Green-Leaf-Derived C6-Aroma Compounds with Potent Antibacterial Action That Act on Both Gram-Negative and Gram-Positive Bacteria

Abstract

All eight C6-aliphatic alcohol and aldehyde compounds in naturally occurring green leaves showed bacteriostatic effects against Staphylococcus aureus IFO 12732, methicillin-resistant S. aureus, Escherichia coli IFO 3301, E. coli O157:H7, and Salmonella enteritidis, with bacteriostatic activities of less than 12.5 microg mL(-1). In this study, the susceptibility of Gram-positive bacteria tested was observed to be greater than that of Gram-negative bacteria. The bactericidal action of the aldehyde compounds was found to be much stronger than that of the alcohol compounds under both liquid and gaseous conditions. The most effective compound was (3E)-hexenal at concentrations of 0.1 and 1 microg mL(-1), which killed 2.1 x 10(5) cfu mL(-1) of S. aureus IFO 12732 and 1.4 x 10(5) cfu mL(-1) of E. coli IFO 3301, respectively, by direct contact with the compound. Lethality of (3E)-hexenal against S. aureus IFO 12732 and E. coli IFO 3301 was also observed as a result of gaseous contact at concentrations of 3 and 30 microg mL(-1), respectively. The bactericidal effects of 30 microg mL(-1) (3E)-hexenal were thoroughly maintained throughout periods of 2 days and 1 day against S. aureus IFO 12732 and E. coli IFO 3301, respectively, by a complex formation with alpha-cyclodextrin.

Airborne Induction and Priming of Plant Defenses against a Bacterial Pathogen

“…All three compounds have repeatedly been reported in the context of plant pathogenesis: nonanal and 2-ethyl hexanol were found in the headspace of potato (Solanum tuberosum) tubers infected with different fungi (de Lacy Costello et al, 2001) and of various biological control bacteria (Dilantha Fernando et al, 2005), nonanal was released from whiteflyinfected beans (Phaseolus vulgaris; Birkett et al, 2003), and both nonanal and 2-ethyl hexanol were reported to have in vitro antifungal (Dilantha Fernando et al, 2005) and bactericidal (Nakamura and Hatanaka, 2002) activities.…”

“…However, although 2-ethyl hexanol has repeatedly been reported in the context of pathogenesis (de Lacy Costello et al, 2001;Nakamura and Hatanaka, 2002;Dilantha Fernando et al, 2005), the compound is also a very common contaminant. In fact, no convincing study has ever reported a clear case of plant-derived 2-ethyl hexanol (W. Boland, personal communication).…”

The Arabidopsis her1 mutant implicates GABA in E‐2‐hexenal responsiveness

“…In addition, C6-aldehydes and alcohols possess fungicidal and bactericidal activity (Hamilton-Kemp et al, 1992;Nakamura and Hatanaka, 2002;Prost et al, 2005). These data, in combination with the observation that C6-volatiles can be released after infection with pathogenic fungi and bacteria (Croft et al, 1993;Shiojiri et al, 2006a), suggest that a possible physiological role of these volatiles is to limit pathogen growth.…”

Changes in Volatile Profiles and Activity of Hydroperoxide Lyase and Alcohol Dehydrogenase During the Development of Cabernet Sauvignon Grapes (Vitis vinifera L.)

“…GLVs are not only the main source of volatiles in fruit and vegetables -they also have important physiological functions. They are critical signals that help plants recognise and compete with other organisms (Matsui et al, 2006) and also impart resistance to pathogenic bacteria and insects (Nakamura & Hatanaka, 2002;Tufariello et al, 2012). Furthermore, GLVs are similar to the aroma from spices in the food and beverage industry (Kalua & Boss, 2009).…”