The anti-HIV actions of 7- and 10-substituted camptothecins

Characterization of camptothecin by analytical methods and determination of anticancer potential against prostate cancer

Background

Objective of present research work is to develop and validate cost-effective analytical tool for determination of camptothecin (CPT) and determine its anticancer potential against prostate cancer LNCaP cell lines. Structural elucidation has been performed by mass spectrometry, Fourier transform infrared spectroscopy, nuclear magnetic resonance spectroscopy, and MTT assay utilized for in vitro cytotoxicity where spectrometric method was used for estimation of camptothecin.

Results

Mass spectra showed peak at 349.2 which matches to standard molecular weight of camptothecin. FTIR and NMR spectra conformed functional moieties and structure of isolated camptothecin which was nearly equal to values mentioned in standard structure of camptothecin. IC50 values of CPT against LNCaP cell lines was found to be 3.561 μg/ml. Lambda max of CPT was found to be at 225 nm and calibration curve found to be linear over the concentration range from 2 to 70 μg/ml of camptothecin. Developed method was found to be linear, accurate, and precise. LOD and LOQ were found to be 0.0524 μg/ml and 0.1614 μg/ml, respectively. Developed method has % relative standard deviation less than one which is reproducible hence % recovery was found to be 99.80%.

Conclusions

FTIR, NMR, and mass spectrometry results conforms isolated compound was camptothecin; cytotoxicity study proves it has strong potential in treatment of prostate carcinoma as competent alternative to chemotherapy in the form of herbal medicine and the developed UV method proves to be valid, sensitive, and applicable for rapid, accurate, precise, and economical determination of camptothecin.

Diversity in Chemical Structures and Biological Properties of Plant Alkaloids

Phytochemicals belonging to the group of alkaloids are signature specialized metabolites endowed with countless biological activities. Plants are armored with these naturally produced nitrogenous compounds to combat numerous challenging environmental stress conditions. Traditional and modern healthcare systems have harnessed the potential of these organic compounds for the treatment of many ailments. Various chemical entities (functional groups) attached to the central moiety are responsible for their diverse range of biological properties. The development of the characterization of these plant metabolites and the enzymes involved in their biosynthesis is of an utmost priority to deliver enhanced advantages in terms of biological properties and productivity. Further, the incorporation of whole/partial metabolic pathways in the heterologous system and/or the overexpression of biosynthetic steps in homologous systems have both become alternative and lucrative methods over chemical synthesis in recent times. Moreover, in-depth research on alkaloid biosynthetic pathways has revealed numerous chemical modifications that occur during alkaloidal conversions. These chemical reactions involve glycosylation, acylation, reduction, oxidation, and methylation steps, and they are usually responsible for conferring the biological activities possessed by alkaloids. In this review, we aim to discuss the alkaloidal group of plant specialized metabolites and their brief classification covering major categories. We also emphasize the diversity in the basic structures of plant alkaloids arising through enzymatically catalyzed structural modifications in certain plant species, as well as their emerging diverse biological activities. The role of alkaloids in plant defense and their mechanisms of action are also briefly discussed. Moreover, the commercial utilization of plant alkaloids in the marketplace displaying various applications has been enumerated.

Enhanced production of camptothecin by immobilized callus of Ophiorrhiza mungos and a bioinformatic insight into its potential antiviral effect against SARS-CoV-2

Camptothetin (CPT) is a quinoline alkaloid originally isolated from the Chinese tree, Camptotheca acuminata Decne. CPT was found to have anticancerous and antiviral properties. Derivatives of natural CPT, including topothecan and irinotecan are used clinically to treat a variety of cancers. Apart from Camptotheca acuminata Decne, CPT production was also found in the perennial plant Ophiorrhiza mungos. In this study we attempted the immobilization of the tissue culture grown callus of Ophiorrhiza mungos for the continuous production of a higher concentration of CPT. As evident from previous studies about the antiviral effects of CPT, we wanted to bioinformatically analyze the binding potential of CPT towards two important proteins of SARS-CoV-2, protease (M^pro) and RNA dependent RNA polymerase (RdRp). Further docking analysis of the CPT against the exterior spike glycoprotein of SARS-CoV-2 was also done to determine their potential interaction. The immobilized callus of Ophiorrhiza mungos produced CPT at a concentration of 420 µg/l by the end of 12 days of growth. The HPLC analysis was done to determine the purity of the CPT synthesized by the immobilization technique. The bioinformatic analysis revealed a higher binding efficiency of CPT and its derivatives, toptecan and irinotecan against M^pro and RdRp. The docking analysis of CPT against the spike glycoprotein of SARS-CoV-2 showed hydrogen bonding with the amino acids at K466 with a bond distance of 2.56A° and K355 with a bond distance of 2.40A°. This finding was of particular importance that other compounds including hydroxychloroquine sulphate, lopinavir and ivermectin could bind with the spike protein only by weak Vander wall bonds and no hydrogen bond formation was noticed. Our studies hence evaluate the efficiency of CPT against SARS-CoV-2, by potentially blocking the interaction of the spike glycoprotein with the angiotensin-converting enzyme 2 (ACE2) receptor found on host cells.

Design and characterization of camptothecin gel for treatment of epidermoid carcinoma

Background

The objective of present research work is to design and characterize camptothecin gel using Carbopol-934 for the treatment of epidermoid carcinoma. Optimized herbal gel formulations were evaluated for homogeneity and appearance, viscosity, extrudability, spreadability, drug content, drug release, pH, and in vitro skin cancer activity on A431 cell lines.

