Molecular simulations probing Kushecarpin A as a new lipoxygenase inhibitor

In-vitro antioxidant, lipoxygenase inhibitory, and in-vivo muscle relaxant potential of the extract and constituent isolated from Diospyros kaki (Japanese Persimmon)

Diospyros kaki (Japanese persimmon) is cultivated specious of the Diospyros genus. D. kaki is a multi-medicinal application in the folk system for the cure of ischemic stroke, angina, atherosclerosis, muscle relaxation, internal hemorrhage, hypertension, high cough, and infectious disease. The main objective of this study was the isolated bioactive metabolites from chloroform fractions of D. kaki. The extract and fractions were then tested for various in-vitro (antioxidant and lipoxygenase) and in-vivo (muscle relaxant) activities. The repeated chromatographic separation of chloroform extract afforded compound 1. Compound 1, n-hexane, and chloroform fractions were evaluated for in vitro antioxidant, lipoxygenase inhibitory, and in vivo muscle relaxant potency. The chloroform extract has 79.54% interaction with DPPH at higher concentrations (100 μg/ml) while the compound exhibited a maximum effect of 95.09% at 100 μg/ml. Compound 1 exhibited significant lipoxygenase inhibitory activity with an IC₅₀ value of 36.98 μM followed by a chloroform extract of 57.09 μM. Similarly, compound 1 and chloroform extract showed excellent muscle relaxant effects at a higher dose. From this investigation, it is concluded that extracts and pure compounds exhibited promising antioxidant, lipoxygenase inhibitory, and muscle relaxant activity. This study excellently rationalizes the traditional usage of D. kaki in curing various diseases. Furthermore, the docking results indicate, that the isolated compound fits well into the active site of the lipoxygenase, and makes strong interactions with the target protein.

Anti-nociceptive and Anti-inflammatory Activities of Asparacosin A Involve Selective Cyclooxygenase 2 and Inflammatory Cytokines Inhibition: An in-vitro, in-vivo, and in-silico Approach

Triterpenes possess anti-inflammatory and anti-nociceptive effects. In this study anti-inflammatory activities of Asparacosin A were evaluated' using in-vitro cyclooxygenases 1 and 2 (COX-1/2) inhibition assays. Moreover, anti-nociceptive activities were assessed in-vivo by carrageenan-induced paw edema test, xylene-induced ear edema tests, and acetic acid-induced writhing and formalin tests. Additionally molecular docking was conducted to elucidate the binding mechanism of the compound and to correlate the in-vitro findings with the in-silico data. Oral administration of Asparacosin A at the doses of 10, 20, and 40 mg/kg induced significant anti-inflammatory effects (^*p < 0.05, ^**p < 0.01, and ^***p < 0.001) in a dose-dependent manner in both models. Asparacosin A also inhibited the human recombinant COX-2 enzyme and caused a dose-dependent decrease in the levels of TNF-α, IL-1β, and PGE2 in the carrageenan-induced paws. Moreover, Asparacosin A displayed significant anti-nociceptive effects (^*p < 0.05, ^**p < 0.01, ^***p < 0.001) at the doses of 10, 20, and 40 mg/kg in acetic-acid induced writhing test. However, in formalin test, Asparacosin A (10–40 mg/kg, p.o) produced anti-nociceptive effects only in the late phase, similar to the effect observed with the reference drug celecoxib (50 mg/kg, p.o). Molecular docking was carried out on both COX-1 and COX-2 structures which revealed that Asparacosin A targets allosteric binding site similar to the binding mode of the selective COX inhibitor. In conclusion, Asparacosin A exhibits anti-inflammatory and peripheral anti-nociceptive activities which are likely mediated via inhibition of COX-2 enzyme and inflammatory cytokines. Furthermore, Asparacosin A can serve as a model to obtain new and more selective potent anti-inflammatory and anti-nociceptive drugs.

15-Lipoxygenase inhibition of Commelina benghalensis, Tradescantia fluminensis, Tradescantia zebrina

OBJECTIVE

To evaluate the 15-lipoxygenase inhibitory activity of the methanol leaf extracts of Commelina benghalensis, Tradescantia fluminensis (T. fluminensis) and Tradescantia zebrina.

