Design and synthesis of novel quinic acid derivatives: in vitro cytotoxicity and anticancer effect on glioblastoma.

Aim: Quinic acid (QA) is a cyclic polyol exhibiting anticancer properties on several cancers. However, potential role of QA derivatives against glioblastoma is not well established. Methodology & results: Sixteen novel QA derivatives and QA-16 encapsulated poly (lactic-co-glycolic acid) nanoparticles (QA-16-NPs) were screened for their anti-glioblastoma effect using standard cell and molecular biology methods. Presence of a tertiary hydroxy and silylether groups in the lead compound were identified for the antitumor activity. QA-16 have 90% inhibition with the IC50 of 10.66 µM and 28.22 µM for LN229 and SNB19, respectively. The induction of apoptosis is faster with the increased fold change of caspase 3/7 and reactive oxygen species. Conclusion: QA-16 and QA-16-NPs shows similar cytotoxicity effect, providing the opportunity to use QA-16 as a potential chemotherapeutic agent.

Current Advances in Naturally Occurring Caffeoylquinic Acids: Structure, Bioactivity, and Synthesis.

Caffeoylquinic acids (CQAs) are a broad class of secondary metabolites that have been found in edible and medicinal plants from various families. It has been 100 years since the discovery of chlorogenic acid in 1920. In recent years, a number of naturally derived CQAs have been isolated and structurally elucidated. Accumulated evidence demonstrate that CQAs have a wide range of biological activities, such as antioxidation, antibacterial, antiparasitic, neuroprotective, anti-inflammatory, anticancer, antiviral, and antidiabetic effects. Up to date, some meaningful progresses on the biosynthesis and total synthesis of CQAs have also been made. Therefore, it is necessary to comprehensively summarize the structure, biological activity, biosynthesis, and chemical synthesis of CQAs. This review provides extensive coverage of naturally occurring CQAs discovered from 1990 until 2020. Modern isolation techniques, chemical data (including structure, biosynthesis, and total synthesis), and bioactivity are summarized. This would be helpful for further research of CQAs as potential pharmaceutical agents.

Synthesis and In Vitro Evaluation of Caffeoylquinic Acid Derivatives as Potential Hypolipidemic Agents.

A series of novel caffeoylquinic acid derivatives of chlorogenic acid have been designed and synthesized. Biological evaluation indicated that several synthesized derivatives exhibited moderate to good lipid-lowering effects on oleic acid-elicited lipid accumulation in HepG2 liver cells. Particularly, derivatives 3d, 3g, 4c and 4d exhibited more potential lipid-lowering effect than the positive control simvastatin and chlorogenic acid. Further studies on the mechanism of 3d, 3g, 4c and 4d revealed that the lipid-lowering effects were related to their regulation of TG levels and merit further investigation.

Mechanism underlying inhibitory effect of six dicaffeoylquinic acid isomers on melanogenesis and the computational molecular modeling studies.

Dicaffeoylquinic acid (DCQA), which contain 2 caffeic acids and a quinic acid, is 6 isomeric compounds (1,3-, 1,4-, 1,5-, 3,4-, 3,5-, and 4,5-DCQA). In this study, the mechanism underlying the inhibitory effect of DCQA isomers on melanogenesis in B16F1 murine melanoma cells stimulated by melanocyte stimulating hormone (α-MSH) was evaluated. DCQA isomers showed inhibitory effects on melanogenesis in α-MSH-stimulated B16F1 cells. Furthermore, the anti-melanogenesis activities of 1,5-DCQA and 4,5-DCQA were 61% and 84%, respectively, which were greater than that of arbutin (35%). For cell-free tyrosinase, 3,4-DCQA and 4,5-DCQA indicated high inhibitory effects, similar to the activity to arbutin (35%) at 25 µM. DCQA isomers inhibited the melanogenic enzymes including tyrosinase and dopachrome tautomerase (DCT) on α-MSH-stimulated B16F1 cells. Interestingly, 4,5-DCQA, the most potent inhibitor of melanogenesis among the six DCQA isomers, significantly downregulated the expression of microphthalmia-associated transcription factor (MITF), tyrosinase-related protein 1 (TRP1) containing tyrosinase, and DCT. In particular, the inhibitory mechanism of 4,5-DCQA on MITF expression was elucidated, revealing that 4,5-DCQA inhibits the phosphorylation of cAMP response element-binding protein (CREB) by attenuating cAMP generation during melanogenesis. A molecular docking study was conducted to elucidate the inhibitory mechanism of 4,5-DCQA on cAMP production. DCQA isomers dock to the residues of adenylyl cyclase with a distance of <3 Å, except for 1,3-DCQA. Especially, 4,5-DCQA showed Full Fitness of -1304.68 kcal/mol and △G of -8.33 kcal/mol, as well as H-bonding with adenylyl cyclase at ILE953 and LYS930 residues. In conclusion, DCQA isomers have different effects on melanogenesis depending on their structure. Especially, 4,5-DCQA has depigmentation activity through the inhibitory effect on cellular tyrosinase directly and binding effect on adenylyl cyclase, resulting in the downregulation of MITF protein, thereby reducing the expression of melanogenic enzymes.

