GSC Biological and Pharmaceutical Sciences, 2019, 06(03), 024–030 Available online at GSC Online Press Directory GSC Biological and Pharmaceutical Sciences e-ISSN: 2581-3250, CODEN (USA): GBPSC2 Journal homepage: https://www.gsconlinepress.com/journals/gscbps  Corresponding author E-mail address: Copyright © 2019 Author(s) retain the copyright of this article. This article is published under the terms of the Creative Commons Attribution Liscense 4.0. (R ESEARCH A RTICLE ) Boiling increase antioxidant activity, total phenolic content and total flavonoid content in Plectranthus amboinicus leaves Muhamad Shamsul * and Mat Ali Siti Fatimah Zahrah Faculty of Agro Based Industry, Universiti Malaysia Kelantan, Locked Bag No 100, 17600 Jeli, Kelantan, Malaysia. Publication history: Received on 13 February 2019; revised on 28 February 2019; accepted on 05 March 2019 Article DOI: https://doi.org/10.30574/gscbps.2019.6.3.0023 Abstract The effect of boiling on antioxidant activity, total phenolic content (TPC) and total flavonoid content (TFC) in the ethanol extracts from Plectranthus amboinicus leaves were studied. The dried leaves were boiled in water for 0 (control), 30, 60, 90 and 120 minutes, then extracted with ethanol to produce ethanol extracts. The ethanol extracts were subjected to three antioxidant assays, i.e., 2, 2-diphenyl-1-picrylhydrazyl (DPPH), 2, 2’-azino-bis (3-ethylbenzothiazoline-6- sulphonic acid) (ABTS) and ferric reducing antioxidant power (FRAP). TPC and TFC in extracts were determined by Folin-Ciocalteu assay and aluminium chloride colorimetric assay, respectively. The results of DPPH, ABTS and FRAP assays indicated that the antioxidant of extracts were significantly (p < 0.05) more potent than the control and also increased when the boiling time was increased. Furthermore, TPC and TFC in extracts from boiled samples were significantly (p < 0.05) higher than the control and correlated with antioxidant activity. This study revealed that boiling of P. amboinicus leaves were increased its antioxidant activity, TPC and TFC as determine in ethanol extracts, and suggested that boiling can be used as a method for enhancing antioxidant activity of P. amboinicus. Keywords: Plectranthus amboinicus; Antioxidant; Total phenolic content; Total flavonoid content 1. Introduction Fats and oils are important substances during food processing and also use as ingredients in a variety of foods. They act as heat transfer medium, emulsifier, texture controller, flavor enhancer and nutritive substance [1-4]. However, autoxidation of fats and oils is one of the limiting factors in a food product's shelf life as noticeable by rancid odour and flavour, but can be prevented by using antioxidant agents [2-3]. In current food industry, synthetic antioxidant agents such as butylated hydroxyanisole, butylated hydroxytoluene and tertiary-butyl hydroquinone regularly used as antioxidant food preservative [5]. Unfortunately, all of these agents have long been linked to several adverse reaction such as allergy, asthma, dermatitis, flushing, headache, stomach problems, joint pain and weight gain [6-7]. Owing to good reputation, naturally occurring antioxidants are gaining more attention and choice of consumer for substitute the synthetic antioxidants [8-9]. Plectranthus amboinicus (Lamiaceae) or Indian borage is a soft-stem plant with a strong oregano-like minty aroma and flavor mainly cultivated and used in traditional medicine or culinary purposes by in tropical and subtropical regions such as India, Southeast Asian (Malaysia, Indonesia, Thailand), China, Taiwan, West Asia (Egypt) and United States of America (Hawaii) [10]. This plant is propagated by stem cutting and grows well in drained soil with enough water. Height of plant can reach up to 1 meter or more after five months [11]. In culinary, fresh or dried leaves were used as a food additive to enhance flavour and aroma in marinate meats, fritter, wine and beer as well as to increase a shelf life of food [12-14].