Irreversible inhibition of human immunodeficiency virus type 1 integrase by dicaffeoylquinic acids

Transforming stressed plants into healthy foods

This paper presents the current status of transforming stressed plants into healthy foods and the future trends in this emerging field. Herein, we describe the three major key elements to advance this field, including a better understanding of the mode of action of oxidative stress on nutraceutical biosynthesis under pre- and postharvest scenarios either converting plants into biofactories of nutraceuticals or creating 'functional fresh produce' while preserving quality. We discuss the need of designing healthy products based on stressed fresh produce and by-products and present a pragmatic strategy to enhance nutraceuticals in plants, and finally we propose designing appropriate studies with stressed plants targeting immunomodulatory properties to determine preventive and therapeutic effects against chronic diseases and the appropriate recommended dose.

Identification and evaluation of a novel tribenzamide derivative as an inhibitor targeting the entry of the respiratory syncytial virus

Human respiratory syncytial virus (RSV) is the leading cause of severe lower respiratory tract infections in infants, the elderly, and the immunocompromised, yet no licensed vaccine and only limited therapeutic options for prevention and treatment are available, which poses a global health challenge and emphasizes the urgent medical need for novel antiviral agents. In the current study, a novel potent small molecule inhibitor of RSV was identified by performing a screening and structure optimization campaign, wherein a naturally occurring dicaffeoylquinic acid (DCQA) compound served as a chemical starting point. The reported benzamide derivative inhibitor, designated as 2f, was selected for its improved stability and potent antiviral activity from a series of investigated structurally related compounds. 2f was well tolerated by cells and able to inhibit RSV infection with a half maximal inhibitory concentration (IC₅₀) of 35 nM and a favorable selectivity index (SI) of 3742. Although the exact molecular target for 2f is not known, in vitro mechanism of action investigations revealed that the compound inhibits the early stage of infection by interacting with RSV virion and interferes primarily with the attachment and potentially with the virus-cell fusion step. Moreover, intranasal administration of 2f to mice simultaneously or prior to intranasal infection with RSV significantly decreased viral load in the lungs, pointing to the in vivo potential of the compound. Our results suggest that 2f is a viable candidate for further preclinical development and evaluation as an antiviral agent against RSV infections.

Natural products for infectious microbes and diseases: an overview of sources, compounds, and chemical diversities

As coronavirus disease 2019 (COVID-19) threatens human health globally, infectious disorders have become one of the most challenging problem for the medical community. Natural products (NP) have been a prolific source of antimicrobial agents with widely divergent structures and a range vast biological activities. A dataset comprising 618 articles, including 646 NP-based compounds from 672 species of natural sources with biological activities against 21 infectious pathogens from five categories, was assembled through manual selection of published articles. These data were used to identify 268 NP-based compounds classified into ten groups, which were used for network pharmacology analysis to capture the most promising lead-compounds such as agelasine D, dicumarol, dihydroartemisinin and pyridomycin. The distribution of maximum Tanimoto scores indicated that compounds which inhibited parasites exhibited low diversity, whereas the chemistries inhibiting bacteria, fungi, and viruses showed more structural diversity. A total of 331 species of medicinal plants with compounds exhibiting antimicrobial activities were selected to classify the family sources. The family Asteraceae possesses various compounds against C. neoformans, the family Anacardiaceae has compounds against Salmonella typhi, the family Cucurbitacea against the human immunodeficiency virus (HIV), and the family Ancistrocladaceae against Plasmodium. This review summarizes currently available data on NP-based antimicrobials against refractory infections to provide information for further discovery of drugs and synthetic strategies for anti-infectious agents.

Callus culture as a new approach for the production of high added value compounds in Ilex paraguariensis: genotype influence, medium optimization and compounds identification

Ilex paraguariensis (yerba mate) is a native species from South America and is a rich source of bioactive compounds. There is a lack of research efforts on the phytochemical investigation of callus culture from this species. In the present study, an effort was made to optimize callus culture conditions and to identify secondary compounds. Calli were induced from 10 genotypes using leaf explants and the best genotype was selected to evaluate the effects of cytokinin types and concentrations on callus induction and biomass accumulation. The best genotype and cytokinin treatment were used to conduct one last experiment with sucrose concentrations in culture media and its effects on calli biomass, antioxidant activity and secondary compounds accumulation. Callus initiation was genotype dependent, and the 6-156-6 line had the best response. Zeatin supplemented medium showed higher callus induction rate (82%) and higher biomass accumulation after 120 days (328.2 mg). Higher biomass and secondary compounds accumulation were observed for calli on 3% sucrose medium. Antioxidant activity was not affected by sucrose concentrations. Yerba mate callus culture allowed the accumulation of chlorogenic acid, cryptochlorogenic acid, neochlorogenic acid, 3,4-dicaffeoylquinic acid, 3,5-dicaffeoylquinic acid, 4,5-dicaffeoylquinic acid, theobromine and caffeine.

Caffeoylquinic Acids with Potential Biological Activity from Plant In vitro Cultures as Alternative Sources of Valuable Natural Products

BACKGROUND

For a long time, the researchers have been looking for new efficient methods to enhance production and obtain valuable plant secondary metabolites, which would contribute to the protection of the natural environment through the preservation of various plant species, often rare and endangered. These possibilities offer plant in vitro cultures which can be performed under strictly-controlled conditions, regardless of the season or climate and environmental factors. Biotechnological methods are promising strategies for obtaining the valuable plant secondary metabolites with various classes of chemical compounds including caffeoylquinic acids (CQAs) and their derivatives. CQAs have been found in many plant species which are components in the daily diet and exhibit a wide spectrum of biological activities, including antioxidant, immunomodulatory, antihypertensive, analgesic, anti-inflammatory, hepato- and neuroprotective, anti-hyperglycemic, anticancer, antiviral and antimicrobial activities. They have also been found to offer protection against Alzheimer's disease, and play a role in weight reduction and lipid metabolism control, as well as modulating the activity of glucose-6-phosphatase involved in glucose metabolism.

METHODS

This work presents the review of the recent advances in use in vitro cultures of various plant species for the alternative system to the production of CQAs and their derivatives. Production of the secondary metabolites in in vitro culture is usually performed with cell suspension or organ cultures, such as shoots and adventitious or transformed roots. To achieve high production of valuable secondary metabolites in in vitro cultures, the optimization of the culture condition is necessary with respect to both biomass accumulation and metabolite content. The optimization of the culture conditions can be achieved by choosing the type of medium, growth regulators or growth conditions, selection of high-productivity lines or culture period, supplementation of the culture medium with precursors or elicitor treatments. Cultivation for large-scale in bioreactors and genetic engineering: Agrobacterium rhizogenes transformation and expression improvement of transcriptional factor or genes involved in the secondary metabolite production pathway are also efficient strategies for enhancement of the valuable secondary metabolites.

