Natural product-inspired esters and amides of ferulic and caffeic acid as dual inhibitors of HIV-1 reverse transcriptase

Recent developments of pyrimidine appended HIV-1 non-nucleoside reverse transcriptase inhibitors

Acquired Immune Deficiency Syndrome (AIDS) is an ailment that progressively weakens the immune system and is responsible for being the sole cause of 630,000 deaths worldwide in 2023. It is a potentially fatal condition that promotes the growth of malignancies and secondary infection. Viruses like Human Immunodeficiency Virus (HIV-1) and Hepatitis B virus (HBV) employ an enzyme, reverse transcriptase (RT), to replicate their genomes and spread across the host genome. RT has proved to be one of the most important therapeutic targets for the treatment of AIDS as well as for the development of new HIV-1 medications. The pyrimidine nucleus has been described as a dynamic cornerstone in developing new anti-HIV-1 medications and represents a familiar motif found in various marketed anti-HIV-1 drugs, such as diaryl pyrimidines (DAPYs). The rapid emergence of drug-resistant viral strains due to mutations in the HIV-1 RT structure along with their unfavourable pharmacokinetics present new challenges. Recent years have witnessed tremendous progress in the design and discovery of new substituted pyrimidines as potent and selective non-nucleoside reverse transcriptase inhibitors (NNRTIs). Further, the current developments in the field of X-ray crystallography and molecular modeling have remarkably augmented the design strategies, with simultaneous improvement in the resistance profiles. This article comprehensively reviews recent trends in the design and development of pyrimidine-based HIV-1 NNRTIs. The study emphasizes their biological activities, structure-activity relationship, and docking studies to guide the rational design of NNRTIs with desired potency, safety, and efficacy.

Identification of HIV-1 Reverse Transcriptase-Associated Ribonuclease H Inhibitors Based on 2-Hydroxy-1,4-naphthoquinone Mannich Bases

There is a strong demand for new and efficient antiviral compounds. A series of 2-hydroxy-1,4-naphthoquinone Mannich bases were screened for their HIV-1-RNase H inhibitory activity. An HIV-1-RNase H assay was used to study the RNase H inhibition by the test compounds. Docking of active derivatives into the active site of the enzyme was carried out. Compounds 1e and 2k showed distinctly higher HIV-1-RNase H inhibitory activity (IC50 = 2.8-3.1 µM) than the known inhibitors RDS1759 and compound 13. The binding mode and possible interactions of 1e and 2k with the HIV-1-RNase H active site were determined using molecular docking, which led to the identification of salient and concealed pharmacophoric features of these molecules. The docking analysis revealed that there are significant differences in the binding mode of these compounds within the active site of the target enzyme. A selection of HIV-1-RNase H-inhibitory Mannich bases was tested for antiviral activity against HIV-1, and compound 2k showed the highest activity at low toxicity to host cells. The lawsone Mannich bases 1e and 2k also underwent a preliminary screening for activity against SARS-CoV-2, and compound 1e was found to inhibit SARS-CoV-2 replication (IC50 = 11.2 µM).

HRAMS Proteomics Insights on the Anti-Filarial Effect of Ocimum sanctum: Implications in Phytochemical-Based Drug-Targeting and Designing

Lymphatic filariasis (LF) continues to impact 657 million individuals worldwide, resulting in lifelong and chronic impairment. The prevalent anti-filarial medications-DEC, albendazole, and ivermectin-exhibit limited adulticidal efficacy. Despite ongoing LF eradication programs, novel therapeutic strategies are essential for effective control. This study examines the mechanism of action of Ocimum sanctum on the filarial parasites Setaria cervi via a synergistic biochemical and proteomics methodology. The ethanolic extract of Ocimum sanctum (EOS) demonstrated potential anti-filarial action in the MTT reduction experiment, with an LC50 value of 197.24 µg/mL. After EOS treatment, an elevation in lipid peroxidation (51.92%), protein carbonylation (48.99%), and NADPH oxidase (88.88%) activity, along with a reduction in glutathione (GSH) (-39.23%), glutathione reductase (GR) (-60.17%), and glutathione S transferase (GST) (-50.48%) activity, was observed. The 2D gel electrophoresis identified 20 decreased and 11 increased protein spots in the EOS-treated parasites relative to the control group. Additionally, in drug docking analysis, the EOS bioactive substances ursolic acid, rutin, and rosmarinic acid show a significant binding affinity with the principal differentially expressed proteins. This paper demonstrates, for the first time, that the anti-filarial efficacy of EOS is primarily facilitated by its impact on energy metabolism, antioxidant mechanisms, and stress response systems of the parasites.

Nanoarchitecturing of Mo2C nanospheres on carbon cloth as an electrochemical sensing platform for determination of caffeic acid in tea samples

In the present paper, carbon cloth (CC) as a flexible substrate was modified by molybdenum carbide nanospheres (Mo2C NSs @CC) by the drop-coating method to develop a sensitive electrochemical platform for detecting caffeic acid. The uniform Mo2C NSs were prepared via an easy route followed by pyrolyzing the precursor of the Mo-polydopamine (Mo-PDA) NSs. The Mo2C NSs were characterized and analyzed by X-ray diffraction (XRD), field emission scanning electron microscopy/energy dispersive X-ray spectroscopy (FE-SEM/EDS), Raman spectroscopy (RS), and electrochemical methods. CC not only gave a flexible feature to the sensor but also provided a larger surface area for Mo2C NSs. Meanwhile, the excellent conductivity and large electroactive specific surface area of Mo2C NSs exhibited excellent electrocatalytic performance for caffeic acid determination. The developed sensor showed high sensitivity and selectivity, good reproducibility, and long-term stability with a limit of detection (LOD) and a wide linear range of 0.001 μM (S/N = 3) and 0.01-50 μM, respectively. In addition, the Mo2C NSs @CC sensor showed a promising application prospect for the detection of caffeic acid in green and black tea samples, indicating its importance in food safety and the food industry.

