Endostemon tereticaulis (poir.) M.Ashby is a species of the Lamiaceae family present in Niger. This plant is used in traditional medicine due to its various biological potentialities. The present study investigated the chemical composition of the essential oil and the antibacterial activity of the essential oil and ethanolic extract of Endostemon tereticaulis against resistant pathogenic bacteria. Gas chromatography-mass spectrometry analysis of the essential oil led to the identification of 43 compounds representing 99.55% of the total essential oil. The major components were caryophyllene oxide (15.17%) followed by α-humulene (13.96%), α-copaene (11.75%), ( E)-β-caryophyllene (8.44%), and δ-cadinene (6.78%). The antibacterial activity was tested against multiresistant Acinetobacter baumannii P1483, Salmonella spp. H1548, extended-spectrum β-lactamase- Escherichia coli Bu8566, Enterobacter cloacae Bu147, Proteus mirabilis Bu190 , Pseudomonas aeruginosa (ATCC 27853), Klebsiella pneumoniae (ATCC 700603), Escherichia coli (ATCC 25922), Enterococcus faecium H3434, methicillin-resistant Staphylococcus aureus P1123, and Staphylococcus aureus (ATCC 25923). The antibacterial assays revealed that the essential oil was more active than the ethanolic extract against the studied bacteria with minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) values ranging from 0.06 to 2 mg/mL. Also, the ethanolic extract was effective against the bacteria tested with MIC and MBC values ranging from 0.12 to 3 mg/mL. This study showed that Endostemon tereticaulis essential oil is rich in bioactive compounds. Ethanolic extract and essential oil exhibited potential antibacterial activity. These results provide a scientific basis for the use of this plant in traditional medicine. The current study described for the first time the antibacterial activity of Endostemon tereticaulis.

In the present study, the chemical composition, antioxidant and antibacterial activities of the essential oil obtained by hydrodistillation of the aerial parts of Englerastrum gracillimum Th. C. E. Fries growing in Niger were investigated. Gas chromatography-mass spectrometry (GC–MS) analysis of the essential oil resulted in the identification of 42 compounds representing 97.9% of the total oil constituents. The major compounds of the essential oil were: α-humulene (30.5%), followed by cubenol (19.8%), γ-muurolene (14.0%), ( E)-β-caryophyllene (5.8%), β-gurjunene (5.2%), and curzerene (4.9%). The antioxidant activity of the essential oil was determined by using the free radical-scavenging activity (2,2 diphenyl-1-picrylhydrazyl: DPPH˙) and ferric reducing antioxidant power assays. The essential oil showed good antioxidant potential with both methods. The antibacterial activity was evaluated against multi-resistant Acinetobacter baumannii P1483, extended-spectrum β-lactamase (ESBL) -Escherichia coli Bu8566, Salmonella spp. H1548, Proteus mirabilis Bu190 , Enterobacter cloacae Bu147, Pseudomonas aeruginosa (ATCC 27853), Escherichia coli (ATCC 25922), Klebsiella pneumoniae (ATCC 700603), methicillin-resistant Staphylococcus aureus P1123, Enterococcus faecium H3434, and Staphylococcus aureus (ATCC 25923) using the agar disc diffusion and microdilution methods. The essential oil exhibited good antibacterial activity. The highest antibacterial effect was observed against Staphylococcus aureus ATCC 25923 and methicillin-resistant Staphylococcus aureus P1123 with minimal inhibitory concentration (MIC) values of 0.03 mg/mL and 0.06 mg/mL, respectively. These data are of scientific importance for the valorization of aromatic and medicinal plants of Niger, especially E. gracillimum. This study reports for the first time the antioxidant and antibacterial activities of this essential oil.

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