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BACKGROUNDTraditional 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.RESULTSAmong 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).CONCLUSIONSThe 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

Rosemary ethanol extract (REE) from Rosmarinus officinalis was identified by LC‐ESI‐MS/MS and 12 compounds were found. Among them, rosmarinic acid (389.78 μg/mg in REE), luteolin‐3ʹ‐O‐glucuronide (325.58 μg/mg), luteolin‐5‐O‐glucuronide (120.92 μg/mg), and geniposide (120.83 μg/mg) are the major components. The antioxidant activity evaluation of REE by off‐line HPLC methods indicated that among the 12 compounds, rosmarinic acid had the strongest scavenging activities in both DPPH· and ·OH. The cytotoxicity experiment showed that REE with the concentration ranges from 1 to 100 µg/ml did not significantly affect the cell viability of HeLa, while inhibitory rate reduced to 62.3% when the concentration was increased to 1,000 µg/ml. The results of intracellular antioxidation assay showed that the ability of REE in reducing the reactive oxygen species (ROS) in HeLa cells was higher than rosmanol, and lower than rosmarinic acid without cell toxicity. Practical applications Plant polyphenols are essential components of functional foods, due to their antioxidant and enzyme inhibition activities. This paper is the first study about the quantification of antioxidant compounds, antioxidant activity evaluation, and their cellular antioxidant activity of polyphenols extract from R. officinalis toward HeLa cells. We aimed to elucidate the chemical composition and recognition of antioxidant components with DPPH and OH free radicals scavenging activity. In addition, the polyphenols dose‐response correlations with cellular antioxidant activity were also determined. These results indicated that off‐line HPLC method with DPPH and OH free radicals as markers is available for screening antioxidant activity of polyphenols from the mixture.

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.