New Antioxidant Caffeate Esters of Fatty Alcohols Identified in Robinia pseudoacacia

The stem bark of black locust (Robinia pseudoacacia L.) was extracted, and nine antioxidant compounds (R1-R9) were detected by high-performance thin-layer chromatography combined with the radical scavenging 2,2-diphenyl-1-picrylhydrazyl (DPPH•) assay, multi-detection, and heated electrospray high-resolution mass spectrometry. For structure elucidation, the methanolic crude extract was fractionated by solid-phase extraction, and the compounds were isolated by reversed-phase high-performance liquid chromatography with diode array detection. The structures of isolated compounds were elucidated by nuclear magnetic resonance and attenuated total reflectance Fourier-transform infrared spectroscopy as well as gas chromatography-mass spectrometry to determine the double bond position. 3-O-Caffeoyl oleanolic acid (R1), oleyl (R2), octadecyl (R3), gadoleyl (R4), eicosanyl (R5), (Z)-9-docosenyl (R6), docosyl (R7), tetracosyl (R8), and hexacosanyl (R9) caffeates were identified. While R1 has been reported in R. pseudoacacia stem bark, the known R3, R5, R7, R8, and R9 are described for the first time in this species, and the R2, R4, and R6 are new natural compounds. All nine caffeates demonstrated antioxidant activity. The antioxidant effects of the isolated compounds R1-R8 were quantified by a microplate DPPH• assay, with values ranging from 0.29 to 1.20 mol of caffeic acid equivalents per mole of isolate.

Discovery of Benzisothiazolone Derivatives as Bifunctional Inhibitors of HIV-1 Reverse Transcriptase DNA Polymerase and Ribonuclease H Activities

The ribonuclease H (RNase H) active site of HIV-1 reverse transcriptase (RT) is the only viral enzyme not targeted by approved antiretroviral drugs. Using a fluorescence-based in vitro assay, we screened 65,239 compounds at a final concentration of 10 µM to identify inhibitors of RT RNase H activity. We identified 41 compounds that exhibited 50% inhibitory concentration (i.e., IC50) values < 1.0 µM. Two of these compounds, 2-(4-methyl-3-(piperidin-1-ylsulfonyl)phenyl)benzo[d]isothiazol-3(2H)-one (1) and ethyl 2-(2-(3-oxobenzo[d]isothiazol-2(3H)-yl)thiazol-4-yl)acetate (2), which both share the same benzisothiazolone pharmacophore, demonstrate robust antiviral activity (50% effective concentrations of 1.68 ± 0.94 µM and 2.68 ± 0.54, respectively) in the absence of cellular toxicity. A limited structure-activity relationship analysis identified two additional benzisothiazolone analogs, 2-methylbenzo[d]isothiazol-3(2H)-one (3) and N,N-diethyl-3-(3-oxobenzo[d]isothiazol-2(3H)-yl)benzenesulfonamide (4), which also resulted in the inhibition of RT RNase H activity and virus replication. Compounds 1, 2 and 4, but not 3, inhibited the DNA polymerase activity of RT (IC50 values~1 to 6 µM). In conclusion, benzisothiazolone derivatives represent a new class of multifunctional RT inhibitors that warrants further assessment for the treatment of HIV-1 infection.

Lipid oxidation in emulsions: New insights from the past two decades

Lipid oxidation constitutes the main source of degradation of lipid-rich foods, including food emulsions. The complexity of the reactions at play combined with the increased demand from consumers for less processed and more natural foods result in additional challenges in controlling this phenomenon. This review provides an overview of the insights acquired over the past two decades on the understanding of lipid oxidation in oil-in-water (O/W) emulsions. After introducing the general structure of O/W emulsions and the classical mechanisms of lipid oxidation, the contribution of less studied oxidation products and the spatiotemporal resolution of these reactions will be discussed. We then highlight the impact of emulsion formulation on the mechanisms, taking into consideration the new trends in terms of emulsifiers as well as their own sensitivity to oxidation. Finally, novel antioxidant strategies that have emerged to meet the recent consumer's demand will be detailed. In an era defined by the pursuit of healthier, more natural, and sustainable food choices, a comprehensive understanding of lipid oxidation in emulsions is not only an academic quest, but also a crucial step towards meeting the evolving expectations of consumers and ensuring the quality and stability of lipid-rich food products.

