Investigation of Antimicrobial, Antioxidant, and Cytotoxic Activities of Boesenbergia rotunda rhizome extract

Abstract

In recent years, antimicrobial resistance (AMR) has become a global threat to public health. In Hawai’i, there is an increasing rate of staph infections of methicillin-resistant Staphylococcus aureus (MRSA), and, hence, a need for new agents to combat the increase of AMR bacteria. This study evaluates the antimicrobial, antioxidant, and cytotoxic activities of Hawaiian-grown Boesenbergia rotunda. Test bacteria included clinical isolates of Gram-positive MRSA and methicillin-susceptible S. aureus (MSSA) as well as Gram-negative Serratia marcescens and Escherichia coli. Five compounds–cardamonin, pinostrobin, pinocembrin, pinostrobin chalcone, and isopanduratin A–were isolated from the ethyl acetate extract of B. rotunda rhizome, and their structures were identified by NMR spectroscopy. These samples exhibited antimicrobial activity against MRSA and MSSA strains, with minimum inhibitory concentration (MIC) values between 128 and 2 µg/mL, with isopanduratin A giving MIC values as low as 2 µg/mL. The antioxidant potential of samples was examined using ferric-reducing antioxidant power (FRAP) assay. At 1 mg/mL of tested samples, FRAP values ranged between 8.74 to 17.76 µM/µg, with pinostrobin chalcone exhibiting the highest FRAP value (17.76 ± 0.65 μM/μg). Moreover, cytotoxicity was measured via sulforhodamine B (SRB) assay. Cardamonin (IC50 of 19.43 ± 0.33 μM) and isopanduratin A (IC50 of 26.84 ± 1.06 μM) exhibited effectiveness against the lung cancer cell line A549. Compounds from B. rotunda showed potent antimicrobial effect against MRSA and MSSA strains as well as antioxidant and cytotoxic activities, and may have the potential for further evaluation and development for pharmaceutical applications.