Extraction and quality analysis of volatile oils from onions by coupling pilot and laboratory equipment based on multi-rectification

Characterization of the Volatile Compounds of Onion with Different Fresh-Cut Styles and Storage Temperatures

The flavor of fresh onion and its processed products is an important index with which to evaluate its quality. In this study, the highly volatile compounds of onion with different fresh-cut styles (bulb, ring, and square) and different storage temperatures (4 °C, 20 °C, and 25 °C) were characterized at the molecular level, focusing in particular on the volatile sulfur compounds. Headspace-gas chromatography-ion mobility spectrometry (HS-GC-IMS) and headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS) were employed. A total of 14 highly volatile compounds were identified in onion samples by HS-GC-IMS, and the square sample contained more volatile components. (E,E)-2,4-heptadianal, ethyl acetate, 2-methyl-1-pentanol, 2-pentylfuran, propyl acetate, and 2,6-dimethylpyrazine were produced in the ring and square samples when stored at higher temperatures, while pentanal, 2-heptenal, hexanal were decreased after cutting. Simultaneously, 16 sulfur compounds were identified in onions by HS-SPME-GC-MS. The sulfur compounds profile of the bulbs was significantly different from that of the rings and squares at any temperature. When stored at a low temperature (4 °C), cutting onions into a ring or square shape produced more sulfur. However, at higher temperatures (20 °C and 25 °C), fresh-cutting decreased the sulfur concentration. The total content of sulfur compounds was higher in the same cut style stored at higher temperatures (20 °C or 25 °C). 2-Mercapto-3,4-dimethyl-2,3-dihydrothiophene and 2,4-dimethylthiophene were formed during storage; however, (E)-1-(prop-1-en-1-yl)-3-propyltrisulfane, 1-(1-(methylthio)propyl)-2-propyldisulfane, (Z)-1-(1-propenyldithio)propyl disulfide, dipropyl trisulfide, and methyl 1-(1-propenylthio)propyl disulfide were lost from all samples after storage.

Health Benefits of the Flavonoids from Onion: Constituents and Their Pronounced Antioxidant and Anti-neuroinflammatory Capacities

Onion is the most widely cultivated vegetable around the world. In this study, the isolation, concentration, quantification, and bioactivity evaluation of the phenolics in onion peels were investigated. Thirty-four phenolics, including 17 flavonoids and 17 nonflavonoid phenolics, were purified and identified. Among them, there were 2 new unusual epoxyflavanones and a new phenolic constituent, as well as 13 unreported constituents from the genus Allium. The total flavonoids were concentrated, and finally obtained 90.25% of flavonoid content extract. Fifteen main flavonoids were quantified using an ultra-performance liquid chromatography-photodiode array (UPLC-PDA), and quercetin (36.94%) and quercetin 4'-O-β-d-glucopyranoside (15.81%) were the richest contents of flavonoids. The antioxidant and anti-neuroinflammatory capacities were evaluated, and the bioactive results indicated that the flavonoids in onion exhibited pronounced activities. The study suggested that the flavonoids in onion peels could be used in functional food.

Optimisation of steam distillation extraction oil from onion by response surface methodology and its chemical composition

Oil extraction from onion was performed by steam distillation. Response surface methodology was applied to evaluate the effects of ratio of water to raw material, extraction time, zymolysis temperature and distillation times on yield of onion oil. The maximum extraction yield (1.779%) was obtained as following conditions: ratio of water to raw material was 1, extraction time was 2.5 h, zymolysis temperature was 36° and distillation time was 2.6 h. The experimental values agreed well with those predicted by regression model. The chemical composition of extracted onion oil under the optimum conditions was analysed by gas chromatography-mass spectrometry technology. The results showed that sulphur compounds, like alkanes, sulphide, alkenes, ester and alcohol, were the major components of onion oil.

Evaluation of the effects of active fractions of chinese medicine formulas on IL-1β, IL-6, and TNF-α release from ANA-1 murine macrophages

ETHNOPHARMACOLOGICAL RELEVANCE

Yaotongning (YTN) is a traditional Chinese Medicine (TCM) that contains ten component medicinal materials (CMMs) and uses Chinese rice wine as a vehicle to enhance its efficacy. YTN has been used for rheumatoid arthritis (RA) treatment in China for decades and has been reported to have anti-inflammatory and analgesic effects, as well as to strengthen the immune system.

AIM OF THE STUDY

The present work quantitatively evaluated the in vitro effects of active fractions from the ten CMMs that make up YTN and eight additional herbs commonly used in TCM formulas for RA treatment, as well as different combinations of these active fractions, on cellular immune response; the findings were used to determine which active fractions are responsible for promoting an immune response, and to assess whether YTN is superior to other similar formulas and whether YTN can be improved by simplifying its formula from the point of its cellular immunomodulatory activity.

MATERIALS AND METHODS

Using the YTN formulation principles and some concepts in combinatorial chemistry, 27 TCM samples were designed by combining some or all of the active fractions of YTN and other eight herbs used for RA treatment. Release of interleukin-1β (IL-1β), interleukin-6 (IL-6), and tumor necrosis factor-alpha (TNF-α) from ANA-1 murine macrophages was measured using an enzyme-linked immunosorbent assay (ELISA). The immunoregulatory effects of the TCM samples were evaluated by comparing their half-effective concentrations (EC50) for stimulating the release of these cytokines.

RESULTS

Among the investigated active fractions, the flavonoids from Carthamus tinctorius (Fct), Davallia mariesii (Fdm), and Cinnamomum cassia Twig volatile oils (Vca) from the eight selected herbs effectively promoted IL-1β and IL-6 release from ANA-1 cells. Saponins from the YTN CMM Glycyrrhiza uralensis (Sgu) were the most potent promoters of IL-1β and TNF-α release. The aqueous extract of YTN CMM Eupolyphaga sinensis (Ves) strongly enhanced the release of IL-1β, IL-6, and TNF-α from ANA-1 cells. The EC50 values for stimulating the secretion of IL-1β, IL-6, and TNF-α could be determined for only six samples. The full YTN formula and the sample containing 50% Glycyrrhiza uralensis saponins, 25% of the mixture of alkaloids, and 25% of the mixture of all flavonoids exhibited good comprehensive cellular immunomodulatory activity. The immunomodulatory activity of the complete YTN formula was better than that of the sample containing all active fractions of YTN without Chinese rice wine (the YTN vehicle).

CONCLUSIONS

Sgu and Ves are the primary active fractions of YTN involved in stimulating immune responses. The YTN prescription was reasonably effective at promoting cellular immune responses. Chinese rice wine, the YTN vehicle, strengthened the immunoregulatory activity of YTN. The results of this study demonstrate that the YTN recipe could be improved by reducing the number of CMMs and altering some active fractions without reducing its activity to promote cellular immune responses.