Variation in chemical constituents of essential oils of the fresh, dried and fermented leaves of Premna serratifolia

Abstract

This study aimed to identify the composition of the essential oils of the fresh, dried and fermented leaves of Premna serratifolia by gas chromatography-mass spectrometry (GC-MS) using DB-5 and Carbowax 20M columns. A total of 77, 82 and 90 compounds were detected, which involved the main compound categories of hydrocarbons, terpenoids, and phenolics. Amyl vinyl carbinol (15.8-32.6%), linalool (11.1-15.1%), phytol (7.7-12.5%), salicylic acid methyl ester (3.9-7.2%) and (E)-caryophyllene (3.1-6.6%) were predominant components of the fresh leaf oils. After drying and fermentation, the chemical compositions were changed by various reactions. The amounts of amyl vinyl carbinol were decreased to 6.3-13.8% and 6.9-11.5% after drying and fermentation, respectively. Likewise, linalool and phytol were decreased to 6.3-7.5% and 7.3-9.0% after drying, and decreased to 5.3-7.9% and 2.0-3.4% after fermentation, respectively. In both the dried and the fermented leaf oils, alpha-humulene was disappeared and beta-myrcene was detected as a new compound. The noticeable changes in chemical composition after drying process were much increasing in the amount of (E)-caryophyllene (6.6-12.2%) to become the most abundant compound, and the hydrolysis of palmitic acid ethyl ester to palmitic acid (5.0%). The fermentation method could dramatically increase the amounts of phenolic compounds especially p-vinylanisole (2.4-41.1%) which became the major compound, marked decrease the phytol and found acorenone B (4.4%) as a new compound. The present study demonstrated that drying and fermentation processes affected the volatile composition of the leaves of P. serratifolia.