Development and Evaluation of Oleanolic Acid Dosage Forms and Its Derivatives.

Oleanolic acid is a pentacyclic triterpenoid compound that exists widely in medicinal herbs and other plants. Because of the extensive pharmacological activity, oleanolic acid has attracted more and more attention. However, the structural characteristics of oleanolic acid prevent it from being directly made into new drugs, which limits the application of oleanolic acid. Through the application of modern preparation techniques and methods, different oleanolic acid dosage forms and derivatives have been designed and synthesized. These techniques can improve the water solubility and bioavailability of oleanolic acid and lay a foundation for the new drug development. In this review, the recent progress in understanding the oleanolic acid dosage forms and its derivatives are discussed. Furthermore, these products were evaluated comprehensively from the perspective of characterization and pharmacokinetics, and this work may provide ideas and references for the development of oleanolic acid preparations.

Semi-synthesis and Structure-Activity Relationship of Neuritogenic Oleanene Derivatives.

(3S,4R)-23,28-Dihydroxyolean-12-en-3-yl (2E)-3-(3,4-dihydroxyphenyl)acrylate (1 a), which possesses significant neuritogenic activity, was isolated from the traditional Chinese medicine (TCM) plant, Desmodium sambuense. To confirm the structure and to assess biological activity, we semi-synthesized 1 a from commercially available oleanolic acid. A series of novel 1 a derivatives was then designed and synthesized for a structure-activity relationship (SAR) study. All synthetic derivatives were characterized by analysis of spectral data, and their neuritogenic activities were evaluated in assays with PC12 cells. The SAR results indicate that the number and position of the hydroxy groups on the phenyl ring and the triterpene moiety, as well as the length of the (saturated or unsaturated) alkyl chain that links the phenyl ring with the triterpene critically influence neuritogenic activity. Among all the tested compounds, 1 e [(3S,4R)-23,28-dihydroxyolean-12-en-3-yl (2E)-3-(3,4,5-trihydroxyphenyl)acrylate] was found to be the most potent, inducing significant neurite outgrowth at 1 µm.

Synthesis and evaluation of 2-cyano-3, 12-dioxooleana-1, 9(11)-en-28-oate-13ß, 28-olide as a potent anti-inflammatory agent for intervention of LPS-induced acute lung injury.

The present study was designed to synthesize 2-Cyano-3, 12-dioxooleana-1, 9(11)-en-28-oate-13ß, 28-olide (1), a lactone derivative of oleanolic acid (OA) and evaluate its anti-inflammatory activity. Compound 1 significantly diminished nitric oxide (NO) production and down-regulated the mRNA expression of iNOS, COX-2, IL-6, IL-1ß, and TNF-α in lipopolysaccharide (LPS)-stimulated RAW264.7 cells. Further in vivo studies in murine model of LPS-induced acute lung injury (ALI) showed that 1 possessed more potent protective effects than the well-known anti-inflammatory drug dexamethasone by inhibiting myeloperoxidase (MPO) activity, reducing total cells and neutrophils, and suppressing inflammatory cytokines expression, and thus ameliorating the histopathological conditions of the injured lung tissue. In conclusion, compound 1 could be developed as a promising anti-inflammatory agent for intervention of LPS-induced ALI.

CDDO and Its Role in Chronic Diseases.

There has been a continued interest in translational research focused on both natural products and manipulation of functional groups on these compounds to create novel derivatives with higher desired activities. Oleanolic acid, a component of traditional Chinese medicine used in hepatitis therapy, was modified by chemical processes to form 2-cyano-3,12-dioxoolean-1,9-dien-28-oic acid (CDDO). This modification increased anti-inflammatory activity significantly and additional functional groups on the CDDO backbone have shown promise in treating conditions ranging from kidney disease to obesity to diabetes. CDDO's therapeutic effect is due to its upregulation of the master antioxidant transcription factor Nuclear factor erythroid 2-related factor 2 (Nrf2) through conformational change of Nrf2-repressing, Kelch-like erythroid cell-derived protein with CNC homology-associated protein 1 (Keap1) and multiple animal and human studies have verified subsequent activation of Nrf2-controlled antioxidant genes via upstream Antioxidant Response Element (ARE) regions. At the present time, positive results have been obtained in the laboratory and clinical trials with CDDO derivatives treating conditions such as lung injury, inflammation and chronic kidney disease. However, clinical trials for cancer and cardiovascular disease have not shown equally positive results and further exploration of CDDO and its derivatives is needed to put these shortcomings into context for the purpose of future therapeutic modalities.