Identification of caffeoylquinic acid derivatives as natural protein tyrosine phosphatase 1B inhibitors from Artemisia princeps.

Considerable attention has been paid to protein tyrosine phosphatase 1B (PTP1B) inhibitors as a potential therapy for diabetes, obesity, and cancer. Ten caffeoylquinic acid derivatives (1-10) from leaves of Artemisia princeps Pamp. (Asteraceae) were identified as natural PTP1B inhibitors. Among them, chlorogenic acid (3) showed the most potent inhibitory activity (IC50 11.1 µM). Compound 3 was demonstrated to be a noncompetitive inhibitor by a kinetic analysis. Molecular docking simulation suggested that compound 3 bound to the allosteric site of PTP1B. Furthermore, compound 3 showed remarkable selectivity against four homologous PTPs. According to these findings, compound 3 might be potentially valuable for further drug development.

The Synthesized Plant Metabolite 3,4,5-Tri-O-Galloylquinic Acid Methyl Ester Inhibits Calcium Oxalate Crystal Growth in a Drosophila Model, Downregulates Renal Cell Surface Annexin A1 Expression, and Decreases Crystal Adhesion to Cells.

The plant metabolite 3,4,5-tri-O-galloylquinic acid methyl ester (TGAME, compound 6) was synthesized, and its potential effect on calcium oxalate monohydrate (COM) crystal binding to the surface of Madin-Darby canine kidney cells type I (MDCKI) and crystal growth in a Drosophila melanogaster Malpighian tubule (MT) model were investigated. Membrane, cytosolic, and total annexin A1 (AxA1), α-enolase, and heat shock protein 90 (HSP90) amounts were examined by Western blot analysis after subcellular fractionation, then confirmed by immunofluorescence staining of cultured cells. Pretreatment of MDCKI cells with TGAME for up to 6 h significantly diminished COM crystal binding in a concentration-dependent manner. TGAME significantly inhibited AxA1 surface expression by immunofluorescence microscopy, whereas intracellular AxA1 increased. Western blot analysis confirmed AxA1 expression changes in the membrane and cytosolic fractions of compound-treated cells, whereas whole cell AxA1 remained unchanged. TGAME also significantly decreased the size, number, and growth of calcium oxalate (CaOx) crystals induced in a Drosophila melanogaster MT model and possessed a potent antioxidant activity in a DPPH assay.

Synthesis of new dicinnamoyl 4-deoxy quinic acid and methyl ester derivatives and evaluation of the toxicity against the pea aphid Acyrthosiphon pisum.

New dicinnamoyl (caffeoyl, feruloyl, ortho and para-coumaroyl) 4-deoxyquinic acid and esters were synthesized by using a new 4-deoxy quinic acid triol intermediate. The optimisation of both coupling and deprotection steps allowed the preparation in good yields of the target products either as the carboxylic acid or the methyl ester form. Eight new compounds were evaluated for their ability to influence the feeding behaviour of the pea aphid Acyrthosiphon pisum. Artificial diet bioassays showed that two compounds are toxic (mortality and growth inhibition) at lower concentrations than the reference 3,5-dicaffeoyl quinic acid.

