Havkin-Frenkel, D., Department of Plant Biology and Pathology, Rutgers, The State University of New Jersey, New-Brunswick, NJ, United States
Dudai, N., Agricultural Research Organization, Newe Ya'ar Research Center, Ramat Yishay, Israel
van der Mheen, H., Elburg, Netherlands

Purpose of review: Herbs contain a volatile fraction containing essential oils and a non-volatile fraction containing compounds with biological activity, including antioxidant activity. However, there is an overwhelming amount of information on antioxidant activity in herbs, without knowing which fraction contributed to this activity. The purpose of this review is to highlight the specific fraction that contributes to the antioxidant activity in herbs and to describe appropriate techniques for preserving the active and beneficial compounds in herbal wastes. Findings: A protocol for controlled growth, harvest, distillation and postharvest distillation processes that enables the protection of activity of compounds in post-distillation material has been developed and can be applied to herbal wastes from sources such as Origanum spp., Mentha spicata and Mentha piperita. This process results in a new commercial product from oregano with biological activity as an antioxidant, a wound-healing and anti-inflammatory agent, anti-microbial and anti-aging properties. Direction for future research: New studies on cultivation and postharvest handling and extraction protocols might reinforce and highlight the value-added for post-distillation residue from herbs. © 2011 Stewart Postharvest Solutions (UK) Ltd.