RESULTS

Many studies have been reported to obtain highly productive plant in vitro cultures with respect to CQAs. Among these valuable secondary metabolites, the most abundant compound accumulated in in vitro cultures was 5-CQA (chlorogenic acid). Highly productive cultures with respect to this phenolic acid were Leonurus sibiricus AtPAP1 transgenic roots, Lonicera macranthoides and Eucomia ulmoides cell suspension cultures which accumulated above 20 mg g-1 DW 5-CQA. It is known that di- and triCQAs are less common in plants than monoCQAs, but it was also possible to obtain them by biotechnological methods.

CONCLUSION

The results indicate that the various in vitro cultures of different plant species can be a profitable approach for the production of CQAs. In particular, an efficient production of these valuable compounds is possible by Lonicera macranthoides and Eucomia ulmoides cell suspension cultures, Leonurus sibiricus transformed roots and AtPAP1 transgenic roots, Echinacea angustifolia adventitious shoots, Rhaponticum carthamoides transformed plants, Lavandula viridis shoots, Sausera involucrata cell suspension and Cichorium intybus transformed roots.

Characterization of Nine Compounds Isolated from the Acid Hydrolysate of Lonicera fulvotomentosa Hsu et S. C. Cheng and Evaluation of Their In Vitro Activity towards HIV Protease

In this study, we isolated nine compounds from the acid hydrolysate of the flower buds of Lonicera fulvotomentosa Hsu et S. C. Cheng and characterized their chemical structures using ¹H-NMR, ¹³C-NMR, and electron ionization mass spectroscopy (EI-MS). These compounds were identified as β-sitosterol (1), 5,5′-dibutoxy-2,2′-bifuran (2), nonacosane-10-ol (3), ethyl (3β)-3,23-dihydroxyolean-12-en-28-oate (4), oleanolic acid (5), ethyl caffeate (6), caffeic acid (7), isovanillin (8), and hederagenin (9), with 4 as a new triterpene compound. Inhibitory activity against human immunodeficiency virus (HIV) protease was also evaluated for the compounds, and only ethyl caffeate, caffeic acid, and isovanillin (6, 7, and 8) exhibited inhibitory effects, with IC₅₀ values of 1.0 μM, 1.5 μM, and 3.5 μM, respectively. Molecular docking with energy minimization and subsequent molecular dynamic (MD) simulation showed that ethyl caffeate and caffeic acid bound to the active site of HIV protease, while isovanillin drifted out from the active site and dissociated into bulk water during MD simulations, and most of the binding residues of HIV protease have been previously identified for HIV protease inhibitors. These results suggest that caffeic acid derivatives may possess inhibitory activities towards HIV protease other than previously reported inhibitory activities against HIV integrase, and thus ethyl caffeate and caffeic acid could be used as lead compounds in developing potential HIV protease inhibitors, and possibly even dual-function inhibitors against HIV.

Structural Elucidation of cis/trans Dicaffeoylquinic Acid Photoisomerization Using Ion Mobility Spectrometry-Mass Spectrometry

Due to the recently uncovered health benefits and anti-HIV activities of dicaffeoylquinic acids (diCQAs), understanding their structures and functions is of great interest for drug discovery efforts. DiCQAs are analytically challenging to identify and quantify since they commonly exist as a diverse mixture of positional and geometric (cis/trans) isomers. In this work, we utilized ion mobility spectrometry coupled with mass spectrometry to separate the various isomers before and after UV irradiation. The experimental collision cross sections were then compared with theoretical structures to differentiate and identify the diCQA isomers. Our analyses found that naturally the diCQAs existed predominantly as trans/trans isomers, but after 3 h of UV irradiation, cis/cis, cis/trans, trans/cis, and trans/trans isomers were all present in the mixture. This is the first report of successful differentiation of cis/trans diCQA isomers individually, which shows the great promise of IMS coupled with theoretical calculations for determining the structure and activity relationships of different isomers in drug discovery studies.

Deciphering the influence of column chemistry and mass spectrometry settings for the analyses of geometrical isomers of L-chicoric acid

Resolving the chemo-diversity of plant extract samples is an essential step for in-depth analyses of natural products which often exhibit promising biological activities. One of the challenges in this endeavor has been the confident differentiation of geometrical isomers. In this study, we investigated these aspects in chromatography (column chemistry and mobile phase composition) and mass spectrometry settings with regards to better differentiation of geometrical isomers. A standard of a hydroxycinnamic acid (HCA) derivative, L-chicoric acid (L-CA) - a di-acylated caffeoyltartaric acid ester found in a number of plant families - was used. Geometrical isomers of L-CA were formed by exposing the compound to ultraviolet (UV) radiation, to mimic the natural environment. The high performance liquid chromatography photo-diode array (HPLC-PDA) and ultra-high performance liquid chromatography mass spectrometry (UHPLC-MS) platforms were used to analyze the trans and cis geometrical isomers of L-CA. The HPLC-PDA results confirmed the generation of two cis geometrical isomers following UV exposure of the authentic trans-L-CA standard. Furthermore, the HPLC-PDA analyses demonstrated that the changes in both column chemistry (reverse-phase: C₁₈, biphenyl, phenyl-hexyl and pentafluorophenyl propyl) and mobile phase composition (aqueous acetonitrile and aqueous methanol) affect the chromatographic elution profiles of the L-CA isomers. The MS results, on the other hand, revealed undisputed fragmentation differences between the geometrical isomers of L-CA. Thus, this study demonstrates that the identification of the L-CA isomers can be achieved more efficiently and confidently with good chromatography coupled to well-optimized mass spectrometry conditions, a requirement which has been proven impossible with other types of HCA derivatives. Moreover, differences in the binding modes of L-CA geometrical isomers to the HIV type 1 integrase enzyme were observed, suggesting a synergistic anti-HIV-1 activity of these isomers.