Synthesis and Antibacterial Activity of Alkylated Diamines and Amphiphilic Amides of Quinic Acid Derivatives.

Different series of N-alkylated diamines and their derivatives condensed to quinic acid were synthesized and tested for antibacterial properties against Staphylococcus aureus, Staphylococcus epidermidis, Pseudomonas aeruginosa, and Mycobacterium tuberculosis. The lipophilic chain and carbohydrate moiety modulate the antibacterial activity and the compounds showed a structure-activity relationship. Overall, 11 compounds displayed better activity than chloramphenicol against Gram-positive and Gram-negative bacteria. Monoalkylated amines 2a-h displayed an activity similar to that of ethambutol against Mycobacterium tuberculosis.

Synthesis and characterization of an anti-apoptotic immunosuppressive compound for improving the outcome of islet transplantation.

Mycophenolic acid (MPA) is a commonly used immunosuppressive drug for human islet transplantation. However, it is toxic to transplanted islets, causing primary nonfunction. We recently synthesized a quinic acid derivative, 1,3,4,5-tetrahydroxy-N-propylcyclohexanecarboxamide (KZ41), which has anti-inflammatory and anti-apoptotic effects. We hypothesized that the conjugate (E)-2,3,5-trihydroxy-5-(propylcarbamoyl) cyclohexyl 6-(4-ethoxy-6-methoxy-7-methyl-3-oxo-1,3-dihydroisobenzofuran-5-yl)-4-methylhex-4-enoate (JP-3-110), which is composed of KZ41 and MPA through esterification, can suppress the immune rejection while inducing less toxicity. Early characterization showed that the solubility of JP-3-110 was significantly higher than that of MPA, though JP-3-110 was still poorly water-soluble. The ester bond connecting KZ41 and MPA is stable for a limited duration (<4 weeks). Pharmacological studies demonstrated that JP-3-110 induced significantly less activated caspase 3 and apoptotic cell death of human islets than MPA, while maintaining an equally potent immunosuppressive effect. A similar immunosuppressive effect of JP-3-110 and MPA in humanized NOD.Cg-Prkdc(scid)Il2rg(tm1Wjl)/SzJ (NOD scid gamma, NSG) mice with adoptively transferred human immunity was observed. Taken together, our results demonstrated that JP-3-110 can be a safer immunosuppressive agent for human islet transplantation.

Mechanistic basis of the inhibition of type II dehydroquinase by (2S)- and (2R)-2-benzyl-3-dehydroquinic acids.

The structural changes caused by the substitution of the aromatic moiety in (2S)-2-benzyl-3-dehydroquinic acids and its epimers in C2 by electron-withdrawing or electron-donating groups in type II dehydroquinase enzyme from M. tuberculosis and H. pylori has been investigated by structural and computational studies. Both compounds are reversible competitive inhibitors of this enzyme, which is essential in these pathogenic bacteria. The crystal structures of M. tuberculosis and H. pylori in complex with (2S)-2-(4-methoxy)benzyl- and (2S)-2-perfluorobenzyl-3-dehydroquinic acids have been solved at 2.0, 2.3, 2.0, and 1.9 Å, respectively. The crystal structure of M. tuberculosis in complex with (2R)-2-(benzothiophen-5-yl)methyl-3-dehydroquinic acid is also reported at 1.55 Å. These crystal structures reveal key differences in the conformation of the flexible loop of the two enzymes, a difference that depends on the presence of electron-withdrawing or electron-donating groups in the aromatic moiety of the inhibitors. This loop closes over the active site after substrate binding, and its flexibility is essential for the function of the enzyme. These differences have also been investigated by molecular dynamics simulations in an effort to understand the significant inhibition potency differences observed between some of these compounds and also to obtain more information about the possible movements of the loop. These computational studies have also allowed us to identify key structural factors of the H. pylori loop that could explain its reduced flexibility in comparison to the M. tuberculosis loop, specifically by the formation of a key salt bridge between the side chains of residues Asp18 and Arg20.

First diastereoselective synthesis of methyl caffeoyl- and feruloyl-muco-quinates.

