Determination of triterpenic acids in human serum by high-performance liquid chromatography: triterpenoid interaction with serum protein

Oleanolic acid improves antioxidant capacity and the abundance of Faecalibacterium prausnitzii in the intestine of broilers

This study investigated the effect of dietary oleanolic acid (OA) addition on broiler intestinal morphology, intestinal antioxidant capacity, changes in cecum microbiota, and the relationship between microbiota and antioxidant capacity. A total of 288 Arbor Acres broilers at 1-day-old broilers were reared, and they were randomly divided into four groups. The control and experimental groups were fed the basal diet and the basal diet supplemented with 50, 100, and 150 mg/kg OA for a total of 42 d respectively. The results showed that OA does not affect the performance of broiler chickens. The OA supplementation increased the ratio between jejunum villus height and crypt depth (P < 0.05). The expression of antioxidant enzymes (GSH-PX and CAT) and antioxidant-related genes (HO-1, NQO1, Nrf2, and CAT) was significantly increased in the jejunum and cecum (P < 0.05). In addition, jejunal T-AOC activity (P < 0.05) and cecum antioxidant-related gene GPX-1 expression (P < 0.01) were significantly increased. The expression of oxidation-related genes (NOX and ROMO1) was significantly down-regulated in both jejunum and cecum (P < 0.05). The addition of 150 mg/kg of OA increased the relative abundance of potentially beneficial bacteria and Faecalibacterium prausnitzii was significantly and positively correlated with the expression levels of antioxidant-related genes. In conclusion, the addition of OA to the diet may improve the intestinal antioxidant capacity and modulate the intestinal microbiota of broilers. Moreover, OA improved intestinal antioxidant capacity by increasing the relative abundance of F. prausnitzii.

Nanoemulsions of betulinic acid stabilized with modified phosphatidylcholine increase the stability of the nanosystems and the drug's bioavailability

Betulinic acid (BA) is a natural compound with significant potential for treating various diseases, including cancer and AIDS, and possesses additional anti-inflammatory and antibacterial properties. However, its clinical application is limited because of its low solubility in water, which impairs its distribution within the body. To overcome this challenge, nanoemulsions have been developed to improve the bioavailability of such poorly soluble drugs. This study investigated modified phosphatidylcholine (PC), where some fatty acids were replaced with conjugated linoleic acid (CLA) to stabilize BA nanoemulsions. The modified PC was used to prepare nanoemulsions with droplet sizes of up to 45 nanometers. These nanoemulsions maintained stability for 60 days at room temperature (25°C±2°C) and under refrigeration (5°C±1°C), with no signs of instability. Nanoemulsions stabilized with CLA-modified PC achieved a higher drug encapsulation rate (93.5±4.3 %) than those using natural PC (82.8±4.2 %). In an in vivo model, both nanoemulsion formulations significantly increased BA absorption, with CLA-modified PC enhancing absorption by 21.3±1.3 times and natural PC by 20±2.3 times compared to the free drug. This suggests that nanoemulsions with modified PC could improve the stability and efficacy of BA in clinical applications.

Olea europaea L. Leaves as a Source of Anti-Glycation Compounds

High concentrations of advanced glycation end products (AGEs) have been linked to diseases, including diabetic complications. The pathophysiological effects of AGEs are mainly due to oxidative stress and inflammatory processes. Among the proteins most affected by glycation are albumin, the most abundant circulating protein, and collagen, which has a long biological half-life and is abundant in the extracellular matrix. The potential cellular damage caused by AGEs underscores the importance of identifying and developing natural AGE inhibitors. Indeed, despite initial promise, many synthetic inhibitors have been withdrawn from clinical trials due to issues such as cytotoxicity and poor pharmacokinetics. In contrast, natural products have shown significant potential in inhibiting AGE formation. Olea europaea L. leaves, rich in bioactive compounds like oleuropein and triterpenoids, have attracted scientific interest, emphasizing the potential of olive leaf extracts in health applications. This study investigates the anti-glycation properties of two polyphenol-rich extracts (OPA40 and OPA70) and a triterpene-enriched extract (TTP70) from olive leaves. Using in vitro protein glycation methods with bovine serum albumin (BSA)-glucose and gelatin-glucose systems, this study assesses AGE formation inhibition by these extracts through native polyacrylamide gel electrophoresis (N-PAGE) and autofluorescence detection. OPA40 and OPA70 exhibited strong, dose-dependent anti-glycation effects. These effects were corroborated by electrophoresis and further supported by similar results in a gelatin-glucose system. Additionally, TTP70 showed moderate anti-glycation activity, with a synergistic effect of its components. The results support the real possibility of using olive leaf bioproducts in ameliorating diabetic complications, contributing to sustainable bio-economy practices.