The Effect of Geometrical Isomerism of 3,5-Dicaffeoylquinic Acid on Its Binding Affinity to HIV-Integrase Enzyme: A Molecular Docking Study

A potent plant-derived HIV-1 inhibitor, 3,5-dicaffeoylquinic acid (diCQA), has been shown to undergo isomerisation upon UV exposure where the naturally occurring 3 ^trans ,5 ^trans -diCQA isomer gives rise to the 3 ^cis ,5 ^trans -diCQA, 3 ^trans ,5 ^cis -diCQA, and 3 ^cis ,5 ^cis -diCQA isomers. In this study, inhibition of HIV-1 INT by UV-induced isomers was investigated using molecular docking methods. Here, density functional theory (DFT) models were used for geometry optimization of the 3,5-diCQA isomers. The YASARA and Autodock VINA software packages were then used to determine the binding interactions between the HIV-1 INT catalytic domain and the 3,5-diCQA isomers and the Discovery Studio suite was used to visualise the interactions between the isomers and the protein. The geometrical isomers of 3,5-diCQA were all found to bind to the catalytic core domain of the INT enzyme. Moreover, the cis geometrical isomers were found to interact with the metal cofactor of HIV-1INT, a phenomenon which has been linked to antiviral potency. Furthermore, the 3 ^trans ,5 ^cis -diCQA isomer was also found to interact with both LYS156 and LYS159 which are important residues for viral DNA integration. The differences in binding modes of these naturally coexisting isomers may allow wider synergistic activity which may be beneficial in comparison to the activities of each individual isomer.

Isolation of 4,5-O-Dicaffeoylquinic Acid as a Pigmentation Inhibitor Occurring in Artemisia capillaris Thunberg and Its Validation In Vivo

There is a continual need to develop novel and effective melanogenesis inhibitors for the prevention of hyperpigmentation disorders. The plant Artemisia capillaris Thunberg (Oriental Wormwood) was screened for antipigmentation activity using murine cultured cells (B16-F10 malignant melanocytes). Activity-based fractionation using HPLC and NMR analyses identified the compound 4,5-O-dicaffeoylquinic acid as an active component in this plant. 4,5-O-Dicaffeoylquinic acid significantly reduced melanin synthesis and tyrosinase activity in a dose-dependent manner in the melanocytes. In addition, 4,5-O-dicaffeoylquinic acid treatment reduced the expression of tyrosinase-related protein-1. Significantly, we could validate the antipigmentation activity of this compound in vivo, using a zebrafish model. Moreover, 4,5-O-dicaffeoylquinic acid did not show toxicity in this animal model. Our discovery of 4,5-O-dicaffeoylquinic acid as an inhibitor of pigmentation that is active in vivo shows that this compound can be developed as an active component for formulations to treat pigmentation disorders.

Hyperpigmentation mechanism of methyl 3,5-di-caffeoylquinate through activation of p38 and MITF induction of tyrosinase

Methyl 3,5-di-caffeoylquinate (3,5-diCQM) has been used for the treatment of various diseases in oriental medicine, but its effect on melanogenesis has not been reported yet. In this study, the molecular mechanism of 3,5-diCQM-induced melanogenesis was investigated. It was found that 3,5-diCQM induced synthesis of melanin pigments in murine B16F10 melanoma cells in a concentration-dependent manner. Treatment of cells with 3,5-diCQM for 48 h increased extracellular and intracellular melanin production and tyrosinase activity. The expressions of tyrosinase, tyrosinase-related protein 1 (TRP1), and TRP2 were up-regulated in a dose-dependent manner 48 h after 3,5-diCQM treatment. Western blot analysis showed that 3,5-diCQM increased the phosphorylation of p38 mitogen-activated protein kinase and cAMP responsive element binding as well as the expression of microphthalmia-associated transcription factor. In addition, 3,5-diCQM-stimulated cAMP production, and 3,5-diCQM-induced tyrosinase activity and melanin synthesis were attenuated by H89, a protein kinase A inhibitor. These results suggested that 3,5-diCQM-mediated activation of the p38 pathway may represent a novel approach for an effective therapy for vitiligo and hair graying.

Cross-talk between signaling pathways: the link between plant secondary metabolite production and wounding stress response

Plants subjected to wounding stress produce secondary metabolites. Several of these metabolites prevent chronic diseases and can be used as colorants, flavors, and as antimicrobials. This wound-induced production of plant secondary metabolites is mediated by signaling-molecules such as reactive oxygen species (ROS), ethylene (ET) and jasmonic acid (JA). However, their specific role and interactions that modulate the wound-respond in plants is not fully understood. In the present study, a subtractive cDNA library was generated, to better understand the global response of plants to wounding stress. Carrot (Daucus carota) was used as a model system for this study. A total of 335 unique expressed sequence tags (ESTs) sequences were obtained. ESTs sequences with a putative identity showed involvement in stress-signaling pathways as well as on the primary and secondary metabolism. Inhibitors of ROS biosynthesis, ET action, and JA biosynthesis alone and in combination were applied to wounded-carrots in order to determine, based on relative gene expression data, the regulatory role of ET, JA, and ROS on the wound-response in plants. Our results demonstrate that ROS play a key role as signaling-molecules for the wound-induced activation of the primary and secondary metabolism whereas ET and JA are essential to modulate ROS levels.

Comparison of anti-bacterial activity of three types of di-O-caffeoylquinic acids in Lonicera japonica flowers based on microcalorimetry

The anti-bacterial activities of three types of di-O-caffeoylquinic acids (diCQAs) in Lonicera japonica flowers, a traditional Chinese medicine (TCM), on Bacillus shigae growth were investigated and compared by microcalorimetry. The three types of diCQAs were 3, 4-di-O-caffeoylquinic acid (3, 4-diCQA), 3, 5-di-O-caffeoylquinic acid (3, 5-diCQA), and 4, 5-di-O-caffeoylquinic acid (4, 5-diCQA). Some qualitative and quantitative information of the effects of the three diCQAs on metabolic power-time curves, growth rate constant k, maximum heat-output power Pm, and the generation time tG, total heat output Qt, and growth inhibitory ratio I of B. shigae were calculated. In accordance with a thermo-kinetic model, the corresponding quantitative relationships of k, Pm, Qt, I and c were established. Also, the half-inhibitory concentrations of the drugs (IC50) were obtained by quantitative analysis. Based on the quantity-activity relationships and the IC50 values, the sequence of inhibitory activity was 3, 5-diCQA > 4, 5-diCQA > 3, 4-diCQA. The results illustrate the possibility that the caffeoyl ester group at C-5 is the principal group that has a higher affinity for the bacterial cell, and that the intramolecular distance of the two caffeoyl ester groups also has an important influence on the anti-bacterial activities of the diCQAs.