We report on a diastereoselective synthesis of six derivatives of caffeoyl- and feruloyl-muco-quinic acids. All the muco-quinic acid derivatives were obtained in excellent yield in five steps starting from quinic acid, caffeic acid and ferulic acid. Allyl ether protection of trans-hydroxy cinnamic acids was here introduced to chlorogenic acids synthesis. We show that muco-quinic acid derivatives, which are formally diastereoisomers of chlorogenic acids, can be readily distinguished by their tandem mass spectra.

Structure-activity relationship of caffeoylquinic acids on the accelerating activity on ATP production.

Caffeoylquinic acid (CQA) is one of the phenylpropanoids which have various bioactivities such as antioxidant, antibacterial, anticancer, antihistamic, and other biological effects. We previously reported that 3,5-di-O-caffeoylquinic acid inhibited amyloid ß(1-42)-induced cellular toxicity on human neuroblastoma SH-SY5Y cells and increased the mRNA expression level of glycolytic enzymes and the intracellular ATP level. To investigate structure-activity relationship on the accelerating activity on ATP production, we synthesized 1,4,5-tri-O-caffeoylquinic acid, 4,5-di-O-caffeoylquinic acid, 3,4,5-tri-O-caffeoylquinic acid, and other derivatives. Additionally, we evaluated intracellular ATP level in SH-SY5Y treated with each CQA derivative. As a result, 3,4,5-tri-O-caffeoylquinic acid showed the highest accelerating activity on ATP production among tested compounds. It was suggested that caffeoyl groups bound to quinic acid are important for activity and the more caffeoyl groups are bound to quinic acid, the higher accelerating activity on ATP production exhibits.

First chemical synthesis and in vitro characterization of the potential human metabolites 5-o-feruloylquinic acid 4'-sulfate and 4'-O-glucuronide.

Feruloylquinic acids are a major class of biologically active phenolic antioxidants in coffee beans, but their metabolic fate is poorly understood. The present study investigated the phase II metabolism of feruloylquinic acids with selected human sulfotransferases (SULT1A1 and SULT1E1) and uridine 5'-diphosphoglucuronosyltransferases (UGT1A1 and UGT1A9). For unequivocal metabolite identification, the chemical synthesis of two potential human metabolites of 5-O-feruloylquinic acid, the 4'-sulfated and 4'-O-glucuronidated conjugates, has been performed for the first time. Following incubation with human SULT1A1 or SULT1E1, formation of 5-O-feruloylquinic acid 4'-O-sulfate was confirmed by matching its HPLC and MS data with those of the authentic standard. On the other hand, no glucuronide conjugates were detected after incubation with human uridine 5'-diphosphoglucuronosyltransferases. These results suggest that sulfation can take place on the ferulic acid moiety of feruloylquinic acids and may be a major metabolic pathway for feruloylquinic acids in humans.

Synthesis, anti-fungal and 1,3-ß-D-glucan synthase inhibitory activities of caffeic and quinic acid derivatives.

New derivatives of caffeic acid and quinic acid were synthesized and their anti-fungal and inhibitory activities on fungal 1,3-ß-glucan synthase were determined in comparison with those of the corresponding chlorogenic acid derivatives. All the chlorogenic, quinic and caffeic acid derivatives that were coupled with an H(2)N-orn-4-(octyloxy) aniline group (1, 1b and 1c) displayed potent activities in both anti-fungal and inhibition of 1,3-glucan synthase assays. Compounds 1 and 1c inhibited the fungal membrane enzyme with the potency comparable to that of a known 1,3-ß-D-glucan synthase inhibitor, aculeacin A. The results revealed that the anti-fungal activity of the chlorogenic acid derivative with a free amino group was at least partly due to inhibition of the fungal 1,3-ß-glucan synthase. These results suggest that further investigation on caffeic acid derivatives may lead to the discovery of novel anti-fungal agents with drug-like properties.

How to distinguish between feruloyl quinic acids and isoferuloyl quinic acids by liquid chromatography/tandem mass spectrometry.

All four regioisomers of feruloyl quinic acid and isoferuloyl quinic acid were synthesized and a liquid chromatography/tandem mass spectrometry (LC/MS/MS) method developed that resolves all eight regioisomers. All eight regioisomers can be readily distinguished by their MS/MS spectra in the negative ion mode, illustrating the power of tandem mass spectrometry to elucidate the structures of regioisomeric compounds. Compound identification is possible, either by direct comparison of spectral fingerprints or by rational probing of diagnostic fragment ions, thus allowing the identification of these important classes of natural products and potential human metabolites.

