The compositions of Vietnamese pummelo (Citrus grandis Osbeck), orange (C. sinensis Osbeck), tangerine (C. reticulata Blanco var. tangerine) and lime (C. limonia Osbeck) peel oil samples have been investigated by GC and GC-MS. The essential oils were extracted by the cold-pressing method. Hydrocarbons, followed by aldehydes and alcohols, were the most abundant compounds in all four kinds of samples. Their percentages, respectively, were >98.7%, >97.6%, >98.6% and >95.4% in hydrocarbons; >0.3%, 0.4%, >0.3% and 1.1% in total aldehydes; 0.2%, 0.5%, 0.4% and 0.7% in alcohols. In Vietnamese pummelo oil, -terpinene was not detected, while terpinolene was detected in small amounts and nootkatone only at a level of <0.05%. Orange oil composition was comparable to that of other sweet orange oils. υ-3-Carene was detected at a level of 0.1%. Tangerine oil is easily distinguished from other citrus oils by its content of various aliphatic aldehydes. Lime oil presented a very different composition from the other oils studied. Its limonene content was substantially lower than that of pummelo, orange and tangerine oils, whereas -terpinene,ˇ-pinene and˛-pinene occurred in higher proportions, moreover, the sesquiterpene hydrocarbon fraction of this oil is qualitatively more complex and quantitatively more abundant than in the other oils.

Antimicrobial activities of aminoreductone (AR), a product formed in the initial stages of the Maillard reaction, were investigated using eight clinical isolates of antibiotic-susceptible/resistant pathogenic bacteria: four Pseudomonas aeruginosa, one multi-drug-resistant Pseudomonas aeruginosa (MDRP), one Escherichia coli, one methicillin-susceptible Staphylococcus aureus, and one methicillin-resistant Staphylococcus aureus (MRSA). AR showed advanced growth inhibition effects compared to antibiotics (amikacin, ciprofloxacin, imipenem and levofloxacin) frequently used for the treatment of infectious diseases, and worked synergistically with these antibiotics. The minimum inhibitory concentrations (MIC) of AR ranged from 13 to 20 mM. The bactericidal activity of AR was dose and time dependent. The minimum bactericidal concentration (MBC) was lower for Gram-negative bacteria (32 to 40 mM). These findings suggest that AR, a naturally formed antimicrobial agent present in thermally processed foods, has promising potential for health promotion and for use in medical practices.

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