Dudai, N., Agricultural Research Organization, Newe Ya'ar Research Center, Ramat Yishay, Israel
Segev, D., Agricultural Research Organization, Newe Ya'ar Research Center, Ramat Yishay, Israel
Havkin-Frenkel, D., Dept. Plant Biology and Pathology, Rutgers - The State University of New Jersey, New Brunswick, NJ, United States
Eshel, A., Department of Plant Sciences, Tel Aviv University, Tel Aviv, Israel

Phenolic acids, in free soluble form and cell wall-bound, were extracted from leaves and stems from 40 genetic variants from 25 populations of Mentha longifolia native to Israel. Rosmarinic and caffeic acid were the most abundant freely soluble acids whereas caffeic acid was most abundant among cell wall-bound phenolic acids. Assessment of the total antioxidant efficacy, based on the reduction of 1,1-diphenyl-2-picryldrazyl (DPPH), revealed high antioxidant activity by tissues of many M. longifolia variants, stemming in part, from antioxidant activity of rosmarinic acid. Although phenolic acids in free extractable form comprise a major portion of total phenolic acids, cell wall-bound acids were found in significant amounts and may also contribute to the antioxidant efficacy of the plants.