Structure-function relationships in (poly)phenol-enzyme binding: Direct inhibition of human salivary and pancreatic α-amylases

(Poly)phenols inhibit α-amylase by directly binding to the enzyme and/or by forming starch-polyphenol complexes. Conventional methods using starch as the substrate measure inhibition from both mechanisms, whereas the use of shorter oligosaccharides as substrates exclusively measures the direct interaction of (poly)phenols with the enzyme. In this study, using a chromatography-based method and a short oligosaccharide as the substrate, we investigated the detailed structural prerequisites for the direct inhibition of human salivary and pancreatic α-amylases by over 50 (poly)phenols from the (poly)phenol groups: flavonols, flavones, flavanones, flavan-3-ols, polymethoxyflavones, isoflavones, anthocyanidins and phenolic acids. Despite being structurally very similar (97% sequence homology), human salivary and pancreatic α-amylases were inhibited to different extents by the tested (poly)phenols. The most potent human salivary α-amylase inhibitors were luteolin and pelargonidin, while the methoxylated anthocyanidins, peonidin and petunidin, significantly blocked pancreatic enzyme activity. B-ring methoxylation of anthocyanidins increased inhibition against both human α-amylases while hydroxyl groups at C3 and B3' acted antagonistically in human salivary inhibition. C4 carbonyl reduction, or the positive charge on the flavonoid structure, was the key structural feature for human pancreatic inhibition. B-ring glycosylation did not affect salivary enzyme inhibition, but increased pancreatic enzyme inhibition when compared to its corresponding aglycone. Overall, our findings indicate that the efficacy of interaction with human α-amylase is mainly influenced by the type and placement of functional groups rather than the number of hydroxyl groups and molecular weight.

Olea europaea L. leaf extract mitigates pulmonary inflammation and tissue destruction in Wistar rats induced by concurrent exposure to noise and toluene

This study aimed to investigate the effects of combined exposure to noise (85 dB(A)) and inhaled Toluene (300 ± 10 ppm) on rat lung health. It also aimed to assess the potential therapeutic effects of Olea europaea L. leaves extract (OLE) (40 mg/kg/day) using biochemical, histopathological, and immunohistochemical (IHC) analyses, as well as determination of pro-inflammatory cytokines (TNF-α and IL-1β), and in silico Docking studies. The experiment involved forty-two male Wistar rats divided into seven groups, each exposed to a 6-week/6-hour/day regimen of noise and Toluene. The groups included a control group, rats co-exposed to noise and Toluene, and rats co-exposed to noise and Toluene treated with OLE for different durations. The results indicated that noise and Toluene exposure led to structural damage in lung tissue, oxidative harm, and increased levels of pro-inflammatory cytokines (TNF-α and IL-1β). However, the administration of OLE extract demonstrated positive effects in mitigating these adverse outcomes. OLE treatment reduced lipid peroxidation and enhanced the activities of catalase and superoxide dismutase, indicating its anti-oxidant properties. Furthermore, OLE significantly decreased the levels of pro-inflammatory cytokines compared to the groups exposed to noise and Toluene without OLE treatment. Moreover, the in silico investigation substantiated a robust affinity between COX-2 and OLE components, affirming the anti-inflammatory activity. Overall, our findings suggest that OLE possesses anti-inflammatory and anti-oxidative properties that mitigate the adverse effects of concurrent exposure to noise and Toluene.

A polyphenol-rich plant extract prevents hypercholesterolemia and modulates gut microbiota in western diet-fed mice

Introduction

Totum-070 is a combination of five plant extracts enriched in polyphenols to target hypercholesterolemia, one of the main risk factors for cardiovascular diseases. The aim of this study was to investigate the effects of Totum-070 on cholesterol levels in an animal model of diet-induced hypercholesterolemia.

Methods

C57BL/6JOlaHsd male mice were fed a Western diet and received Totum-070, or not, by daily gavage (1g/kg and 3g/kg body weight) for 6 weeks.

Results

The Western diet induced obesity, fat accumulation, hepatic steatosis and increased plasma cholesterol compared with the control group. All these metabolic perturbations were alleviated by Totum-070 supplementation in a dose-dependent manner. Lipid excretion in feces was higher in mice supplemented with Totum-070, suggesting inhibition of intestinal lipid absorption. Totum-070 also increased the fecal concentration of short chain fatty acids, demonstrating a direct effect on intestinal microbiota.

Discussion

The characterization of fecal microbiota by 16S amplicon sequencing showed that Totum-070 supplementation modulated the dysbiosis associated with metabolic disorders. Specifically, Totum-070 increased the relative abundance of Muribaculum (a beneficial bacterium) and reduced that of Lactococcus (a genus positively correlated with increased plasma cholesterol level). Together, these findings indicate that the cholesterol-lowering effect of Totum-070 bioactive molecules could be mediated through multiple actions on the intestine and gut microbiota.

Olive Leaf Tea Impact on Postprandial Glycemia: A Randomized Cross-Over Trial

This study investigates the effect of olive leaf tea (OLT) on postprandial glycemia in healthy volunteers when ingested with a high-carbohydrate meal, compared with a placebo tea (CON). Healthy adults participated in a double-blind, randomized, placebo-controlled, and cross-over design trial receiving a high-rich carbohydrate meal with either 250 mL of OLT or CON at two different times after a washout period. The sequence order was randomized at a ratio of 1:1. Capillary blood glucose was measured in a 2 h period after ingestion. Eighteen participants were initially randomized. Of these, thirteen completed the trial and were analyzed. The consumption of OLT resulted in a delay in peak time (48.5 ± 4.2 min vs. 35.7 ± 4.0 min, p = 0.03) and a significant increase in glucose area under the curve compared to placebo (14,502.7 ± 640.8 vs. 13,633.3 ± 869.4 mg/dL·min, p = 0.03). Results are depicted as mean ± SEM. The OLT and CON palatability were generally well accepted. No adverse effects were reported. OLT did not ameliorate a glycemic curve induced by carbohydrate-rich meal ingestion, suggesting that at least when ingested acutely in a single meal, OLT does not have antihyperglycemic effects. Future studies should account for chronic consumption providing a better understanding of glycemic regulation over time.

Antidiabetic Potential and Antioxidant Activity of Olea europaea subsp. Cuspidata (Indian Olive) Seed Extracts

The aim of the present study was to evaluate the antioxidant and antidiabetic potential of Indian olive seed extracts. Plant seeds were sequentially extracted with n-hexane, chloroform, methanol, and water. 2,2-Diphenyl-1-picrylhydrazyl (DPPH) scavenging and alpha-amylase inhibitory activities of extracts were carried out. Olea europaea methanolic extract (MEOE) and aqueous extract (AEOE) were orally administered to normoglycemic and alloxan-treated diabetic rats so as to determine their hypoglycemic effect. High-performance liquid chromatography (HPLC) analysis showed gallic acid, ferulic acid, quercetin, and vanillic acid in MEOE. It was found that the methanolic and aqueous extracts exhibited the maximum DPPH and alpha-amylase inhibition activities, respectively. MEOE and AEOE exerted a significant decline in the fasting blood sugar in diabetic animals (p < 0.05); however, they did not cause hypoglycemia in nondiabetic animals. Treatment with MEOE and AEOE reduced the aggravated liver and kidney function biomarkers. Aggravated levels of oxidative stress biomarkers including superoxide dismutase (SOD), catalase (CAT), reduced glutathione (GSH), and malondialdehyde (MDA) were restored by treatment with MEOE. Moreover, MEOE improved the count of islets of Langerhans in the pancreas, fatty changes, and enlarged sinusoidal spaces in the liver and necrosis of the glomerulus and tubular cells of the kidney in diabetic rats. This study showed that the African olive seed extract effectively managed experimental diabetes and restored the normal functions and histology of the liver and kidney in diabetic rats through the reduction of oxidative stress.