Phenolic Compounds in Salicornia spp. and Their Potential Therapeutic Effects on H1N1, HBV, HCV, and HIV: A Review

Despite public health risk mitigation measures and regulation efforts by many countries, regions, and sectors, viral outbreaks remind the world of our vulnerability to biological hazards and the importance of mitigation actions. The saltwater-tolerant plants in the Salicornia genus belonging to the Amaranthaceae family are widely recognized and researched as producers of clinically applicable phytochemicals. The plants in the Salicornia genus contain flavonoids, flavonoid glycosides, and hydroxycinnamic acids, including caffeic acid, ferulic acid, chlorogenic acid, apigenin, kaempferol, quercetin, isorhamnetin, myricetin, isoquercitrin, and myricitrin, which have all been shown to support the antiviral, virucidal, and symptom-suppressing activities. Their potential pharmacological usefulness as therapeutic medicine against viral infections has been suggested in many studies, where recent studies suggest these phenolic compounds may have pharmacological potential as therapeutic medicine against viral infections. This study reviews the antiviral effects, the mechanisms of action, and the potential as antiviral agents of the aforementioned phenolic compounds found in Salicornia spp. against an influenza A strain (H1N1), hepatitis B and C (HBV/HCV), and human immunodeficiency virus 1 (HIV-1), as no other literature has described these effects from the Salicornia genus at the time of publication. This review has the potential to have a significant societal impact by proposing the development of new antiviral nutraceuticals and pharmaceuticals derived from phenolic-rich formulations found in the edible Salicornia spp. These formulations could be utilized as a novel strategy by which to combat viral pandemics caused by H1N1, HBV, HCV, and HIV-1. The findings of this review indicate that isoquercitrin, myricetin, and myricitrin from Salicornia spp. have the potential to exhibit high efficiency in inhibiting viral infections. Myricetin exhibits inhibition of H1N1 plaque formation and reverse transcriptase, as well as integrase integration and cleavage. Isoquercitrin shows excellent neuraminidase inhibition. Myricitrin inhibits HIV-1 in infected cells. Extracts of biomass in the Salicornia genus could contribute to the development of more effective and efficient measures against viral infections and, ultimately, improve public health.

5-Nitro-3-(2-(4-phenylthiazol-2-yl)hydrazineylidene)indolin-2-one derivatives inhibit HIV-1 replication by a multitarget mechanism of action

In the effort to identify and develop new HIV-1 inhibitors endowed with innovative mechanisms, we focused our attention on the possibility to target more than one viral encoded enzymatic function with a single molecule. In this respect, we have previously identified by virtual screening a new indolinone-based scaffold for dual allosteric inhibitors targeting both reverse transcriptase-associated functions: polymerase and RNase H. Pursuing with the structural optimization of these dual inhibitors, we synthesized a series of 35 new 3-[2-(4-aryl-1,3-thiazol-2-ylidene)hydrazin-1-ylidene]1-indol-2-one and 3-[3-methyl-4-arylthiazol-2-ylidene)hydrazine-1-ylidene)indolin-2-one derivatives, which maintain their dual inhibitory activity in the low micromolar range. Interestingly, compounds 1a, 3a, 10a, and 9b are able to block HIV-1 replication with EC₅₀ < 20 µM. Mechanism of action studies showed that such compounds could block HIV-1 integrase. In particular, compound 10a is the most promising for further multitarget compound development.

Targeting Interfacial Location of Phenolic Antioxidants in Emulsions: Strategies and Benefits

It is important to have larger proportions of health-beneficial polyunsaturated lipids in foods, but these nutrients are particularly sensitive to oxidation, and dedicated strategies must be developed to prevent this deleterious reaction. In food oil-in-water emulsions, the oil-water interface is a crucial area when it comes to the initiation of lipid oxidation. Unfortunately, most available natural antioxidants, such as phenolic antioxidants, do not spontaneously position at this specific locus. Achieving such a strategic positioning has therefore been an active research area, and various routes have been proposed: lipophilizing phenolic acids to confer them with an amphiphilic character; functionalizing biopolymer emulsifiers through covalent or noncovalent interactions with phenolics; or loading Pickering particles with natural phenolic compounds to yield interfacial antioxidant reservoirs. We herein review the principles and efficiency of these approaches to counteract lipid oxidation in emulsions as well as their advantages and limitations.

Recent advances on dual inhibitors targeting HIV reverse transcriptase associated polymerase and ribonuclease H

Reverse transcriptase (RT) plays an indispensable role in the replication of human immunodeficiency virus (HIV) through its associated polymerase and ribonuclease H (RNase H) activities during the viral RNA genome transformation into proviral DNA. Due to the fact that HIV is a highly mutagenic virus and easily resistant to single-target RT inhibitors, dual inhibitors targeting HIV RT associated polymerase and RNase H have been developed. These dual inhibitors have the advantages of increasing efficacy, reducing drug resistance, drug-drug interactions, and cytotoxicity, as well as improving patient compliance. In this review, we summarize recent advances in polymerase/RNase H dual inhibitors focusing on drug design strategies, and structure-activity relationships and share new insights into developing anti-HIV drugs.

Application of cinnamic acid in the structural modification of natural products: A review

Natural products can generally exhibit a variety of biological activities, but most show mediocre performance in preliminary activity evaluation. Natural products often require structural modification to obtain promising lead compounds. Cinnamic acid (CA) is readily available and has diverse biological activities and low cytotoxicity. Introducing CA into natural products may improve their performance, enhance biological activity, and reduce toxic side effect. Herein, we aimed to discuss related applications of CA in the structural modification of natural products and provide a theoretical basis for future derivatization and drug development of natural products. Published articles, web databases (PubMed, Science Direct, SCI Finder, and CNKI), and clinical trial websites (https://clinicaltrials.gov/) related to natural products and CA derivatives were included in the discussion. Based on the inclusion criteria, 128 studies were selected and discussed herein. Screening natural products of CA derivatives allowed for classification by their biological activities. The full text is organized according to the biological activities of the derivatives, with the following categories: anti-tumor, neuroprotective, anti-diabetic, anti-microbial, anti-parasitic, anti-oxidative, anti-inflammatory, and other activities. The biological activity of each CA derivative is discussed in detail. Notably, most derivatives exhibited enhanced biological activity and reduced cytotoxicity compared with the lead compound. CA has various advantages and can be widely used in the synthesis of natural product derivatives to enhance the properties of drug candidates or lead compounds.