Plants as biofactories: glyphosate-induced production of shikimic acid and phenolic antioxidants in wounded carrot tissue

The use of plants to produce chemical compounds with pharmaceutical and nutraceutical applications has intensified in recent years. In this regard, genetic engineering is the most commonly used tool to generate crop lines with enhanced concentrations of desirable chemicals. However, growing genetically modified plants is still limited because they are perceived as potential biological hazards that can create an ecological imbalance. The application of postharvest abiotic stresses on plants induces the accumulation of secondary metabolites and thus can be used as an alternative to genetic modification. The present project evaluated the feasibility of producing shikimic acid (SA) and phenolic compounds (PC) in wounded carrots ( Daucus carota ) treated with glyphosate. The spray application of a concentrated glyphosate solution on wounded carrot tissue increased the concentrations of SA and chlorogenic acid by ∼1735 and ∼5700%, respectively. The results presented herein demonstrate the potential of stressed carrot tissue as a biofactory of SA and PC.

3,5-Dicaffeoylquinic acid isolated from Artemisia argyi and its ester derivatives exert anti-leucyl-tRNA synthetase of Giardia lamblia (GlLeuRS) and potential anti-giardial effects

An aqueous ethanol extract of Artemisia argyi inhibited the aminoacylation activity of LeuRS from Giardia lamblia (GlLeuRS). The bioassay-guided fractionation of the extract led to the isolation of 3,5-dicaffeoylquinic acid (1), with an IC₅₀ of 5.82 μg/mL. The ester derivatives of 1 were also found to possess strong anti-GlLeuRS effects, with IC₅₀ values of 1.79, 5.51 and 2.56 μg/mL respectively. Anti-giardial assay showed that the derivatives, especially 3,5-dicaffeoylquinic acid propyl ester (4) (IC₅₀=4.62 μg/mL), were effective at killing G. lamblia.

Plants as biofactories: physiological role of reactive oxygen species on the accumulation of phenolic antioxidants in carrot tissue under wounding and hyperoxia stress

Plants subjected to postharvest abiotic stresses synthesize secondary metabolites with health-promoting properties. Here, we report the potential use of carrots (Daucus carota) as biofactories of caffeoylquinic acids when subjected to wounding and hyperoxia stresses. Wounding stress induced an increase of ∼287% in total phenolic content (PC) in carrots stored for 48 h at 20 °C. This increase was higher (∼349%) in the wounded tissue treated with hyperoxia stress. To further understand the physiological role of reactive oxygen species (ROS) as a signaling molecule for the stress-induced accumulation of phenolics in carrots, the respiration rate as well as the enzymatic activities of NADPH oxidase, superoxide dismutase, ascorbate peroxidase, and catalase were evaluated. Likewise, shredded carrots were treated with diphenyleneiodonium chloride solution to block NADPH oxidase ROS productions, and the phenylalanine ammonia lyase activity and total PC were evaluated. Results demonstrated that ROS play a key role as a signaling molecule for the stress-induced accumulation of PC in carrots.

Influence of environmental factors on composition of phenolic antioxidants of Achillea collina Becker ex Rchb

Effects of environmental growth conditions on the antioxidant capacity, total phenolic content and composition of Achillea collina Becker ex Rchb. were investigated. Methanol extracts and infusions obtained from leaves and inflorescences of plants cultivated in the Italian Alps at two different altitudes (600 and 1050 m a.s.l.) were evaluated. Infusions exhibited the highest antioxidant capacity (1/IC(50) values from 4.35 ± 0.72 to 8.90 ± 0.74), total phenolic content (from 31.39 ± 4.92 to 49.36 ± 5.70 mg gallic acid equivalents (GAE) g(-1) DW), chlorogenic acid (from 9.21 ± 1.52 to 31.27 ± 6.88 mg g(-1) DW), 3,5-di-O-caffeoylquinic acid (from 12.28 ± 3.25 to 25.13 ± 1.99 mg g(-1) DW) and 4,5-di-O-caffeoylquinic acid (from 7.38 ± 1.01 to 12.78 ± 2.61 mg g(-1) DW) content. Climate (as influenced by altitude) was shown to be the main environmental factor influencing yarrow composition and properties. Leaf extracts from the higher experimental site showed a 2-4-fold increase of chlorogenic acid level. Achillea collina can be considered as a very good source of bioactive phenolic compounds, and growing it at high altitude may constitute an effective way to significantly enhance its quality for both medicinal and nutritional uses.

Design, synthesis, and biological evaluation of novel hybrid dicaffeoyltartaric/diketo acid and tetrazole-substituted L-chicoric acid analogue inhibitors of human immunodeficiency virus type 1 integrase

Fourteen analogues of the anti-HIV-1 integrase (IN) inhibitor L-chicoric acid (L-CA) were prepared. Their IC(50) values for 3'-end processing and strand transfer against recombinant HIV-1 IN were determined in vitro, and their cell toxicities and EC(50) against HIV-1 were measured in cells (ex vivo). Compounds 1-6 are catechol/β-diketoacid hybrids, the majority of which exhibit submicromolar potency against 3'-end processing and strand transfer, though only with modest antiviral activities. Compounds 7-10 are L-CA/p-fluorobenzylpyrroloyl hybrids, several of which were more potent against strand transfer than 3'-end processing, a phenomenon previously attributed to the β-diketo acid pharmacophore. Compounds 11-14 are tetrazole bioisosteres of L-CA and its analogues, whose in vitro potencies were comparable to L-CA but with enhanced antiviral potency. The trihydroxyphenyl analogue 14 was 30-fold more potent than L-CA at relatively nontoxic concentrations. These data indicate that L-CA analogues are attractive candidates for development into clinically relevant inhibitors of HIV-1 IN.

Prediction of the interaction of HIV-1 integrase and its dicaffeoylquinic acid inhibitor through molecular modeling approach

An essential step in the life cycle of human immunodeficiency virus type 1 (HIV-1) is integration of the double-stranded retroviral DNA into the genome of the host cell. HIV-1 integrase, the enzyme that inserts the vital DNA into the host chromosome, is an attractive and rational target for anti-AIDS drug design because it is essential for HIV replication and there are no known counterparts in the host cell. Inhibitors of this enzyme have a great potential to complement the therapeutic use of HIV protease and reverse transcriptase inhibitors. Natural products have provided a source of new drug candidates for anti-AIDS therapy. Dicaffeoylquinic acids, isolated from traditional medicinal plants, are a novel class of integrase inhibitors. These compounds are potent inhibitors of HIV-1 replication in cultured cell lines and catalytic activities of integrase in vitro. They are therefore promising compounds for developing new anti-AIDS drugs. To understand how the inhibitors work and therefore design more potent and specific inhibitors, we have used molecular modeling techniques to investigate the binding modes of 3,4-dicaffeoylquinic acid. Our computational modeling study demonstrated that the inhibitor of this compound on HIV integrase is likely to proceed by two different but equivalent mechanisms with one bound to the active site region of the enzyme and another docked into the binding pocket located on the other side of the catalytic site. Our study will be of help to design new pharmaceuticals for the treatment of AIDS.

