Identifying ornamental plants as new natural antioxidant and antimicrobial sources is always of great importance for the ornamental and horticultural industries. The antimicrobial activities of leaves and fruits peel essential oils of twelve ornamental and horticultural crops were determined by screening against wide spectrum of fungi and bacteria, and their respective in vitro antioxidant capacity was evaluated. Furthermore, the anticancer activities against several cancer cells, and one normal human cell line (HEK-293) were examined. Origanum vulgare L. essential oil showed the best antioxidant, antibacterial and anticancer activities compared to screened crops by means of the DPPH and linoleic acid assays for antioxidants, MIC and MBC values for antibacterial activities and IC50 for antiproliferative activities. Such important activities in O. vulgare was attributed to high pulegone ratio (77.45%) as revealed by the GC/MS assay. Rosmarinus officinallis L. essential oil showed the highest antifungal activities by means of lowest MIC and MFC values which might be attributed to 1, 8-cineole (19.60%), camphor (17.01%) and α-pinene (15.12%). We suggest that oxygenated monoterpenes (i.e. linalool, terpinen-4-ol and pulegone) and monoterpene hydrocarbons play an important role in the essential oil antioxidant, antibacterial, antifungal and anticancer activities of diverse Egyptian ornamental and horticultural crops. Some species showed bioactivities similar to standards compounds and might be suitable for pharmaceutical and food industries.

New strategies have to be introduced for the management of agricultural and public health insects to overcome the problems associated with long-term use of synthetic insecticides. Plant-based natural products are among the possible and available alternatives to be applied for insect management. Among the plant secondary metabolites, monoterpenes have been widely studied for their applications in insect control. In this review, we focus on the studies describing the insecticidal and grain protection activities of monoterpenes against stored product insects. In addition, the biosynthesis and chemistry of monoterpenes as well as their possible modes of action and commercialization opportunities are summarized. The present review emphasizes the importance of monoterpenes as target-specific, biodegradable, environmentally safe grain protectants as well as their possible practical use as a tool in integrated pest management programs.