Bioguided identification of antimicrobial compounds from Chrysopogon zizaniodes (L.) Roberty root essential oil

Aim: To determine the group of compounds from Chrysopogon zizaniodes root essential oil that have antimicrobial activity. Materials & methods: Thin-layer chromatography coupled to direct bioautography was used to determinate the fraction(s) having antimicrobial activity against methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Enterococcus faecalis (VREF). Through GC-MS identification, the fractions with the greatest similarity to the active thin-layer chromatography fraction were used to determinate the MIC. Results: The subfraction 8 from column chromatography was responsible for the best MIC for MRSA (62.5 μg/ml) and VREF (125 μg/ml). Five compounds possibly responsible for antimicrobial activity were preliminary identified. Conclusion: We suggest that Cedr-8-en-13-ol, could be the more relevant compound involved in the antimicrobial activity in this study.

Discovery of Antibacterial Dietary Spices That Target Antibiotic-Resistant Bacteria

Although spice extracts are well known to exhibit antibacterial properties, there is lack of a comprehensive evaluation of the antibacterial effect of spices against antibiotic-resistant bacteria. In the present study, ethanolic extracts from a total of 67 spices were comprehensively investigated for their in vitro antibacterial activities by agar well diffusion against two common food-borne bacteria, Staphylococcus aureus and Salmonella enteritidis, with multi-drug resistance. Results showed that S. aureus was generally more sensitive to spice extracts than S. enteritidis. Of the 67 spice extracts, 38 exhibited antibacterial activity against drug-resistant S. aureus, while only four samples were effective on drug-resistant S. enteritidis. In addition, 11 spice extracts with inhibition zones greater than 15 mm were further verified for their broad-spectrum antibacterial properties using another 10 drug-resistant S. aureus strains. It was found that five spice extracts, including galangal, fructus galangae, cinnamon, yellow mustard seed, and rosemary, exhibited the highest antibacterial capacity. Further cytotoxicity of these 11 spices was determined and LC₅₀ values were found to be more than 100 μg/mL except for galangal, rosemary, and sage, whose LC₅₀ values were 9.32 ± 0.83, 19.77 ± 2.17, and 50.54 ± 2.57, respectively. Moreover, the antioxidant activities (ferric-reducing antioxidant power (FRAP) and trolox equivalent antioxidant capacity (TEAC) values) and total phenolic content (TPC) of spice extracts were determined to establish possible correlations with the antibacterial activity. Although the antibacterial effect was positively correlated with the antioxidant activities and TPC, the correlation was weak (r < 0.5), indicating that the antibacterial activity could also be attributed to other components besides antioxidant polyphenols in the tested spice extracts. In conclusion, dietary spices are good natural sources of antibacterial agents to fight against antibiotic-resistant bacteria, with potential applications as natural food preservatives and natural alternatives to antibiotics in animal feeding.