Model and experiences of initiating collaboration with traditional healers in validation of ethnomedicines for HIV/AIDS in Namibia

Many people with Human Immunodeficiency Virus/Acquired Immunodeficiency Syndrome (HIV/AIDS) in Namibia have access to antiretroviral drugs but some still use traditional medicines to treat opportunistic infections and offset side-effects from antiretroviral medication. Namibia has a rich biodiversity of indigenous plants that could contain novel anti-HIV agents. However, such medicinal plants have not been identified and properly documented. Various ethnomedicines used to treat HIV/AIDS opportunistic infections have not been scientifically validated for safety and efficacy. These limitations are mostly attributable to the lack of collaboration between biomedical scientists and traditional healers. This paper presents a five-step contextual model for initiating collaboration with Namibian traditional healers in order that candidate plants that may contain novel anti-HIV agents are identified, and traditional medicines used to treat HIV/AIDS opportunistic infections are subjected to scientific validation. The model includes key structures and processes used to initiate collaboration with traditional healers in Namibia; namely, the National Biosciences Forum, a steering committee with the University of Namibia (UNAM) as the focal point, a study tour to Zambia and South Africa where other collaborative frameworks were examined, commemorations of the African Traditional Medicine Day (ATMD), and consultations with stakeholders in north-eastern Namibia. Experiences from these structures and processes are discussed. All traditional healers in north-eastern Namibia were willing to collaborate with UNAM in order that their traditional medicines could be subjected to scientific validation. The current study provides a framework for future collaboration with traditional healers and the selection of candidate anti-HIV medicinal plants and ethnomedicines for scientific testing in Namibia.

Interaction of bioactive components caffeoylquinic Acid derivatives in Chinese medicines with bovine serum albumin

Five caffeoylquinic acid derivatives (CQAs), including methyl 3,4-di-O-caffeoylquinate (3,4-diCQM), methyl 3,5-di-O-caffeoylquinate (3,5-diCQM), 3,4-di-O-caffeoylquinic acid (3,4-diCQA), 3,5-di-O-caffeoylquinic acid (3,5-diCQA) and chlorogenic acid (CA), were isolated from Lonicera fulvotomentosa HSU et S. C. CHENG to be used as model compounds. The binding of these bioactive components to bovine serum albumin (BSA) was investigated by fluorescence quenching method. The results showed that there were binding affinities for CQAs with BSA, and the binding constants ranked in the following order: 3,4-diCQM>3,5-diCQM<3,4-diCQA>3,5-diCQA>CA, under the physiological conditions, which suggested that the numbers and the substituted positions of caffeoyl group as well as the esterification of carboxyl group in the molecular structures appeared to contribute moderate effects to the interaction processes. Furthermore, the Stern-Volmer curves demonstrated that CQAs caused the fluorescence quenching through a static quenching procedure. Thermodynamic analysis indicated that both hydrophobic and electrostatic interactions played major roles in stabilizing the complex. The binding distance for each binding reaction was also calculated by the Föster theory.

Simultaneous determination of 1,5-dicaffeoylquinic acid and its active metabolites in human plasma by liquid chromatography-tandem mass spectrometry for pharmacokinetic studies

1,5-Dicaffeoylquinic acid (1,5-DCQA), a potent HIV-1 integrase inhibitor, is undergoing an evaluation as a promising novel HIV therapeutic agent. Here, we report a simple, rapid and robust LC-MS/MS method for simultaneous determination of 1,5-DCQA and its two active metabolites, 1-caffeoyl-5-feruoylquinic acid (1,5-CFQA) and 1,5-O-diferuoylquinic acid (1,5-DFQA) in human plasma. The quantitation of the target compounds was determined by selected reaction monitoring (SRM) mode using electrospray ionization (ESI). Good linearity was obtained in the 3-500 ng/ml range for each analyte and the analytical method was validated in terms of specificity, precision, accuracy, recovery, stability and matrix effect. These assays gave R.S.D.% values for precision always lower than 13.8% and R.E.% values for accuracy between -8.9 and 0.9%. In addition, the specificity, extraction recovery, stability and matrix effect were satisfactory too. Using the measured plasma concentrations of 1,5-DCQA and its active metabolites in five healthy volunteers, pharmacokinetic profiles of 1,5-DCQA and its active metabolites were evaluated, which supported the clinical pharmacokinetic studies successfully. Due to its high sensitivity, specificity and simplicity, the method could be used for pharmacokinetic studies of both 1,5-DCQA and its active metabolite, and for routine monitoring of their levels in human plasma.

Evolution in caffeoylquinic acid content and histolocalization during Coffea canephora leaf development

BACKGROUND AND AIMS

Caffeoylquinic acids are cinnamate conjugates derived from the phenylpropanoid pathway. They are generally involved in plant responses to biotic and abiotic stress and one of them, chlorogenic acid (5-O-caffeoylquinic acid, 5-CQA), is an intermediate in the lignin biosynthesis pathway. Caffeoylquinic acids, and particularly 5-CQA, are accumulated in coffee beans, where they can form vacuolar complexes with caffeine. Coffea canephora beans are known to have high caffeoylquinic acid content, but little is known about the content and diversity of these compounds in other plant parts. To gain new insights into the caffeoylquinic acid metabolism of C. canephora, caffeoylquinic acid content and in situ localization were assessed in leaves at different growth stages.

METHODS

HPLC analyses of caffeoylquinic acid content of leaves was conducted in conjunction with detailed histochemical and microspectrofluorometrical analysis.

KEY RESULTS AND CONCLUSIONS

HPLC analyses revealed that caffeoylquinic acid content was 10-fold lower in adult than in juvenile leaves. The most abundant cinnamate conjugate was 5-CQA, but dicaffeoylquinic acids (particularly in juvenile leaves) and feruloylquinic acids were also present. Using specific reagents, histochemical and microspectrofluorometrical analysis showed that caffeoylquinic acids (mono- and di-esters) were closely associated with chloroplasts in very young leaves. During leaf ageing, they were found to first accumulate intensively in specific chlorenchymatous bundle sheath cells and then in phloem sclerenchyma cells. The association with chloroplasts suggests that caffeoylquinic acids have a protective role against light damage. In older tissues, their presence in the leaf vascular system indicates that they are transported via phloem and confirms their involvement in lignification processes. In accordance with the hypothesis of a complex formation with caffeine, similar tissue distribution was observed for alkaloids and this is further discussed.

