Anti-HIV Agents From Nature: Natural Compounds From Hypericum hircinum and Carbocyclic Nucleosides From Iridoids

Regioselective Deacetylation in Nucleosides and Derivatives

Nucleoside analogues are a promising class of natural compounds in the pharmaceutical industry, and many antiviral, antibacterial and anticancer drugs have been created through structural modification of nucleosides scaffold. Acyl protecting groups, especially the acetyl group, play an important role in the protection of hydroxy groups in nucleoside synthesis and modification; consequently, numerous methodologies have been put forth for the acetylation of free nucleosides. However, for nucleosides that contain different O- and N-based functionalities, selective deprotection of the acetyl group(s) in nucleosides has been studied little, despite its practical significance in simplifying the preparation of partially or differentially substituted nucleoside intermediates. In this mini-review, recent approaches for regioselective deacetylation in acetylated nucleosides and their analogues are summarized and evaluated. Different regioselectivities (primary ester, secondary ester, full de-O-acetylation, and de-N-acetylation) are summarized and discussed in each section.

Ligand-Based Drug Design of Genipin Derivatives with Cytotoxic Activity against HeLa Cell Line: A Structural and Theoretical Study

Cervical cancer is a malignant neoplastic disease, mainly associated to HPV infection, with high mortality rates. Among natural products, iridoids have shown different biological activities, including cytotoxic and antitumor effects, in different cancer cell types. Geniposide and its aglycone Genipin have been assessed against different types of cancer. In this work, both iridoids were evaluated against HeLa and three different cervical cancer cell lines. Furthermore, we performed a SAR analysis incorporating 13 iridoids with a high structural similarity to Geniposide and Genipin, also tested in the HeLa cell line and at the same treatment time. Derived from this analysis, we found that the dipole moment (magnitude and direction) is key for their cytotoxic activity in the HeLa cell line. Then, we proceeded to the ligand-based design of new Genipin derivatives through a QSAR model (R2 = 87.95 and Q2 = 62.33) that incorporates different quantum mechanic molecular descriptor types (ρ, ΔPSA, ∆Polarizability2, and logS). Derived from the ligand-based design, we observed that the presence of an aldehyde or a hydroxymethyl in C4, hydroxyls in C1, C6, and C8, and the lack of the double bond in C7-C8 increased the predicted biological activity of the iridoids. Finally, ten simple iridoids (D9, D107, D35, D36, D55, D56, D58, D60, D61, and D62) are proposed as potential cytotoxic agents against the HeLa cell line based on their predicted IC50 value and electrostatic features.

Bichromonol, a dimeric coumarin with anti-HIV activity from the stem bark of Hypericum roeperianum

Infectious diseases caused by viruses like HIV and SARS-COV-2 (COVID-19) pose serious public health threats. In search for new antiviral small molecules from chemically underexplored Hypericum species, a previously undescribed atropisomeric C8-C8' linked dimeric coumarin named bichromonol (1) was isolated from the stem bark of Hypericum roeperianum. The structure was elucidated by MS data and NMR spectroscopy. The absolute configuration at the biaryl axis was determined by comparing the experimental ECD spectrum with those calculated for the respective atropisomers. Bichromonol was tested in cell-based assays for cytotoxicity against MT-4 (CC₅₀ = 54 µM) cells and anti-HIV activity in infected MT-4 cells. It exhibits significant activity at EC₅₀ = 6.6-12.0 µM against HIV-1 wild type and its clinically relevant mutant strains. Especially, against the resistant variants A17 and EFV^R, bichromonol is more effective than the commercial drug nevirapine and might thus have potential to serve as a new anti-HIV lead.

Phytochemistry, synthesis, analytical methods, pharmacological activity, and pharmacokinetics of loganin: A comprehensive review

Iridoid glycosides (IGs) are found in many medicinal and edible plants, such as Gardenia jasminoides, Cistanche tubulosa, Eucommia ulmoides, Rehmanniae Radix, Lonicera japonica, and Cornus officinalis. Loganin, an IG, is one of the main active ingredient of Cornus officinalis Sieb. et Zucc., which approved as a medicinal and edible plant in China. Loganin has been widely concerned due to its extensive pharmacological effects, including anti-diabetic, antiinflammatory, neuroprotective, and anti-tumor activities, etc. Studies have shown that these underlying mechanisms include anti-oxidation, antiinflammation and anti-apoptosis by regulating a variety of signaling pathways, such as STAT3/NF-κB, JAK/STAT3, TLR4/NF-κB, PI3K/Akt, MCP-1/CCR2, and RAGE/Nox4/p65 NF-κB signaling pathways. In order to better understand the research status of loganin and promote its application in human health, this paper systematically summarized the phytochemistry, analysis methods, synthesis, pharmacological properties and related mechanisms, and pharmacokinetics based on the research in the past decades.

