Retention behaviour of conjugated and isolated n-alkadienes

Amazon Rainforest Hidden Volatiles-Part I: Unveiling New Compounds from Acmella oleracea (L.) R.K. Jansen Essential Oil

Motivated by the culinary and ethnopharmacological use of Acmella oleracea (L.) R.K. Jansen, this study aimed to unveil new chemical compounds from its essential oil (EO). Acmella oleracea, known for its anesthetic and spicy properties, has been used in traditional medicine and cuisine, particularly in Northern Brazil. Through a detailed GC-MS analysis, 180 constituents were identified, including 12 tentatively identified long-chain α-keto esters of various acids. Additionally, 18 new esters were synthesized for structural verification. This research expands the known chemical diversity of A. oleracea EO, providing a basis for potential pharmacological applications. The identification of new natural products, including homologs and analogs of acmellonate, underscores the EO's rich chemical profile and its potential for novel bioproduct development.

Retention of long-chain acetylenic hydrocarbons on non-polar stationary phases

The retention indices of methyl and trimethylsilyl esters of octadeca-, eicosa- and tricosa-ynoic fatty acids containing acetylenic bonds were measured on non-polar stationary phase (dimethylsilicone with 5% phenyl groups). An unusually large increase in retention is observed for compounds containing conjugated and methylene interrupted acetylenic bonds. The additional increase in retention index as a result of the presence of one conjugated acetylenic bond is roughly equivalent to the retention increase caused by lengthening of the hydrocarbon chain for one carbon atom. The increase in retention for methylene interrupted bonds constitutes approximately 50% increase for conjugated triple bonds. A further increase in interruption substantially decreases the effect. Based on available literature data and the results of this work, the contributions of conjugated acetylenic and olefinic bonds, and methylene interrupted acetylenic bonds to retention were estimated.

Data mining for seeking an accurate quantitative relationship between molecular structure and GC retention indices of alkenes by projection pursuit

Primary data mining on alkenes for seeking an accurate quantitative relationship between the molecular structure and retention indices of gas chromatography is developed in this paper. Based on the results obtained from projection pursuit, all alkenes investigated show an interesting classification. Thus, a new variable named class distance variable of alkenes, which essentially describes information about the branch, position of the double bonds, the number of double bonds, and so on for alkenes, is proposed. With the help of the new variable, both fitting and prediction accuracy of the regression model can be dramatically improved. The results obtained in this work show that the technique of projection pursuit developed in statistics is a quite promising tool for seeking an accurate quantitative structure-retention relationship (QSRR).