Assessment of seasonal variation of the bioactive oleuropein in Olea europaea L. leaves cultivated in Saudi Arabia

Plants secondary metabolites undergoes qualitative and quantitative variation due to environmental and growth factors. It is a crucial factor to select the proper time for collection of medicinal plants to assure maximum content of active components reflected as maximum efficacy. Olive leaves (Olea europaea L.) are known traditionally for their antidiabetic effect. The secoiridoid glycoside oleuropein is the main active component of Olive leaves responsible for the biological activity. The current study was conducted to monitor the seasonal variation of oleuropein in Olives leaves collected from the same location. To achieve this goal a validated HPLC method following the ICH guidelines was established. Separation was conducted using RP18 column and a mobile phase consisted of ultrapure water containing 20% acetonitrile and 1% acetic acid. Detection was performed at 254 nm with 1 mL/min flow rate. The method was simple, linear, accurate, precise, specific and robust. The analyses revealed considerable variations in the level of oleuropein throughout the year. This variation cannot be explained by temperature variation during the year. Two points of high levels of oleuropein were detected prior to flowering stage and ripening of the fruits. The levels of growth regulators most likely is responsible for the increased production of oleuropein. It is recommended that leaves intended for medicinal use to be collected during the fruiting stage prior to fruit ripening.

Therapeutic Properties and Use of Extra Virgin Olive Oil in Clinical Nutrition: A Narrative Review and Literature Update

Extra virgin olive oil (EVOO) is a cornerstone of the Mediterranean diet (MedD). In this narrative review, we synthesize and illustrate the various characteristics and clinical applications of EVOO and its components—such as oleic acid, hydroxytyrosol, and oleuropein—in the field of clinical nutrition and dietetics. The evidence is split into diet therapy, oleic acid-based enteral nutrition formulations and oral supplementation formulations, oleic acid-based parenteral nutrition, and nutraceutical supplementation of minor components of EVOO. EVOO has diverse beneficial health properties, and current evidence supports the use of whole EVOO in diet therapy and the supplementation of its minor components to improve cardiovascular health, lipoprotein metabolism, and diabetes mellitus in clinical nutrition. Nevertheless, more intervention studies in humans are needed to chisel specific recommendations for its therapeutic use through different formulations in other specific diseases and clinical populations.

Oleanolic Acid: Extraction, Characterization and Biological Activity

Oleanolic acid, a pentacyclic triterpenoid ubiquitously present in the plant kingdom, is receiving outstanding attention from the scientific community due to its biological activity against multiple diseases. Oleanolic acid is endowed with a wide range of biological activities with therapeutic potential by means of complex and multifactorial mechanisms. There is evidence suggesting that oleanolic acid might be effective against dyslipidemia, diabetes and metabolic syndrome, through enhancing insulin response, preserving the functionality and survival of β-cells and protecting against diabetes complications. In addition, several other functions have been proposed, including antiviral, anti-HIV, antibacterial, antifungal, anticarcinogenic, anti-inflammatory, hepatoprotective, gastroprotective, hypolipidemic and anti-atherosclerotic activities, as well as interfering in several stages of the development of different types of cancer; however, due to its hydrophobic nature, oleanolic acid is almost insoluble in water, which has led to a number of approaches to enhance its biopharmaceutical properties. In this scenario, the present review aimed to summarize the current knowledge and the research progress made in the last years on the extraction and characterization of oleanolic acid and its biological activities and the underlying mechanisms of action.

Olive Leaf Extract Supplementation Combined with Calorie-Restricted Diet on Reducing Body Weight and Fat Mass in Obese Women: Result of a Randomized Control Trial

The present trial aims to evaluate a supplementation of the olive leaf extract (OLE) in adjunct with a weight loss diet on anthropometric indices, glycemic indices, lipid profile, as well as the level of adipokines, and free fatty acid in obese women. We carried out an 8-week randomized, placebo-controlled, double-blind, parallel-group, clinical trial. The participants were randomly stratified according to age and they were assigned to one of the two study groups: Standard weight loss diet (estimated daily energy requirements minus 500 kcal) + OLE supplementation (n = 35) in intervention group or Standard weight loss diet (estimated daily energy requirements minus 500 kcal) + placebo (n = 35) in placebo group. The study groups were homogeneous regarding the baseline age, height, weight, body mass index (BMI), waist circumferences, married status, and physical activity levels (p > 0.05). The results of analysis of covariance presented significant decreases in BMI, fat mass, and body weight in the OLE group compared to those in the placebo group (p < 0.05). At the end of the study, the serum levels of fasting blood sugar, insulin, low-density lipoprotein cholesterol, total cholesterol, leptin, fatty free acid, and homeostasis model assessment–insulin resistance significantly decreased, and serum levels of high-density lipoprotein cholesterol and adiponectin elevated in the intervention group (p < 0.05). Based on results it seems that the addition of OLE to a hypocaloric diet for 8-week compared with a hypocaloric diet alone may be more effective in modifying obesity and metabolic risk factors.

Possible Synergistic Antidiabetic Effects of Quantified Artemisia judaica Extract and Glyburide in Streptozotocin-Induced Diabetic Rats via Restoration of PPAR-α mRNA Expression

Simple Summary

A considerable number of diabetic patients are in favour of using oral antidiabetic drugs in combination with certain herbs instead of using oral antidiabetic drugs alone. Artemisia judaica (AJ) is one of the herbs documented to have antidiabetic effects. This study examined the effect of using combination of A. judaica extract (AJE) and the oral hypoglycemic drug glyburide (GLB, 5 mg/kg) on diabetic rats. Fasting blood glucose (FBG), insulin levels, glycated hemoglobin (HbA1c) percentage, serum lipid profile, and oxidative stress biomarkers were estimated. The histopathological examination of the pancreas and the immunohistochemical analysis of anti-insulin, anti-glucagon, and anti-somatostatin protein expressions were also performed. The analysis of the hepatic mRNA expression of peroxisome proliferator-activated receptor α (PPAR-α) and nuclear factor erythroid 2-related factor-2 (Nrf2) genes was performed using quantitative reverse transcription-polymerase chain reaction (qRT-PCR). Combination of GLB and 500 mg/kg of AJE highly improved FBG, insulin levels, HbA1c, and lipid profile in blood when compared with GLB monotherapy. Furthermore, GLB plus 500 mg/kg of AJE combination was the most successful in restoring insulin content in the β-cells and diminished the levels of glucagon and somatostatin of the α- and δ-endocrine cells in the pancreatic islets, restoring PPAR-α and Nrf2 mRNA expression in the liver. In conclusion, these data indicate that GLB plus 500 mg/kg of AJE combination gives greater glycemic improvement than GLB monotherapy.

Abstract

Several members of the genus Artemisia are used in both Western and African traditional medicine for the control of diabetes. A considerable number of diabetic patients switch to using oral antidiabetic drugs in combination with certain herbs instead of using oral antidiabetic drugs alone. This study examined the effect of Artemisia judaica extract (AJE) on the antidiabetic activity of glyburide (GLB) in streptozotocin (STZ)-induced diabetes. Forty-two male Wistar rats were divided into seven equal groups. Normal rats of the first group were treated with the vehicle. The diabetic rats in the second–fifth groups received vehicle, GLB (5 mg/kg), AJE low dose (250 mg/kg), and AJE high dose (500 mg/kg), respectively. Groups sixth–seventh were treated with combinations of GLB plus the lower dose of AJE and GLB plus the higher dose of AJE, respectively. All administrations were done orally for eight weeks. Fasting blood glucose (FBG) and insulin levels, glycated hemoglobin (HbA1c) percentage, serum lipid profile, and biomarkers of oxidative stress were estimated. The histopathological examination of the pancreas and the immunohistochemical analysis of anti-insulin, anti-glucagon, and anti-somatostatin protein expressions were also performed. The analysis of the hepatic mRNA expression of PPAR-α and Nrf2 genes were performed using quantitative RT-PCR. All treatments significantly lowered FBG levels when compared with the STZ-control group with the highest percentage reduction exhibited by the GLB plus AJE high dose combination. This combination highly improved insulin levels, HbA1c, and lipid profile in blood of diabetic rats compared to GLB monotherapy. In addition, all medicaments restored insulin content in the β-cells and diminished the levels of glucagon and somatostatin of the α- and δ-endocrine cells in the pancreatic islets. Furthermore, the GLB plus AJE high dose combination was the most successful in restoring PPAR-α and Nrf2 mRNA expression in the liver. In conclusion, these data indicate that the GLB plus AJE high dose combination gives greater glycemic improvement in male Wistar rats than GLB monotherapy.