Synthesis, anti-HIV and anti-oxidant activities of caffeoyl 5,6-anhydroquinic acid derivatives.

In our continued research on chlorogenic acid analogues and derivatives with improved bioactivity, we have synthesized some caffeoyl 5,6-anhydroquinic acid derivatives. The 1,7 acetonides of chlorogenic acid (15), and of the mono-caffeoyl 5,6-anhydroquinic acids (7-8) showed appreciable anti-HIV activity. The 3,4-dicaffeoyl 5,6-anhydroquinic acid (12) exhibited an anti-HIV activity twice as that of 3,5-dicaffeoylquinic acid (22). The caffeoyl 5,6-anhydroquinic acid derivatives displayed potent anti-oxidant activities. The mono-caffeoyl 5,6-anhydroquinic acids (10-11) were more than twice stronger than chlorogenic acid (21) on SOD-like activity.

Synthesis and biological evaluation of quinic acid derivatives as anti-inflammatory agents.

Quinic acid (QA) esters found in hot water extracts of Uncaria tomentosa (a.k.a. cat's claw) exert anti-inflammatory activity through mechanisms involving inhibition of the pro-inflammatory transcription factor nuclear factor kappa B (NF-kappaB). Herein, we describe the synthesis and biological testing of novel QA derivatives. Inhibition of NF-kappaB was assessed using A549 (Type II alveolar epithelial-like) cells that stably express a secreted alkaline phosphatase (SEAP) reporter driven by an NF-kappaB response element. A549-NF-kappaB cells were stimulated with TNF-alpha (10 ng/mL) in the presence or absence of QA derivative for 18 hours followed by measurement of SEAP activity. Amide substitution at the carboxylic acid position yielded potent inhibitors of NF-kappaB. A variety of modifications to the amide substitution were tolerated with the N-propyl amide derivative being the most potent. Further examination of the SAR demonstrated that acetylation of the hydroxyl groups reduced NF-kappaB inhibitory activity. QA amide derivatives lacked anti-oxidant activity and were found to be neither anti-proliferative nor cytotoxic at concentrations up to 100 microM. In conclusion, we have discovered a novel series of non-toxic QA amides that potently inhibit NF-kappaB, despite their lack of anti-oxidant activity. Mechanistic studies and pre-clinical efficacy studies in various inflammatory animal models are on-going.

A novel efficient and versatile route to the synthesis of 5-O-feruloylquinic acids.

A novel synthesis of 5-O-feruloylquinic acid, a polyphenolic compound found in coffee beans, and its methyl ester derivative has been optimized. The sequence involves 6 steps and is compatible with the preparation of potential human metabolites of these compounds. The key reaction is a Knoevenagel condensation of 4-hydroxy-3-methoxy-benzaldehyde and a malonate ester of quinic acid.

Novel and efficient syntheses of (-)-methyl 4-epi-shikimate and 4,5-epoxy-quinic and -shikimic acid derivatives as key precursors to prepare new analogues.

We have developed simple methods that provide a rapid entry into the synthesis of a series of quinate and shikimate analogues, including (-)-methyl 4-epi-shikimate and the 4,5-epoxy analogues of the parent acids. Epoxy derivatives of quinic and shikimic acids were converted into methyl scyllo-quinate and (+)-methyl 3-epi-shikimate, respectively, by processes involving a regio- and stereoselective epoxide ring opening. The strategies described take place through short, high-yield reaction sequences.

A concise, enantioselective approach to (-)-quinic acid.

[reaction: see text] An expedient, enantioselective synthesis of a key precursor to (-)-quinic acid has been achieved from an ephedrine-derived morpholine-dione. The salient features of this approach are a highly diastereoselective conversion of the dione to a dialkenyl morpholinone and a subsequent ring-closing metathesis reaction. Removal of the ephedrine portion generates an enantiomerically enriched hydroxycyclohexene carboxamide that is readily converted to the quinic acid precursor.