Metabolic Profiling of Millingtonia hortensis L.f. Leaves Using UHPLCMS/MS and Evaluation of its Antioxidant, Cytotoxic, Anticholinesterase Activities and Molecular Docking

Abstract

Background: Millingtonia hortensis L.f. known as Tree Jasmine or Indian Cork tree, stands as the only species within the genus Millingtonia and it is originated from South-East Asia, it belongs to family Bignoniaceae. The genus name, Millingtonia, is in honor of Sir Thomas Millington, the English botanist, while hortensis means “grown in gardens”. The phytochemical screening of M. hortensis L.f. showed the presence of different chemical classes as carbohydrates, tannins, saponins, flavonoids, cyclohexylethanoid glycosides, and volatile oil. Different pharmacological actions were reported such as antiproliferative, antimutagenic, antibacterial, antifungal, and antioxidant activities. Aim: This study aims to investigate the phytochemical constituents of M. hortensis L.f. and evaluate its biological activities. Material and Methods: The total ethanolic extract M. hortensis L.f. was assessed by LC-MS/MS profiling followed by spectrophotometric determination of total phenolics and flavonoids. For biological evaluation, the antioxidant activity was assessed using (DPPH, ABTS, FRAP, and ORAC) assays. In-vitro cytotoxic study was performed using colorectal cancer (LS-513) and hepatocellular carcinoma (HepG2) cell lines and also anticholinesterase activity was determined. Furthermore, some of the identified compounds were analyzed by molecular docking studies to determine the binding affinity between the ligands and the enzyme (acetylcholinesterase). Results: The LC-MS/MS analysis of the total ethanolic extract resulted in identification of twenty eight compounds. The level of total phenolic contents was (34.137 ± 0.509 µg Gallic acid Eq/mg) in the total ethanolic extract while the level of total flavonoid content in total ethanolic extract was (10.256 ± 0.579 µg Rutin Eq/mg). The results of ABTs, ORAC and DPPH antioxidant assays demonstrated that dichloromethane fraction of M. hortensis L.f. leaves has the highest effect for free radical scavenging, while the n-hexane extract showed the highest effect for free radical scavenging in the FRAP assay, in-vitro cytotoxic activity showed that the total ethanolic extract has the least IC50 which indicates its highest activity compared to the other fractions, anticholinesterase activity obtained by Ellman’s method indicates that dichloromethane fraction showed a significant activity against AChE causing 80.6 ± 0.007 % inhibition while ethyl acetate fraction showed least activity against AChE causing 31.8 ± 0.02 % inhibition at 0.1 mg/mL concentration. The molecular docking study revealed that apigenin was found to be more potent than hispidulin due to the strong interactions with amino acid residue SerA:200, HisA:440 and those of the peripheral region are crucial for strong inhibitory activities against AChE. Conclusions: The results of this study revealed that the plant’s identified phenolics and flavonoids, as detected in the LC-MS/MS analysis, may be correlated with the plant’s notable antioxidant, cytotoxic, and anticholinesterase activities.