Polyphenol contents and antioxidant activity of Maydis stigma extracts Zoran Maksimovic ´ a, * , - Dord - e Malenc ˇic ´ b , Nada Kovac ˇevic ´ a a Institute of Pharmacognosy, School of Pharmacy, University of Belgrade, Vojvode Stepe 450, 11221 Belgrade, Serbia and Montenegro b Faculty of Agriculture, University of Novi Sad, Trg Dositeja Obradovic ´a 8, 21000 Novi Sad, Serbia and Montenegro Received 23 January 2004; received in revised form 31 August 2004; accepted 6 September 2004 Available online 11 November 2004 Abstract The antioxidant activity and contents of various polyphenol classes in the silks of fifteen maize hybrids with economic impor- tance in Serbia were evaluated. Total polyphenols, tannins and proanthocyanidins were determined spectrophotometrically, after extraction of plant material with 70% aqueous acetone under sonication at room temperature. In addition, flavonoid content was determined. Antioxidant activity of aqueous acetone extracts was evaluated by FRAP assay. A positive linear correlation between antioxidant activity and contents of all investigated polyphenol classes was established. The highest antioxidant activity was observed in the extract of NS 640 hybrid, which had high levels of all polyphenol classes examined. Results suggested strongly that polyphenol content should be considered as an important feature of the herbal drug Maydis stigma. For that reason, the bio- logical source of this herbal drug needs to be more precisely defined, as observed activities and polyphenol contents were greatly dependent on plant material source. Ó 2004 Elsevier Ltd. All rights reserved. Keywords: Maize silk; Maydis stigma; Zea mays; Antioxidant activity; FRAP assay; Polyphenols 1. Introduction The herbal drug Maydis stigma (dried cut stigmata of maize female flowers, Zea mays L. ssp. mays, Poaceae) is recognized and used, both in traditional and official medicine, as a mild diuretic, urinary demulcent, to pass stones and gravel from kidneys and urinary bladder, against benign prostatic hyperplasia, cystitis, gout, chronic nephritis and similar ailments (Tucakov, 1990; British Herbal Pharmacopoeia, 1996; Czygan, 1997). Similar findings have been published in several ethno- pharmacological studies dedicated to surveys of popu- larly used medicinal plants in various regions, or the plants used specifically for medical treatment of urolog- ical disorders (Bastien, 1983; Ca ´ceres et al., 1987; Yes ßilada et al., 1995). A previous paper describes the influence of methanol extracts of commercial samples of herbal drug M. stigma on lipid peroxidation in liposomes, induced by a Fe 2+ / ascorbate system (Maksimovic ´ and Kovac ˇevic ´, 2003). The authors believe this to be the first report on antioxi- dant activity of M. stigma. Pursuing research on poten- tially useful pharmacological effects of this herbal drug, the possibility that observed antioxidant activity might depend significantly on appropriate choice of its biolog- ical source was investigated. It is generally accepted that maize can neither be found in the nature as a wild-growing plant, nor is capa- ble to survive without human influence and care (Jevtic ´, 0960-8524/$ - see front matter Ó 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.biortech.2004.09.006 * Corresponding author. Tel.: +381 11 3970 379ext.721; fax: +381 11 3972 840. E-mail address: zmaksim1@pharmacy.bg.ac.yu (Z. Maksimovic ´). Bioresource Technology 96 (2005) 873–877