Composition, Antioxidant, and Cytotoxic Activities of the Essential Oils from Fresh and Air-Dried Aerial Parts of Pallenis spinosa.

This study was performed to determine the chemical composition, antioxidant and cytotoxic effects of essential oils extracted from the aerial parts of fresh (F-PSEO) and air-dried (D-PSEO) Pallenis spinosa. The composition of the oils was analyzed by gas chromatography (GC) and GC/mass spectrometry, the antioxidant activity by free radical scavenging and metal chelating assays, and their cytotoxicity by a flow cytometry analysis. The primary components in both oils were sesquiterpene hydrocarbons and oxygentated sesquiterpenes. F-PSEO contained 36 different compounds; α-cadinol (16.48%), germacra-1(10),5-diene-3,4-diol (14.45%), γ-cadinene (12.03%), and α-muurolol (9.89%) were the principal components. D-PSEO contained 53 molecules; α-cadinol (19.26%), δ-cadinene (13.93%), α-muurolol (12.88%), and germacra-1(10),5-diene-3,4-diol (8.41%) constituted the highest percentages. Although both oils exhibited a weak radical scavenging and chelating activity, compared to α-tocopherol and ascorbic acid, D-PSEO showed a 2-fold greater antioxidant activity than F-PSEO. Furthermore, low doses of F-PSEO were able to inhibit the growth of leukemic (HL-60, K562, and Jurkat) and solid tumor cells (MCF-7, HepG2, HT-1080, and Caco-2) with an IC50 range of 0.25 - 0.66 μg/ml and 0.50 - 2.35 μg/ml, respectively. F-PSEO showed a ca. 2 - 3-fold stronger cytotoxicity against the tested cells than D-PSEO. The potent growth inhibitory effect of the plant essential oil encourages further studies to characterize the molecular mechanisms of its cytotoxicity.