Artemisia species (Asteraceae), widespread throughout the world, are a group of important medicinal plants. The extracts of two medicinal plants of this genus, Artemisia scoparia Waldst. & Kit. and A. spicigera C. Koch, were evaluated for potential antimalarial, free-radical-scavenging and insecticidal properties, using the heme biocrystallisation and inhibition assay, the DPPH assay and the contact toxicity bioassay using the pest Tribolium castaneum, respectively. The methanol extracts of both species showed strong free-radical-scavenging activity and the RC50 values were 0.0317 and 0.0458 mg/mL, respectively, for A. scoparia and A. spicigera. The dichloromethane extracts of both species displayed a moderate level of potential antimalarial activity providing IC50 at 0.778 and 0.999 mg/mL for A. scoparia and A. spicigera, respectively. Both species of Artemisia showed insecticidal properties. However, A. spicigera was more effective than A. scoparia.

The GC-MS analyses of Origanum majorana L. (OME) and Origanum vulgare L. (OVE), Lamiaceae, essential oils helped identification of 39 (96.4% of the total oils) and 43 (92.9% of the total oils) components, respectively. The major constituents of OME were terpinene-4-ol (20.9%), linalool (15.7%), linalyl-acetate (13.9%), limonene (13.4%) and α-terpineol (8.57%), whereas, thymol (21.6%), carvacrol (18.8%), o-cymene (13.5%) and α-terpineol (8.57%) were the main components of OVE. In the disc diffusion and the resazurin microtitre assays, OME showed better antibacterial activity than OVE with larger zones of inhibition (16.5-27.0 mm) and smaller MIC (40.9-1250.3 μg/mL) against the tested bacterial strains. Only OVE displayed anti-heme biocrystallization activity with an IC50 at 0.04 mg/mL. In the DPPH assay, OVE showed better radical-scavenging activity than OME (IC50=65.5 versus 89.2 μg/mL) and both OME and OVE inhibited lionleic acid oxidation. However, in the bleaching β-carotene assay, OVE exhibited better antioxidant activity than OME. In the MTT assay, OME was more cytotoxic than OVE against different cancer cell types, such as MCF-7, LNCaP and NIH-3T3, with IC50s of 70.0, 85.3 and 300.5 μg/mL, respectively. Overall, some components of OME and OVE may have antiparasitic and chemotherapeutic activity.