The Importance of Traditional Chinese Medicine in the Intervention and Treatment of HIV while Considering its Safety and Efficacy

Natural products have been considered a potential resource for the development of novel therapeutic agents, since time immemorial. It is an opportunity to discover cost-effective and safe drugs at the earliest, with the goal to hit specific targets in the HIV life cycle. Natural products with inhibitory activity against human immunodeficiency virus are terpenes, coumarins, flavonoids, curcumin, proteins, such as lectins, laccases, bromotyrosines, and ribosome-inactivating proteins. Terpenes inhibit virus fusion, lectins and flavonoids have an inhibitory impact on viral binding, curcumin and flavonoids inhibit viral DNA integration. The most important medicinal plants which have been used in traditional Chinese medicinal sciences with anti-HIV properties are Convallaria majalis, Digitalis lanata, Cassia fistula, Croton macrostachyus, Dodonaea angustifolia, Ganoderma lucidum, Trametes versicolor, Coriolus versicolor, Cordyceps sinensis, Gardenia jasminoides, Morus alba, Scutellaria baicalensis, Ophiopogon japonicus, Platycodon grandiflorus, Fritillaria thunbergii, Anemarrhena asphodeloides, Trichosanthes kirilowii, Citrus reticulata, Glycyrrhiza uralensis, Rheum officinale, Poria cocos, Rheum palmatum, Astragalus membranaceus, Morinda citrifolia, Potentilla kleiniana, Artemisia capillaris, Sargassum fusiforme, Piperis longi fructus, Stellera chamaejasme, Curcumae rhizoma, Dalbergia odorifera lignum, Arisaematis Rhizoma preparatum, and Phellodendron amurense. The information provided is gathered from randomized control experiments, review articles, and analytical studies and observations, which are obtained from different literature sources, such as Scopus, Google Scholar, PubMed, and Science Direct from July 2000 to August 2023. The aim of this review article is to survey and introduce important medicinal plants and herbs that have been used for the treatment of HIV, especially the medicinal plants that are common in traditional Chinese medicine, as research to date is limited, and more evidence is required to confirm TCM,s efficacy.

Polyphenolic compounds from rapeseeds (Brassica napus L.): The major types, biofunctional roles, bioavailability, and the influences of rapeseed oil processing technologies on the content

The rapeseed (Brassica napus L.) are the important oil bearing material worldwide, which contain wide variety of bioactive components with polyphenolic compounds considered the most typical. The rapeseed polyphenols encompass different structural variants, and have been considered to have many bioactive functions, which are beneficial for the human health. Whereas, the rapeseed oil processing technologies affect their content and the biofunctional activities. The present review of the literature highlighted the major types of the rapeseed polyphenols, and summarized their biofunctional roles. The influences of rapeseed oil processing technologies on these polyphenols were also elucidated. Furthermore, the directions of the future studies for producing nutritional rapeseed oils preserved higher level of polyphenols were prospected. The rapeseed polyphenols are divided into the phenolic acids and polyphenolic tannins, both of which contained different subtypes. They are reported to have multiple biofunctional roles, thus showing outstanding health improvement effects. The rapeseed oil processing technologies have significant effects on both of the polyphenol content and activity. Some novel processing technologies, such as aqueous enzymatic extraction (AEE), subcritical or supercritical extraction showed advantages for producing rapeseed oil with higher level of polyphenols. The oil refining process involved heat or strong acid and alkali conditions affected their stability and activity, leading to the loss of polyphenols of the final products. Future efforts are encouraged to provide more clinic evidence for the practical applications of the rapeseed polyphenols, as well as optimizing the processing technologies for the green manufacturing of rapeseed oils.

Current medicinal chemistry strategies in the discovery of novel HIV-1 ribonuclease H inhibitors

During HIV-1 genome replication, the viral reverse transcriptase-associated ribonuclease H (RT-associated RNase H) activity hydrolyzes the RNA strand of RNA/DNA heteroduplex intermediates. As of today, HIV-1 RNase H inhibitors (RHIs) remain at an investigational level, although none of them reached clinical trials. Therefore, RNase H remains as an attractive target for drug design and development. In this paper, we review the current status of medicinal chemistry strategies aimed at the discovery of novel RHIs, while discussing problems encountered in their characterization and further development, thereby providing an update on recent progress in the field.

Hybrid molecules based on caffeic acid as potential therapeutics: A focused review

Caffeic acid-based compounds possess a high degree of structural diversity and show a variety of pharmacological properties, providing a useful framework for the discovery of new therapeutic agents. They are well-known analogues of antioxidants found in many natural products and synthetic compounds. The present review surveys the recent developments in structure-activity relationships (SAR) and mechanism of action (MOA) of various caffeic acid-containing compounds that play important roles in the design and synthesis of new bioactive molecules with antioxidant, antidiabetic, antiviral, antibacterial, anticancer, anti-inflammatory, and other properties. This review should provide inspiration to scientists in the research fields of organic synthesis and medicinal chemistry related to the development of new antioxidants with versatile therapeutic potential.

Can plant-derived anti-HIV compounds be used in COVID-19 cases?