Effects of Totum-63 on glucose homeostasis and postprandial glycemia: a translational study

Global prevalence of type 2 diabetes (T2D) is rising and may affect 700 million people by 2045. Totum-63 is a polyphenol-rich natural composition developed to reduce the risk of T2D. We first investigated the effects of Totum-63 supplementation in high-fat diet (HFD)-fed mice for up to 16 wk and thereafter assessed its safety and efficacy (2.5 g or 5 g per day) in 14 overweight men [mean age 51.5 yr, body mass index (BMI) 27.6 kg·m^-2] for 4 wk. In HFD-fed mice, Totum-63 reduced body weight and fat mass gain, whereas lean mass was unchanged. Moreover, fecal energy excretion was higher in Totum-63-supplemented mice, suggesting a reduction of calorie absorption in the digestive tract. In the gut, metagenomic analyses of fecal microbiota revealed a partial restoration of HFD-induced microbial imbalance, as shown by principal coordinate analysis of microbiota composition. HFD-induced increase in HOMA-IR score was delayed in supplemented mice, and insulin response to an oral glucose tolerance test was significantly reduced, suggesting that Totum-63 may prevent HFD-related impairments in glucose homeostasis. Interestingly, these improvements could be linked to restored insulin signaling in subcutaneous adipose tissue and soleus muscle. In the liver, HFD-induced steatosis was reduced by 40% (as shown by triglyceride content). In the subsequent study in men, Totum-63 (5 g·day^-1) improved glucose and insulin responses to a high-carbohydrate breakfast test (84% kcal carbohydrates). It was well tolerated, with no clinically significant adverse events reported. Collectively, these data suggest that Totum-63 could improve glucose homeostasis in both HFD-fed mice and overweight individuals, presumably through a multitargeted action on different metabolic organs.NEW & NOTEWORTHY Totum-63 is a novel polyphenol-rich natural composition developed to reduce the risk of T2D. Totum-63 showed beneficial effects on glucose homeostasis in HFD-fed mice, presumably through a multitargeted action on different metabolic organs. Totum-63 was well tolerated in humans and improved postprandial glucose and insulin responses to a high-carbohydrate breakfast test.

Phenolic profile, antioxidant and enzyme inhibitory activities of underutilized spices from Central Africa

The aim of the present study is to evaluate phytochemical profile, antioxidant and enzyme inhibitory activity of some underutilized Cameroon spice extracts, viz. The fruit of Xylopia africana, the fruit and the bulb of Aframomum sulcatum; and the bark of Hypodaphnis zenkeri. Four different solvent combinations were used for extraction of phytochemicals. Highest total polyphenol, flavonoid and tannin contents were observed in X. africana extract 10.32 ± 0.49 g gallic acid eq/100 g of dry matter, 146.66 ± 4.15 mg quercetin eq/100 g of dry matter, 452.44 ± 2.7 mg tannic acid eq/100 g spices dry matter. Methanol extracts revealed the presence of chlorogenic acid (0.790-4.312), vanillic acid (0.830-19.768), epicatechin (25.386-34.707), p-coumaric acid (1.127-12.652), protosynapic acid (0.221-186.562) and T-cinnamic acid (3.794-52.58) mg/100 g dry spice by HPLC analysis. Extracts of X. africana and H. zenkeri exhibited higher antioxidant activity: DPPH (182.24 ± 2.41 mg ascorbic acid eq/g dry spice), ABTS (9.247 ± 0.004 g trolox eq/100 g spice), hydroxyl free radicals (729.27 ± 3.07 mg mannitol eq/100 g spice) and reducing power (2.351 ± 0.002 g ascorbic acid equivalent/100 g spice). Positive and high correlations existed between the antioxidant activity of extracts obtained with different methods and their corresponding phenolic content. Extract of A. sulcatum highly inhibited porcine pancreatic lipase whereas, X. africana and H. zenkeri extracts highly inhibited α-amylase (98.82 and 99.54% respectively). These spices could be utilized as natural antioxidant sources for the management oxidative stress, lipid and carbohydrate metabolism related diseases.

Olive Tree in Circular Economy as a Source of Secondary Metabolites Active for Human and Animal Health Beyond Oxidative Stress and Inflammation

Extra-virgin olive oil (EVOO) contains many bioactive compounds with multiple biological activities that make it one of the most important functional foods. Both the constituents of the lipid fraction and that of the unsaponifiable fraction show a clear action in reducing oxidative stress by acting on various body components, at concentrations established by the European Food Safety Authority's claims. In addition to the main product obtained by the mechanical pressing of the fruit, i.e., the EVOO, the residual by-products of the process also contain significant amounts of antioxidant molecules, thus potentially making the Olea europea L. an excellent example of the circular economy. In fact, the olive mill wastewaters, the leaves, the pomace, and the pits discharged from the EVOO production process are partially recycled in the nutraceutical and cosmeceutical fields also because of their antioxidant effect. This work presents an overview of the biological activities of these by-products, as shown by in vitro and in vivo assays, and also from clinical trials, as well as their main formulations currently available on the market.

Attenuation of protein glycation by functional polyphenolics of dragon fruit (Hylocereus polyrhizus); an in vitro and in silico evaluation

Chronic hyperglycemia and oxidative stress promote non-enzymatic glycation that leads to the production of advanced glycation end products (AGEs). AGEs casue significant damage to physiological proteins which result in several complications. The scenario also corresponds to the chronic consumption of a diet rich in AGEs. Despite understanding these mechanisms at the molecular level, the discovery of new drugs for these complications is under progress. Natural compounds might have great therapeutic potential for treating glycative consequences. In view of this, the study aimed to evaluate fruit extracts of Hylocereus polyrhizus towards determining its phenolics and flavonoid contents, as well as assessing it's in vitro antiglycative potential through the use of multistage glycation markers (early, intermediate and end stage products of β-aggregation) in sugar-protein model. In vitro hypoglycemic activity of H. polyrhizus extracts was evaluated through α-amylase and α glucosidase inhibitory activities. In vitro antioxidant potential of the fruit extracts was also examined against different free radical types including DPPH and ABTS. Among the different in vitro assays performed, methanolic and acetone extracts of the fruit, with higher phenolics and flavonoid content, have exerted significant antiglycation and antioxidant activities than other extracts namely aqueous, ethanol, hydro-ethanol, hydro-methanol, and petroleum ether. Ultra-Performance Liquid Chromatography coupled with Electrospray Ionization Mass Spectrometry (UPLC-ESI-MS/MS) analysis was employed to identify active polyphenolics that may be responsible for the antiglycative potential of H. polyrhizus. The analysis revealed some high-profile compounds that have well documented for their therapeutic benefits. Additionally, In silico analysis also showed the possible connection between identified compounds and mechanisms of action. 4- Prenylresveratrol, Vicenin, and Luteolin had observed as effectively interact with target protein in molecular docking analysis. This suggests H. polyrhizus as a good source of anti-glycation and antioxidants that may have potential applications for the treatment and prevention of glycation associated diabetic and aging complications.

Sephadex® LH-20, Isolation, and Purification of Flavonoids from Plant Species: A Comprehensive Review

Flavonoids are considered one of the most diverse phenolic compounds possessing several valuable health benefits. The present study aimed at gathering all correlated reports, in which Sephadex^® LH-20 (SLH) has been utilized as the final step to isolate or purify of flavonoid derivatives among all plant families. Overall, 189 flavonoids have been documented, while the majority were identified from the Asteraceae, Moraceae, and Poaceae families. Application of SLH has led to isolate 79 flavonols, 63 flavones, and 18 flavanones. Homoisoflavanoids, and proanthocyanidins have only been isolated from the Asparagaceae and Lauraceae families, respectively, while the Asteraceae was the richest in flavones possessing 22 derivatives. Six flavones, four flavonols, three homoisoflavonoids, one flavanone, a flavanol, and an isoflavanol have been isolated as the new secondary metabolites. This technique has been able to isolate quercetin from 19 plant species, along with its 31 derivatives. Pure methanol and in combination with water, chloroform, and dichloromethane have generally been used as eluents. This comprehensive review provides significant information regarding to remarkably use of SLH in isolation and purification of flavonoids from all the plant families; thus, it might be considered an appreciable guideline for further phytochemical investigation of these compounds.