Antiviral activities of purified compounds from Youngia japonica (L.) DC (Asteraceae, Compositae)

The ethanol extract of a biannual medicinal herb, Youngia japonica (commonly known as Oriental hawk's beard) was reported previously to have potent antiviral activity against respiratory syncytial virus (RSV) cultured in HEp-2 cells. Three anti-microbial agents, namely 3,4-dicaffeoylquinic acid, 3,5-dicaffeoylquinic acid, and luteolin-7-O-glucoside were subsequently purified and chemically characterized from the ethanol extract of Youngia japonica. The two dicaffeoylquinic acids exhibited prominent anti-RSV with 50% inhibitory concentration (IC50) of 0.5 microg/ml in vitro. Luteolin-7-O-glucoside together with the two dicaffeoylquinic acids were also manifested to have some antibacterial activity towards the causal agents of food-borne disease, namely Vibrio cholerae and Vibrio parahaemolyticus at the concentration of 2mg/ml. Bacillus cereus was sensitive to 3,4-dicaffeoylquinic acid and 3,5-dicaffeoylquinic acid only, but not to luteolin-7-O-glucoside.

Preliminary mapping of a putative inhibitor-binding pocket for human immunodeficiency virus type 1 integrase inhibitors

Molecular modeling studies have identified a putative human immunodeficiency virus (HIV) integrase (IN) inhibitor-binding pocket for l-chicoric acid (l-CA) and other inhibitors of IN (C. A. Sotriffer, H. Ni, and A. McCammon, J. Med. Chem. 43:4109-4117, 2000). By using site-directed mutagenesis of several amino acid residues identified by modeling studies, a common inhibitor-binding pocket on IN was confirmed for l-CA and the diketo acid L-731,988. Specifically, the single mutations E92K, Q148A, K156A, K156R, G140S, and G149S, as well as the double mutations C65S-K156N and H67D-G140A were evaluated for their effects on enzymatic activity and inhibitor susceptibility. Each recombinant IN was attenuated for 3'-end processing and strand transfer activities. Most proteins were also attenuated for disintegration; the IN that contained K156R and C65S-K156N, however, displayed disintegration activity similar to that of IN from HIV(NL4-3). All mutant IN proteins demonstrated decreased susceptibility to l-CA, while all mutant proteins except E92K and K156R demonstrated resistance to L-731,988. These data validate the computer modeling data and demonstrate that l-CA and L-731,988 share an overlapping inhibitor-binding pocket that involves amino acids Q148, C65, and H67. The resistance studies confirm that L-731,988 fills one-half of the inhibitor-binding pocket and binds to Q148 but excludes E92, while l-CA fills the entire binding groove and thus interacts with E92. These results provide "wet laboratory" evidence that molecular models of the HIV IN inhibitor-binding pocket can be used for drug discovery.

Pharmacokinetics and metabolism of 1,5-dicaffeoylquinic acid in rats following a single intravenous administration

1,5-Dicaffeoylquinic acid (1,5-DCQA) is a potentially important HIV-1 integrase inhibitor widely distributed in many plants. To characterize the pharmacokinetic and metabolic properties of 1,5-DCQA in rats following single intravenous administration (160 mg/kg), the plasma concentrations of 1,5-DCQA were measured by high-performance liquid chromatography (HPLC) and the metabolites formed in urine were identified by liquid chromatography-mass spectrometry (LC-MS) in parallel to diode-array detection (DAD). The results showed that the concentrations of 1,5-DCQA in plasma declined rapidly in a biphasic manner with a mean terminal half-life (t(1/2)) of 1.40 h. The mean clearance (CL) and the apparent volume of distribution (Vd(B)) of 1,5-DCQA were 0.44l/h/kg and 0.89l/kg, respectively. A total of 15 metabolites in rat urine were identified, including four isomeric O-mono-methylated (M1-M4), six isomeric O-di-methylated (M5-M10), one isomeric O-mono-methyl-glucuronidated (M11) and four isomeric O-di-methyl-glucuronidated (M12-M15) metabolites. The O-methylation positions of three important metabolites (M1, M2 and M5) were determined (3''-, 3'-, and 3',3''-) by comparing with synthesized standards. These results suggested that the disappearance of 1,5-DCQA from plasma was rapid, and that its quick urinary excretion and extensive metabolism, including methylation and glucuronidation, were two factors causing its rapid elimination from the circulation.

A novel inhibitor of respiratory syncytial virus isolated from ethnobotanicals

A novel low molecular weight compound, CJ 4-16-4, isolated from ethnobotanicals using bioassay-guided fractionation, was found to be a potent inhibitor of respiratory syncytial virus (RSV) in vitro and in vivo. In vitro, a very low micromolar efficacious dose was obtained against at least four of subtype A (RSV-Long, RSV A2, and RSV A6 57754) and one of subtype B (Washington) RSV strains without seeing any significant cytotoxicity to Hep-2, MDCK or Vero cell lines. The drug inhibits growth of RSV in Hep-2 cells maintained in tissue culture at a very low concentration (approximately 0.07 microM) with cell toxicity >400 microM (TI>5880). In a cotton rat model of RSV infection, the drug was able to reduce viral titers by approximately 1 log at dose 12.5 and 25 mg/kg/day, and by >2 log at 100 mg/kg/day. This antiviral activity was specific as influenza A and B and herpes simplex 1 and 2 viruses were not inhibited. The results obtained indicate that CJ 4-16-4 warrants clinical development.

Cluster analysis and three-dimensional QSAR studies of HIV-1 integrase inhibitors

Three-dimensional quantitative structure-activity relationship (3D QSAR) and cluster analysis were applied to a variety of HIV-1 integrase inhibitors. One structure was chosen from each of 11 classes of inhibitors to represent the whole class in descriptor-based cluster analysis. The 11 classes of inhibitors were classified into two groups. The molecular field analysis (MFA) models for these two clusters had r2 values of 0.90 and 0.95 and q2 values of 0.85 and 0.91 that were noticeably enhanced from those of conventional QSAR models. The five test compounds, which were proposed to have a common binding site near the metal in HIV-1 integrase based on docking studies by Sotriffer et al., were utilized to compare the predictive capability of MFA and conventional QSAR models. Among these five compounds, only L-chicoric acid belongs to cluster 1 and the other four belong to cluster 2. MFA models give better overall predictions and more importantly the activity of these test compounds is better predicted by the MFA model derived from the cluster each test compound belongs to. The necessity of dividing the inhibitors into two groups to obtain predictive QSAR models supports the likelihood of two separate binding sites.

