Antimicrobial activities of bamboo (Phyllostachys heterocycla cv. Pubescens) leaf essential oil and its major components

This research aimed to investigate the seasonal variations and antibacterial activities of essential oils (EOs) and their major components from bamboo leaves. The Phyllostachys heterocycla cv. Pubescens leaves have undergone steam distillation to prepare EOs; leaves collected in autumn had the highest amount of EOs (0.33%). Chemical characterization by gas chromatography/mass spectrometry (GC/MS) allowed the identification of 36 compounds. The major compounds (%) were ketones (52.25), alcohols (17.79), carboxylic acids (9.41) and alkane hydrocarbons (7.68), which included 6, 5, 7 and 9 distinct compounds, respectively. Antibacterial activities were registered against Gram-negative bacteria [Escherichia coli (minimum inhibitory concentration [MIC] = 2.25 mg/mL)], Gram-positive bacteria [Bacillus subtilis (MIC = 2.25 mg/mL)] and Saccharomyces cerevisiae. The antibacterial effect of the three major monomeric compounds (tricosane, cedrol and hexadecanoic acid) in bamboo leaf EOs and their mixtures was studied. We showed for the first time that tricosane had antimicrobial activity. We found that cedrol had the strongest antibacterial effect, followed by hexadecanoic acid. Cedrol at 5 mg/mL had the largest inhibition zones of up to 14.93 mm against Flavobacterium SHL45. The antimicrobial effect of the equal mixture ratio of the three monomers was higher than that when tricosane and hexadecanoic acid were tested alone, and was also higher than that of the combination of any two of them.