Deriving valorization of phenolic compounds from olive oil by-products for food applications through microencapsulation approaches: a comprehensive review

Nowadays, olive oil consumption is correlated to many health benefits, essentially due to the presence of antioxidants, especially phenolic compounds, which fostered its intensive production worldwide. During olive oil extraction, through continuous or discontinuous processes, many olive oil by-products are generated. These by-products constitute an environmental problem regarding its management and disposal. They are phytotoxic and biotoxic due to their high content of phenolic compounds, presenting contrastingly relevant health benefits due to their potent radical scavenging activities. In the framework of the disposal and management of olive oil by-products, treatment, and valorization approaches are found. As currently, the majority of the valorization techniques applied have a null market value, alternative strategies for the obtainment of innovative products as fortified foods are being investigated. The recovery and valorization strategies of olive oil by-products may comprise extraction and further encapsulation of bioactive compounds, as an innovative valorization blueprint of phenolic compounds present in these by-products. The majority of phenolic compounds present in olive oil by-products possess limited application on the food industry since they are promptly amended by environmental factors like temperature, pH, and light. Consequently, they must be protected previously ending in the final formulation. Prior to foods fortification with phenolic-rich extracts obtained from olive oil by-products, they should be protected through microencapsulation approaches, allowing a sustained release of phenolic compounds in the fortified foods, without losing their physicochemical properties. The combined strategies of extraction and microencapsulation will contribute to promoting the sustainability of the olive oil sector and aid the food industry to obtain reinvented added-value products.

An Acute, Placebo-Controlled, Single-Blind, Crossover, Dose-Response, Exploratory Study to Assess the Effects of New Zealand Pine Bark Extract (Enzogenol®) on Glycaemic Responses in Healthy Participants

An acute, placebo-controlled, single-blind, crossover, dose-response, exploratory study was designed to investigate the hypoglycaemic effects of New Zealand pine bark extract (Enzogenol®). Twenty-five healthy participants categorised into having a monophasic or complex (biphasic or triphasic) glucose curve shape at the control visit consumed a placebo and Enzogenol® (50 and 400 mg) on three separate occasions before an oral glucose tolerance test (OGTT). In the monophasic group, 50 and 400 mg of Enzogenol® significantly reduced the mean glucose incremental area under the curve (iAUC) compared to control 241.3 ± 20.2 vs. 335.4 ± 34.0 mmol/L·min, p = 0.034 and 249.3 ± 25.4 vs. 353.6 ± 31.5 mmol/L·min, p = 0.012, respectively. The 400 mg dose further reduced the percentage increment of postprandial glucose (%PG) 31.4% ± 7.9% vs. 47.5% ± 8.6%, p = 0.010, glucose peak 7.9 ± 0.3 vs. 8.9 ± 0.3 mmol/L, p = 0.025 and 2h-OGTT postprandial glucose (2hPG) 6.1 ± 0.3 vs. 6.7 ± 0.3 mmol/L, p = 0.027. Glucose iAUC was not significantly different in the complex group, except for reductions in %PG 28.7% ± 8.2% vs. 43.4% ± 5.9%, p = 0.012 after 50 mg dose and 27.7% ± 5.4% vs. 47.3% ± 7.2%, p = 0.025 after 400 mg dose. The results suggest that Enzogenol® may have hypoglycaemic effects in healthy participants, especially those exhibiting monophasic shapes.

A review of Algerian medicinal plants used in the treatment of diabetes

ETHNOPHARMACOLOGICAL RELEVANCE

Plants are traditionally used in Algeria to treat many disorders, including diabetes mellitus. Knowledge of the plants that are used may provide insight on their properties, for further exploration. This study reviewed all the available published and unpublished reports concerning the use of herbal medicines in the treatment of diabetes in Algeria.

AIM OF THE STUDY

To describe the plants used in Algeria to treat diabetes, as reported in the literature.

MATERIAL AND METHODS

Systematic review of ethnobotanical papers published in the medical literature, from literature databases (Pubmed, Web of Science), as well as Google, for English, French and Arabic -language publication, and a manual search of local libraries and bookshops, as well as the university repository of PhD and master's theses. The reference lists of the papers retrieved were also examined for further papers.

RESULTS

Many plants are cited in the ethnobotanical surveys, but only very few pharmacological studies were found. In the ethnobotanical surveys, 171 plants were reported, from 58 families of which the most often cited were Asteraceae, Lamiaceae and Apiaceae. The plants with the best evidence of use and activity are: Anabasis articulata (Forssk.) Moq., Trigonella foenum-graecum L., Centaurium erythraea Rafn, Artemisia herba-alba Asso, Marrubium vulgare L., Agathophora alopecuroides (Delile) Fenzl ex Bunge, Anabasis articulata (Forssk.) Moq., Hammada elegans (Bunge) Botsch., Helianthemum kahiricum Delile, Salsola baryosma (Schult.) Dandy, Salsola vermiculata L., Olea europaea L.

CONCLUSION

Traditional herbal medicines are still very much used in Algeria to control diabetes. However they are generally poorly characterized and none have been properly tested in man. There is a need for systematic evaluation of the more commonly used plants to confirm their antidiabetic activity, identify possible mechanimss of action, and recommend best use.

Suppression of Src and Syk in the NF-κB signaling pathway by Olea europaea methanol extract is leading to its anti-inflammatory effects

ETHNOPHARMACOLOGICAL RELEVANCE

Olea europaea L., (Oleaceae) has been used widely in folk medicine in the European Mediterranean islands, India, Asia, and other parts of the world. Although this plant has high ethnopharmacological value for treating inflammatory diseases, the molecular mechanisms of how it inhibits the inflammatory response are not fully understood. In this study, we sought to identify the anti-inflammatory mechanisms of this plant.

MATERIALS AND METHODS

Using macrophages, we investigated the effects of O. europaea L. methanol extract (Oe-ME) and ethanol extract (Oe-EE) on the production of inflammatory mediator nitric oxide (NO) and prostaglandin E₂ (PGE₂), the expression levels of pro-inflammatory genes and intracellular inflammatory signaling activities.

RESULTS

Oe-ME and Oe-EE suppressed the production of NO in lipopolysaccharide-(LPS-), Pam3CSK4-, and poly (I:C)-stimulated RAW264.7 cells; importantly, no cytotoxicity was observed. Oe-ME and Oe-EE reduced production of PGE₂ without exhibiting cytotoxicity. The mRNA expression levels of cyclooxygenase-2 (COX-2), inducible NO synthase (iNOS), IL-6, IL-1β, and tumor necrosis factor (TNF)-α were down-regulated by Oe-ME and Oe-EE. Nuclear fraction and whole lysate immunoblotting analyses and overexpression experiments strongly suggested that Oe-ME decreased the translocation of p65 and p50 (nuclear factors of the NF-κB subunit) as well as Src and Syk.

CONCLUSION

These results suggest that Oe-ME exerts its anti-inflammatory effects by targeting Src and Syk in the NF-κB signaling pathway.

Dietary polyphenols modulate starch digestion and glycaemic level: a review

Polyphenols, as one group of secondary metabolite, are widely distributed in plants and have been reported to show various bioactivities in recent year. Starch digestion not only is related with food industrial applications such as brewing but also plays an important role in postprandial blood glucose level, and therefore insulin resistance. Many studies have shown that dietary phenolic extracts and pure polyphenols can retard starch digestion in vitro, and the retarding effect depends on the phenolic composition and molecular structure. Besides, dietary polyphenols have also been reported to alleviate elevation of blood glucose level after meal, indicating the inhibition of starch digestion in vivo. This review aims to analyze how dietary polyphenols affect starch digestion both in vitro and in vivo. We can conclude that the retarded starch digestion in vitro by polyphenols results from inhibition of key digestive enzymes, including α-amylase and α-glucosidase, as well as from interactions between polyphenols and starch. The alleviation of postprandial hyperglycemia by polyphenols might be caused by both the inhibited starch digestion in vivo and the influenced glucose transport. Therefore, phenolic extracts or pure polyphenols may be alternatives for preventing and treating type II diabetes disease.

