cedrene and humulene

The formation of highly oxidized multifunctional organic compounds (HOMs) from the ozonolysis of three sesquiterpenes, α-cedrene, β-caryophyllene, and α-humulene, was investigated for the first time. Sesquiterpenes contribute 2.4% to the global carbon emission of biogenic volatile organic compounds (BVOCs) and can be responsible for up to 70% of the regional BVOC emissions. HOMs were detected with chemical ionization-atmospheric pressure interface-time-of-flight mass spectrometry and nitrate and acetate ionization. Acetate ions were more sensitive toward highly oxidized RO2 radicals containing a single hydroperoxide moiety. Under the chosen reaction conditions, product formation was dominated by highly oxidized RO2 radicals which react with NO, NO2, HO2, and other RO2 radicals under atmospheric conditions. The ozonolysis of sesquiterpenes resulted in molar HOM yields of 0.6% for α-cedrene (acetate), 1.8% for β-caryophyllene (acetate), and 1.4% for α-humulene (nitrate) afflicted with an uncertainty factor of 2. Molar yields of highly oxidized RO2 radicals were identical with HOM yields measuring the corresponding closed-shell products. HOM formation from ozonolysis of α-cedrene was explained by an autoxidation mechanism initiated by ozone attack at the double bond similar to that found in the ozonolysis of cyclohexene and limonene.

Topics: Acetates; Atmosphere; Free Radicals; Ions; Mass Spectrometry; Monocyclic Sesquiterpenes; Nitrates; Oxidation-Reduction; Oxygen; Ozone; Polycyclic Sesquiterpenes; Sesquiterpenes; Volatile Organic Compounds

The composition of essential oil isolated from Senecio nudicaulis Wall. ex DC. growing wild in Himachal Pradesh, India, was analysed, for the first time, by capillary gas chromatography (GC) and GC-mass spectrometry. A total of 30 components representing 95.3% of the total oil were identified. The essential oil was characterised by a high content of oxygenated sesquiterpenes (54.97%) with caryophyllene oxide (24.99%) as the major component. Other significant constituents were humulene epoxide-II (21.25%), α-humulene (18.75%), β-caryophyllene (9.67%), epi-α-cadinol (2.90%), epi-α-muurolol (2.03%), β-cedrene (1.76%), longiborneol (1.76%), 1-tridecene (1.16%) and citronellol (1.13%). The oil was screened for antioxidant activity using DPPH, ABTS and nitric oxide-scavenging assay. The oil was found to exhibit significant antioxidant activity by scavenging DPPH, ABTS and nitric oxide radicals with IC50 values of 10.61 ± 0.14 μg mL(- 1), 11.85 ± 0.28 μg mL(- 1) and 11.29 ± 0.42 μg mL(- 1), respectively.

Topics: Acyclic Monoterpenes; Alkenes; Antioxidants; Gas Chromatography-Mass Spectrometry; India; Monocyclic Sesquiterpenes; Monoterpenes; Oils, Volatile; Plant Oils; Plants, Medicinal; Polycyclic Sesquiterpenes; Senecio; Sesquiterpenes; Terpenes