374 Changes in Antioxidant Attributes of Mint (Mentha arvensis L.) as Affected by Foliar Application of Selected Plant Growth Enhancers Maryam Aslam 1,2 , Bushra Sultana 1,* , Farooq Anwar 3,4,* , Hassan Munir 5 , Gökhan Zengin 6 and Apdurahman Aktümsek 6 1 Department of Chemistry, University of Agriculture Faisalabad-38040, Pakistan 2 Department of Chemistry, Govt. College Women University, Faisalabad, Pakistan 3 Department of Pharmaceutical Chemistry, College of Pharmacy, Prince Sattam bin Abdulaziz University, AlKharj- 11942, Saudi Arabia 4 Department of Chemistry, University of Sargodha-40100, Sargodha, Pakistan 5 Department of Crop Physiology, University of Agriculture, Faisalabad 38040, Pakistan 6 Department of Biology, Selcuk University, Konya, Turkey * Authors for correspondence; e-mail: bushrasultana2005@yahoo.com, fqanwar@yahoo.com The study mainly investigated the effect of exogenous applications of selected plant growth enhancers (PGEs) on the yield of extractable antioxidant components, the total phenolic content (TPC) and the antioxidant activity of mint (Mentha arvensis L.). PGEs including humic acid (HA, 10%, 25% and 30%), 6-benzyl amino purine (6-BAP at 25 ppm, 50 ppm, and 75 ppm), and Moringa oleifera leaf extract (MOLE, fresh, 1-month-old and 2-month-old) were applied as foliar treatments. Humic acid (HA) was also used as a seed priming agent wherein the seeds were spread in HA solution for 6 h, 9 h and 12 h, respectively, prior to sowing. The second seed priming agent bio-fertilizer (BF) was applied in slurry form to seeds for 30 min before sowing. Analysis of the PGE-applied mint samples relative to the control showed that the total phenolic content was 6.297–21.043 mg GAE/g of dry matter (DM); reducing power was 0.542–1.911 (at 10 mg/mL extract concentration); and the 2,2- diphenyl-1-picryhydrzyl (DPPH) free radical scavenging capacity (IC 50 ) was 0.212–0.504 µg/mL, indicating a significant improvement (enhancement) in the antioxidant attributes of the plants. Generally, the MOLE-applied mint samples had greater phenolic and antioxidant activity compared with the other treatments, showing the effectiveness of exogenous applications of Moringa plant material in enhancing the yield and functional food value of the herb. Key Words: Mentha arvensis L., mint, Moringa oleifera leaf extract, plant growth enhancers, polyphenols, radical scavengers, reducing potential Abbreviations: 6-BAP – 6-benzyl amino purine, BF – biofertilizer, DAE – days after emergence, DPPH – 2,2- diphenyl-1-picryhydrzyl, GAE – gallic acid equivalent, HA – humic acid, MOLE – Moringa oleifera leaf extract, PGE – plant growth enhancer, TPC – total phenolic content INTRODUCTION Several herbal plants are not only useful in providing nutrition and flavor; they are also used as ingredients in the preparation of cosmetics, perfumes, beverages, and phytomedicine due to the presence of bioactive components such as natural antioxidants, limonene, carvonem and menthol (Garg et al. 2012). Recent investigations also revealed that many herbs and spices possess multiple biological functions including antimicrobial, anti-mutagenic, antioxidant, hypo- lipidemic, anti-spasmodic, anti-carcinogenic and anti- inflammatory activities (Hussain et al. 2008; Bouchouka et al. 2012). Mint (Mentha arvensis L.), one of the most important herbs, is well known for its medicinal and pharmacological effects. The whole mint plant has antibacterial and antiseptic activities. Mint leaves yield essential oil with menthol as the major chemical component (40–90% of the oil constituents) (Verma et al. 2010a). The essential oil and the derived menthol from mint are extensively used in the pharmaceutical industry, and are also popularly used in perfumes, cosmetics and aromatherapy (Pasha et al. 2012). As a medicinal and culinary herb, mint is also well known for its carminative, stimulant, stomachic, antispasmodic and diuretic activities (Arumugam et al. 2006; Chaudhary et al. 2012). In folk medicine, it has been used to combat headache, cough, indigestion, toothache, muscular pain and skin diseases. Mint extracts and the isolated essential oil contain several high-value bioactives such as flavonoids, phenolic acids, terpenoids (monoterpenes, sesquiterpenes, triterpenes), tocopherols, phytols, carotenoids and tannins. The occurrence of these bioactives can be linked to the multiple medicinal and biological activities of this valuable herb (Londonkar and Poddar 2009). At present, sustainable agricultural management practices and organic farming have sought to ensure eco- friendly farming techniques for natural resources and ISSN 0031-7454 PHILIPP AGRIC SCIENTIST Vol. 98 No. 4, 374–381 December 2015 The Philippine Agricultural Scientist Vol. 98 No. 4 (December 2015)