Chemoprotective effects of butanol fraction of Buchholzia coriacea (Capparidaceae) against type 2 diabetes and oxidative stress in male Wistar rats

Recent studies have shown that Type 2 diabetes (T2D) in rats can result through a synergy that links obesity to insulin resistance and β-cell dysfunction. The present study achieved T2D via high fructose (20%^w/v, p.o.), streptozotocin single dose (40 mg/kg, i.p.) (HFSTZ) in rats. Also, chemoprotective potential of butanol fraction of Buchholzia coriacea (BFBC) was demonstrated. Control normal and diabetic untreated (HFSTZ-induced T2D) rats received CM-cellulose (1 mg/kg, p.o.). Diabetic rats received intragastric BFBC (20, 200, 400 mg/kg), glibenclamide (0.07 mg/kg), and BFBC (200 mg/kg) plus glibenclamide treatments, respectively. 2,2-Diphenyl-1-picrylhydrazyl, nitric oxide radical, hydroxyl radical scavenging activities, and α-amylase inhibition were assessed. After 2 weeks of treatments, blood glucose levels, lipid profiles, renal and liver function, serum insulin as well as in vivo oxidative stress biomarkers were assessed. BFBC shows highest antioxidants and α-amylase inhibitory activities in vitro HFSTZ-induced T2D produced hyperglycemia (P<0.05-0.001; F = 5.26-26.47), serum hyperinsulinemia (six-folds) plus elevated lipid peroxidation levels. Similarly, there were altered lipid profiles, liver and renal biomarker enzymes plus weight loss. BFBC administration alone or in combination with glibenclamide reversed T2D symptomatologies in treated animals, and improved body weights against control diabetic rats. In vivo antioxidant activities also improved while histological sections in treated rats show reduced tissue damage in pancreas, kidneys, liver, and heart, respectively. Oleic, stearic, 2-methyl-pyrrolidine-2-carboxylic, and n-hexadecanoic acids were present in BFBC in large quantities given GC-MS analysis. Overall, data from the present study suggest chemoprotective potentials of BFBC against HFSTZ-induced T2D rats.

Olive leaves extract attenuates type II diabetes mellitus-induced testicular damage in rats: Molecular and biochemical study

Diabetes mellitus (DM) has emerged as a public healthcare problem. Sustained hyperglycemia has been linked with many complications including impaired male fertility Olive tree (Olea europaea L.) leaves have been extensively used in traditional remedies worldwide to control blood glucose level in DM. In this study, the beneficial role of olive leaves extract (OLE) was investigated to combat diabetes-induced adverse effect on testicular tissues. Thirty male Wistar rats were divided into 5 equal groups: normal control group, streptozotocin (STZ)-diabetic group and diabetic groups which were given glibenclamide (GLB) or OLE at 250 and 500 mg/kg for 9 weeks to investigate the efficiency of olive leaves extract (OLE) in reducing the deleterious effect of diabetes on the reproductive system of male rats. Rats were checked for serum glucose, insulin, testosterone and gonadotropins. Also, testicular antioxidants, epididymal sperm characteristics and testicular histopathology were assessed. Expression of the testicular steroidogenic enzymes, cholesterol side-chain cleavage enzyme (P450 scc) and 17β-hydroxysteroid dehydrogenase (17β-HSD) was examined. Moreover, androgen receptor and proliferating cell nuclear antigen (PCNA) protein immunohistochemistry were assessed in testes. STZ-induced diabetes significantly increased serum glucose. However, STZ significantly decreased serum levels of insulin, testosterone, follicle stimulating hormone (FSH) and luteinizing hormone (LH). Marked reductions in testicular antioxidants with elevated malondialdehyde (MDA) parallel with deterioration of the testicular histoarchitecture and epididymal sperm characteristics were recorded. Administration of GLB or OLE (250 and 500 mg/kg) resulted in a significant recovery of the above mentioned parameters in STZ-diabetic rats. Interestingly, OLE shows greater glycemic improvement and testicular protection than GLB with the highest percentage protection exhibited by the OLE high dose. Furthermore, OLE significantly induced testicular steroidogenesis in diabetic rat as evidenced by elevated P450 scc and 17β-HSD mRNA expression. The study proves that OLE possesses a potential protective role against diabetes-induced reproductive disorders, which may be due to its antioxidant activity and its ability to normalize testicular steroidogenesis.

Safety assessment of ethanolic extract of Olea europaea L. leaves after acute and subacute administration to Wistar rats

Olea europaea L., popularly known as olive, is a plant widely used worldwide. Its leaves, fruit and oil are extensively consumed and present important pharmacological properties. However, studies regarding the toxicity of olive leaves are still limited in the literature. Therefore, the aim of the study was to investigate acute and subacute oral toxicities of the ethanolic extract of olive leaves (EEO) in Wistar rats through histopathology and biochemical and hematological parameters. Acute toxicity was assessed using a single dose of 2000 mg/kg of EEO administered by oral gavage to male and female rats. To assess subacute toxicity, EEO was administered during 28 days at different doses (100, 200 and 400 mg/kg) to male and female rats. At the end of the experiments, the liver and kidney were removed and examined microscopically, and blood was collected for hematological and biochemical parameters. A single dose of 2000 mg/kg did not induce mortality or any signs of toxicity among the animals treated. Animals exposed to EEO during 28 days did not present sign of abnormalities. Results demonstrated that EEO did not induce toxicity after exposure to single and repeated doses. However, more studies are needed to fully understand implications for human safety.

Nutritional implications of olives and sugar: attenuation of post-prandial glucose spikes in healthy volunteers by inhibition of sucrose hydrolysis and glucose transport by oleuropein

Purpose

The secoiridoid oleuropein, as found in olives and olive leaves, modulates some biomarkers of diabetes risk in vivo. A possible mechanism may be to attenuate sugar digestion and absorption.

Methods

We explored the potential of oleuropein, prepared from olive leaves in a water soluble form (OLE), to inhibit digestive enzymes (α-amylase, maltase, sucrase), and lower [¹⁴C(U)]-glucose uptake in Xenopus oocytes expressing human GLUT2 and [¹⁴C(U)]-glucose transport across differentiated Caco-2 cell monolayers. We conducted 7 separate crossover, controlled, randomised intervention studies on healthy volunteers (double-blinded and placebo-controlled for the OLE supplement) to assess the effect of OLE on post-prandial blood glucose after consumption of bread, glucose or sucrose.

Results

OLE inhibited intestinal maltase, human sucrase, glucose transport across Caco-2 monolayers, and uptake of glucose by GLUT2 in Xenopus oocytes, but was a weak inhibitor of human α-amylase. OLE, in capsules, in solution or as naturally present in olives, did not affect post-prandial glucose derived from bread, while OLE in solution attenuated post-prandial blood glucose after consumption of 25 g sucrose, but had no effect when consumed with 50 g of sucrose or glucose.

Conclusion

The combined inhibition of sucrase activity and of glucose transport observed in vitro was sufficient to modify digestion of low doses of sucrose in healthy volunteers. In comparison, the weak inhibition of α-amylase by OLE was not enough to modify blood sugar when consumed with a starch-rich food, suggesting that a threshold potency is required for inhibition of digestive enzymes in order to translate into in vivo effects.

Olive tree (Olea europaea L.) leaf as a waste by-product of table olive and olive oil industry: a review

Research into finding new uses for by-products of table olive and olive oil industry are of great value not only to the economy but also to the environment where olives are grown and to the human health. Since leaves represent around 10% of the total weight of olives arriving at the mill, it is worth obtaining high added-value compounds from those materials for the preparation of dietary supplements, nutraceuticals, functional food ingredients or cosmeceuticals. In this review article, olive tree (Olea europaea L.) leaf is reviewed as being a potential inexpensive, renewable and abundant source of biophenols. The importance of this agricultural and industrial waste is emphasised by means of describing its availability, nutritional and therapeutic effects and studies conducted on this field. © 2017 Society of Chemical Industry.

Inhibition of key enzymes linked to type 2 diabetes by compounds isolated from Aframomum melegueta fruit

CONTEXT

The use of Aframomum melegueta K. Schum. (Zingiberaceae) fruit for treatment of diabetes has recently been established in Nigeria. However, compounds responsible for the antidiabetic action have not been identified.

OBJECTIVE

The present study carried out the bioassay-guided isolation of possible bioactive compounds responsible for the antidiabetic action of A. melegueta fruit.