Principal Bioactive Properties of Oleanolic Acid, Its Derivatives, and Analogues

Natural products have always played an important role in pharmacotherapy, helping to control pathophysiological processes associated with human disease. Thus, natural products such as oleanolic acid (OA), a pentacyclic triterpene that has demonstrated important activities in several disease models, are in high demand. The relevant properties of this compound have motivated re-searchers to search for new analogues and derivatives using the OA as a scaffold to which new functional groups have been added or modifications have been realized. OA and its derivatives have been shown to be effective in the treatment of inflammatory processes, triggered by chronic diseases or bacterial and viral infections. OA and its derivatives have also been found to be effective in diabetic disorders, a group of common endocrine diseases characterized by hyperglycemia that can affect several organs, including the liver and brain. This group of compounds has been reported to exhibit significant bioactivity against cancer processes in vitro and in vivo. In this review, we summarize the bioactive properties of OA and its derivatives as anti-inflammatory, anti-bacterial, antiviral, anti-diabetic, hepatoprotective, neuroprotective, and anticancer agents.

Bioavailability and systemic transport of oleanolic acid in humans, formulated as a functional olive oil

Evidence of the pharmacological activity of oleanolic acid (OA) suggests its potential therapeutic application. However, its use in functional foods, dietary supplements, or nutraceuticals is hindered by limited human bioavailability studies. The BIO-OLTRAD trial is a double-blind, randomized controlled study with 22 participants that received a single dose of 30 mg OA formulated as a functional olive oil. The study revealed that the maximum serum concentration of OA ranged from 500 to 600 ng mL-1, with an AUC0-∞ value of 2862.50 ± 174.50 ng h mL-1. Furthermore, we discovered a physiological association of OA with serum albumin and triglyceride-rich lipoproteins (TRL). UV absorption spectra showed conformational changes in serum albumin due to the formation of an adduct with OA. Additionally, we demonstrated that TRL incorporate OA, reaching a maximum concentration of 140 ng mL-1 after 2-4 hours. We conjecture that both are efficient carriers to reach target tissues and to yield high bioavailability.

Pentacyclic Triterpenes from Olive Leaves Formulated in Microemulsion: Characterization and Role in De Novo Lipogenesis in HepG2 Cells

Olea europaea L. leaves contain a wide variety of pentacyclic triterpenes (TTPs). TTPs exhibit many pharmacological activities, including antihyperlipidemic effects. Metabolic alterations, such as dyslipidemia, are an established risk factor for hepatocellular carcinoma (HCC). Therefore, the use of TTPs in the adjunctive treatment of HCC has been proposed as a possible method for the management of HCC. However, TTPs are characterized by poor water solubility, permeability, and bioavailability. In this work, a microemulsion (ME) loading a TTP-enriched extract (EXT) was developed, to overcome these limits and obtain a formulation for oral administration. The extract-loaded microemulsion (ME-EXT) was fully characterized, assessing its chemical and physical parameters and release characteristics, and the stability was evaluated for two months of storage at 4 °C and 25 °C. PAMPA (parallel artificial membrane permeability assay) was used to evaluate the influence of the formulation on the intestinal passive permeability of the TTPs across an artificial membrane. Furthermore, human hepatocarcinoma (HepG2) cells were used as a cellular model to evaluate the effect of EXT and ME-EXT on de novo lipogenesis induced by elevated glucose levels. The effect was evaluated by detecting fatty acid synthase expression levels and intracellular lipid accumulation. ME-EXT resulted as homogeneous dispersed-phase droplets, with significantly increased EXT aqueous solubility. Physical and chemical analyses showed the high stability of the formulation over 2 months. The formulation realized a prolonged release of TTPs, and permeation studies demonstrated that the formulation improved their passive permeability. Furthermore, the EXT reduced the lipid accumulation in HepG2 cells by inhibiting de novo lipogenesis, and the ME-EXT formulation enhanced the inhibitory activity of EXT on intracellular lipid accumulation.

