Extraction of essential oils Fruits of I. verum Hook. were procured from the local market in Malaysia and were identified by Mr. Shanmugan A/P Vellosamy, the School of Biological Sciences, Universiti Sains Malaysia. After removing dust and other foreign matter, the fruits were crushed into a coarse powder with an electric grinder (National, MJ-176NR, China). Approximately 500 g of powder was soaked in 2 L of analytical grade ethanol in an airtight container. Subsequently, the container was placed in a shaker at 40 °C for 48 h. The soaked material was then filtered using a Whatman grade 1 filter paper, and the reddish brown filtrate was evaporated using a rotary evaporator to form a thick, viscous, dark brown mass. Upon further drying in a hot air oven at 35 °C, the crude extract was separated into two portions, i.e., oily and dark brown solid mass. The oils were then separated from the residue, and the extracts were kept in a fridge at 4 °C in airtight containers until further experimentation. The stock solution of EOs, i.e., test sample (10 mg/mL), was prepared in DMSO for in vitro assays (Asif et al., 2014; Wong et al., 2014).