Antioxidative Activities of Volatile Extracts from Green Tea, Oolong Tea, and Black Tea

• Published in: Journal of agricultural and food chemistry Vol. 51; no. 25; pp. 7396 - 7401
• Main Authors: Yanagimoto, Kenichi, Ochi, Hirotomo, Lee, Kwang-Geun, Shibamoto, Takayuki
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 03.12.2003
• Subjects: Aldehydes - analysis; Aldehydes - chemistry; Antioxidants - analysis; Biological and medical sciences; Camellia sinensis - chemistry; Carboxylic Acids - analysis; Carboxylic Acids - chemistry; Coffee, tea and other stimulative beverage industries; Food industries; Fundamental and applied biological sciences. Psychology; General pharmacology; Hot Temperature; Linoleic Acids - chemistry; Medical sciences; Methylene Chloride; Oxidation-Reduction; Pharmacognosy. Homeopathy. Health food; Pharmacology. Drug treatments; Plant Extracts - chemistry; Plant Leaves - chemistry; Volatilization; Pharmacognosy; Stimulant plant; Identification; roasted green tea; oolong tea; Antioxidant; Black tea; Biological activity; Dose activity relation; Tissue extract; Torrefaction; Camellia sinensis; Health food; Dicotyledones; Angiospermae; Spermatophyta; Oxidation; Green tea; volatile antioxidants; Theaceae
• ISSN: 0021-8561; 1520-5118
• DOI: 10.1021/jf030127i

Antioxidative activities of volatile extracts from six teas (one green tea, one oolong tea, one roasted green tea, and three black teas) were investigated using an aldehyde/carboxylic acid assay and a conjugated diene assay. The samples were tested at levels of 20, 50, 100, and 200 μg/mL of dichloromethane. The results obtained from the two assays were consistent. All extracts except roasted green tea exhibited dose-dependent inhibitory activity in the aldehyde/carboxylic acid assay. A volatile extract from green tea exhibited the most potent activity in both assays among the six extracts. It inhibited hexanal oxidation by almost 100% over 40 days at the level of 200 μg/mL. The extract from oolong tea inhibited hexanal oxidation by 50% in 15 days. In the case of the extract from roasted green tea, the lowest antioxidative activity was obtained at the level of 200 μg/mL, suggesting that the extract from roasted green tea contained some pro-oxidants. The extracts from the three black teas showed slight anti- or proactivities in both assays. The major volatile constituents of green tea and roasted green tea extracts, which exhibited significant antioxidative activities, were analyzed using gas chromatography−mass spectrometry. The major volatile chemicals with possible antioxidative activity identified were alkyl compounds with double bond(s), such as 3,7-dimethyl-1,6-octadien-3-ol (8.04 mg/kg), in the extract from green tea and heterocyclic compounds, such as furfural (7.67 mg/kg), in the extract from roasted green tea. Benzyl alcohol, which was proved to be an antioxidant, was identified both in a green tea extract (4.67 mg/kg) and in a roasted tea extract (1.35 mg/kg). Keywords: Black tea; green tea; oolong tea; roasted green tea; volatile antioxidants