Vol 10, Issue 7, 2017 Online - 2455-3891 Print - 0974-2441 ANALYSIS OF THE ANTIOXIDANT ACTIVITY OF GERANIOL EMPLOYING VARIOUS IN-VITRO MODELS: RELEVANCE TO NEURODEGENERATION IN DIABETIC NEUROPATHY SATHYA N PRASAD 1,2 *, MURALI MURALIDHARA 2 1 Department of Biochemistry, School of Life Sciences, Vels University, Chennai, Tamil Nadu, India. 2 Department of Biochemistry and Nutrition, CSIR, Central Food Technological Research Institute, Mysuru, Karnataka, India. Email: sathya1prasad@gmail.com Received: 19 March 2017, Revised and Accepted: 14 April 2017 ABSTRACT Objective: The aim of this study was to analyze antioxidant effect of geraniol (GE) in different in vitro models. Methods: Initially, the antioxidant activity of GE was assessed by diphenyl picrylhydrazyl radical (DPPH) assay. The modulatory effect of GE against 2,2’-azobis(2-amidinopropane) dihydrochloride induced lipid peroxidation in rat brain regions (cortex and cerebellum) and sciatic nerve (SN) homogenates was determined. Further, the effect of GE was assessed against hyperglycemia-induced oxidative stress (OS) in SHSY5Y, a human neuroblastoma cell line. Results: GE proved to be a good scavenger of DPPH free radical (inhibitory concentration 50% [IC 50 ] value = 663 nmol) and could lower the lipid peroxidation levels in rat brain tissue and SN homogenates (25-40%). Further, it rescued the SHSY5Y cells from hyperglycemia-induced death. Co- exposure of GE with the IC 50 level of glucose (100 mM) lowered the levels of reactive oxygen species, hydrogen peroxides and 3-nitrotyrosine levels with concomitant elevation in the glutathione levels (about two folds). Conclusion: Collectively from these findings and other studies previously conducted (from our lab and others) emphasize the potential benefit of GE against oxidative stress (OS), a progressive pathological feature of neurodegenerative disorders. Keywords: Geraniol, Antioxidant, In vitro studies, Diabetic neuropathy. INTRODUCTION Oxidative stress (OS) has been understood as one of the prominent features leading to the progression of diabetic neuropathy (DN) and other neurodegenerative disorders (NDD) [1,2]. Development of higher levels of reactive oxygen species (ROS) and reactive nitrogenous species (RNS) is evident in the nervous tissue in various NDD such as Alzheimer’s disease (AD) and Parkinson’s disease (PD). These reactive species include hydroxyl radical, superoxide, nitric oxide, hydrogen peroxide, and peroxynitrites. Overproduction of ROS/RNS, with a concomitant, compromised antioxidant defense system results in significant protein oxidation, lipid peroxidation and nucleic acid oxidation [1]. These oxidized molecules with hampered structure/function lead to various cellular processes including inflammatory response, mitochondrial dysfunction, and possibly apoptosis in NDD [2-4]. DN is a common neurodegenerative complication with no definite pharmacological solution because of its multifactorial etiology [5]. In this scenario, plant-derived compounds with multiple target might play a role in drug discovery and development. A number of studies have demonstrated potential health-promoting properties of natural products as therapeutics for NDD [6-8]. Several epidemiological reports have documented the influence of dietary habits on lower incidence of NDD. In particular, a significant positive correlation between the consumption of polyphenolic phytochemical-rich foods and the prevention of certain neurological diseases, has been emphasized. Many bioactives such as eugenol, bacopasides, withanolide, and curcumin have been investigated for their neuroprotective function in various NDD models [9-11]. Geraniol (GE) is a bioactive belonging to the class of monoterpenoids [12]. It is found as an important constituent of essential oils of various aromatic herbs. It has a pleasant aroma and is characteristic of rose oil and citrus fruits [12,13]. It is also found in differential amounts in several herbs such as coriander and allspice. It has applications due to its aroma in food and beverage industries as a flavoring agent. It is also found in a wide range of cleansing products and cosmetics for its appealing odor [13,14]. In the recent past, several studies have recognized the pharmacological potential of GE in different models [15-17]. Its pharmacological property is by virtue of its antioxidant and anti-inflammatory properties [18,19]. However, phytochemicals in general and polyphenols, in particular, can also exert pro-oxidant activities under certain experimental conditions [20]. To date, neither pro-oxidant nor antioxidant activities have yet been clearly established to occur in humans. The mechanism through which such dietary supplementation may diminish deleterious effects taking place during degenerative processes of a given disease is not clearly understood. In this study, an attempt has been made to investigate the antioxidant potential of GE in brain and sciatic nerve (SN) homogenates. This was followed by the investigation of the modulatory potency of GE in SHSY5Y, neuroblastoma cell line, under hyperglycemic condition simulating DN. These studies were designed based on the data pertaining to the modulatory effects of GE obtained in in vivo studies from the same lab earlier [16,21]. METHODS GE, diphenyl picrylhydrazyl radical (DPPH), 2,2’-Azobis(2- amidinopropane) dihydrochloride (AAPH), KRBS reagent, thiobarbituric acid (TBA), trichloroacetic acid, glacial acetic acid, sodium nitroprusside, Griess reagent, hydrogen peroxide, Lowry’s reagent, and FC reagent were purchased from Aldrich-Sigma and SRL. All other chemicals and solvents were of analytical grade and were purchased from local suppliers of manufacturers such as Merck, Hi- media, Sigma and SRL. © 2017 The Authors. Published by Innovare Academic Sciences Pvt Ltd. This is an open access article under the CC BY license (http://creativecommons. org/licenses/by/4. 0/) DOI: http://dx.doi.org/10.22159/ajpcr.2017.v10i7.18564 Research Article