case of oregano and peppermint. Lower activity was observed in the case of rosemary (Rosmarinus officinalis L.), marjoram (Majorana hortensis), hyssop (Hyssopus officinalis L.), sweet basil (Ocimum basilicum), and lovage (Levisticum officinale Koch.). The inhibitory activity of the herb extracts was monitored also during the autooxidation of lard. Very high antioxidant capacity was observed mainly in sage samples, but also in marjoram and Greek oregano. The extracts of peppermint, oregano, rosemary, winter savory, lemon balm and hyssop showed middle activity comparable to that of alpha-tocopherol. The antioxidant capacity of sweet basil and lovage was insignificant.