Search

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]

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]

• Ovalbumin (Oval)–ribose glycation induced by vacuum freeze-drying (VFD) was studied. • Oval conformational structure significantly changed during VFD-induced glycation. • The glycation extents in terms of glycated sites and DSP were analyzed by LC–HRMS. • This study gave relationships between VFD time and conformation and glycated sites. Ovalbumin (Oval)–ribose glycation induced by vacuum freeze-drying (VFD) was studied. The protein conformational changes based on fluorescence, ultraviolet and circular dichroism spectra were evident with the increase in VFD time. The glycated sites and the average degree of substitution per peptide molecule (DSP) were determined using LC–HRMS. Lysine was shown to be the sole glycated site. Two glycated sites and the minimum DSP values were found during the first 6 h of VFD and increased to nine and the maximum DSP values after 48 h of VFD. The glycated sites located on the protein surface were mostly more active than those in the folded or helical regions, and the hydrophilic/hydrophobic environment could also influence DSP values. This study gave relationships between VFD time and the conformational structure and glycated sites of VFD-treated Oval–ribose system, providing a theoretical basis for VFD technique-based protein food and drug industries. [ABSTRACT FROM AUTHOR]

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]

• 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]