Polyphenols and Triterpenes Combination in an In Vitro Model of Cardiac Damage: Protective Effects

Olive products contain high levels of monounsaturated fatty acids as well as other minor components such as triterpenic alcohols and other pentacyclic triterpenes, which together form the main triterpenes of virgin olive oil. Olive fruits and leaves contain significant amounts of hydrophilic and lipophilic bioactives including flavones, phenolic acids and phenolic alcohols, amongst others. Several studies have shown the benefits of these substances on the cardiovascular system. Regardless, little is known about the specific combination of bioactive compounds in cardiovascular health. Thus, we aimed to test the combination of a triterpenes (TT70) and a polyphenols (HT60) olive oil bioactive extract in H9c2 cells under stress conditions: LPS and H2O2 stimulation. To evaluate the effectiveness of the combination, we measured cell viability, superoxide production and protein expression of caspase 3, eNOS, peNOS, TNF-α and Il-6. Overall, cells stimulated with LPS or H2O2 and co-incubated with the combination of triterpenes and polyphenols had increased cell survival, lower levels of superoxide anion, lower protein expression of eNOS and higher expression of peNOS, increased protein expression of SOD-1 and lower protein expression of TNF-α and Il-6. The specific combination of HT60+TT70 is of great interest for further study as a possible treatment for cardiovascular damage.

Molecular Mechanisms Underlying the Effects of Olive Oil Triterpenic Acids in Obesity and Related Diseases

Dietary components exert protective effects against obesity and related metabolic and cardiovascular disturbances by interfering with the molecular pathways leading to these pathologies. Dietary biomolecules are currently promising strategies to help in the management of obesity and metabolic syndrome, which are still unmet medical issues. Olive oil, a key component of the Mediterranean diet, provides an exceptional lipid matrix highly rich in bioactive molecules. Among them, the pentacyclic triterpenic acids (i.e., oleanolic acid) have gained clinical relevance in the last decade due to their wide range of biological actions, particularly in terms of vascular function, obesity and insulin resistance. Considering the promising effects of these triterpenic compounds as nutraceuticals and components of functional foods against obesity and associated complications, the aim of our review is to decipher and discuss the main molecular mechanisms underlying these effects driven by olive oil triterpenes, in particular by oleanolic acid. Special attention is paid to their signaling and targets related to glucose and insulin homeostasis, lipid metabolism, adiposity and cardiovascular dysfunction in obesity. Our study is aimed at providing a better understanding of the impact of dietary components of olive oil in the long-term management of obesity and metabolic syndrome in humans.

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.

Modulation of Lipid Transport and Adipose Tissue Deposition by Small Lipophilic Compounds

Small lipophilic molecules present in foods of plant origin have relevant biological activities at rather low concentrations. Evidence suggests that phytosterols, carotenoids, terpenoids, and tocopherols can interact with different metabolic pathways, exerting beneficial effects against a number of metabolic diseases. These small molecules can modulate triacylglycerol absorption in the intestine and the biosynthesis of chylomicrons, the lipid carriers in the blood. Once in the bloodstream, they can impact lipoprotein clearance from blood, thereby affecting fatty acid release, incorporation into adipocytes and triglyceride reassembling and deposit. Consequently, some of these molecules can regulate pathophysiological processes associated to obesity and its related conditions, such as insulin resistance, metabolic syndrome and type-2 diabetes. The protective capacity of some lipophilic small molecules on oxidative and chemotoxic stress, can modify the expression of key genes in the adaptive cellular response, such as transcription factors, contributing to prevent the inflammatory status of adipose tissue. These small lipophilic compounds can be incorporated into diet as natural parts of food but they can also be employed to supplement other dietary and pharmacologic products as nutraceuticals, exerting protective effects against the development of metabolic diseases in which inflammation is involved. The aim of this review is to summarize the current knowledge of the influence of dietary lipophilic small biomolecules (phytosterols, carotenoids, tocopherols, and triterpenes) on lipid transport, as well as on the effects they may have on pathophysiological metabolic states, related to obesity, insulin resistance and inflammation, providing an evidence-based summary of their main beneficial effects on human health.

