Antibiofilm and Enzyme Inhibitory Potentials of Two Annonaceous Food Spices, African Pepper (Xylopia aethiopica) and African Nutmeg (Monodora myristica)

Abstract

Food pathogens represent an important health threat, and it is relevant to study the effect of foodstuffs such as spices which can inhibit bacterial growth. This study reports the antimicrobial, antibiofilm, and enzyme (Acetylcholinesterase, Butyrylcholinesterase, urease, tyrosinase) inhibitory activities of two medicinal food spices belonging to the Annonaceae family, <i>Monodora myristica</i> and <i>Xylopia aethiopica</i>. GC-MS (gas chromatography mass spectrometry) analysis of silylated samples of Methanol-Dicloromethane (50:50) extracts of both plants led to the identification of nine compounds in <i>M. myristica</i> and seven compounds in <i>X. aethiopica</i>. <i>M. myristica</i> and <i>X. aethiopica</i> had the same minimum inhibitory concentration (MIC) values of 0.625 mg/mL and 2.5 mg/mL on <i>C. albicans</i> and <i>E. coli</i>, respectively. However, <i>M. myristica</i> had better activity than <i>X. aethiopica</i> on <i>Staphylococcus aureus</i>, while <i>Pseudomonas aeruginosa</i> was more susceptible to <i>X. aethiopica</i> than <i>M. myristica</i>. The lowest MIC value was 0.1325 mg/mL, exhibited by <i>M. myristica</i> on <i>S. aureus</i>. Both extracts showed good antibiofilm activity. On <i>S. aureus</i>, at the same concentration, <i>M. myristica</i> had better antibiofilm activity than <i>X. aethiopica</i>. On <i>E. coli</i> and <i>Candida albicans</i>, <i>X. aethiopica</i> had better antibiofilm activity than <i>M. myristica</i> at the same concentration. <i>X. aethiopica</i> showed better violacein inhibition in <i>Chromobacterium violaceum</i> CV12472, as its percentage inhibition of violacein varied from 80.5% ± 3.0% at MIC to 5.6 ± 0.2 at MIC/8, as compared to <i>M. myristica</i> with 75.1% ± 2.5% at MIC and 15.5% ± 1.1% at MIC/8. The anti-motility activity by swimming and swarming inhibition on <i>P. aeruginosa</i> PA01 was low at test concentrations and in both models, <i>M. myristica</i> showed higher motility inhibition than <i>X. aethiopica</i>. Although in enzyme inhibitory assays all extracts had low inhibitions compared to standards tested at the same concentrations, the results show that these plants can be used to manage food-borne infections.