Rapid differentiation of three Chamaecyparis species (Cupressaceae) grown in Taiwan using solid-phase microextraction-gas chromatography/mass spectrometry, cluster analysis, and principal component analysis

Biosynthetic pathways and metabolic engineering of spice flavors

Historically, spices have played an important economic role, due to their large applications and unique flavor. The supply and cost of spice materials and their corresponding natural products are often affected by environmental, geopolitical and climatic conditions. Secondary metabolite composition, including certain flavor compounds in spice plants, is recognized and considered closely related to plant classification. Both genes and enzymes involved in the biosynthesis of spice flavors are constantly identified, which provides insight into metabolic engineering of flavor compounds (i.e. aroma and pungent compounds) from spice plants. In this review, a systematic meta-analysis was carried out based on a comprehensive literature survey of the flavor profiles of 36 spice plants from nine families. We also reviewed typical biosynthetic pathways and metabolic engineering of most representative aroma and pungent compounds that may assist in the future study of spice plants as biosynthetic factories facing a new challenge in creating spice products.

Rapid differentiation of Chinese hop varieties (Humulus lupulus) using volatile fingerprinting by HS-SPME-GC-MS combined with multivariate statistical analysis

BACKGROUND

Hops impart flavor to beer, with the volatile components characterizing the various hop varieties and qualities. Fingerprinting, especially flavor fingerprinting, is often used to identify 'flavor products' because inconsistencies in the description of flavor may lead to an incorrect definition of beer quality. Compared to flavor fingerprinting, volatile fingerprinting is simpler and easier.

RESULTS

We performed volatile fingerprinting using head space-solid phase micro-extraction gas chromatography-mass spectrometry combined with similarity analysis and principal component analysis (PCA) for evaluating and distinguishing between three major Chinese hops. Eighty-four volatiles were identified, which were classified into seven categories. Volatile fingerprinting based on similarity analysis did not yield any obvious result. By contrast, hop varieties and qualities were identified using volatile fingerprinting based on PCA. The potential variables explained the variance in the three hop varieties. In addition, the dendrogram and principal component score plot described the differences and classifications of hops.

CONCLUSION

Volatile fingerprinting plus multivariate statistical analysis can rapidly differentiate between the different varieties and qualities of the three major Chinese hops. Furthermore, this method can be used as a reference in other fields. © 2018 Society of Chemical Industry.

Comparison of the Profile and Composition of Volatiles in Coniferous Needles According to Extraction Methods

The enantiomeric distribution and profile of volatiles in plants, which affect the biological and organoleptic properties, can be varied depending on extraction methods as well as their cultivars. The secondary volatile components of the needles of three conifer cultivars (Chamaecyparispisifera, Chamaecyparisobtusa, and Thujaorientalis) were compared. Furthermore, the effects of three different extraction methods—solid-phase microextraction (SPME), steam distillation (SD), and solvent extraction (SE)—on the composition and enantiomeric distribution of those volatiles were elucidated. Monoterpene hydrocarbons predominated in all samples, and the compositions of sesquiterpenes and diterpenes differed according to the cultivar. In particular, the yields of oxygenated monoterpenes and sesquiterpenes were greatest for SD, whereas those of sesquiterpenes and diterpenes were highest for SE. On the other hand, more monoterpenes with higher volatility could be obtained with SPME and SD than when using SE. In addition, the enantiomeric composition of nine chiral compounds found in three cultivars differed according to their chemotype. There were also some differences in the yielded oxygenated monoterpenes and sesquiterpene hydrocarbons, but not monoterpene hydrocarbons, according to the extraction method. These results demonstrate that the extraction methods used as well as the cultivars influence the measured volatile profiles and enantiomeric distribution of coniferous needle extracts.

Rapid discrimination and feature extraction of three Chamaecyparis species by static-HS/GC-MS

This study aimed to develop a rapid and accurate analytical method for discriminating three Chamaecyparis species (C. formosensis, C. obtusa, and C. obtusa var. formosana) that could not be easily distinguished by volatile compounds. A total of 23 leaf samples from three species were analyzed by static-headspace (static-HS) coupled with gas chromatography-mass spectrometry (GC-MS). The static-HS procedure, whose experimental parameters were properly optimized, yielded a high Pearson correlation-based similarity between essential oil and VOC composition (r = 0.555-0.999). Thirty-six major constituents were identified; along with the results of cluster analysis (CA), a large variation in contents among the three different species was observed. Principal component analysis (PCA) methods illustrated graphically the relationships between characteristic components and tree species. It was clearly demonstrated that the static-HS-based procedure enhanced greatly the speed of precise analysis of chemical fingerprint in small sample amounts, thus providing a fast and reliable tool for the prediction of constituent characteristics in essential oil, and also offering good opportunities for studying the role of these feature compounds in chemotaxonomy or ecophysiology.

Seasonal variation and resin composition in the Andean tree Austrocedrus chilensis

Little is known about the changes in resin composition in South American gymnosperms associated with the different seasons of the year. The diterpene composition of 44 resin samples from seven Austrocedrus chilensis (Cupressaceae) trees, including male and female individuals, was investigated in three different seasons of the year (February, June and November). Twelve main diterpenes were isolated by chromatographic means and identified by gas chromatography-mass spectrometry and nuclear magnetic resonance (NMR). The diterpene composition was submitted to multivariate analysis to find possible associations between chemical composition and season of the year. The principal component analysis showed a clear relation between diterpene composition and season. The most characteristic compounds in resins collected in summer were Z-communic acid (9) and 12-oxo-labda-8(17),13E-dien-19 oic acid methyl ester (10) for male trees and 8(17),12,14-labdatriene (7) for female trees. For the winter samples, a clear correlation of female trees with torulosic acid (6) was observed. In spring, E-communic acid (8) and Z-communic acid (9) were correlated with female trees and 18-hydroxy isopimar-15-ene (1) with male tree resin. A comparison between percent diterpene composition and collection time showed p < 0.05 for isopimara-8(9),15-diene (2), sandaracopimaric acid (4), compound (7) and ferruginol (11).

Characteristic aroma-active compounds of floral scent in situ from Barringtonia racemosa and their dynamic emission rates

Barringtonia racemosa is a nocturnal flowering plant. Information on its floral volatiles and the dynamic emission profiles was very limited. In this study, the floral volatiles of B. racemosa were monitored hourly during its florescence via detached and in situ collection for the first time. The dynamic odor activity value (OAV) was calculated to elucidate the active aroma components of floral scent. Results of compositional analyses showed that the predominant floral volatiles were linalool and phenylacetaldehyde. Their emission started around 8:00 p.m., and the peak emissions were 20541 and 18234 ng h(-1) flower(-1), respectively, during 10:00 p.m.-2:00 a.m. Results from dynamic OAV profiling revealed that linalool (409 min(-1)) and phenylacetaldehyde (547 min(-1)) had higher OAVs than other components (<10 min(-1)), indicating that linalool and phenylacetaldehyde contributed mainly to the floral scent with a strong, sweet, and pleasant aroma.