Oleanolic Acid, a Compound Present in Grapes and Olives, Protects against Genotoxicity in Human Mammary Epithelial Cells

Oleanolic acid (AO) and maslinic acid (MA) are constituents of the skins of different fruits, including olives and white or red grapes. Although both compounds are known to have beneficial properties against different types of cancers, thus far, there are no studies about their chemopreventive effects in human breast cancer. Thus, we sought to elucidate whether both compounds possess chemopreventive activity. Two cell lines of human breast cancer cells and one noncancerous human mammary epithelial cells were used to determine the effects of OA and MA. The results showed that OA inhibited the proliferation and increased the oxidative stress of highly invasive cells. Additionally, OA decreased oxidative stress and oxidative damage to the DNA in human mammary epithelial cells. These results suggest that OA could act as a chemopreventive agent in human breast cancer and could inhibit the proliferation of highly invasive breast cancer cells.

GC-FID determination and pharmacokinetic studies of oleanolic acid in human serum

Analytical interest of OA determination in human serum has increased owing to the increasing interest in pharmaceutical research by pharmaceutical properties. A simple, specific, precise and accurate GC method with flame ionization detector (FID) developed and validated for the determination of oleanolic acid (OA) in human serum (HS). To an aliquot of HS, internal standard was added and a combination of liquid-liquid extraction with a mixture of diethyl ether-isopropyl alcohol, filtration and consecutive GC resulted in separation and quantification of OA. The organic phase was analyzed using a GC system equipped with a 30 × 0.25 mm i.d. Rtx-65TG capillary column and FID detection. Total chromatographic time was 10 min and no interfering peaks from endogenous components in blank serum were observed. The OA/internal standard peak area ratio was linearly fitted to the OA concentration (r = 0.992) over the range 10-1500 ng/mL. The mean serum extraction recovery of OA was 96.7 ± 1.0% and the lower limit of quantification based on 5 mL of serum was 10.7 ng/mL. The intra-day coefficient of variation ranged from 1.3 to 3.6% and inter-day varied from 1.4 to 4.5%. The developed method was used to study the pharmacokinetics of OA after oral administration in humans. The assay was simple, sensitive, precise and accurate for the use in the study of the mechanisms of absorption and distribution of OA in humans.

De novo sequencing and comparative analysis of holy and sweet basil transcriptomes

Background

Ocimum L. of family Lamiaceae is a well known genus for its ethnobotanical, medicinal and aromatic properties, which are attributed to innumerable phenylpropanoid and terpenoid compounds produced by the plant. To enrich genomic resources for understanding various pathways, de novo transcriptome sequencing of two important species, O. sanctum and O. basilicum, was carried out by Illumina paired-end sequencing.

Results

The sequence assembly resulted in 69117 and 130043 transcripts with an average length of 1646 ± 1210.1 bp and 1363 ± 1139.3 bp for O. sanctum and O. basilicum, respectively. Out of the total transcripts, 59648 (86.30%) and 105470 (81.10%) from O. sanctum and O. basilicum, and respectively were annotated by uniprot blastx against Arabidopsis, rice and lamiaceae. KEGG analysis identified 501 and 952 transcripts from O. sanctum and O. basilicum, respectively, related to secondary metabolism with higher percentage of transcripts for biosynthesis of terpenoids in O. sanctum and phenylpropanoids in O. basilicum. Higher digital gene expression in O. basilicum was validated through qPCR and correlated to higher essential oil content and chromosome number (O. sanctum, 2n = 16; and O. basilicum, 2n = 48). Several CYP450 (26) and TF (40) families were identified having probable roles in primary and secondary metabolism. Also SSR and SNP markers were identified in the transcriptomes of both species with many SSRs linked to phenylpropanoid and terpenoid pathway genes.

