ABSTRACT
Lichens produce secondary metabolites that have many pharmaceutical activities such as antimicrobial, antioxidant, antiviral, anticancer, antigenotoxic, anti-inflammatory, analgesic and antipyretic activities. However, there is limited research on their efflux pump inhibitory activities. Twelve phytochemicals were isolated from Usnea aciculifera, and their activity of AcrAB-TolC efflux pump inhibition was evaluated. Four potential compounds, which are diffractaic acid (2), 8' -O- methylstictic acid (5), 3-hydroxy-4-(methoxycarbonyl)-2,5-dimethylphenyl 2,4-dimethoxy-3,6-dimethylbenzoate (8) and 3-hydroxy-4-(methoxycarbonyl)-2,5-dimethylphenyl 2-hydroxy-4-methoxy-3,6-dimethylbenzoate (9), were found by virtual screening using pharmacophore and 2D-QSAR model. Compound 8 exhibited AcrB inhibition activity in vitro with an accumulation H33342 percentage compared with untreated control of 202% at a concentration of 50 µM and increased the antibacterial activity of levofloxacin by four-fold at a concentration of 200 µM. By molecular docking and molecular dynamics (MD) simulation, the binding affinity of depside and depsidone derivatives to AcrB was also clarified. Despite the poor docking score to the AcrB binding site, compound 8 was the most stable among the four complexes at 20 ns of MD simulation. The analysis of long MD at 100 ns indicated that compound 8 interacts strongly with the residues in the distal pocket, creating a stable complex with ΔGbind of -31.51 kcal.mol-1. According to the ADMETlab 2.0 web server's predictions of pharmacokinetics and toxicities, compound 8 has the potential for drug development.Communicated by Ramaswamy H. Sarma.
ABSTRACT
Two new lignans, pseuderesinol (1), pseuderanoside (2) and a new triterpene, pseuderanic acid (3) were isolated from the dried root of Pseuderanthemum carruthersii (SEEM.) GUILL. var. atropurpureum (BULL.) FOSB. (Acanthaceae), together with ten known compounds, including five lignans, (+)-eudesmin (4), (+)-magnolin (5), (+)-syringaresinol (6), (+)-episyringaresinol (7), (+)-1-hydroxysyringaresinol (8) and five triterpenes, squalene (9), oleanolic acid (10), lupeol (11), betulin (12), betulinic acid (13). Their chemical structures were elucidated by 1D- and 2D-NMR, computational quantum chemistry, as well as high resolution-electrospray ionization (HR-ESI)-MS spectroscopic analysis. The acetylcholinesterase inhibition and cytotoxic activities against HeLa and MCF-7 cancer cell lines were evaluated on some purified compounds at the concentration of 100 µg/mL. Pseuderesinol (1) and magnolin (5) exhibited moderate cytotoxic activities against the MCF-7 cancer cell line.
