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A sensitive and selective method of ultra‐fast GC electronic nose (E‐nose) coupled with chemical methodology was developed for both identifying the chemical constituents of essential oil from star anise (EOSA) and the screening of the radical scavenging activity of each compound in EOSA quickly without the isolation of monomers by comparing the change of the chromatographic peak area of every component in EOSA before and after the reaction with the free radicals. The results showed the main components of EOSA were anethole (36.42%), limonene (20.77%), α‐terpinene (6.51%), and α‐phellandrene(5.61%). Among all chemical components, p‐menthatriene showed the strongest scavenging ability both in 1,1'‐diphenyl‐2‐picrylhydrazine (DPPH) and hydroxyl (OH) radicals, and p‐cymenene showed the strongest scavenging ability in 2,2'‐azino‐bis(3‐ethyl‐benzothiazoline‐6‐sulphonate) (ABTS) radical, with scavenging rates of 93.00 ± 0.56%, 79.50 ± 0.78%, and 70.80 ± 0.32%, respectively. The reliability and feasibility of using E‐nose to identify chemical constituents of EOSA were verified by gas chromatography‐tandem mass spectrometry(GC‐MS/MS). Practical applications: The essential oils are the complex mixtures and important constituents in natural edible spices. How to evaluate and screen the radical scavenging activity of each component in the mixtures is a very challenging project. The traditional chemical methods are mainly used to evaluate total radical scavenging activity and antioxidant activity of essential oils. The compounds in the mixture need to be separated into individuals in advance if we want to know the bioactivity of each component and their radical scavenging activity in the past. The paper has developed a simple and convenient ultra‐fast GC E‐nose method. This method can not only quickly identify the chemical components of essential oil from star anise, but also quickly evaluate the radical scavenging activity of each compound in the essential oil from star anise. The proposed method can be applied to almost any other essential oils and volatile mixtures. [ABSTRACT FROM AUTHOR]

The chemical components of an edible spice, sweet ginger (Alpinia coriandriodora D. Fang) essential oil (AEO) were identified by an ultra‐fast gas chromatography electronic nose (E‐nose) and the main components were β‐pinene (27.9%), 1,8‐cineole (17.3%), p‐cymene (13.5%), camphene (7.3%), myrcene (5.4%), and pseudolimonene (4.3%). The antioxidant activity of each component was evaluated and the mechanisms of scavenging free radical were studied by E‐nose combined with chemical methodology. Decanal and α‐copaene in AEO showed strong scavenging activities against DPPH radical, and the scavenging rates were over 85%. Decanal had a strong scavenging activity for ABTS radical and the scavenging rate was more than 60%. Similarly, terpinen‐4‐ol and eugenol had strong scavenging abilities to OH radical and the scavenging rates were more than 50%. Gas chromatography‐mass spectrography results showed that it was feasible to identify the chemical components of essential oil by E‐nose, and the similarity reached 88.9%. Practical applications: Many essential oils have antioxidant activities and can be used in functional foods. In the present work, the antioxidant active components in AEO were identified and screened by ultra‐fast GC E‐nose. We aimed to target the components with strong antioxidant activity quickly and efficiently through the analysis of the reaction process of DPPH, ABTS and OH radicals with a high scavenging rate in a short time. These results indicate that ultra‐fast GC E‐nose can be used to screen the antioxidant active components in the essential oil. [ABSTRACT FROM AUTHOR]

BACKGROUND Traditional chemical methods were mainly used to evaluate the total antioxidant activity of essential oils. How to determine the bioactivity of each compound in mixtures is an interesting research topic. Nowadays, an ultra‐fast gas chromatography electronic nose (E‐nose) has been gradually used in the detection of volatile compounds, but the screening of the active components of essential oils has not been reported. E‐nose coupled with chemical methodology was established using the essential oil from rosemary (EOR) as a specific application example. The proposed method can both identify the chemical constituents of EOR and quickly screen the antioxidant by comparing the change of chromatographic peak area of every component in EOR before and after reaction with free radicals. RESULTS: Among all chemical constituents in EOR, verbenone, eucalyptol and o‐cymene showed the strongest scavenging abilities 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 67.9%, 39.5%, and 69.9%. The reliability and feasibility of using E‐nose to identify chemical constituents of EOR were verified by gas chromatography‐tandem mass spectrometry (GC–MS/MS). The GC–MS/MS results showed that the main components of EOR were α‐pinene (422.2 μg g−1), p‐cymene (208.4 μg g−1), camphor (203.5 μg g−1), verbenone (160.2 μg g−1), and eucalyptol (129.1 μg g−1). CONCLUSIONS: The E‐nose methods can be used as a complementary method to traditional spectrophotometric techniques. Furthermore, this study will be of great significance for the rapid screening of antioxidant active components in essential oils from natural products. © 2020 Society of Chemical Industry [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]