Conclusion

This is the first report of a comparative transcriptome analysis of Ocimum species and can be utilized to characterize genes related to secondary metabolism, their regulation, and breeding special chemotypes with unique essential oil composition in Ocimum.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2164-15-588) contains supplementary material, which is available to authorized users.

Bioavailability and activity of natural food additive triterpenoids as influenced by protein

Triterpenoids were thought to be biologically ineffective for a very long time, but aggregating proof on their widely ranging pharmacological activities paired with a dubious toxicity portrait has motivated regenerated attraction for human health and disease. In the current contribution, our central goal was to integratively dissect the biointeraction of two typical triterpenoids, ursolic acid and oleanolic acid, by the most fundamental macromolecule bovine serum albumin (BSA) by employing molecular modeling, steady state and time-resolved fluorescence, and circular dichroism spectra at the molecular scale. Based on molecular modeling, subdomain IIA, which matches Sudlow's site I, was allocated to retain high affinity for triterpenoids, but the affinity of ursolic acid with subdomain IIA is somewhat inferior compared to that of oleanolic acid, probably because the affinity differentiation arises from the different positions of the methyl group on the E-ring in the two triterpenoids. This sustains the site-specific ligands, and hydrophobic 8-anilino-1-naphthalenesulfonic acid probe results in arranging the triterpenoids at the warfarin-azapropazone site. The data of steady state and time-resolved fluorescence indicated that the recognition of triterpenoids by BSA produced quenching by a static type, in other words, the ground state BSA-triterpenoid complex formation with the affinities of 1.507/1.734, 1.042/1.186, and 0.8395/0.9863 × 10(4) M(-1) at 298, 304, and 310 K for ursolic acid/oleanolic acid, respectively. Thermodynamic analyses show that the basic forces acting between BSA and triterpenoids are hydrogen bonds, van der Waals forces, and hydrophobic interactions; this occurrence provoked the alterations of the BSA spatial structure with a noticeable decline of α-helix evoking perturbation of the protein, as stemmed from circular dichroism, synchronous fluorescence, and three-dimensional fluorescence measurements. We anticipate that the complexation of plant triterpenoids with protein delineated here may be exploited as a biologically relevant model for evaluating the physiologically applicable noncovalent complexes in in vivo examination of triterpenoid properties such as accumulation, bioavailability, and distribution.

Bioactive properties of the main triterpenes found in olives, virgin olive oil, and leaves of Olea europaea

Oleanolic acid, maslinic acid, uvaol, and erythrodiol are the main triterpenes present in olives, olive tree leaves, and virgin olive oil. Their concentration in virgin olive oil depends on the quality of the olive oil and the variety of the olive tree. These triterpenes are described to present different properties, such as antitumoral activity, cardioprotective activity, anti-inflammatory activity, and antioxidant protection. Olive oil triterpenes are a natural source of antioxidants that could be useful compounds for the prevention of multiple diseases related to cell oxidative damage. However, special attention has to be paid to the concentrations used, because higher concentration may lead to cytotoxic or biphasic effects. This work explores all of the bioactive properties so far described for the main triterpenes present in virgin olive oil.

Dietary oleanolic acid mediates circadian clock gene expression in liver independently of diet and animal model but requires apolipoprotein A1