MATERIALS AND METHODS

The A. melegueta fruit was sequentially extracted using ethyl acetate (EtOAc), ethanol and water, and the most active extract (EtOAc) was subjected to column chromatography on a silica gel column using solvent gradient systems of hexane (HEX):EtOAc and EtOAc:MeOH and the isolation of compounds was guided by α-glycosidase and α-amylase inhibitory activities at various concentrations (30-240 μg/mL).

RESULTS

According to the results, 3 arylalkanes, 6-paradol (1), 6-shogaol (2) and 6-gingerol (3) and a pentacyclic triterpene, oleanolic acid (4) were isolated from A. melegueta fruit. All the compounds exhibited inhibitory effects against α-amylase and α-glucosidase. 6-Gingerol (3) and oleanolic acid (4) showed higher inhibitory activity against α-amylase (IC50: 6-gingerol: 81.78 ± 7.79 μM; oleanolic acid: 91.72 ± 1.63 μM) and α-glucosidase (IC50: 6-gingerol: 21.55 ± 0.45 μM; oleanolic acid: 17.35 ± 0.88 μM) compared to the standard drug, acarbose and other isolated compounds. The kinetics of the enzyme action of the compounds showed a noncompetitive mode of inhibition.

CONCLUSION

The data of this study suggest that the 6-gingerol (3) and oleanolic acid (4) showed higher α-amylase and α-glucosidase inhibitory action and therefore could be responsible for the antidiabetic activity of A. melegueta fruit.

Bioassay-guided fractionation and identification of α-amylase inhibitors from Syzygium cumini leaves

CONTEXT

Pancreatic α-amylase and α-glucosidase inhibitors serve as important strategies in the management of blood glucose. Even though Syzygium cumini (L.) Skeels (Myrtaceae) (SC) is used extensively to treat diabetes; scientific evidence on antidiabetic effects of SC leaves is scarce.

OBJECTIVE

SC leaf extract was investigated for α-amylase inhibitory effect and continued with isolation and identification of α-amylase inhibitors.

MATERIALS AND METHODS

Bioassay-guided fractionation was conducted using in vitro α-amylase inhibitory assay (with 20-1000 μg/mL test material) to isolate the inhibitory compounds from ethyl acetate extract of SC leaves. Structures of the isolated inhibitory compounds were elucidated using 1H NMR and 13C NMR spectroscopic analysis and direct TLC and HPLC comparison with authentic samples. Study period was from October 2013 to October 2015.

RESULTS

An active fraction obtained with chromatographic separation of the extract inhibited porcine pancreatic α-amylase with an IC50 of 39.9 μg/mL. Furthermore, it showed a strong inhibition on α-glucosidase with an IC50 of 28.2 μg/mL. The active fraction was determined to be a 3:1 mixture of ursolic acid and oleanolic acid. Pure ursolic acid and oleanolic acid showed IC50 values of 6.7 and 57.4 μg/mL, respectively, against α-amylase and 3.1 and 44.1 μg/mL respectively, against α-glucosidase.

DISCUSSION AND CONCLUSIONS

The present study revealed strong α-amylase and α-glucosidase inhibitory effects of ursolic acid and oleanolic acid isolated from SC leaves for the first time validating the use of SC leaves in antidiabetic therapy.

Oleuropein improves glucose tolerance and lipid profile in rats with simultaneous renovascular hypertension and type 2 diabetes

Oleuropein mediates most of the beneficial effects of olive products. This study examined the role of oxidative stress in the effects of oleuropein on lipid profile and blood glucose in rats with simultaneous renovascular hypertension and type 2 diabetes. Eight groups (n = 7-9 each) of male Sprague-Dawley rats including a control, a type 2 diabetic, a renovascular hypertensive, a sham, a simultaneously hypertensive diabetic receiving vehicle, and 3 simultaneously hypertensive-diabetic receiving 20, 40, or 60 mg/kg/day oleuropein were used. Four weeks after treatment, blood glucose, lipid profile, and biomarkers of oxidative stress were measured, and glucose tolerance test (GTT) was performed. Simultaneously hypertensive diabetic rats had significantly higher blood pressure, blood glucose, and serum total cholesterol, low-density lipoprotein cholesterol (LDL-C), triglyceride and malondialdehyde. They also had lower serum high-density lipoprotein cholesterol, erythrocyte superoxide dismutase, and impaired glucose tolerance. Oleuropein significantly reduced blood pressure, blood glucose, and serum total cholesterol, LDL-C, triglyceride and malondoaldehyde. It also increased serum high-density lipoprotein cholesterol, erythrocyte superoxide dismutase, and improved glucose tolerance. The findings show that the model is associated with impaired glucose tolerance, and adverse lipid profile. They also show that oleuropein, partly by an antioxidant mechanism, improves glucose tolerance and changed lipid profile favorably.

Differential α-amylase/α-glucosidase inhibitory activities of plant-derived phenolic compounds: a virtual screening perspective for the treatment of obesity and diabetes

Recently, due to their biological properties, polyphenol-rich functional foods have been proposed to be unique supplementary and nutraceutical treatments for diabetes mellitus. Inhibition of α-amylase and α-glucosidase enzymes using natural products (especially polyphenols) is a novel oral policy to regulate carbohydrate metabolism and hyperglycemia. The present study aims to evaluate the α-amylase and α-glucosidase inhibitory activity of 26 polyphenols using molecular docking and virtual screening studies. The results speculate that among selected compounds caffeic acid, curcumin, cyanidin, daidzein, epicatechin, eridyctiol, ferulic acid, hesperetin, narenginin, pinoresinol, quercetin, resveratrol and syringic acid can significantly inhibit the α-glucosidase enzyme. In addition, catechin, hesperetin, kaempferol, silibinin and pelargonidin are potent α-amylase inhibitors. Therefore the primary structure of polyphenols can change the inhibitory effect versus the α-amylase and α-glucosidase enzymes. Finally, we speculate that consumption of polyphenol-rich functional foods (by considering the best dose of each compound and assessing their possible side effects) in diabetic patients may be useful for regulating carbohydrate metabolism and related disorders. The findings of the current study may also shed light on a way of generating a new class of amylase/glucosidase inhibitors that will discriminately inhibit the on-target enzymes with negligible undesired off-target side effects.

Oleanolic acid and ursolic acid as potential inhibitors of human salivary α-amylase: insights from in vitro assays and in silico simulations

It is known that inhibiting α-amylase, an important enzyme in digestion of starch and glycogen, is a useful strategy for treating disorders in carbohydrate uptake. Two natural components distributed in many fruits and plants, oleanolic acid and ursolic acid, are endowed with important pharmacological activities and wide therapeutic possibilities. Until now, only a tiny fraction of their applications have been identified and exploited. Our in vitro inhibition studies demonstrated that oleanolic acid and ursolic acid non-competitively inhibit the activity and function of human salivary α-amylase. The molecular simulations revealed that oleanolic acid and ursolic acid interact with amino acid residues within the binding pocket of human salivary α-amylase, among which the side chain of Arg195 and Asp 197 was supposed to be important in imparting the inhibitory activity of triterpenoids. The present work will provide meaningful information for future development of functional drugs for the treatment of disorders in carbohydrate metabolism. Graphical abstract This work is valuable for providing a deeper insight into the interaction mechanism of oleanolic acid and ursolic acid with α-amylase.

Olive Polyphenols and the Metabolic Syndrome

Here, the effects of consuming polyphenol-rich olive products, including olive leaves, their crude extract, and extra virgin olive oil, on aspects of the metabolic syndrome are reviewed. We have sought to summarize the available scientific evidence from dietary intervention trials demonstrating a role for these phytochemicals in ameliorating aberrant glucose metabolism, high blood pressure and elevated blood lipids, and we discuss the potential mechanisms underpinning these observations. Searches for relevant literature published in English were conducted via PubMed and Science Direct. Based on published dietary intervention studies, there is convincing evidence to show that olive polyphenols, independently of olive lipids, reduce risk factors for metabolic syndrome, in particular by improving blood sugar and blood pressure control, and in reducing low density lipoprotein oxidation. There is more limited evidence to suggest that the consumption of olive polyphenols or related products can reduce body weight and visceral fat or impede weight gain, and similarly there are some limited data suggesting improved lipid profiles. There is some mechanistic data to support observations made in human volunteers, but further work is needed in this area. The consumption of olive polyphenols within the context of a healthy pattern of food intake may, in part, explain the reduced risk of metabolic disease associated with adherence to the Mediterranean diet.