Results

Mass and Infrared Spectra respectively conforms molecular weight and functional groups present in camptothecin. All the formulations F1 to F5 showed good homogeneity, pH from 6.68 to 6.90, spreadability in the range of 15.81–23.37 gm.cm/s, extrudability 85.51–90.45% w/w, drug content 89.12–96.64%, and in vitro diffusion 88.36–98.40%, respectively. The drug release study showed that all the formulations followed a diffusion-controlled, zero-order release mechanism. Anticancer activity results indicate that camptothecin gel induce cell death in A-439 cells having IC50 48.03 μg and % apoptosis 54.67 ± 4.58.

Conclusion

Topical delivery of camptothecin alleviates the side effects caused by systemic chemotherapy; hence, the developed herbal gel formulation can be effectively useful to deliver camptothecin in the treatment of epidermoid carcinoma on A-431 cells.

Safe approaches for camptothecin delivery: Structural analogues and nanomedicines

Twenty-(S)-camptothecin is a strongly cytotoxic molecule with excellent antitumor activity over a wide spectrum of human cancers. However, the direct formulation is limited by its poor water solubility, low plasmatic stability and severe toxicity, which currently limits its clinical use. As a consequence, two strategies have been developed in order to achieve safe and efficient delivery of camptothecin to target cells: structural analogues and nanomedicines. In this review, we summarize recent advances in the design, synthesis and development of camptothecin molecular derivatives and supramolecular vehicles, following a systematic classification according to structure-activity relationships (structural analogues) or chemical nature (nanomedicines). A series of organic, inorganic and hybrid materials are presented as nanoplatforms to overcome camptothecin restrictions in administration, biodistribution, pharmacokinetics and toxicity. Nanocarriers which respond to a variety of stimuli endogenously (e.g., pH, redox potential, enzyme activity) or exogenously (e.g., magnetic field, light, temperature, ultrasound) seem the best positioned therapeutic materials for optimal spatial and temporal control over drug release. The main goal of this review is to be used as a source of relevant literature for others interested in the field of camptothecin-based therapeutics. To this end, final remarks on the most important formulations currently under clinical trial are provided.

An analog of camptothecin inactive against Topoisomerase I is broadly neutralizing of HIV-1 through inhibition of Vif-dependent APOBEC3G degradation

Camptothecin (CPT) is a natural product discovered to be active against various cancers through its ability to inhibit Topoisomerase I (TOP1). CPT analogs also have anti-HIV-1 (HIV) activity that was previously shown to be independent of TOP1 inhibition. We show that a cancer inactive CPT analog (O2-16) inhibits HIV infection by disrupting multimerization of the HIV protein Vif. Antiviral activity depended on the expression of the cellular viral restriction factor APOBEC3G (A3G) that, in the absence of functional Vif, has the ability to hypermutate HIV proviral DNA during reverse transcription. Our studies demonstrate that O2-16 has low cytotoxicity and inhibits Vif-dependent A3G degradation, enabling A3G packaging into HIV viral particles that results in A3G signature hypermutations in viral genomes. This antiviral activity was A3G-dependent and broadly neutralizing against sixteen HIV clinical isolates from groups M (subtypes A-G), N, and O as well as seven single and multi-drug resistant strains of HIV. Molecular modeling predicted binding near the PPLP motif crucial for Vif multimerization and activity. O2-16 also was active in blocking Vif degradation of APOBEC3F (A3F). We propose that CPT analogs not active against TOP1 have novel therapeutic potential as Vif antagonists that enable A3G-dependent hypermutation of HIV.

Inhibitory Effect of Camptothecin against Rice Bacterial Brown Stripe Pathogen Acidovorax avenae subsp. avenae RS-2

Camptothecin (CPT) has anticancer, antiviral, and antifungal properties. However, there is a dearth of information about antibacterial activity of CPT. Therefore, in this study, we investigated the inhibitory effect of CPT on Acidovorax avenae subsp. avenae strain RS-2, the pathogen of rice bacterial brown stripe, by measuring cell growth, DNA damage, cell membrane integrity, the expression of secretion systems, and topoisomerase-related genes, as well as the secretion of effector protein Hcp. Results indicated that CPT solutions at 0.05, 0.25, and 0.50 mg/mL inhibited the growth of strain RS-2 in vitro, while the inhibitory efficiency increased with an increase in CPT concentration, pH, and incubation time. Furthermore, CPT treatment affected bacterial growth and replication by causing membrane damage, which was evidenced by transmission electron microscopic observation and live/dead cell staining. In addition, quantitative real-time PCR analysis indicated that CPT treatment caused differential expression of eight secretion system-related genes and one topoisomerase-related gene, while the up-regulated expression of hcp could be justified by the increased secretion of Hcp based on the ELISA test. Overall, this study indicated that CPT has the potential to control the bacterial brown stripe pathogen of rice.

Perspectives on biologically active camptothecin derivatives

Camptothecins (CPTs) are cytotoxic natural alkaloids that specifically target DNA topoisomerase I. Research on CPTs has undergone a significant evolution from the initial discovery of CPT in the late 1960s through the study of synthetic small-molecule derivatives to investigation of macromolecular constructs and formulations. Over the past years, intensive medicinal chemistry efforts have generated numerous CPT derivatives. Three derivatives, topotecan, irinotecan, and belotecan, are currently prescribed as anticancer drugs, and several related compounds are now in clinical trials. Interest in other biological effects, besides anticancer activity, of CPTs is also growing exponentially, as indicated by the large number of publications on the subject during the last decades. Therefore, the main focus of the present review is to provide an ample but condensed overview on various biological activities of CPT derivatives, in addition to continued up-to-date coverage of anticancer effects.

Chen, Zheng, et al. Anti-HIV Actions of 7- and 10-Substituted Camptothecins. Molecules, 2010, 15, 138-148

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