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Essential oils were extracted from white and black peppers ( Piper nigrum L.) by green and solvent-free ultrasonic-microwave assisted extraction (UMAE), microwave assisted extraction (MAE) and ultrasonic assisted extraction (UAE), and the efficiency and free radical scavenging activities of the essential oils by different extraction methods were compared in order to illuminate their advantages and disadvantages. The oil yield and superoxide radical scavenging activity of white pepper by UMAE were both significantly higher than those oil extracted by MAE and UAE, implying that UMAE was far more efficient extracting method than MAE and UAE. The same trends were also found for black pepper. Meanwhile, the bioactive compounds of the essential oils from white and black peppers were also characterized and compared by GC coupled with mass spectrometry (GC–MS) and electronic nose based on fast gas chromatography (GC). The essential oil from black pepper contained more monoterpenes than the oil from white pepper, while white pepper oil showed higher content of sesquiterpenes than black pepper. For the different extraction methods, generally, UMAE could obtain more monoterpenes and sesquiterpenes than MAE and UAE. UMAE should be an emerging effective green extraction technique for essential oil from P. nigrum because of the maximum extraction yields, shortest extraction time and solvent-free. The electronic nose has been proven as a useful tool for quick analysis and discrimination of the essential oils by different extraction methods. [ABSTRACT FROM AUTHOR]

• A method for quickly evaluating antioxidant activity was established. • Evaluation process without complex and time-consuming purification. • Antioxidant and radical scavenging mechanisms were explained. • Spikenard essential oil was analyzed and the accuracy was improved. As a new rapid detection technology, ultra-fast gas chromatography electronic nose (E-nose) can accurately distinguish and identify different odor ingredients based on the retention index and data processing system in a short time. The chemical components of spikenard (Nardostachys chinensis) essential oil (SEO) were detected by E-nose and verified by GC–MS with 94 % accuracy. Combining E-nose with traditional chemical methodology including E-nose-DPPH, E-nose-ABTS and E-nose−OH were used to quickly evaluate the antioxidant activity of each component of SEO. The results showed that the main components of SEO were calarene, β-maaliene, valerena-4,7(11)-diene, aristolene, γ-terpinene, and seychellene. Furthermore, SEO showed the best scavenging ability in ABTS than DPPH or OH radicals, and the highest scavenging rates are 95.0 % for ABTS, 72.4 % for DPPH and 73.0 % for OH radical, respectively. Among all ingredients of SEO, β-maaliene (70.6 %, 52.3 %, 26.4 %), calarene (69.5 %, 41.6 %, 22.5 %), valerena-4,7(11)-diene (78.1 %, 46.2 %, 6.4 %) and β-cadinene (78.8 %, 51.4 %, 7.1 %) have scavenging effects for ABTS, DPPH and OH radicals. [ABSTRACT FROM AUTHOR]

• Electronic nose coupled with chemical methodology was very simple and effective. • Screening process does not involve complex and time-consuming purification. • A method for quickly screening radical scavenging activity was established. • Essential oil from Magnolia biondii was analyzed and the accuracy was improved. An electronic nose (E-nose) coupled with chemical methodology was established, which can quickly screen and evaluate the radical scavenging activity of each component in the essential oil from Magnolia biondii Pamp (EOMB) without time-consuming and laborious separation of pure compounds. The method was established based on the differences of peak areas of the antioxidant components in EOMB before and after reaction with free radicals. Qualitative and quantitative analyses of EOMB were performed by gas chromatography coupled with mass spectrometry (GC–MS/MS). The radical scavenging activities were evaluated by E-nose coupled with chemical methodology. The results showed that the major components of EOMB were β-pinene (854.2 μg/g), sabinene (753.0 μg/g), α-pinene (437.2 μg/g), farnesol (272.2 μg/g), α-myrcene (190.7 μg/g), epi -cubebol (188.2 μg/g) and eucalyptol (147.1 μg/g). Among all chemical components in EOMB, α-terpineol, ç-cadinene and α-phellandrene showed the strongest scavenging ability in 1,1′-diphenyl-2- picrylhydrazine (DPPH), 2,2′-azino-bis(3-ethyl-benzothiazoline-6-sulphonate) (ABTS) and hydroxyl (OH) radicals, respectively, with scavenging rates of 84.1 %, 89.1 % and 54.1 %. [ABSTRACT FROM AUTHOR]