Yield and In Vitro Antioxidant Potential of Essential Oil from Aerva javanica (Burm. f.) Juss. ex Schul. Flower with Special Emphasis on Seasonal Changes

The essential oil (EO) of the desert cotton (Aerva javanica (Burm. f.) Juss. ex Schul.) was extracted by hydrodistillation, from A. javanica flowers growing in the sandy soils of the United Arab Emirates (UAE) wild desert. The influence of seasonal variation on flowers' EO yield was studied. The flowers' EO yield obtained from spring samples (0.011%) was significantly the highest followed by early summer (0.009%), winter (0.007%), and autumn samples (0.006%), respectively. The flowers' EO antioxidant analysis were tested by DPPH, FRAP and ABTS assays (in vitro). Results proved that A. javanica flowers' EO, isolated during the four seasons, is a good source of natural bioactive antioxidants. Based on the three tested assays, the highest antioxidant activity was recorded in the spring. Testing of the chemical composition of the flowers' EO was conducted for the season with the highest yield and the best antioxidant performance, recorded in spring, by a combination of gas chromatograph (GC) and gas chromatograph-mass spectrometer (GC-MS). This led to the identification of 29 volatile components, in which the flowers' oil was characterized by angustione as a major compound. Photos by scanning electron microscope (SEM) showed prominent availability of star-shaped trichomes in the epidermis of the flowers.