People living with HIV are more exposed to the adverse health effects of the worldwide COVID-19 pandemic. The pandemic's health and social repercussions may promote drug abuse and inadequate HIV management among this demographic. The coronavirus pandemic of 2019 (COVID-19) has caused unprecedented disruption worldwide in people's lives and health care. When the COVID-19 epidemic was identified, people with HIV faced significant obstacles and hurdles to achieving optimal care results. The viral spike protein (S-Protein) and the cognate host cell receptor angiotensin-converting enzyme 2 (ACE2) are both realistic and appropriate intervention targets. Calanolides A, Holy Basil, Kuwanon-L, and Patentiflorin have anti-HIV effects. Our computational biology study investigated that these compounds all had interaction binding scores related to S protein of coronavirus of -9.0 kcal /mol, -7.1 kcal /mol, -9.1 kcal /mol, and -10.3 kcal/mol/mol, respectively. A combination of plant-derived anti-HIV compounds like protease inhibitors and nucleoside analogs, which are commonly used to treat HIV infection, might be explored in clinical trials for the treatment of COVID-19.

Eco-friendly synthesis of sulphur-doped graphenes with applicability in caffeic acid electrochemical assay

A new electrode based on glassy carbon modified with a sulphur-doped graphene material was successfully developed and applied for caffeic acid (CA) voltammetric detection and quantification. The structural features of sulphur-doped graphene (exfGR-S) characterized by different physicochemical and analytical techniques are presented. Cyclic voltammetry (CV) technique was employed to evaluate the electrochemical behavior of both bare glassy carbon (GCE) and modified GCE/exfGr-S electrodes towards CA oxidation. The study revealed that the modified electrode exhibits superior electrochemical performances compared to the bare electrode, with a broad CA detecting range (from 0.1 to 100.0 µM), a low detection limit 3.03 × 10^-8 M), excellent anti-interference capabilities, as well as good stability and repeatability. The developed electrochemical sensor appears to be a promising candidate for real sample quality control analysis since it successfully displayed its ability to directly detect CA in commercially available coffee product without any pretreatment.

Ketone Analog of Caffeic Acid Phenethyl Ester Exhibits Antioxidant Activity via Activation of ERK-Dependent Nrf2 Pathway

Due to their robust antioxidant properties, phenolic acids and their analogs are extensively studied for their ability to activate cellular antioxidant pathways, including nuclear factor (erythroid-derived-2)-like 2 (Nrf2)-antioxidant response element (ARE) pathway. Caffeic, ferulic, and gallic acid are well-studied members of phenolic acids. Constant efforts are made to improve the pharmacological effects and bioavailability of phenolic acids by synthesizing their chemical derivatives. This study determines how modifications of the chemical structure of these phenolic acids affect their antioxidant and cytoprotective activities. We have selected six superior antioxidant compounds (12, 16, 26, 35, 42, and 44) of the 48 caffeic acid phenethyl ester (CAPE) analogs based on their ability to scavenge free radicals in vitro using standard antioxidant assays. These compounds exhibited minimal toxicity as indicated by cell cycle and cytochrome C release assays. Among these compounds, 44, the ketone analog of CAPE, exhibited the ability to increase p-Nrf2 (Ser40) levels in 293T cells (p < 0.05). Further, 44, exhibited its antioxidant effect in Drosophila Melanogaster as indicated by an increase in mRNA levels of Nrf2 and GPx (p < 0.05). Finally, the ability of 44 to activate the antioxidant pathway was abolished in the presence of extracellular signal-regulated kinase (ERK) inhibitor in 293T cells. Thus, we identify 44, the ketone analog of CAPE, as a unique antioxidant molecule with the function of ERK-mediated Nrf2 activation.

Flavonoids and Acid-Hydrolysis derivatives of Neo-Clerodane diterpenes from Teucrium flavum subsp. glaucum as inhibitors of the HIV-1 reverse transcriptase-associated RNase H function

Bioassay-guided fractionation of the ethyl acetate extract from Teucrium flavum subsp. glaucum, endowed with inhibitory activity towards the HIV-1 reverse transcriptase–associated RNase H function, led to the isolation of salvigenin (1), cirsimaritin (2) and cirsiliol (3) along with the neo-clerodanes teuflavin (4) and teuflavoside (5). Acid hydrolysis of the inactive teuflavoside provided three undescribed neo-clerodanes, flavuglaucins A-C (7-9) and one known neo-clerodane (10). Among all neo-clerodanes, flavuglaucin B showed the highest inhibitory activity towards RNase H function with a IC₅₀ value of 9.1 μM. Molecular modelling and site-directed mutagenesis analysis suggested that flavuglaucin B binds into an allosteric pocket close to RNase H catalytic site. This is the first report of clerodane diterpenoids endowed with anti-reverse transcriptase activity. Neo-clerodanes represent a valid scaffold for the development of a new class of HIV-1 RNase H inhibitors.

Plant Secondary Metabolites with an Overview of Populus

Populus trees meet continuous difficulties from the environment through their life cycle. To warrant their durability and generation, Populus trees exhibit various types of defenses, including the production of secondary metabolites. Syntheses derived from the shikimate-phenylpropanoid pathway are a varied and plentiful class of secondary metabolites manufactured in Populus. Amongst other main classes of secondary metabolites in Populus are fatty acid and terpenoid-derivatives. Many of the secondary metabolites made by Populus trees have been functionally described. Any others have been associated with particular ecological or biological processes, such as resistance against pests and microbial pathogens or acclimatization to abiotic stresses. Still, the functions of many Populus secondary metabolites are incompletely understood. Furthermore, many secondary metabolites have therapeutic effects, leading to more studies of secondary metabolites and their biosynthesis. This paper reviews the biosynthetic pathways and therapeutic impacts of secondary metabolites in Populus using a genomics approach. Compared with bacteria, fewer known pathways produce secondary metabolites in Populus despite P. trichocarpa having had its genome sequenced.

