Preliminary insight on diarylpentanoids as potential antimalarials: In silico, in vitro pLDH and in vivo zebrafish toxicity assessment

Malaria remains a major public health problem worldwide, including in Southeast Asia. Chemotherapeutic agents such as chloroquine (CQ) are effective, but problems with drug resistance and toxicity have necessitated a continuous search for new effective antimalarial agents. Here we report on a virtual screening of ∼300 diarylpentanoids and derivatives, in search of potential Plasmodium falciparum lactate dehydrogenase (PfLDH) inhibitors with acceptable drug-like properties. Several molecules with binding affinities comparable to CQ were chosen for in vitro validation of antimalarial efficacy. Among them, MS33A, MS33C and MS34C are the most promising against CQ-sensitive (3D7) with EC50 values of 1.6, 2.5 and 3.1 μM, respectively. Meanwhile, MS87 (EC50 of 1.85 μM) shown the most active against the CQ-resistant Gombak A strain, and MS33A and MS33C the most effective P. knowlesi inhibitors (EC50 of 3.6 and 5.1 μM, respectively). The in vitro cytotoxicity of selected diarylpentanoids (MS33A, MS33C, MS34C and MS87) was tested on Vero mammalian cells to evaluate parasite selectivity (SI), showing moderate to low cytotoxicity (CC50 > 82 μM). In addition, MS87 exhibited a high SI and the lowest resistance index (RI), suggesting that MS87 may exert effective parasite inhibition with low resistance potential in the CQ-resistant P. falciparum strain. Furthermore, the in vivo toxicity of the molecules on early embryonic development, the cardiovascular system, heart rate, motor activity and apoptosis were assessed in a zebrafish animal model. The overall results indicate the preliminary potential of diarylpentanoids, which need further investigation for their development as new antimalarial agents.

Toxicity and teratogenicity effects of valproic acid on zebrafish (Danio rerio) embryos in relation to autism spectrum disorder

Valproic acid (VPA) is a widely prescribed antiepileptic drug with various medicinal efficacies. Accumulated evidence implied that prenatal exposure to VPA is highly associated with autism spectrum disorder (ASD). In this study, the zebrafish were exposed to a set of VPA concentrations (0, 5, 10, 20, 40, 80, 160, 320, 640, 1280, and 2560 μM) at 5 h post fertilization (hpf) to 120 hpf. The adverse effects of VPA were extensively studied through the evaluations on the mortality, heartbeats, spontaneous tail coiling, and hatching rate. Morphological observations were conducted at 120 hpf, following the exposure termination. Basic locomotor responses and anxiety-like behavioral alterations evaluated for behavioral impairments are the hallmark feature of ASD. The exposure to VPA at teratogenic concentrations reduced the aforementioned parameters in a dose-dependent manner (p ≤ .05). At the selected non-teratogenic concentrations of VPA, the treated larvae demonstrated profound alterations of basic locomotor responses. No significant changes of anxiety and thigmotactic behaviors were observed on the VPA-treated fish compared to the control (p ≥ .005). This study depicted that embryonic zebrafish exposure to VPA produced significant toxicity and teratogenicity effects as well as the alterations of basic behavioral responses. Overall, this study provides a fundamental insight of the toxicity effects at morphological and behavioral levels to facilitate the understanding of ASD mechanisms at different molecular levels.

Chemical Composition and Evaluation of the α-Glucosidase Inhibitory and Cytotoxic Properties of Marine Algae Ulva intestinalis, Halimeda macroloba, and Sargassum ilicifolium

