Phytochemical annotation, identification, and isolation of eleusine indica (l.) gaertn., and its antiproliferative and antibacterial activities / Nur Syahirah Mad Sukor

Eleusine indica, locally known as ‘rumput sambau’ is traditionally used to treat various ailments including sprained muscle, asthma, influenza, and pneumonia. Pharmacological investigations revealed that this plant possesses diverse arrays of activities such as antibacterial, cytotoxic, antiinflammatory, antiplasmodial, and hepatoprotective. Despite many reports on its traditional uses and wide array of biological activities, limited chemical databases are available for this plant. Thus, the aims of this study were to identify and isolate phytochemicals from E. indica through conventional (hexane extract), and advanced (methanolic extract) tandem LCMS-based annotation techniques, and to evaluate its antiproliferative and antibacterial activities. The phytochemicals were annotated through tandem LCMS-based analysis using MZmine, GNPS, Compound Discoverer and SIRIUS platforms. Isolation and structural elucidation of phytochemicals were carried out using various chromatographic and spectroscopic techniques, respectively. The antiproliferative activity was evaluated using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay against human liver cancer (HepG2) and African green monkey kidney epithelial normal (Vero) cell lines, while the antibacterial activity was assessed using disc and agar well diffusion methods against eight bacterial strains namely Yernisia Enterocolitica, Enterobacter cloacae, Shigella sonnei, Salmonella enterica, Staphylococcus cohnii, Staphylococcus haemolyticus, Enterobacter Aerogenes and Serratia marcescens with ciprofloxacin as the positive control. A total of 65 phytochemicals were annotated and identified, while 42 were characterized in methanolic extract. A phytochemical annotated as loliolide (Me-1) was subjected to further isolation, purification, and structural elucidation process to verify the reliability on the annotated phytochemicals. The structure of Me-1 was confirmed to be loliolide (10 mg), thus consequently increase the level of confidence in the other phytochemicals identification. This is the first report on the loliolide isolation from E. indica. Phytochemistry work on the hexane extract afforded two compounds elucidated as stigmasterol (8 mg) and β-sitosterol (7 mg). The hexane and methanolic extracts exhibit low activity against both cell lines with the IC50 value of 91.02 ± 5.74 and 85.30 ± 3.03 μg/mL, but more selective towards cancer cells compared to the normal cells with 10.99 and 7.50 SI values, respectively. The hexane extract showed diverse antibacterial activity, while the methanolic extract was more selective towards the bacteria Y. enterocolitica subsp. enterocolitica, E. aerogenes and S. sonnei with inhibition zone range of 8 – 12 mm.