Impact of phenolic-rich olive leaf extract on blood pressure, plasma lipids and inflammatory markers: a randomised controlled trial

PURPOSE

Dietary polyphenols have been demonstrated to favourably modify a number of cardiovascular risk markers such as blood pressure (BP), endothelial function and plasma lipids. We conducted a randomised, double-blind, controlled, crossover trial to investigate the effects of a phenolic-rich olive leaf extract (OLE) on BP and a number of associated vascular and metabolic measures.

METHODS

A total of 60 pre-hypertensive [systolic blood pressure (SBP): 121-140 mmHg; diastolic blood pressure (DBP): 81-90 mmHg] males [mean age 45 (±SD 12.7 years, BMI 26.7 (±3.21) kg/m2] consumed either OLE (136 mg oleuropein; 6 mg hydroxytyrosol) or a polyphenol-free control daily for 6 weeks before switching to the alternate arm after a 4-week washout.

RESULTS

Daytime [-3.95 (±SD 11.48) mmHg, p = 0.027] and 24-h SBP [-3.33 (±SD 10.81) mmHg, p = 0.045] and daytime and 24-h DBP [-3.00 (±SD 8.54) mmHg, p = 0.025; -2.42 (±SD 7.61) mmHg, p = 0.039] were all significantly lower following OLE intake, relative to the control. Reductions in plasma total cholesterol [-0.32 (±SD 0.70) mmol/L, p = 0.002], LDL cholesterol [-0.19 (±SD 0.56) mmol/L, p = 0.017] and triglycerides [-0.18 (±SD 0.48), p = 0.008] were also induced by OLE compared to control, whilst a reduction in interleukin-8 [-0.63 (±SD 1.13) pg/ml; p = 0.026] was also detected. Other markers of inflammation, vascular function and glucose metabolism were not affected.

CONCLUSION

Our data support previous research, suggesting that OLE intake engenders hypotensive and lipid-lowering effects in vivo.

Inhibition of α-glucosidase and α-amylase by Spanish extra virgin olive oils: The involvement of bioactive compounds other than oleuropein and hydroxytyrosol

Despite the wide use of extra virgin olive oil (EVOO) to combat several diseases, the antidiabetic and anti-cholinesterase activity of Spanish EVOO have not been assessed. In order to evaluate which compounds are responsible for these activities of five Spanish EVOOs, in addition to flavonoids, we investigated for the first time the effect of the contents of carotenoids, fatty acids (FAs), and phytoprostanes (PhytoPs) on four enzymes: α-glucosidase, α-amylase, acetylcholinesterase, and butyrylcholinesterase. The extracts of these five Spanish EVOOs were found to contain three flavones, three carotenoids, six FAs, and seven classes of PhytoPs. The samples exhibited no in vitro anti-cholinesterase activity but presented strong antidiabetic activity, in the order: 'Arbequina'≈'Picual'≈'Cuquillo'>'Hojiblanca'>'Cornicabra'. The samples showed a higher in vitro hypoglycemic effect than individual or mixed standards, possibly due to interaction between multiple identified compounds and/or a very complex multivariate interaction between other factors.

Antiurolithic effect of olive oil in a mouse model of ethylene glycol-induced urolithiasis

Purpose

At present, commercially available antiurolithic drugs have more adverse effects than potential therapeutic or preventive effects with chronic use. With this in mind, the present study was designed to assess the antiurolithic effect of olive oil in a mouse model of ethylene glycol (EG)-induced urolithiasis.

Materials and Methods

Adult albino mice were divided into 6 groups. Group I was fed the vehicle only. Group II was supplemented with 0.75% EG alone in drinking water during the experimental period to initiate deposition of calcium oxalate in kidneys, which leads to urolithiasis in animals. Groups III (olive oil control group) through V were fed olive oil orally at various doses during the experimental period. Group VI received cystone (750 mg/kg). Groups IV–VI additionally received 0.75% EG in drinking water ad libitum. SPSS ver.17.0 was used for statistical analysis.

Results

The study results showed significantly higher levels of serum urea, uric acid, and creatinine (p<0.05) in group II than in groups III–VI and I. Administration of olive oil at different doses restored the elevated serum parameters in groups IV and V compared with group II. Urine and kidney calcium, oxalate, and phosphate levels in groups IV–VI were significantly lower (p<0.05) than in animals with EG-induced urolithiasis (group II). Group V mice showed a significant restoration effect on serum as well as urine and kidney parameters compared with group II.

Conclusions

Supplementation with olive oil (1.7 mL/kg body weight) reduced and prevented the growth of urinary stones, possibly by inhibiting renal tubular membrane damage due to peroxidative stress induced by hyperoxaluria.

Dietary flavonoid aglycones and their glycosides: Which show better biological significance?

The dietary flavonoids, especially their glycosides, are the most vital phytochemicals in diets and are of great general interest due to their diverse bioactivity. The natural flavonoids almost all exist as their O-glycoside or C-glycoside forms in plants. In this review, we summarized the existing knowledge on the different biological benefits and pharmacokinetic behaviors between flavonoid aglycones and their glycosides. Due to various conclusions from different flavonoid types and health/disease conditions, it is very difficult to draw general or universally applicable comments regarding the impact of glycosylation on the biological benefits of flavonoids. It seems as though O-glycosylation generally reduces the bioactivity of these compounds - this has been observed for diverse properties including antioxidant activity, antidiabetes activity, anti-inflammation activity, antibacterial, antifungal activity, antitumor activity, anticoagulant activity, antiplatelet activity, antidegranulating activity, antitrypanosomal activity, influenza virus neuraminidase inhibition, aldehyde oxidase inhibition, immunomodulatory, and antitubercular activity. However, O-glycosylation can enhance certain types of biological benefits including anti-HIV activity, tyrosinase inhibition, antirotavirus activity, antistress activity, antiobesity activity, anticholinesterase potential, antiadipogenic activity, and antiallergic activity. However, there is a lack of data for most flavonoids, and their structures vary widely. There is also a profound lack of data on the impact of C-glycosylation on flavonoid biological benefits, although it has been demonstrated that in at least some cases C-glycosylation has positive effects on properties that may be useful in human healthcare such as antioxidant and antidiabetes activity. Furthermore, there is a lack of in vivo data that would make it possible to make broad generalizations concerning the influence of glycosylation on the benefits of flavonoids for human health. It is possible that the effects of glycosylation on flavonoid bioactivity in vitro may differ from that seen in vivo. With in vivo (oral) treatment, flavonoid glycosides showed similar or even higher antidiabetes, anti-inflammatory, antidegranulating, antistress, and antiallergic activity than their flavonoid aglycones. Flavonoid glycosides keep higher plasma levels and have a longer mean residence time than those of aglycones. We should pay more attention to in vivo benefits of flavonoid glycosides, especially C-glycosides.

Identification of Predominant Phytochemical Compounds and Cytotoxic Activity of Wild Olive Leaves (Olea europaea L. ssp. sylvestris) Harvested in South Portugal

This study has been aimed at providing a qualitative and quantitative evaluation of selected phytochemicals such as phenolic acids, flavonoids, oleuropein, fatty acids profile, and volatile oil compounds, present in wild olive leaves harvested in Portugal, as well as at determining their antioxidant and cytotoxic potential against human melanoma HTB-140 and WM793, prostate cancer DU-145 and PC-3, hepatocellular carcinoma Hep G2 cell lines, as well as normal human skin fibroblasts BJ and prostate epithelial cells PNT2. Gallic, protocatechuic, p-hydroxybenzoic, vanillic acids, apigenin 7-O-glucoside, luteolin 7-O-glucoside, and rutin were identified in olive leaves. The amount of oleuropein was equal to 22.64 g/kg dry weight. (E)-Anethole (32.35%), fenchone (11.89%), and (Z)-3-nonen-1-ol (8%) were found to be the main constituents of the oil volatile fraction, whereas palmitic, oleic, and alpha-linolenic acid were determined to be dominating fatty acids. Olive leaves methanol extract was observed to exerted a significant, selective cytotoxic effect on DU-145 and PC-3 cell lines. Except the essential oil composition, evaluated wild olive leaves, with regard to their quantitative and qualitative composition, do not substantially differ from the leaves of other cultivars grown for industrial purposes and they reveal considerable antioxidant and cytotoxic properties. Thus, the wild species may prove to be suitable for use in traditional medicine as cancer chemoprevention.