Oleanolic acid is a triterpene widely distributed throughout the plant kingdom and present in virgin olive oil at a concentration of 57 mg/kg. To test the hypotheses that its long-term administration could modify hepatic gene expression in several animal models and that this could be influenced by the presence of APOA1-containing high-density lipoproteins (HDLs), diets including 0.01% oleanolic acid were provided to Apoe- and Apoa1-deficient mice and F344 rats. Hepatic transcriptome was analyzed in Apoe-deficient mice fed long-term semipurified Western diets differing in the oleanolic acid content. Gene expression changes, confirmed by reverse transcriptase quantitative polymerase chain reaction, were sought for their implication in hepatic steatosis. To establish the effect of oleanolic acid independently of diet and animal model, male rats were fed chow diet with or without oleanolic acid, and to test the influence of HDL, Apoa1-deficient mice consuming the latter diet were used. In Apoe-deficient mice, oleanolic acid intake increased hepatic area occupied by lipid droplets with no change in oxidative stress. Bmal1 and the other core component of the circadian clock, Clock, together with Elovl3, Tubb2a and Cldn1 expressions, were significantly increased, while Amy2a5, Usp2, Per3 and Thrsp were significantly decreased in mice receiving the compound. Bmal1 and Cldn1 expressions were positively associated with lipid droplets. Increased Clock and Bmal1 expressions were also observed in rats, but not in Apoa1-deficient mice. The core liver clock components Clock-Bmal1 are a target of oleanolic acid in two animal models independently of the diets provided, and this compound requires APOA1-HDL for its hepatic action.

Determination of maslinic acid, a pentacyclic triterpene from olives, in rat plasma by high-performance liquid chromatography

Maslinic acid, a pentacyclic triterpene from olives, has been reported to exert beneficial effects on health, including anticarcinogenic activity. Despite its importance, little is known about its bioavailability in both humans and animals. A fundamental step for this evaluation consisted of measuring this compound in blood. Therefore, a simple high-performance liquid chromatography (HPLC) method with diode array detection has been developed. Maslinic acid contained in plasma was extracted twice using ethyl acetate. After centrifugation, the organic fraction was evaporated to dryness and the residue was reconstituted with methanol/water (75:25, v/v) and analyzed by HPLC. The method was validated by obtaining a linear correlation (r(2) = 0.999) and an average recovery of 99%. Precision expressed as the coefficient of variation ranged from 1.23 to 9.06%. The oral administration of maslinic acid (50 mg/kg) to rats and its subsequent detection in plasma showed that the method is suitable for absorption, distribution, and metabolism studies.

Bioavailability, distribution, and antioxidative effects of selected triterpenes in mice

This study analyzed the content of eight triterpenes (oleanolic acid, ursolic acid, arjunolic acid, asiatic acid, boswellic acid, corosolic acid, madecassic acid, and maslinic acid) in ten vegetables and eight fruits. These compounds at 0.5% were supplied to mice for 4 or 8 weeks. The bioavailability, tissue distribution, and antioxidative protection of these triterpenes were examined. Results showed that triterpenes were detected in eight vegetables and six fruits. Basil and brown mustard contained seven test triterpenes, in the range of 14-102 mg/100 g dry weight. The level of each triterpene in plasma, brain, heart, liver, kidney, colon, and bladder increased as the feeding period was increased from 4 weeks to 8 weeks (P < 0.05). Renal homogenates from mice with triterpene intake had greater antioxidative effects against glucose-induced glutathione loss and malondialdehyde and oxidized glutathione production when compared with those from control groups (P < 0.05). These data support that these triterpenes were absorbed and deposited in their intact forms, which in turn exerted in vivo antioxidative protection.

Fruit cuticular waxes as a source of biologically active triterpenoids

The health benefits associated with a diet rich in fruit and vegetables include reduction of the risk of chronic diseases such as cardiovascular disease, diabetes and cancer, that are becoming prevalent in the aging human population. Triterpenoids, polycyclic compounds derived from the linear hydrocarbon squalene, are widely distributed in edible and medicinal plants and are an integral part of the human diet. As an important group of phytochemicals that exert numerous biological effects and display various pharmacological activities, triterpenoids are being evaluated for use in new functional foods, drugs, cosmetics and healthcare products. Screening plant material in the search for triterpenoid-rich plant tissues has identified fruit peel and especially fruit cuticular waxes as promising and highly available sources. The chemical composition, abundance and biological activities of triterpenoids occurring in cuticular waxes of some economically important fruits, like apple, grape berry, olive, tomato and others, are described in this review. The need for environmentally valuable and potentially profitable technologies for the recovery, recycling and upgrading of residues from fruit processing is also discussed.