Semisynthesis of Derivatives of Oleanolic Acid from Syzygium aromaticum and Their Antinociceptive and Anti-Inflammatory Properties.

Oleanolic acid is a pentacyclic triterpenoid compound widely found in plants and well known for its medicinal properties. Oleanolic acid (OA) was isolated from the ethyl acetate extract of Syzygium aromaticum flower buds. Semisynthesis afforded both acetate and ester derivatives. The derived compounds were monitored with thin layer chromatography and confirmed with nuclear magnetic resonance (NMR) spectroscopy, mass spectrometry (MS), Fourier infrared (FT-IR) spectroscopy, and melting point (Mp). All these compounds were evaluated for their analgesic and anti-inflammatory properties at a dose of 40 mg/kg. Significant analgesic and anti-inflammatory effects were noted for all OA-derived compounds. In the formalin-induced pain test, the derivatives showed better analgesic effects compared to their precursor, whereas, in the tale flick test, oleanolic acid proved to be superior in analgesic effects compared to all its derivatives with the exception of the acetyl derivative. Acute inflammatory tests showed that acetyl derivatives possessed better anti-inflammatory activity compared to the other compounds. In conclusion, semisynthesis of oleanolic acid yielded several derivatives with improved solubility and enhanced analgesic and anti-inflammatory properties.

Identificación de metabolitos secundarios de Anredera vesicaria (Yuca hiedra) / Identification of secondary metabolites from Anredera vesicaria (Yuca Hiedra)

Introducción: Anredera vesicaria es una planta muy empleada en la región oriental de Cuba para tratar inflamaciones provocadas por golpes y fracturas, sin embargo, no existen datos de su composición química que justifiquen su uso como antiinflamatorio. Objetivo: identificar metabolitos secundarios de interés medicinal en las hojas, tallos y rizomas de Anredera vesicaria. Métodos: a la biomasa recolectada se le aplicó un proceso de lavado, desinfección, secado y pulverización. Un ejemplar fue identificado y consignado en la serie Catasús, número 2601. Muestras aéreas y subterráneas se sometieron a extracciones con agua y etanol usándose ultrasonido. A los extractos se les realizó tamizaje fitoquímico, cuyos resultados fueron corroborados por cromatografía de capa delgada y espectroscopía ultravioleta e infrarroja.Resultados: se identificaron carbohidratos, fenoles, flavonoides, cumarinas, alcaloides, triterpenos, mucílagos y saponinas. En el extracto etanólico de las hojas se encontró la mayor diversidad de metabolitos secundarios, sin embargo, en los rizomas hay mayor abundancia de fenoles, esteroides y mucílagos. A partir de los rizomas se aisló un sólido blanco amorfo que fue identificado como ácido oleanólico. Conclusiones: la abundancia de triterpenos y mucílagos en Anredera vesicaria podría contribuir con su actividad antiiflamatoria(AU)

