DOI: https://doi.org/10.55373/mjchem.v26i1.50

Keywords: Traditional use; alkaloid; flavonoid; chemometric; Erythrina

Abstract

Erythrina fusca Lour., (Fabaceae) is a flowering plant locally known as "Chengkering", and has been traditionally used to treat certain symptoms associated with bacterial infections. However, limited study is available to support this traditional use, particularly the activity of the flower part against bacterial strains that commonly cause infection on human skin. The present work reports on the in vitro antibacterial activity of E. fusca flower’s extracts [hexane, dichloromethane (DCM), and methanol (MeOH)] against skin infectious bacterial strains namely Staphylococcus aureus, Staphylococcus haemolyticus, Enterobacter cloacae, and Enterobacter aerogenes evaluated through well diffusion method. The variation of the phytochemicals in the extracts and their correlation with the antibacterial activity were determined through proton nuclear magnetic resonance (1H-NMR)-based chemometric analysis. The hexane extract was active against S. aureus and S. haemolyticus strains with 14.00 ± 0.00 and 9.67 ± 0.33 mm zone of inhibition (ZOI), respectively. MeOH extract showed activity against E. cloacae (8.33 ± 0.33 mm) and E. aerogenes (8.17 ± 0.17 mm) strains. While DCM extract was only active against S. aureus (9.67 ± 0.33 mm). The NMR analysis on the extracts lead to the identification of 75 phytochemicals mainly from the alkaloids, flavonoids, pterocarpans, terpenes, saponins, sterols, and phenols classes of compounds. The chemometric analysis revealed the activity against S. haemolyticus was correlated with the flavonoid 5,3′-dihydroxy-4′-methoxy-5′-(3-methyl-1,3-butadienyl)-2′′,2′′-dimethylpyrano-[5,6:6,7]-isoflavanone (47), and the pterocarpans sandwicensin (58) and neorautenol (52). While the activity on E. cloacae, and E. aerogenes was collectively contributed by the alkaloids erysotrine N-oxide (11), 10-hydroxy-11-oxoerysotrine (18), and magnoflorine (33). This suggests that the therapeutic value reported for the plant could be synergically contributed by the above-mentioned phytochemicals. The finding provides evidence to support the plant's traditional use and could be the source of antibacterial agents for further studies.