Hindawi Publishing Corporation Advances in Pharmacological Sciences Volume 2013, Article ID 926047, 6 pages http://dx.doi.org/10.1155/2013/926047 Research Article Antioxidative Properties and Inhibition of Key Enzymes Relevant to Type-2 Diabetes and Hypertension by Essential Oils from Black Pepper Ganiyu Oboh, Ayokunle O. Ademosun, Oluwatoyin V. Odubanjo, and Ifeoluwa A. Akinbola Functional Foods and Nutraceuticals Unit, Department of Biochemistry, Federal University of Technology, P M B. 704, Akure 340001, Nigeria Correspondence should be addressed to Ganiyu Oboh; goboh2001@yahoo.com Received 12 August 2013; Accepted 2 October 2013 Academic Editor: Mustafa F. Lokhandwala Copyright © 2013 Ganiyu Oboh et al. his is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. he antioxidant properties and efect of essential oil of black pepper (Piper guineense) seeds on -amylase, -glucosidase (key enzymes linked to type-2 diabetes), and angiotensin-I converting enzyme (ACE) (key enzyme linked to hypertension) were assessed. he essential oil was obtained by hydrodistillation and dried with anhydrous Na 2 SO 4 , and the phenolic content, radical [1,1-diphenyl-2 picrylhydrazyl (DPPH), 2,2  -azino-bis(3-ethylbenzthiazoline-6-sulphonic acid) (ABTS) and nitric oxide (NO)] scavenging abilities as well as the ferric reducing antioxidant property (FRAP) and Fe 2+ -chelating ability of the essential oil were investigated. Furthermore, the efect on -amylase, -glucosidase, and ACE enzyme activities was also investigated. he characterization of the constituents was done using GC. he essential oil scavenged DPPH ∗ , NO ∗ , and ABTS ∗ and chelated Fe 2+ . -Pinene, -pinene, cis-ocimene, myrcene, allo-ocimene, and 1,8-cineole were among the constituents identiied by GC. he essential oil inhibited -amylase, -glucosidase, and ACE enzyme activities in concentration-dependent manners, though exhibiting a stronger inhibition of -glucosidase than -amylase activities. Conclusively, the phenolic content, antioxidant activity, and inhibition of -amylase, -glucosidase, and angiotensin-1 converting enzyme activities by the essential oil extract of black pepper could be part of the mechanism by which the essential oil could manage and/or prevent type-2 diabetes and hypertension. 1. Introduction Essential oils from aromatic spice plants have been shown to be good antioxidants using various antioxidant assay models [1–3] and the antioxidant activities have been linked to the phenolic contents in some of the oils [4, 5]. Fur- thermore, some medicinal properties of essential oils from aromatic spice plants have been established, especially essen- tial oils from black pepper (Piper guineense) seeds which have been shown to have antimicrobial, antihypertensive, anticonvulsive, and sedative activities [5–7]. Black pepper (Piper guineense) is a spicy plant whose essential oils from the seed and leaves are being extracted and sold in commercial quantities in many countries [8]. Monoterpenes, benzoids, and sesquiterpenes have been identiied among the volatile compounds of the black pepper [9]. In recent years, the management of type-2 diabetes and hypertension through natural sources has been done in two major ways: the scavenging of free radicals and inhibition of key enzymes involved in starch digestion (-amylase and - glucosidase) and high blood pressure (angiotensin-1 convert- ing enzyme). Diabetes has been associated with an increased generation of free radicals and defective antioxidant defense systems [10, 11]. Furthermore, oxidative stress has been impli- cated in the diabetogenic process and in the physiological efects of diabetes [12, 13]. herefore, antioxidant-rich foods have a good dietary intervention in the management of type- 2 diabetes. -Amylase and -glucosidase are two key enzymes that are therapeutic targets in the management of diabetes [14]. hese two enzymes are involved in the breakdown of starch to glucose, thereby increasing the amount of glucose in the