Natural products such as essential oils (EOs) are secondary metabolites that can be obtained from either plant or animal sources or produced by microorganisms. Much attention has been given to exploring the use of secondary metabolites as natural antibacterial agents. This study investigates the antibacterial activity and mechanism of β-caryophyllene, a compound that can be found in various EOs, against Bacillus cereus. The minimum inhibitory concentration of β-caryophyllene against B. cereus was 2.5% (v/v), whereas killing kinetics of β-caryophyllene at minimum inhibitory concentration recorded complete bactericidal activity within 2 hours. Zeta-potential measurement in the cells treated with half the minimum inhibitory concentration of β-caryophyllene at 1.25% (v/v) showed an increase in the membrane permeability surface charge to –3.98 mV, compared to untreated cells (–5.46 mV). Intracellular contents leakage of UV-absorbing materials was detected in the cells treated with β-caryophyllene. Additionally, β-caryophyllene does not interfere with the efflux activity of B. cereus via the ethidium bromide influx/efflux activity. The results revealed that β-caryophyllene was able to alter membrane permeability and integrity of B. cereus, leading to membrane damage and intracellular content leakage, which eventually caused cell death.
DESIGN: Single-blind, controlled, randomized cross-over study. Patients received 5-day aromatherapy treatment using either ginger essential oil or fragrance-matched artificial placebo (ginger fragrance oil) which was instilled in a necklace in an order dictated by the treatment group sequence.
SETTING: Two oncology clinics in the East Coast of Peninsular Malaysia.
MAIN OUTCOME MEASURES: VAS nausea score, frequency of vomiting and HRQoL profile (EORTC QLQ-C30 scores).
RESULTS: Sixty female patients completed the study (age=47.3±9.26 years; Malay=98.3%; on highly emetogenic chemotherapy=86.7%). The VAS nausea score was significantly lower after ginger essential oil inhalation compared to placebo during acute phase (P=0.040) but not sustained for overall treatment effect (treatment effect: F=1.82, P=0.183; time effect: F=43.98, P<0.001; treatment×time effect: F=2.04; P=0.102). Similarly, there was no significant effect of aromatherapy on vomiting [F(1, 58)=0.29, P=0.594]. However, a statistically significant change from baseline for global health status (P<0.001) was detected after ginger essential oil inhalation. A clinically relevant 10 points improvement on role functioning (P=0.002) and appetite loss (P<0.001) were also documented while patients were on ginger essential oil.
CONCLUSION: At present time, the evidence derived from this study is not sufficiently convincing that inhaled ginger aromatherapy is an effective complementary therapy for CINV. The findings for HRQoL were however encouraging with significant improvement in several domains.