Star anise (Illicium verum Hook. f.) essential oil: Antioxidant properties and antibacterial activity against Acinetobacter baumannii

Abstract

The increased resistance of pathogenic bacteria to multiple antimicrobial agents is becoming a significant public health threat. For many pathogenic bacteria there are already limited or no effective antimicrobials available to treat the infections caused by them. Acinetobacter baumannii is a Gram‐negative, biofilm‐forming, nonmotile coccobacillus and a major human pathogen causing hospital‐acquired infections, such as ventilator‐associated pneumonia, bacteraemia, meningitis, and urinary tract and wound infections. There is therefore a clear need to discover new compounds and strategies to overcome widespread antimicrobial resistance, with a focus on A. baumannii strains. Star anise (Illicium verum Hook. f.) has been widely used as an ingredient in traditional Chinese cooking, as a flavouring agent, and as a medicine for over 3000 years; however, the essential oil (EO) isolated from star anise has not been further characterized in terms of its bioactivities and potential applications. In this work, a screening of the biological properties of star anise EO together with its chemical characterization were performed. Special attention was given to the impact of this EO in the formation of biofilms by A. baumannii. It was demonstrated that star anise EO is able to scavenge free radicals, to inhibit lipid peroxidation, and to inhibit protein denaturation, which is associated with its antioxidant and anti‐inflammatory properties. Moreover, the effects of the EO on the planktonic and biofilm cells of A. baumannii, inhibiting the formation of biofilms, dispersing preformed biofilms, and decreasing the capacity of the bacterial cells to adhere to polystyrene, together with its ability to inhibit quorum sensing, were also demonstrated.

Star anise (Illicium verum): Chemical compounds, antiviral properties, and clinical relevance

“…Among all of them, the anethole compounds are responsible for its characteristic taste. Besides, compounds like α-pinene, β-pinene, myrcene, α-phellandrene limonene, γ-terpineol, linalool, α-terpineol, estragole, trans-anethole, α-cubebene carryophyllene oxide, and α-humulene present in the essential oil of SA are also reported to have contained a number of biological activities (Aly, Sabry, Shaheen, & Hathout, 2016;Luís et al, 2019;Wang, Hu, Huang, & Qin, 2011). In addition, a number of procedures have been established for the extraction of the bioactive compounds from this plant species, and, among which, the hydro-distillation, steam distillation, solvent extraction, supercritical fluid CO 2 extraction, hydro-distillationheadspace solvent microextraction, and microwave-assisted extraction process are the most common ones (Rocha & Candido Tietbohl, 2016).…”

Evaluation of the In Vitro Wound-Healing Activity and Phytochemical Characterization of Propolis and Honey

“…The anti-inflammatory activity was determined by evaluating the capacity of the samples to inhibit protein denaturation [17]. Initially, a solution of bovine serum albumin (BSA) (Sigma-Aldrich, USA) at 1% (w/v) in phosphate buffer saline (PBS) solution was prepared.…”

“…Finally, measurements of the absorbances were performed using a spectrophotometer (Helios-Omega, Thermo Scientific, USA) at 620 nm. The percentage of inhibition of protein denaturation (%Inhibition) was determined applying the following equation, %Inhibition = 100 − [(Abs sample × 100)/Abs control ], where Abs control corresponds to the absorbance of the control and Abs sample is the absorbance of each sample [17]. The results were expressed as %Inhibition/100 g sample (honey, propolis, and mixtures of honey with propolis).…”

Julbernardia paniculata and Pterocarpus angolensis: From Ethnobotanical Surveys to Phytochemical Characterization and Bioactivities Evaluation

“…The anti-inflammatory activity was determined by evaluating the capacity of the selected samples to inhibit protein denaturation [45]. Initially, a solution of bovine serum albumin (BSA) at 1% (w/v) in phosphate buffer saline (PBS) was prepared.…”

“…Finally, measurements of the absorbances were performed using a microplate reader (BIO-RAD, Hercules, CA, USA) at 620 nm. The percentage of inhibition of protein denaturation was calculated using the following equation: %I = 100 − [(Abs sample × 100)/Abs control ), where Abs control is the absorbance of the control and Abs sample is the absorbance of each sample [45].…”