METABOLIC PROFILE OF 1,5-DICAFFEOYLQUINIC ACID IN RATS, AN IN VIVO AND IN VITRO STUDY

To explore the metabolism of 1,5-dicaffeoylquinic acid (1,5-DCQA) in rats, liquid chromatography-mass spectrometry in parallel to diode-array detection was used for the rapid detection/characterization of the metabolites formed in bile, urine, and plasma of rats following oral administration of 1,5-DCQA (160 mg/kg). The methylation and glucuronidation of 1,5-DCQA occurring in vitro using rat liver and small intestinal microsomes and cytosols were studied in comparison with those occurring in vivo, and the enzymes involved were also determined. In addition, the anti-HIV (human immunodeficiency virus) activity of three important metabolites was preliminarily evaluated in MT-4 cells infected with HIV-1. A total of 22 metabolites in vivo and in vitro were identified, including four isomeric O-mono-methylated metabolites (M8-M11), nine isomeric O-di-methylated metabolites (M3, M6, M22, and M12-M17), four isomeric O-mono-methyl-glucuronidated metabolites (M2 and M19-M21), four isomeric O-di-methyl-glucuronidated metabolites (M1, M4, M5, and M7), and one glucuronidated metabolite (M18). The O-methylation positions of three important metabolites (M8, M9, and M12) were determined (3''-, 3'-, and 3',3''-) by comparing with synthesized standards. The efficacy experiments showed that M8, M9, and M12 could inhibit HIV replication with IC(50) values of about 25, 25, and 46 microM, respectively. These results suggest that O-methylation and glucuronidation are two important metabolic pathways of 1,5-DCQA, that both rat liver and small intestine can catalyze such reactions by catechol-O-methyltransferase and UDP-glucuronosyltransferases, and that the HIV-1 inhibitory activity of M8, M9, and M12 is comparable to or slightly weaker than that of 1,5-DCQA.

Molecular strategies to inhibit HIV-1 replication

The human immunodeficiency virus type 1 (HIV-1) is the primary cause of the acquired immunodeficiency syndrome (AIDS), which is a slow, progressive and degenerative disease of the human immune system. The pathogenesis of HIV-1 is complex and characterized by the interplay of both viral and host factors. An intense global research effort into understanding the individual steps of the viral replication cycle and the dynamics during an infection has inspired researchers in the development of a wide spectrum of antiviral strategies. Practically every stage in the viral life cycle and every viral gene product is a potential target. In addition, several strategies are targeting host proteins that play an essential role in the viral life cycle. This review summarizes the main genetic approaches taken in such antiviral strategies.

L-chicoric acid inhibits human immunodeficiency virus type 1 integration in vivo and is a noncompetitive but reversible inhibitor of HIV-1 integrase in vitro

The human immunodeficiency virus (HIV) integrase (IN) must covalently join the viral cDNA into a host chromosome for productive HIV infection. l-Chicoric acid (l-CA) enters cells poorly but is a potent inhibitor of IN in vitro. Using quantitative real-time polymerase chain reaction (PCR), l-CA inhibits integration at concentrations from 500 nM to 10 microM but also inhibits entry at concentrations above 1 microM. Using recombinant HIV IN, steady-state kinetic analyses with l-CA were consistent with a noncompetitive or irreversible mechanism of inhibition. IN, in the presence or absence of l-CA, was successively washed. Inhibition of IN diminished, demonstrating that l-CA was reversibly bound to the protein. These data demonstrate that l-CA is a noncompetitive but reversible inhibitor of IN in vitro and of HIV integration in vivo. Thus, l-CA likely interacts with amino acids other than those which bind substrate.

Caffeoylquinic Acids Generated In Vitro in a High-Anthocyanin-Accumulating Sweet potato Cell Line

Accumulation of phenolic compounds has been monitored in a suspension culture of anthocyanin-accumulating sweet potato cell line grown under the conditions of modified Murashige and Skoog high-anthocyanin production medium (APM) over a period of 24 days. Tissue samples extracted with 15% acetic acid were analysed using HPLC at a detection wavelength of 326 nm. Among others, the following derivatives of caffeoylquinic acids were detected: 4,5-dicaffeoylquinic acid, 3,5-dicaffeoylquinic acid, 3,4-dicaffeoylquinic acid, and 3,4,5-tricaffeoylquinic acid. Their total amount reached a maximum of 110 mg/gFW between the 4th and the 15th day of culture growth on APM. The major compound of the phenolic mixture was 3,5-dicaffeoylquinic acid with maximum accumulation level of 80 mg/100 gFW. The potential effects of targeted phenolic compounds on the nutraceutical qualities of in vitro produced anthocyanin-rich extracts are discussed.

Evidence that the retroviral DNA integration process triggers an ATR-dependent DNA damage response

Caffeine is an efficient inhibitor of cellular DNA repair, likely through its effects on ATM (ataxia telangiectasia mutated) and ATR (ATM and Rad3-related) kinases. Here, we show that caffeine treatment causes a dose-dependent reduction in the total amount of HIV-1 and avian sarcoma virus retroviral vector DNA that is joined to host DNA in the population of infected cells and also in the number of transduced cells. These changes were observed at caffeine concentrations that had little or no effect on overall cell growth, synthesis, and nuclear import of the viral DNA, or the activities of the viral integrase in vitro. Substantial reductions in the amount of host-viral-joined DNA in the infected population, and in the number of transductants, were also observed in the presence of a dominant-negative form of the ATR protein, ATRkd. After infection, a significant fraction of these cells undergoes cell death. In contrast, retroviral transduction is not impeded in ATM-deficient cells, and addition of caffeine leads to the same reduction that was observed in ATM-proficient cells. These results suggest that activity of the ATR kinase, but not the ATM kinase, is required for successful completion of the viral DNA integration process and/or survival of transduced cells. Components of the cellular DNA damage repair response may represent potential targets for antiretroviral drug development.