Exploring New Scaffolds for the Dual Inhibition of HIV-1 RT Polymerase and Ribonuclease Associated Functions

Current therapeutic protocols for the treatment of HIV infection consist of the combination of diverse anti-retroviral drugs in order to reduce the selection of resistant mutants and to allow for the use of lower doses of each single agent to reduce toxicity. However, avoiding drugs interactions and patient compliance are issues not fully accomplished so far. Pursuing on our investigation on potential anti HIV multi-target agents we have designed and synthesized a small library of biphenylhydrazo 4-arylthiazoles derivatives and evaluated to investigate the ability of the new derivatives to simultaneously inhibit both associated functions of HIV reverse transcriptase. All compounds were active towards the two functions, although at different concentrations. The substitution pattern on the biphenyl moiety appears relevant to determine the activity. In particular, compound 2-{3-[(2-{4-[4-(hydroxynitroso)phenyl]-1,3-thiazol-2-yl} hydrazin-1-ylidene) methyl]-4-methoxyphenyl} benzamide bromide (EMAC2063) was the most potent towards RNaseH (IC₅₀ = 4.5 mM)- and RDDP (IC₅₀ = 8.0 mM) HIV RT-associated functions.

Scaffold hopping and optimisation of 3',4'-dihydroxyphenyl- containing thienopyrimidinones: synthesis of quinazolinone derivatives as novel allosteric inhibitors of HIV-1 reverse transcriptase-associated ribonuclease H

Bioisosteric replacement and scaffold hopping are powerful strategies in drug design useful for rationally modifying a hit compound towards novel lead therapeutic agents. Recently, we reported a series of thienopyrimidinones that compromise dynamics at the p66/p51 HIV-1 reverse transcriptase (RT)-associated Ribonuclease H (RNase H) dimer interface, thereby allosterically interrupting catalysis by altering the active site geometry. Although they exhibited good submicromolar activity, the isosteric replacement of the thiophene ring, a potential toxicophore, is warranted. Thus, in this article, the most active 2-(3,4-dihydroxyphenyl)-5,6-dimethylthieno[2,3-d]pyrimidin-4(3H)-one 1 was selected as the hit scaffold and several isosteric substitutions of the thiophene ring were performed. A novel series of highly active RNase H allosteric quinazolinone inhibitors was thus obtained. To determine their target selectivity, they were tested against RT-associated RNA-dependent DNA polymerase (RDDP) and integrase (IN). Interestingly, none of the compounds were particularly active on (RDDP) but many displayed micromolar to submicromolar activity against IN.

In Vitro Assessment of the Interaction Potential of Ocimum basilicum (L.) Extracts on CYP2B6, 3A4, and Rifampicin Metabolism

Ocimum basilicum L. or basilicum is a common culinary herb, used as a traditional medicine for various medical conditions including HIV/AIDS and tuberculosis, in Africa. The objective of this study was to evaluate the effect of methanol, ethanol, aqueous and ethyl acetate extracts of the dried leaves and inflorescence of O. basilicum, on the activity of cytochrome P450 enzymes (CYPs) CYP2B6 and 3A4, as well as esterase-mediated metabolism of rifampicin to 25-O-desacetyl rifampicin (25ODESRIF). Human liver microsomes (HLM) were used to evaluate inhibition and CYP2B6/3A4 mRNA expression HepG2 assays were used to measure induction. Furthermore, the phytoconstituents likely involved in causing the observed effect were analyzed using biochemical tests and LC-MS. The aqueous and methanolic extracts showed reversible and time-dependent inhibition (TDI) of CYP2B6 with TDI-IC₅₀s 33.35 μg/ml (IC₅₀ shift-fold >1.5) and 4.93 μg/ml (IC₅₀ shift-fold >7) respectively, while the methanolic and ethanolic extracts inhibited 25ODESRIF formation (IC₅₀s 31 μg/ml, 8.94 μg/ml). In HepG2 assays, the methanolic and ethanolic extracts moderately induced CYP2B6, 3A4 mRNA with 38%-, 28%-fold shift, and 22%-, 44%-fold shift respectively. LC-MS full scans identified phenols rosmarinic acid [m/z 359 (M-H)^-, approximately 2298 mg/L in aqueous extract] and caftaric acid along with flavones salvigenin [m/z 329 (M+H)⁺, approximately 1855 mg/L in ethanolic extract], eupatorin [m/z 345 (M+H)⁺, 668.772 mg/L in ethanolic extract], rutin [m/z 609 (M-H)^-] and isoquercetin [m/z 463 (M-H)^-] and other compounds—linalool [m/z 153 (M-H)^-], hydroxyjasmonic acid [m/z 225 (M-H)^-], eucommiol [m/z 187 (M-H)^-] and trihydroxy octadecenoic acid [m/z 329 (M-H)^-, 530 mg/L in ethanolic extract]. The putative gastrointestinal tract (GIT) concentration for all extracts was calculated as 2,400 μg/ml and hepatic circulation concentrations were estimated at 805.68 μg/ml for the aqueous extract, and 226.56 μg/ml for methanolic extract. Based on the putative GIT concentration, estimated hepatic circulation concentration [I] and inhibition constant K_i, the predicted percentile of inhibition in vivo was highest for the aqueous extract on CYP2B6 (96.7%). The observations indicated that O. basilicum extracts may have the potential to cause clinically relevant herb-drug interactions (HDI) with CYP2B6 and rifampicin metabolism in vivo, if sufficient hepatic concentrations are reached in humans.