Introduction: Anredera vesicaria is a plant very used in the East of Cuba to treat inflammations provoked by blows and fractures, however, data of the chemical composition that justify its use as antiinflamatory don't exist.Objective: To Identify secondary metabolites with medicinal interest in the sheets, stems and rhizomes from Anredera vesicaria. Methods: To the recollected biomass was applied a process of washing, disinfection, drying and pulverization. A sample was identified and consigned in the Catasús series, with number 2601. Aerial and subterranean samples submitted extractions with water and ethanol themselves using ultrasound. To the extracts were carried out the phytochemical screening whose results were corroborated by thin layer chromatography and ultraviolet and infrared spectroscopy. Results: Carbohydrates, phenols, flavonoids, coumarins, alkaloids, triterpenes, mucilages and saponines were identified. In the ethanolic extract from leaves it was found the biggest diversity of secondary metabolites, however, in the rhizomes there are bigger abundance of phenols, steroids and mucilages. Starting from rhizomes was isolate an amorphous white solid which was identified as oleanolic acid.Conclusions: The abundance of triterpenes and mucilages in Anredera vesicaria could to contribute with their anti-inflamatory activit(AU)

Identificación de metabolitos secundarios de Anredera vesicaria (Yuca hiedra) / Identification of secondary metabolites from Anredera vesicaria (Yuca Hiedra)

INTRODUCCIÓN: Anredera vesicaria es una planta muy empleada en la región oriental de Cuba para tratar inflamaciones provocadas por golpes y fracturas, sin embargo, no existen datos de su composición química que justifiquen su uso como antiinflamatorio. OBJETIVO: identificar metabolitos secundarios de interés medicinal en las hojas, tallos y rizomas de Anredera vesicaria. MÉTODOS: a la biomasa recolectada se le aplicó un proceso de lavado, desinfección, secado y pulverización. Un ejemplar fue identificado y consignado en la serie Catasús, número 2601. Muestras aéreas y subterráneas se sometieron a extracciones con agua y etanol usándose ultrasonido. A los extractos se les realizó tamizaje fitoquímico, cuyos resultados fueron corroborados por cromatografía de capa delgada y espectroscopía ultravioleta e infrarroja. RESULTADOS: se identificaron carbohidratos, fenoles, flavonoides, cumarinas, alcaloides, triterpenos, mucílagos y saponinas. En el extracto etanólico de las hojas se encontró la mayor diversidad de metabolitos secundarios, sin embargo, en los rizomas hay mayor abundancia de fenoles, esteroides y mucílagos. A partir de los rizomas se aisló un sólido blanco amorfo que fue identificado como ácido oleanólico. CONCLUSIONES: la abundancia de triterpenos y mucílagos en Anredera vesicaria podría contribuir con su actividad antiiflamatoria.

INTRODUCTION: Anredera vesicaria is a plant very used in the East of Cuba to treat inflammations provoked by blows and fractures, however, data of the chemical composition that justify its use as antiinflamatory don't exist. OBJECTIVE: To Identify secondary metabolites with medicinal interest in the sheets, stems and rhizomes from Anredera vesicaria. METHODS: To the recollected biomass was applied a process of washing, disinfection, drying and pulverization. A sample was identified and consigned in the Catasús series, with number 2601. Aerial and subterranean samples submitted extractions with water and ethanol themselves using ultrasound. To the extracts were carried out the phytochemical screening whose results were corroborated by thin layer chromatography and ultraviolet and infrared spectroscopy. RESULTS: Carbohydrates, phenols, flavonoids, coumarins, alkaloids, triterpenes, mucilages and saponines were identified. In the ethanolic extract from leaves it was found the biggest diversity of secondary metabolites, however, in the rhizomes there are bigger abundance of phenols, steroids and mucilages. Starting from rhizomes was isolate an amorphous white solid which was identified as oleanolic acid. CONCLUSIONS: The abundance of triterpenes and mucilages in Anredera vesicaria could to contribute with their anti-inflamatory activity.

Synthesis of 5,19-(2,6-Dimethylpyridin-4-yl)-trisnorlupane and Oleanane.

Acetylation of the 3,4-seco-derivatives of betulin, allobetulin and 28-oxyallobetulone gave the 5,19-(2,6-dimethylpyridin-4-yl)-4,23,24,20,29,30-hexanorlupane, and 5-(2,6-dimethylpyridin-4-yl)-4,23,24-trisnor-derivatives of oleanane and ursane.