Seaweed has tremendous potentials as an alternative source of high-quality food products that have attracted research in recent times, due to their abundance and diversity. In the present study, three selected seaweed species commonly found in the Malaysian Peninsular, Ulva intestinalis, Halimeda macroloba, and Sargassum ilicifolium, were subjected to preliminary chemical screening and evaluated for α-glucosidase inhibitory and cytotoxic activities against five cancer cell lines. Chemical composition of U. intestinalis, H. macroloba, and S. ilicifolium methanolic extracts was evaluated by Gas Chromatography-Mass Spectrometry (GC-MS) analysis. Our results revealed the highest total carotenoids (162.00 μg g-1 DW), chlorophyll a (313.09 ± 2.53 μg g-1 DW), and chlorophyll b (292.52 ± 8.84 μg g-1 DW) concentrations in U. intestinalis. In the α-glucosidase inhibitory activity, S. ilicifolium demonstrated the lowest efficacy with an IC50 value of 38.491 ppm compared to other species of seaweed. H. macroloba extract, on the other hand, was found to be the most cytotoxic toward MCF-7 and HT 29 cells with IC50 of 37.25 ± 0.58 and 21.32 ± 0.25 μg/mL, respectively, compared to other cell lines evaluated. Furthermore, H. macroloba extract was also found to be less toxic to normal cell (3T3) with IC50 of 48.80 ± 0.11 μg/mL. U. intestinalis extract exhibited the highest cytotoxicity toward Hep G2 cells with IC50 of 23.21 ± 0.11 μg/mL, whereas S. ilicifolium was less toxic to MDA- MB231 cell with IC50 of 25.23 ± 0.11 μg/mL. Subsequently, the GC-MS analysis of the methanolic extracts of these seaweed samples led to the identification of 27 metabolites in U. intestinalis, 22 metabolites in H. macroloba, and 24 metabolites in S. ilicifolium. Taken together, the results of this present study indicated that all the seaweed species evaluated are good seaweed candidates that exhibit potential for cultivation as functional food sources for human consumption and need to be promoted.

Development of diarylpentadienone analogues as alpha-glucosidase inhibitor: Synthesis, in vitro biological and in vivo toxicity evaluations, and molecular docking analysis

A series of aminated- (1-9) and sulfonamide-containing diarylpentadienones (10-18) were synthesized, structurally characterized, and evaluated for their in vitro anti-diabetic potential on α-glucosidase and DPP-4 enzymes. It was found that all the new molecules were non-associated PAINS compounds. The sulfonamide-containing series (compounds 10-18) selectively inhibited α-glucosidase over DPP-4, in which compound 18 demonstrated the highest activity with an IC₅₀ value of 5.69 ± 0.5 µM through a competitive inhibition mechanism. Structure-activity relationship (SAR) studies concluded that the introduction of the trifluoromethylbenzene sulfonamide moiety was essential for the suppression of α-glucosidase. The most active compound 18, was then further tested for in vivo toxicities using the zebrafish animal model, with no toxic effects detected in the normal embryonic development, blood vessel formation, and apoptosis of zebrafish. Docking simulation studies were also carried out to better understand the binding interactions of compound 18 towards the homology modeled α -glucosidase and the human lysosomal α -glucosidase enzymes. The overall results suggest that the new sulfonamide-containing diarylpentadienones, compound 18, could be a promising candidate in the search for a new α-glucosidase inhibitor, and can serve as a basis for further studies involving hit-to-lead optimization, in vivo efficacy and safety assessment in an animal model and mechanism of action for the treatment of T2DM patients.

Antinociceptive activity of methanolic extract of Acmella uliginosa (Sw.) Cass

ETHNOPHARMACOLOGICAL RELEVANCE

Acmella uliginosa (Sw.) Cass. is a medicinal herbaceous plant that is commonly used by the Malay community in Malaysia to relieve pain often associated with mouth ulcers, toothache, sore throat, and stomach ache.

AIM

The study was carried out to investigate the antinociceptive effect of the methanolic extract of A. uliginosa (Sw.) Cass. flowers (MEAU) using murine models of chemicals and thermal nociception.

MATERIALS AND METHODS

Chemicals (acetic acid-induced abdominal constriction and formalin-, capsaicin-, glutamate-induced paw licking test) and thermal models (hot plate test) of nociception in mice were employed to evaluate the MEAU analgesic effect. The extract was given via oral administration at doses of 3, 10, 30 and 100 mg/kg.

RESULTS

It was demonstrated that MEAU produced significant antinociceptive response in all the chemical- and thermal-induced nociception models, which indicates the presence of both centrally and peripherally mediated activities. Furthermore, the reversal of antinociception of MEAU by naloxone suggests the involvement of opioid system in its centrally mediated analgesic activity. Moreover, MEAU-treated mice did not show any significant motor performance alterations. No mortality and signs of toxicity were recorded following treatment of the MEAU.

CONCLUSION

The results from the present study appear to support the folkloric belief in the medicinal properties of A. uliginosa (Sw.) Cass. which against pain at both central and peripheral levels, in which the central antinociception is probably due to the participation of the opioid receptors.