1,2,4-Triazolo[1,5-a]pyrimidines as a Novel Class of Inhibitors of the HIV-1 Reverse Transcriptase-Associated Ribonuclease H Activity

Despite great efforts have been made in the prevention and therapy of human immunodeficiency virus (HIV-1) infection, however the difficulty to eradicate latent viral reservoirs together with the emergence of multi-drug-resistant strains require the search for innovative agents, possibly exploiting novel mechanisms of action. In this context, the HIV-1 reverse transcriptase (RT)-associated ribonuclease H (RNase H), which is one of the few HIV-1 encoded enzymatic function still not targeted by any current drug, can be considered as an appealing target. In this work, we repurposed in-house anti-influenza derivatives based on the 1,2,4-triazolo[1,5-a]-pyrimidine (TZP) scaffold for their ability to inhibit HIV-1 RNase H function. Based on the results, a successive multi-step structural exploration around the TZP core was performed leading to identify catechol derivatives that inhibited RNase H in the low micromolar range without showing RT-associated polymerase inhibitory activity. The antiviral evaluation of the compounds in the MT4 cells showed any activity against HIV-1 (III_B strain). Molecular modelling and mutagenesis analysis suggested key interactions with an unexplored allosteric site providing insights for the future optimization of this class of RNase H inhibitors.

Discovery, synthesis, and optimization of an N-alkoxy indolylacetamide against HIV-1 carrying NNRTI-resistant mutations from the Isatis indigotica root

From an aqueous decoction of the traditional Chinese medicine "ban lan gen" (the Isatis indigotica root), an antiviral natural product CI - 39 was isolated as an NNRTI (non-nucleoside reverse transcriptase inhibitor) (EC50 = 3.40 μM). Its novel structure was determined as methyl (1-methoxy-1H-indol-3-yl)acetamidobenzoate by spectroscopic data and confirmed by single crystal X-ray diffraction. Through synthesis and structure-activity relationship (SAR) investigation of CI - 39 and 57 new derivatives (24 with EC50 values of 0.06-8.55 μM), two optimized derivatives 10f and 10i (EC50: 0.06 μM and 0.06 μM) having activity comparable to that of NVP (EC50 = 0.03 μM) were obtained. Further evaluation verified that 10f and 10i were RT DNA polymerase inhibitors and exhibited better activities and drug resistance folds compared to NVP against seven NNRTI-resistant strains carrying different mutations. Especially, 10i (EC50 = 0.43 μM) was more active to the L100I/K103N double-mutant strain as compared to both NVP (EC50 = 0.76 μM) and EFV (EC50 = 1.08 μM). The molecular docking demonstrated a possible binding pattern between 10i and RT and revealed activity mechanism of 10i against the NNRTI-resistant strains.

Chemo-enzymatic synthesis, characterization, in vitro antioxidant capacity and oxidative stability studies of novel phosphatidylcholines with ω-3/ω-6 PUFAs and phenolic acids

Novel phosphatidylcholines containing PUFAs and phenolic acids were synthesized from egg phosphatidylcholine (PC), PUFAs (docosahexaenoic, arachidonic and linoleic acids) and phenolic acids (caffeic, ferulic and p-coumaric acids) as substrates. The structures of modified PCs were confirmed by spectral analysis and were evaluated for antioxidant activities. The modified PCs containing caffeic and ferulic acids exhibited excellent antioxidant activities compared with butylated hydroxytoluene (BHT) and α-tocopherol. The synthesized compounds were also evaluated for the oxidative stabilities in liposome and organic solvent. The modified PCs showed more oxidative stable compared with standard PUFA-PCs and PUFA-PCs + BHT. Results showed that the oxidative stability decreased with increasing degree of unsaturation in organic solvent whereas in liposomes, increased with increasing degree of unsaturation due to tight packed configuration. In this study, phenolic acids were found to render protections for PUFAs in modified PCs from oxidation. Modified PCs may have great potential for applications in food, cosmetic and pharmaceutical industries.

Ribonuclease H, an unexploited target for antiviral intervention against HIV and hepatitis B virus

Ribonucleases H (RNases H) are endonucleolytic enzymes, evolutionarily related to retroviral integrases, DNA transposases, resolvases and numerous nucleases. RNases H cleave RNA in RNA/DNA hybrids and their activity plays an important role in the replication of prokaryotic and eukaryotic genomes, as well as in the replication of reverse-transcribing viruses. During reverse transcription, the RNase H activity of human immunodeficiency virus (HIV) and hepatitis B virus (HBV) degrades the viral genomic RNA to facilitate the synthesis of viral double-stranded DNA. HIV and HBV reverse transcriptases contain DNA polymerase and RNase H domains that act in a coordinated manner to produce double-stranded viral DNA. Although RNase H inhibitors have not been developed into licensed drugs, recent progress has led to the identification of a number of small molecules with inhibitory activity at low micromolar or even nanomolar concentrations. These compounds can be classified into metal-chelating active site inhibitors and allosteric inhibitors. Among them, α-hydroxytropolones, N-hydroxyisoquinolinediones and N-hydroxypyridinediones represent chemotypes active against both HIV and HBV RNases H. In this review we summarize recent developments in the field including the identification of novel RNase H inhibitors, compounds with dual inhibitory activity, broad specificity and efforts to decrease their toxicity.