Endophytic Microbial Diversity: A New Hope for the Production of Novel Anti-tumor and Anti-HIV Agents as Future Therapeutics

Cancer is a collective name for a variety of diseases that can begin in virtually every organ or body tissue as abnormal cells develop uncontrollably and ten million new cancer cases are diagnosed all over the world at present. Whereas HIV is a virus that makes people susceptible to infection and contributes to the condition of acquired immune deficiency syndrome (AIDS). Almost 37 million people are currently diagnosed with HIV and 1 million people die every year, which is the worst-case scenario. Potential medicinal compounds have played a crucial role in the production of certain clinically beneficial novel anti-cancer and anti-HIV agents that are produced from natural sources especially from plants. These include Taxol, Vinblastine, Podophyllotoxin, Betulinic acid, Camptothecin, and Vincristine, etc. In the past decades, bioactive compounds were extracted directly from the plant sources which was more time consuming, led to low yield productivity, high cost, and bad impact on biodiversity. Endophytes, the microorganisms that reside inside the host plant by not causing any kind of harm to them and have potential applications in agriculture, medicine, pollution, and food industries. Therefore, by isolating and characterizing novel endophytes from medicinal plants and extracting their secondary metabolites to produce useful bioactive compounds can be beneficial for well-being and society as a future therapeutics. This approach is not harmful to biodiversity economical, timesaving, low cost, and can lead to the discovery of various industrial and commercially important novel anti-tumor and anti-HIV agents in the future. The Himalayas are home to several medicinal plants and the endophytic microbial biodiversity of the Himalayan region is also not much explored yet. However, the effect of compounds from these endophytes on anticancer and antiviral activity, especially anti-HIV has been largely unexplored. Hence, the present review is designed to the exploration of endophytic microbial diversity that can give rise to the discovery of various novel potential industrially valuable bioactive compounds that can lessen the rate of such type of pandemic diseases in the future by providing low-cost future therapeutics in future.

Structural and kinetic insights into HIV-1 reverse transcriptase inhibition by farnesiferol C

Human immunodeficiency virus type 1 reverse transcriptase (HIV-1 RT) is the key enzyme for the virus gene replication and the most important target for antiviral therapy. Toxicity, drug resistance and side effects have led to search for new antiviral agents. Farnesiferol C (FC) is a well-known biologically active sesquiterpene coumarin derivative from genus Ferula. The current study was designed to examine the impacts of FC on the structure and function of HIV-1 RT, using some theoretical and experimental methods. FC inhibited HIV-1RT activity via mixed inhibition mechanism (IC₅₀ = 30 μM). Spectroscopic data showed some conformational changes in the secondary as well as tertiary structure of HIV-1RT following the interaction with FC. Results showed that FC could quench the intrinsic fluorescence emission of HIV-1RT through static quenching mechanism. Thermodynamic parameters revealed that hydrogen bondings and van der Waals forces are the major forces in the binding reaction and the low equilibrium constants (K_D) value obtained from surface plasmon resonance data, confirmed the high affinity of FC for HIV-1RT. Molecular docking studies indicated that FC interacts with enzyme through hydrophobic pocket. Taken together, the outcomes of this research revealed that, sesquiterpene coumarines can be used to design natural remedies as anti-HIV agents.

Bis-iridoid and iridoid glycosides: Viral protein R inhibitors from Picrorhiza kurroa collected in Myanmar

Four new bis-iridoid glycosides, saungmaygaosides A-D (1-4), and six known iridoid glycosides (5-10) were isolated from the n-butanol extract of the stems of Picrorhiza kurroa collected in Myanmar. Their structures were elucidated by extensive spectroscopic techniques. All of the isolates were assayed for anti-Vpr activity, using TREx-HeLa-Vpr cells. Among the isolates, saungmaygaoside D (4), sylvestroside IV dimethyl acetal (7), and sweroside (8) were the most potent inhibitors with effective doses of 5 and 10 μM, respectively, without showing any notable cytotoxicities.