RESUMO
Developing new anti-human immunodeficiency virus (HIV) drug candidates that target different sites in HIV-1 replication, with better resistance profiles and lower drug toxicity, is essential to eradicating HIV. This study investigated the potential of fractionated crude extracts of Alternaria alternata as immunomodulatory or anti-HIV drug candidates. Solid-phase extraction (SPE) was used to fractionate A. alternata PO4PR2 using three different columns: MAX (Mixed-mode, strong Anion-eXchange), MCX (Mixed-mode, strong Cation-eXchange), and HLB (Hydrophilic-Lipophilic Balance) with methanol gradient methods (5%, 45%, and 95%). An MTT (3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide) assay was used to assess the cell viability and cytotoxicity of the fractionated crude extract A. alternata PO4PR2 in the TZM-bl cell lines. This was followed by a luciferase-based antiviral assay to assess the antiviral activity of A. alternata PO4PR2. A time of addition (TOA) assay was performed to ascertain the mechanism of inhibition employed by the fractionated crude extract of A. alternata PO4PR2 in the HIV life cycle. The p24 titer was determined using an ELISA, while a luciferase-based antiviral assay was used to evaluate the HIV percentage inhibition for different HIV-1 replication cycles. The TOA assay was established using antiviral drugs that target different sites in the HIV replication cycle. These included maraviroc, azidothymidine, raltegravir, and amprenavir. The immunomodulatory effect of the fractionated crude extracts on CD4+ T cells was measured by a flow cytometric analysis, for which fluorochrome-labelled monoclonal antibodies were used as markers for activation (CD38 and HLA-DR) and exhaustion (PD-1). The MCX fraction demonstrated a more significant anti-HIV inhibition than that of the fractions generated in other columns, with an IC50 of 0.3619 µg/mL, an HIV inhibition of 77%, 5% HLB (IC50: 0.7232 µg/mL; HIV inhibition of 64%), and 5% MAX (IC50: 5.240 µg/mL; HIV inhibition of 67%). It was evident from the time of addition data that the crude extract and the 5% MCX fraction inhibited viral binding (68%), reverse transcription (75%), integration (98%), and proteolysis (77%). It was shown that A. alternata (the MCX fraction) have a significant inhibitory effect on reverse transcription (75% HIV inhibition) and integration (100% HIV inhibition). The 5% MCX (p = 0.0062), 5% HLB (p = 0.0269), and 5% MAX (p = 0.0117) fractionated A. alternata crude extracts had low levels of CD4+ T cell (CD38 + HLA-DR+) activation compared to those of the AZT treatment, while CD4+ T cell activation was insignificant. The 5% MAX and HLB A. alternata fractions may possess immunomodulatory compounds with less anti-HIV-1 activity. A. alternata could be a key source of innovative anti-HIV drugs with immunomodulatory characteristics.
RESUMO
New benzimidazole-1,2,3-triazole-quinoline hybrids and their intermediates, differing in substitutions at the C-2 and/or C6 positions of the benzimidazole ring, were successfully synthesized in 55---80 % yields, with the C6-substituted ones forming as inseparable tautomeric mixtures. The synthesized compounds were fully characterised by FT-IR, 1D- and 2D-NMR, and HRMS. In-depth NMR analysis and DFT molecular calculations showed that the tautomeric mixtures formed in a ratio of almost 1:1 ratio (cis and trans), except for 5 g, where the ratio is 1:2. In vitro antimycobacterial activity evaluation against the H37Rv strain of Mycobacterial tuberculosis was undertaken on all synthesized compounds, and a selected number were further screened for their cytotoxicity on TZM-bl cell lines. Hybrid compounds showed excellent MIC90 activities ranging from 1.07 to 8.66 µM and were all more efficacious than the first-line reference drug, ethambutol (MIC90 = 9.54 µM). In particular, hybrid compounds 5b (MIC90 = 1.54 µM, CC50 = 58.89 µM and % cell viability = 14.07), 5d (MIC90 = 2.08 µM, CC50 = 0.27 µM, and % cell viability = 149.50 %) and 5 g (MIC90 = 1.49 µM, CC50 = 4.62 µM and % cell viability = 44.03) were the most promising. Significantly, 5b and 5 g were over six times more efficacious than ethambutol but exhibited cytotoxicity towards TZM-bl cell-lines compared to 5d, which was over four times more active than ethambutol. The physical combination (mimicking combination therapy) of individual pharmacophoric components making up 5 g were less active, indicating the synergistic effect of hybridization. In addition, more than 60 % of all the synthesized hybrids showed better activity than their respective pharmacophoric components. In silico ADME studies of the hybrids revealed favourable physico-chemical properties, while molecular modeling studies suggested binding interactions with Val 61, Gly 62, Glu 65, Ala 66, and Phe 69 amino acid in a reported similar manner to bedaquiline, an approved quinoline-based anti-TB drug.