Hederagenin as a triterpene template for the development of new antitumor compounds.

In this study, a series of novel C-28 esters and amides derivatives of hederagenin (He) were designed and synthesized in attempt to develop potent antitumor agents. Their structures were confirmed by MS, IR, (1)H NMR and (13)C NMR spectroscopic analyses and their cytotoxic activities were screened in SRB assays using a panel of six human cancer cell lines. Although most of the compounds displayed moderate to high levels of cytotoxic activity they were all more potent than the natural product He. The most active compounds had either an ethylpyrimidinyl (27) or an ethylpyrrolidinyl (28) substituent, with EC50 in the range of 1.1-6.5 µM for six human cancer cell lines. Notably, this corresponds to an approximately 30-fold times greater potency than He.

Changes in Renal Function and Oxidative Status Associated with the Hypotensive Effects of Oleanolic Acid and Related Synthetic Derivatives in Experimental Animals.

PURPOSE: The triterpene oleanolic acid (OA) is known to possess antihypertensive actions. In the present study we to compared the effects of the triterpene on mean arterial blood pressure (MAP) and kidney function following acute administration in normotensive animals with those of its related oleanane synthetic derivatives (brominated oleanolic acid, Br-OA and oleanolic acid methyl ester, Me-OA). We also used experimental models of hypertension to further explore the effects of sub-chronic oral OA treatment and evaluated influences on oxidative status. METHODS: OA was extracted from dried flower buds of Syzygium aromaticum using a previously validated protocol in our laboratory. Me-OA and Br-OA were synthesized according to a method described. Rats were supplemented with lithium chloride (12 mmol L-1) prior to experimentation in order to raise plasma lithium to allow measurements of lithium clearance and fractional excretion (FELi) as indices of proximal tubular Na+ handling. Anaesthetized animals were continuously infused via the right jugular with 0.077M NaCl. MAP was measured via a cannula inserted in the carotid artery, and urine was collected through a cannula inserted in the bladder. After a 3.5 h equilibration, MAP, urine flow, electrolyte excretion rates were determined for 4 h of 1 h control, 1.5 h treatment and 1.5 h recovery periods. OA, Me-OA and Br-OA were added to the infusate during the treatment period. We evaluated sub-chronic effects on MAP and kidney function in normotensive Wistar rats and in two animal models of hypertension, spontaneously hypertensive rats (SHR) and Dahl salt-sensitive (DSS) rats, during 9-week administration of OA (p.o.). Tissue oxidative status was examined in these animals at the end of the study. Increasing evidence suggests that and renal function disturbances and oxidative stress play major roles in the pathogenesis of hypertension. RESULTS: Acute infusion OA and oleanane derivatives displayed qualitatively similar effects in decreasing MAP and increasing urinary Na+ outputs. The drugs increased the FENa and FELi without influencing GFR indicating that at least part of the overall natriuretic effect involved proximal tubular Na+ reabsorption. Sub-chronic OA administration (p.o.) also elicited hypotensive responses in Wistar, DSS and SHR rats. The MAP lowering effect was more marked in hypertensive animals and were positively correlated with increased urinary Na+ excretion. Compared with respective control rats, OA treatment reduced malondialdehyde (MDA, a marker of lipid peroxidation) and increased activities of antioxidant enzymes; superoxide dismutase and glutathione peroxidase in hepatic, cardiac and renal tissues. CONCLUSIONS: OA and oleanane derivatives have similar effects on MAP, kidney function and oxidative stress. The amelioration of oxidative stress and blood pressure lowering effects by OA are more marked in hypertensive animals and correlated with an increased urinary Na+ output. NOVELTY OF THE WORK: The results of this study are novel in that they show 1) a correlation between blood pressure reduction and increased urinary Na+ excretion by OA, 2) a more marked MAP reduction in hypertensive animals and 3) a drug-induced decrease in proximal tubule Na+ reabsorption. The results may also be clinically relevant because OA is effective via oral administration.