Phenylpropanoids and its derivatives: biological activities and its role in food, pharmaceutical and cosmetic industries

Phenylpropanoids and their derivatives are plant secondary metabolites widely present in fruits, vegetables, cereal grains, beverages, spices and herbs. They are known to have multifaceted effects which include antimicrobial, antioxidant, anti-inflammatory, antidiabetic, anticancer activities and as well as exhibits renoprotective, neuroprotective, cardioprotective and hepatoprotective effects. Owing to their antioxidant, antimicrobial and photoprotective properties, these compounds have wide application in the food (preservation, packaging films and edible coating), pharmaceutical, cosmetic and other industries such as textile (colorant), biofuel (antioxidant additive) and sensors (sensing biologically relevant molecules). Phenylpropanoids are present in commercially available dietary supplements and skin care products. In this review, we have presented the current knowledge on the biosynthesis, occurrence, biological activities of phenylpropanoids and their derivatives, along with the mechanism of action and their potential applications in various industries.

Ferulic Acid Esters and Withanolides: In Search of Withania somnifera GABAA Receptor Modulators

Nine compounds, including two undescribed withanolides, withasomniferolides A and B (1 and 2), three known withanolides (3-5), a ferulic acid dimeric ester (6), and an inseparable mixture of three long alkyl chain ferulic acid esters (7-9), were isolated from a GABA_A receptor positive activator methanol extract of the roots of Withania somnifera. The structures of the isolated compounds were elucidated based on NMR, MS, and ECD data analysis. In order to bioassay the single ferulic acid derivatives, compounds 6-9 were also synthesized. The most active compound, docosanyl ferulate (9), was able to enhance the GABA_A receptor inhibitory postsynaptic currents with an IC₅₀ value of 7.9 μM. These results, by showing an ability to modulate the GABA_A receptor function, cast fresh light on the biological activities of the secondary metabolites of W. somnifera roots.

Novel natural non-nucleoside inhibitors of HIV-1 reverse transcriptase identified by shape- and structure-based virtual screening techniques

In this work we report a parallel application of both docking- and shape-based virtual screening (VS) methods, followed by Molecular Dynamics simulations (MDs), for discovering new compounds able to inhibit the human immunodeficiency virus type 1 (HIV-1) reverse transcriptase (RT) RNA-dependent DNA polymerase activity. Specifically, we screened more than 143000 natural compounds commercially available in the ZINC database against the best five RT crystallographic models, taking into account the five approved NNRTIs as query compounds. As a result, 20 hit molecules were selected and tested on biochemical assays for the inhibition of the RNA dependent DNA polymerase RT function and, among them, an indoline pyrrolidine (hit1), an indonyl piperazine (hit2) and an indolyl indolinone (hit3) derivatives were identified as novel non-nucleoside RT inhibitors in the low micromolar range.

Dual HIV-1 reverse transcriptase and integrase inhibitors from Limonium morisianum Arrigoni, an endemic species of Sardinia (Italy)

During our search for potential templates of HIV-1 reverse transcriptase (RT) and integrase (IN) dual inhibitors, the methanolic extract obtained from aerial parts of Limonium morisianum was investigated. Repeated bioassay-guided chromatographic purifications led to the isolation of the following secondary metabolites: myricetin, myricetin 3-O-rutinoside, myricetin-3-O-(6″-O-galloyl)-β-d-galactopyranoside, (-)-epigallocatechin 3-O-gallate, tryptamine, ferulic and phloretic acids. The isolated compounds were tested on both HIV-1 RT-associated RNase H and IN activities. Interestingly, (-)-epigallocatechin-3-O-gallate and myricetin-3-O-(6″-O-galloyl)-β-d-galactopyranoside potently inhibited both enzyme activities with IC₅₀ values ranging from 0.21 to 10.9 μM. Differently, tryptamine and ferulic acid exhibited a significant inhibition only on the IN strand transfer reaction, showing a selectivity for this viral enzyme. Taken together these results strongly support the potential of this plant as a valuable anti HIV-1 drugs source worthy of further investigations.

Natural Products and HIV/AIDS

The study of natural products in biomedical research is not a modern concept. Many of the most successful medical therapeutics are derived from natural products, including those studied in the field of HIV/AIDS. Biomedical research has a rich history of discovery based on screens of medicinal herbs and traditional medicine practices. Compounds derived from natural products, which repress HIV and those that activate latent HIV, have been reported. It is important to remember the tradition in medical research to derive therapies based on these natural products and to overcome the negative perception of natural products as an "alternative medicine."

Phenylpropenoids from Bupleurum fruticosum as Anti-Human Rhinovirus Species A Selective Capsid Binders

The dichloromethane extract of the leaves of Bupleurum fruticosum was found to inhibit the replication of human rhinovirus (HRV) serotypes 14 and 39. Bioassay-guided fractionation led to the isolation of seven phenylpropenol derivatives (3-9), two polyacetylenes (1 and 2), and one monoterpene (10). Compounds 1 and 10 were identified as previously undescribed secondary metabolites after extensive 1D and 2D NMR experiments as well as high-resolution mass spectrometry. Compounds 2, 4, and 5 showed a selective inhibition of viral replication against HRV39 serotype, with 2 and 4 being the most active, with EC₅₀ values of 1.8 ± 0.02 and 2.4 ± 0.04 μM. Mechanism of action studies indicated that 4 behaves not only as a capsid binder, interfering with the early phases of virus replication, but also as a late-phase replication inhibitor. Docking experiments were performed to confirm the ability of the antiviral phenylpropenoids to selectively fit into the hydrophobic pocket of VP1-HRV39.