METHOD

The inhibitory activity was evaluated using a spectrophotometric assay by observing the increase in absorbance at 234 nm due to the formation of the product 13-hydroperoxyoctadecadienoic acid. The extracts were also tested for the presence of terpenoids, saponins, tannins, flavonoids, steroids, phenolic compounds, alkaloids and cardiac glycosides.

RESULTS

All the extracts inhibited the action of 15-lipoxygenase at a concentration of 0.2 µg/mL. T. fluminensis and Tradescantia zebrina exhibited higher than 50% inhibition with T. fluminensis at 87.2%. T. fluminensis was partitioned with ethyl acetate and hexane and their IC50 values were determined at 8.72 µg/mL and 98.04 µg/mL, respectively.

CONCLUSIONS

T. fluminensis is a potentially good source of 15-lipoxygenase inhibitors.

The antiangiogenic activity of Kushecarpin D, a novel flavonoid isolated from Sophora flavescens Ait

AIMS

Kushecarpin D (KD) is a novel flavonoid isolated from the traditional Chinese herbal medicine Kushen (the dried root of Sophora flavescens Ait). As part of our continuous effort to explore Chinese traditional medicinal herbs and to identify novel natural anticancer products, the antiangiogenic properties of KD were examined in vitro using a human umbilical vein endothelial cell line (ECV304).

MAIN METHODS

The SRB and Trypan Blue exclusion assays were used to evaluate the effect of KD on cell proliferation. The antiangiogenic activities of KD were evaluated through studies of cell migration, cell adhesion, and tube formation. DCFH-DA and DHE fluorescent assays were used to detect the reactive oxygen species (ROS) levels. Catalase activity was detected using the colorimetric ammonium molybdate method. Cell cycle and apoptosis were measured using flow cytometry and the Hoechst 33258 staining assay.

KEY FINDINGS

The results indicated that KD showed antiangiogenic activity via inhibitory effects on cell proliferation, cell migration, cell adhesion, and tube formation. ROS levels were down-regulated and catalase activity was up-regulated after treatment with KD. The cell cycle was arrested at the G2/M phase, while no apoptosis was observed using the Hoechst 33258 staining assay or following the flow cytometric analysis of the sub-G1 proportion.

SIGNIFICANCE

The antiangiogenic properties of KD, in combination with its anti-proliferative effect and ability to induce cell cycle arrest without inducing apoptosis, make it a good candidate for development as antitumor agent. However, further studies are essential to elucidate its mechanism of action.

Molecular interactions of 4-acetoxy-plakinamine B with peripheral anionic and other catalytic subsites of the aromatic gorge of acetylcholinesterase: computational and structural insights

CONTEXT

A steroidal alkaloid, 4-acetoxy-plakinamine B (4APB), is a recently discovered marine natural product with inhibitory effect against acetylcholinesterase (AChE), but its mechanism of interaction with the enzyme remains to be elucidated.

OBJECTIVE

The main objective was to study molecular binding mode of the compound, its interactions with catalytic subsites and molecular mechanism behind its significant inhibitory effect.

MATERIALS AND METHODS

All possible interactions of ligands in the binding sites were analyzed using FRED 2.1 and the OMEGA pre-generated multi-conformer library.

RESULTS

Dipole-dipole interactions were observed between the secondary amino group of 4APB and Ser200 at a distance of 3.91 Å and also with Gly117 and Gly118. A further dipole-dipole interaction was between Arg289 and the heterocyclic nitrogen. Hydrogen bonding interactions were observed between Tyr130 and secondary amino and C-4 acetyl groups as well as between heterocyclic nitrogen and Phe288 at a distance of 3.04 Å. Hydrophobic interactions were evident between rings C/D of 4APB and with Phe288, Phe330 and Phe331. The computational studies revealed 4APB's critical molecular interaction with amino acids of peripheral active (PAS) and anionic (AS) subsites.

DISCUSSION

Our data provided molecular evidence for the mixed competitive inhibitory effect of 4APB. For lead optimization, structural insights revealed the N-methyl group of 4APB could be replaced by NH2 moiety to generate a more favorable hydrogen bonding with Glu199. A polar group insertion such as NH2 or OH at certain sites of the 4APB skeleton is also recommended.

CONCLUSION

These computational insights explained the mixed-competitive enzyme kinetic behavior of 4APB. This study outlines a strategy for designing novel derivatives of 4APB with potentially better AChE inhibitory activities through interaction at the PAS and AS sites.