Nutritional supplements modulate fluorescent protein-bound advanced glycation endproducts and digestive enzymes related to type 2 diabetes mellitus

Background

Chronic hyperglycemia enhances the formation of advanced glycation endproducts (AGEs) and reactive oxygen species (ROS), contributing to diabetic complications. Thus, controlling blood glucose levels, inhibiting the formation of AGEs and reducing ROS are key therapeutic targets in early stage type 2 diabetes.

Methods

The inhibitory effects of seven commercial liquid nutritional supplements against carbohydrate hydrolysing enzymes, α-amylase and α-glucosidase, was determined by dinitrosalicylic (DNS) reagent and p-nitrophenyl-α-D-glucopyranoside solution, respectively. Antiglycation activity was determined using the formation of fluorescent protein-bound AGEs. Total phenolic and flavonoid content and antioxidant properties (1,1-diphenyl-2-picrylhydrazyl antioxidant activity (DPPH) and ferric reducing antioxidant power (FRAP)) were determined for correlation among these components and inhibitory activities.

Results

Samoan noni juice showed the greatest inhibitory effects against α-amylase, whereas chlorophyll extracts showed the greatest inhibitory effect against α-glucosidase. Inhibition of α-glucosidase correlated with TFC (r² = 0.766; p < 0.01) and FRAP (r² = 0.750; p < 0.01) whereas no correlation was observed for α-amylase inhibition. All supplements inhibited fluorescent protein-bound AGEs, with the greatest effect exerted by Olive Leaf Extract, Blood Sugar Support (IC₅₀ = 0.5 mg/ml). The IC₅₀ values negatively correlated with TPC (r² = −0.707; p < 0.001) and DPPH scavenging activities (r² = 0.515; p < 0.05).

Conclusion

The findings of this study highlight the potential of liquid nutritional supplements in managing and treating type 2 diabetes mellitus.

Oleanolic, Ursolic, and Betulinic Acids as Food Supplements or Pharmaceutical Agents for Type 2 Diabetes: Promise or Illusion?

Oleanolic (OA), ursolic (UA), and betulinic (BA) acids are three triterpenic acids (TAs) with potential effects for treatment of type 2 diabetes (T2DM). Mechanistic studies showed that these TAs act as hypoglycemic and antiobesity agents mainly through (i) reducing the absorption of glucose; (ii) decreasing endogenous glucose production; (iii) increasing insulin sensitivity; (iv) improving lipid homeostasis; and (v) promoting body weight regulation. Besides these promising beneficial effects, it is believed that OA, UA, and BA protect against diabetes-related comorbidities due to their antiatherogenic, anti-inflammatory, and antioxidant properties. We also highlight the protective effect of OA, UA, and BA against oxidative damage, which may be very relevant for the treatment and/or prevention of T2DM. In the present review, we provide an integrative description of the antidiabetic properties of OA, UA, and BA, evaluating the potential use of these TAs as food supplements or pharmaceutical agents to prevent and/or treat T2DM.

The α-Glucosidase and α-Amylase Enzyme Inhibitory of Hydroxytyrosol and Oleuropein

To date, numerous studies have reported on the antidiabetic properties of various plant extracts through inhibition of carbohydrate-hydrolysing enzymes. The objective of this research was to evaluate the inhibitory effect of the hydroxytyrosol and the oleuropein against α-amylase and α-glucosidase. The hydroxytyrosol was purified from olive leaves. The result shows that the hydroxytyrosol had the strongest α-glucosidase inhibitory effect with IC50 values of 150 μM with mild inhibition against α-amylase. The enzyme kinetic studies, using Lineweaver-Burk indicated that, in the presence of the hydroxytyrosol, the Michaelis-Menton constant (Km) remained constant but the maximal velocity (Vmax) decreased, revealing a non-competitive type of inhibition with inhibition constants; Ki for the formation of the inhibitor-enzyme complex and Kis for the formation of the inhibitor-enzyme-substrate complex of 104.3 and 150.1 μM, respectively. On the other hand, oleuropein showedan uncompetitive inhibition. The concentrations used in this work were below cytotoxic levels observed at 400 μM. However, at 600 μM, the hydroxytyrosol significantly decreased viability of the Caco-2 cells (p < 0.05) and in the case of the oleuropein, there's an increase in cell number compared to control (p < 0.05). These results suggest that the hydroxytyrosol and oleuropein are two potential effective α-glucosidase inhibitors for management of postprandial hyperglycemia.

Efeito da incorporação de folhas de oliveira (Olea europaea L.) no desenvolvimento e qualidade da carne de frangos

Resumo Foi realizada suplementação de folhas de oliveira na ração de frangos na quantidade de 5 e 10 g de folhas/kg de ração e acompanhou-se o desempenho dos animais durante seu crescimento. Depois do abate, as coxas e sobrecoxas foram coletadas e armazenadas a 4 °C (± 1 °C) por 12 dias. Os resultados mostraram melhor conversão alimentar dos frangos que receberam dieta suplementada com 5g/kg. As coxas e sobrecoxas dos frangos que receberam folhas de oliveira apresentaram melhor estabilidade microbiológica que o controle, em que 5 g/kg inibiu o crescimento de Staphylococcus aureus, aeróbios psicrotróficos e mesófilos e 10 g/kg inibiu o crescimento de Enterococcus spp., bactérias ácido láticas, coliformes termotolerantes e totais, Pseudomonas, Clostridium perfringens e Escherichia coli (p < 0,05). Os resultados indicam a possibilidade de uso de folhas de oliveira, como suplemento alimentar, com vistas à melhoria da qualidade microbiológica da carne de frango.

Identification of compounds from high-fat and extra virgin olive oil-supplemented diets in whole mouse liver extracts and isolated mitochondria using mass spectrometry

Nonalcoholic steatohepatitis (NASH) is a fatty liver disorder that could be improved with extra virgin olive oil (EVOO) supplementation in diet. We propose the monitoring, in whole mouse liver extracts and in isolated mitochondria, of the absorption of compounds from three different diets: standard (CT), high-fat (HFD) and high-fat supplemented with EVOO (HFSO). Male mice were submitted to one of the following three diets: CT or HFD for 16 weeks or HFD for 8 weeks followed by additional 8 weeks with HFSO. Following this period, liver was extracted for histological evaluation, mitochondria isolation and mass spectrometry analyses. Diets, liver extracts and Percoll-purified mitochondria were analyzed using ESI-MS and the lipidomics approach. Morphological, histological and spectrometric results indicated a decrease in NASH severity with EVOO supplementation in comparison with animals maintained with HFD. Spectrometric data also demonstrated that some compounds presented on the diets are absorbed by the mitochondria. EVOO was shown to be a potential therapeutic alternative in food for NASH. Our results are in accordance with the proposition that the major factor that influences different responses to diets is their composition - and not only calories - especially when it comes to studies on obesity.

Traditional Uses, Phytochemistry, and Pharmacology of Olea europaea (Olive)

Aim of the Review. To grasp the fragmented information available on the botany, traditional uses, phytochemistry, pharmacology, and toxicology of Olea europaea to explore its therapeutic potential and future research opportunities. Material and Methods. All the available information on O. europaea was collected via electronic search (using Pubmed, Scirus, Google Scholar, and Web of Science) and a library search. Results. Ethnomedical uses of O. europaea are recorded throughout the world where it has been used to treat various ailments. Phytochemical research had led to the isolation of flavonoids, secoiridoids, iridoids, flavanones, biophenols, triterpenes, benzoic acid derivatives, isochromans, and other classes of secondary metabolites from O. europaea. The plant materials and isolated components have shown a wide spectrum of in vitro and in vivo pharmacological activities like antidiabetic, anticonvulsant, antioxidant, anti-inflammatory, immunomodulatory, analgesic, antimicrobial, antiviral, antihypertensive, anticancer, antihyperglycemic, antinociceptive, gastroprotective, and wound healing activities. Conclusions. O. europaea emerged as a good source of traditional medicine for the treatment of various ailments. The outcomes of phytochemical and pharmacological studies reported in this review will further expand its existing therapeutic potential and provide a convincing support to its future clinical use in modern medicine.