Human immunodeficiency virus type-1 integrase containing a glycine to serine mutation at position 140 is attenuated for catalysis and resistant to integrase inhibitors

L-chicoric acid (L-CA) is a potent inhibitor of HIV integrase (IN) in vitro. In this report, the effects of a glycine to serine mutation at position 140 (G140S) on HIV IN and its effects on IN inhibitor resistance are described. HIV containing the G140S mutation showed a delay in replication. Using real-time polymerase chain reaction, the delay was secondary to a failure in integration. The mutant protein (IN(G140S)) was attenuated approximately four-fold for catalysis under equilibrium conditions compared to wild-type IN (IN(WT)) and attenuated five-fold in steady-state kinetic analysis of disintegration. Fifty percent inhibitory concentration assays were performed with IN inhibitors against both IN proteins in disintegration and strand transfer reactions. IN(G140S) was resistant to both L-CA and L-731,988, a diketoacid. HIV containing the mutation was resistant to both inhibitors as well. The G140S mutation attenuates IN activity and confers resistance to IN inhibitors, suggesting that diketoacids and L-CA interact with a similar binding site on HIV IN.

Angiotensin converting enzyme inhibitors from Cuscuta japonica Choisy

Bioassay-guided fractionation of the EtOAc-soluble extract of Cuscuta japonica afforded 3,5-Di-O-caffeoylquinic acid (1). methyl 3,5-Di-O-caffeoylquinate (2). 3,4-Di-O-caffeoylquinic acid (3). and methyl 3,4-Di-O-caffeoylquinate (4). Purification of these compounds was conducted with the application of various chromatographic methods. The structures of the compounds were elucidated on the basis of MS and NMR data analysis. Compounds 1-4 inhibited the angiotensin I converting enzyme activity in a dose-dependent manner. Compounds 1-4 showed the 50% inhibitory concentration values of 596, 483, 534, and 460 micro M, respectively. The presence of these active components may be responsible, at least in part, for the antihypertensive action of traditional crude drug Cuscuta Semen.

Inhibition of human immunodeficiency virus type 1 isolates by the integrase inhibitor L-731,988, a diketo Acid

L-731,988 inhibits human immunodeficiency virus (HIV) replication through integrase. In this study, approximately 600 nM L-731,988 inhibited the replication of 12 HIV type 1 isolates from multiple clades, including primary isolates and cloned viruses. These data suggest that diketo acids or their derivatives may prove useful on a worldwide basis in treating HIV infection.

Isolation of two highly potent and non-toxic inhibitors of human immunodeficiency virus type 1 (HIV-1) integrase from Salvia miltiorrhiza

Water soluble extracts of the herbal plant, Salvia miltiorrhiza (Danshen) exhibited potent effect against HIV-1 integrase activity in vitro and viral replication in vivo. We have developed an extensive purification scheme to isolate effective, non-toxic inhibitors against human immunodeficiency virus type 1 (HIV-1) using the 3'-processing activity of integrase as a purification guide and assay. Two water soluble compounds, M(5)22 and M(5)32, have been discovered by isolating them from S. miltiorrhiza roots in purities of >99.5% as shown by NMR spectral analysis with yields of 0.018 and 0.038%, respectively. Structural determination revealed that M(5)22 is lithospermic acid and M(5)32 is lithospermic acid B. These two structurally related compounds are potent anti-HIV inhibitors and showed no cytotoxicity to H9 cells at high concentrations (CC(100)>297 microM for M(5)22 and >223 microM for M(5)32). The IC50 for inhibition of 3'-processing by HIV-1 integrase was found to be 0.83 microM for M(5)22 and 0.48 microM for M(5)32. In addition, M(5)22 and M(5)32 inhibited HIV-1 integrase catalytic activities of 3'-joining to the target DNA with IC50 of 0.48 microM for M(5)22 and 0.37 microM for M(5)32. Furthermore, kinetic and mechanistic studies suggested that drug binding to HIV-1 integrase and inhibition of enzymatic activity occur at a fast rate. Both M(5)22 and M(5)32 do not prevent HIV entry in H9 cells. They also show no inhibition of reverse transcriptase activity in infected cells. The levels of intracellular strong stop and full-length viral DNA remained unchanged following drug treatment. However, both inhibitors strongly suppressed the acute HIV-1 infection of H9 cells with IC50 values of 2 and 6.9 microM for M(5)22 and M(5)32, respectively. Thus these two selective integrase inhibitors hold promise as a novel class of therapeutic drugs for AIDS based on their high potencies and absence of cytotoxicity.

HIV integrase as a target for antiviral chemotherapy

One of the three key enzymes encoded by the pol gene of HIV is a M(r) 32 000 protein called HIV integrase. This viral enzyme is involved in the integration of HIV DNA into host chromosomal DNA. There appears to be no functional equivalent of the enzyme in human cells. The biochemical mechanism of integration of HIV DNA into the host cell genome involves a carefully defined sequence of DNA tailoring (3'-processing) and coupling (joining or integration) reactions. In spite of some effort in this area targeted at the discovery of therapeutically useful inhibitors of this viral enzyme, there are no drugs for HIV/AIDS in clinical use where the mechanism of action is inhibition of HIV integrase. Thus, new knowledge on inhibitors of this enzyme is of critical importance in the anti-HIV drug discovery area. The focus of this review will be on several classes of compounds, including nucleotides, dinucleotides, oligonucleotides and miscellaneous small molecules such as heterocyclic systems, natural products, diketo acids and sulfones, that have been discovered as inhibitors of HIV integrase. Special emphasis in the review will be placed on discoveries from my laboratory on HIV integrase inhibitors that are non-natural, nuclease-resistant dinucleotides. Comments on future directions and the prospects for developing integrase inhibitors as therapeutic antiviral agents are discussed.

Analysis of artichoke (Cynara cardunculus L.) extract by means of micellar electrokinetic capillary chromatography

The main constituents of artichoke extract were separated by micellar electrokinetic chromatography (MEKC), using a buffer consisting of 100 mM sodium dodecyl sulfate (SDS) in 20 mM sodium dihydrogen phosphate, 20 mM disodium tetraborate (pH 8.6) as background electrolyte. Optimum separation voltage of 28 kV (positive polarity) and a capillary temperature of 25 degrees C gave the best analysis. The UV detection was performed at 200 nm. The method was successfully used to analyze plant and drug samples as well as for the study of artichoke antioxidant activity. The quantitative MEKC results were in good agreement to those obtained previously by reversed-phase high-performance liquid chromatography (RP-HPLC).

Retroviral integrase inhibitors year 2000: update and perspectives

HIV-1 integrase is an essential enzyme for retroviral replication and a rational target for the design of anti-AIDS drugs. A number of inhibitors have been reported in the past 8 years. This review focuses on the recent developments in the past 2 years. There are now several inhibitors with known sites of actions and antiviral activity. The challenge is to convert these leads into drugs that will selectively target integrase in vivo, and can be added to our antiviral armamentarium.