Synthesis and biological evaluation of ambradiolic acid as an inhibitor of glycogen phosphorylase.

Ambradiolic acid (3) with oleanane skeleton is a natural pentacyclictriterpene. The first synthesis of 3 starting from 23-hydroxybetulinic acid (2) has been accomplished in 12-steps with a total yield of 18.1% in our study. Compound 3 was further biologically evaluated and found to exhibit significant inhibitory activity against rabbit muscle glycogen phosphorylase (GP) with an IC50 value of 12.4 µM, suggesting it could be a potential lead compound for the development of hypoglycemic drugs.

Synthesis of cyclocaric acid A and comparison to material from Cyclocarya paliurus.

Components previously reported from Cyclocarya paliurus include the oleananes cyclocaric acids A and B, with cyclocaric acid A possessing an oxetane ring. Isolation of cyclocaric acid A from the plant extract and comparison to the literature report show that the compound originally reported as cyclocaric acid A is, in fact, hederagenin. This was confirmed by independent synthesis of the oxetane and indicates that cyclocaric acid A may not actually be a natural product.

Synthesis and characterization of amino acid conjugates of oleanolic acid and their in vitro cytotoxic effect on HCC cell lines.

Oleanolic acid (3ß-hydroxy-olean-12-en-28-oic acid; OA-01), a pentacyclic triterpene, exhibit a wide range of pharmacological and biological activities. We have isolated oleanolic acid from methanolic extract of Periploca aphylla, collected from surroundings of Karachi in the month of February. Furthermore, four known and two new C-28 amino acid conjugates of oleanolic acid were prepared to explore potential of these compounds on HCCs and one breast cancer cell line. Cytotoxic effects revealed that as compare to parent compound (OA-01), two derivatives OA-04 (p<0.0001) and OA-06 (p<0.01) showed significantly increased/higher inhibition rates.

Triterpene sapogenins with oleanene skeleton: chemotypes and biological activities.

Critical survey of a selected class of pentacyclic triterpenes--the oleanane family, is presented based on current literature in order to underline their value for medicinal chemistry and drug development potential. Oleanenes may be considered as a renewable resource of valuable research materials which are structurally diverse, inherently biocompatible and have built-in affinity for many categories of functional proteins. Although availability of particular compounds from natural sources may be very low, synthetic methods elaborated by generations of chemists, secure a way to obtaining desirable structures from commercial starting materials.

Development of oleanane-type triterpenes as a new class of HCV entry inhibitors.

Development of hepatitis C virus (HCV) entry inhibitors represents an emerging approach that satisfies a tandem mechanism for use with other inhibitors in a multifaceted cocktail. By screening Chinese herbal extracts, oleanolic acid (OA) was found to display weak potency to inhibit HCV entry with an IC50 of 10 µM. Chemical exploration of this triterpene compound revealed its pharmacophore requirement for blocking HCV entry, rings A, B, and E, are conserved while ring D is tolerant of some modifications. Hydroxylation at C-16 significantly enhanced its potency for inhibiting HCV entry with IC50 at 1.4 µM. Further modification by conjugation of this new lead with a disaccharide at 28-COOH removed the undesired hemolytic effect and, more importantly, increased its potency by ~5-fold (54a, IC50 0.3 µM). Formation of a triterpene dimer via a linker bearing triazole (70) dramatically increased its potency with IC50 at ~10 nM. Mechanistically, such functional triterpenes interrupt the interaction between HCV envelope protein E2 and its receptor CD81 via binding to E2, thus blocking virus and host cell recognition. This study establishes the importance of triterpene natural products as new leads for the development of potential HCV entry inhibitors.

Synthesis of novel derivatives of esculentoside A and its aglycone phytolaccagenin, and evaluation of their haemolytic activity and inhibition of lipopolysaccharide-induced nitric oxide production.

