Bài báo khoa học

Results showed that no significant difference in both yield and chemical diversity was found between L. umbellata and L. khasyana oils (Table 1). Hydrodistillation of leaves gave light yellow oils of two Litsea species in 0.21% and 0.19%, respectively. L. umbellata essential oil contains 24 terpene compounds (made up 90.64% of total oil) with major components as patchoulene (23.03%), β-caryophyllene (15.72%), aromadendrene (14.96%), and germacrene D (12.76%). The essential oil from L. khasyana leaves consists of 27 terpenes (accounting for 87.13% of the chromatographical components), of which patchoulene (21.25%) and β-caryophyllene (11.64%) were the main constituents. Being different from previous studies that introduced monoterpenes as the major fraction in essential oils of some Litsea species in Vietnam [3–5], our results recorded the basic components of L. umbellata and L. khasyana essential oils as sesquiterpene hydrocarbons. It is interesting that patchoulene and β-caryophyllene are the most abundant constituents in both oils. No previous study introduced the presence and activity of patchoulene in Litsea plants, although it is known to characterize the aroma and biological activity of patchouli oil [9]. β-Caryophyllene was known as the major compound in Vietnam L. helferi [3], Indian L. quinqueflora and L. deccanensis [10], and Taiwan L. acuminate [11] plants and contributed to antioxidant, antibiotic, anticarcinogenic, and anti-inflammatory activities of oils [12, 13]. The high content of patchoulene and β-caryophyllene in the essential oil from both L. umbellata and L. khasyana plants may contribute to their biological activities. The antioxidant activity of leaf essential oils from L. umbellata and L. khasyana plants was evaluated and compared to that of Trolox, an antioxidant standard (Table 2). Both oils expressed strong activity in DPPH and ABTS free radical scavenging, which were 1.61–1.83-fold higher than standard Trolox, while the highest activity was their antioxidant power, which were 2.59 mg TEAC⋅g–1 dw (of L. umbellata oil) and 2.43 mg TEAC⋅g–1 dw (of L. khasyana oil). No significant difference in antioxidant activity was found between the two oils; however, all DPPH, ABTS, and FRAP values of L. umbellata essential oil were always higher than that of L. khasyana; the difference was probably due to certain components presented in each oil.