Identification, Comparison and Classification of Volatile Compounds in Peels of 40 Apple Cultivars by HS–SPME with GC–MS

Aroma is an important quality indicator for apples and has a great influence on the overall flavour and consumer acceptance. However, the information of the aroma volatile compounds in apple peels is largely unknown. In this study, evaluation of volatile compounds in peels of 40 apple cultivars was carried out using headspace solid-phase microextraction (HS-SPME) coupled with gas chromatography-mass spectrometry (GC-MS). A total of 78 volatile compounds were identified, including 47 esters, 12 aldehydes, 5 alcohols, 3 ketones, 1 acid and 10 others. Eight volatile compounds were common in all apple cultivars. Cultivar Changfu No. 2 contained the highest number of volatile compounds (47), while Qinyue contained the least (20). Honey Crisps had the highest volatile content, at 27,813.56 ± 2310.07 µg/kg FW, while Huashuo had the lowest volatile content, at 2041.27 ± 120.36 µg/kg FW. Principal component analysis (PCA) clustered the 40 apple cultivars into five groups. Aroma is cultivar-specific, volatile compounds of hexyl butyrate, hexyl 2-methylbutyrate and hexyl hexanoate, together with hexanal, (E)-2-hexenal, 1-hexanol, estragole and α-farnesene could be proposed for apple cultivar classification in the future.

Sex Pheromone of the Alfalfa Plant Bug, Adelphocoris lineolatus: Pheromone Composition and Antagonistic Effect of 1-Hexanol (Hemiptera: Miridae)

The sex pheromone composition of alfalfa plant bugs, Adelphocoris lineolatus (Goeze), from Central Europe was investigated to test the hypothesis that insect species across a wide geographical area can vary in pheromone composition. Potential interactions between the pheromone and a known attractant, (E)-cinnamaldehyde, were also assessed. Coupled gas chromatography-electroantennography (GC-EAG) using male antennae and volatile extracts collected from females, previously shown to attract males in field experiments, revealed the presence of three physiologically active compounds. These were identified by coupled GC/mass spectrometry (GC/MS) and peak enhancement as hexyl butyrate, (E)-2-hexenyl butyrate and (E)-4-oxo-2-hexenal. A ternary blend of these compounds in a 5.4:9.0:1.0 ratio attracted male A. lineolatus in field trials in Hungary. Omission of either (E)-2-hexenyl-butyrate or (E)-4-oxo-2-hexenal from the ternary blend or substitution of (E)-4-oxo-2-hexenal by (E)-2-hexenal resulted in loss of activity. These results indicate that this Central European population is similar in pheromone composition to that previously reported for an East Asian population. Interestingly, another EAG-active compound, 1-hexanol, was also present in female extract. When 1-hexanol was tested in combination with the ternary pheromone blend, male catches were reduced. This compound showed a dose-response effect with small doses showing a strong behavioral effect, suggesting that 1-hexanol may act as a sex pheromone antagonist in A. lineolatus. Furthermore, when (E)-cinnamaldehyde was field tested in combination with the sex pheromone, there was no increase in male catch, but the combination attracted both males and females. Prospects for practical application are discussed.

Guide to Harvesting Heracleum Persicum: How Essential Oil Composition and Phenolic Acid Profile Fluctuate at Different Phenological Stages?

BACKGROUN: Heracleum persicum commonly named Golpar, is a principal native medicinal plant in Iran. Collecting H. persicum at the appropriate growing stage is the key factor to achieve the high phytochemical quality to meet consumer’s needs. In the present experiment, the aerial parts of this plant were harvested at up to six different developmental stages during the growing season to determine the phytochemical profiles. RESULTS: Our results indicated that the highest essential oil yield and extract were obtained in the mid-mature seed stage (3.5%),) and floral budding stage (10.40%). In the vegetative stage, limonene (18.05), in floral budding stage, caryophyllene (14.07), anethole (14.55%), and β-bisabolene (12.56%), in the full flowering stage, myristicin (15.02%), and hexyl butyrate (9.05%); in the early development of seeds stage, hexyl butyrate (32.08%), and octyl acetate (11.67%); in the mid-mature seeds stage hexyl butyrate (38.75%), octyl acetate (14.47%); in the late-mature/ripe seeds stage, hexyl butyrate (23.59%), and octyl acetate (10.48%) recorded as the main components. The analysis of phenolic acids demonstrated cinnamic acid, p-coumaric acid, p-hydroxybenzoic acid, ferulic acid, and rosmarinic acid as the main phenolic acids. The highest phenolic acids content was obtained in the floral budding stage (287.40 mg g –1 dry extract). Cinnamic acid was found as the major phenolic compound in the vegetative stage following by floral budding, the full flowering stage, the early development of seeds and late-mature/ripe seeds stages. P-coumaric acid was the most abundant phenolic compounds in the mid-mature seeds stage. The development stage has a significant impact on the content and composition of both essential oil and phenolic acid composition. CONCLUSION: In this regard, the harvest time of H. persicum aerial parts can be selected to achieve the highest secondary metabolites of interest. The results of this study can be used as a guideline for grower to obtain the highest amount of desirable metabolites, beneficial in the food and pharmaceutical industries as well as economic benefits.