A series of 46 compounds derived from esculentoside A and its aglycone were synthesized and characterized. The effect of these compounds on lipopolysaccharide (LPS)-induced NO production, haemolytic activity, and cell viability was evaluated. Structure-activity relationship was established by comparing the derivatives of esculentoside A with its aglycone derivatives. Both the aglycone and its derivatives showed higher inhibitory effects on LPS-induced NO production, and lower haemolytic activities than esculentoside A and its derivatives.

Amyrin esters induce cell death by apoptosis in HL-60 leukemia cells.

Four derivatives of an α,ß-amyrin mixture were synthesized by acylation with appropriate anhydrides. The structures of the compounds were confirmed by means of IR and (1)H and (13)C NMR. The compounds were screened for cytotoxic activity using four human tumor cell lines (HL-60, MDAMB-435, SF-295 and HCT-8) and normal peripheral blood mononuclear cells (PBMC). 3-O-Carboxymaleinate of α,ß-amyrin (3a/3b) were found to be the only active compounds of the series (high cytotoxicity), showing IC(50) values ranging from 1.8 to 3µM. In PBMC, 3a/3b were not toxic, suggesting selectivity for tumor cells. To better understand the mechanism of action involved in the cytotoxicity of 3a/3b, HL-60 cells treated with 3a/3b were examined for morphological changes, DNA fragmentation, cell cycle perturbation, externalization of phosphatidylserine and activation of caspases 3/7, with doxorubicin serving as the positive control. The results indicate that the cytotoxicity of 3a/3b involves the induction of cell death by apoptosis.

Synthesis and biological evaluation of oleanolic acid derivatives as inhibitors of protein tyrosine phosphatase 1B.

Protein tyrosine phosphatase 1B (PTP1B) is a negative regulator in the process of insulin signaling and a promising drug target for diabetes and obesity. Derivatives of oleanolic acid were synthesized and evaluated as PTP1B inhibitors. Several derivatives exhibited moderate to good inhibitory activities against PTP1B, with 25f displaying the most promising inhibition (IC(50) = 3.12 µM). Structure-activity relationship analyses of these derivatives demonstrated that the integrity of the A ring and 12-ene moieties was important in the retention of PTP1B enzyme inhibitory activities. In addition, hydrophilic and acidic groups as well as the distance between the oleanene and acid moieties were associated with PTP1B inhibitory activities. Possible binding modes of 25f were explored by molecular docking simulations.

Synthesis and evaluation of a novel series of heterocyclic oleanolic acid derivatives with anti-osteoclast formation activity.

Oleanolic acid with anti-bone resorption effect was an active component discovered in a medicinal plant of Achyranthes bidentata. A series of heterocyclic derivatives of oleanolic acid including indole, pyrazine, quinoxaline, quinoline moieties and their natural amino acid amides were synthesized. Their inhibitory activity on the formation of osteoclast-like multinucleated cells (OCLs) and cytotoxicity of the selected derivatives were evaluated. Among the derivatives, compounds 2a and 8a displayed quite a potent activity even at 200 nM. The structure-activity relationships of the derivatives were also discussed.

Oleanolic acid and its derivatives: new inhibitor of protein tyrosine phosphatase 1B with cellular activities.

Protein tyrosine phosphatase 1B is a key factor in the negative regulation of insulin pathway and a promising target for treatment of diabetes and obesity. Herein, a series of competitive inhibitors were optimized from oleanolic acid, a natural triterpenoid identified against PTP1B by screening libraries of traditional Chinese medicinal herbs. Modifying at 3 and 28 positions, we obtained compound 13 with a K(i) of 130 nM, which exhibited good selectivity between other phosphatases involved in insulin pathway except T-cell protein tyrosine phosphatase. Further evaluation in cell models illustrated that the derivatives enhanced insulin receptor phosphorylation in CHO/hIR cells and also stimulated glucose uptake in L6 myotubes with or addition of without insulin.