Chemical Composition of Fruit Essential Oil of Endemic Malabaila pastinacifolia

The water distilled essential oil (EO) from the fruits of Malabaila pastinacfolia Boiss & Balansa (Apiaceae), an endemic species from Turkey, was analyzed using GC-FID and GC-MS systems. The analysis revealed 38 compounds accounting for 97.6% of the EO. Hexyl butyrate (47.2 %), hexyl hexanoate (22.7%) and α-terpinyl acetate (11.1 %) were found as the main constitutes. This is the first report on the EO composition of M. pastinacfolia.

Effect on Catalytic Ability of Solid Super Acid SO42-/ZrO2-TiO2-SiO2-Al2O3 Modified by Y, La and Chitosan

In the present study, catalyst of SO42-/ZrO2-TiO2-SiO2-Al2O3 has been prepared by sol-gel method and doped by Y, La and Chitosan, respectively. The catalytic ability of modified catalysts for the synthesis of hexyl butyrate has been tested. It has been shown that the catalytic ability has been improved obviously after modification. Under the best experimental conditions, with Y doping 1%, La doped 1.5% and Chitosan doped 4%, the catalytic ability has been improved from 76.7% to 90.7%, 92.1% and 93.9%. Characterized by XRD, SEM and IR, it has been found that the grain sizes of catalysts are smaller which due to higher specific surface andimprove the catalytic ability. With abundant amino groups at the surface, the Chitosan doping improves the capacity of SO42- for catalysts.

Sex Pheromones ofStenotus rubrovittatusandTrigonotylus caelestialium, Two Mirid Bugs Causing Pecky Rice, and Their Application to Insect Monitoring in Japan

Two mirid bugs,Stenotus rubrovittatusandTrigonotylus caelestialium(Heteroptera: Miridae), are important pests that infest rice crops in many regions of Japan. Males of each species were attracted to traps baited with conspecific, unmated females. Hexyl butyrate, (E)-2-hexenyl butyrate, and (E)-4-oxo-2-hexenal were identified as possible female-produced sex pheromone components forS. rubrovittatus, whereas hexyl hexanoate, (E)-2-hexenyl hexanoate, and octyl butyrate were found to be sex pheromone components forT. caelestialium. Pheromone doses and ratios were optimized for attraction of males of each species. Sticky traps set up close to or below the top of the plant canopy were optimal for monitoring these species, and trap catches were almost constant when traps were placed 7 or more meters in from the edge of a paddy field. Mixed lures, in which the six compounds from both species were loaded onto a single septum, or separate lures for each species, deployed in a single trap, were equally effective for monitoring both species simultaneously.

Antennal and Behavioral Responses of Lygus lineolaris (Palisot de Beauvois) (Heteroptera: Miridae) to Metathoracic Scent Gland Compounds

Hexyl and (E)-2-hexenyl butyrates and (E)-4-oxo-2-hexenal are major components of the metathoracic scent gland (MSG) secretion and aeration samples of many plant bugs (Miridae), including the tarnished plant bug, Lygus lineolaris (Palisot de Beauvois). Laboratory and field experiments were performed (1) to determine the extent to which MSG-produced compounds are detected by antennae of L. lineolaris males and females, and (2) to elucidate the behavioral activity associated with the antennally active MSG compounds. The three major MSG-produced compounds elicited strong antennal responses by both sexes. In Y-track olfactometer tests, attraction of males to virgin females was significantly reduced when a dispenser loaded with hexyl butyrate was placed with the virgin females. Hexyl butyrate tested alone against a blank control significantly repelled males. In the field, ternary and partial binary combinations of these three EAD-active compounds failed to attract either sex, whereas virgin females attracted a significant number of males. However, addition of hexyl butyrate and/or (E)-2-hexenyl butyrate to virgin female-baited traps significantly reduced the number of males caught compared with the level of the blank control traps. This might be due either to a negative effect on pheromone release by the females or direct repellency of males, or both. These MSG compounds may be useful for mating disruption and other pest management tactics against economically important plant bugs.