Research Article Effects of a Proprietary Standardized Orthosiphon stamineus Ethanolic Leaf Extract on Enhancing Memory in Sprague Dawley Rats Possibly via Blockade of Adenosine A 2A Receptors Annie George, 1 Sasikala Chinnappan, 1 Yogendra Choudhary, 2 Vandana Kotak Choudhary, 2 Praveen Bommu, 2 and Hoi Jin Wong 1 1 Biotropics Malaysia Berhad, Lot 21 Jalan U1/19, Section U1, Hicom-Glenmarie Industrial Park, 40150 Shah Alam, Selangor, Malaysia 2 Ethix Pharma Laboratories, Karbala Road, Bilaspur 495001, Chhattisgarh, India Correspondence should be addressed to Annie George; annie.g@biotropicsmalaysia.com Received 26 June 2015; Revised 26 September 2015; Accepted 27 September 2015 Academic Editor: Gerald Munch Copyright © 2015 Annie George et al. Tis 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. Te aim of the study was to explore a propriety standardized ethanolic extract from leaves of Orthosiphon stamineus Benth in improving impairments in short-term social memory in vivo, possibly via blockade of adenosine A 2A receptors (A2AR). Te ethanolic extract of O. stamineus leaves showed signifcant in vitro binding activity of A2AR with 74% inhibition at 150 g/ml and signifcant A2AR antagonist activity with 98% inhibition at 300 g/mL. A signifcant adenosine A 1 receptor (A1R) antagonist activity with 100% inhibition was observed at 300 g/mL. Its efect on learning and memory was assessed via social recognition task using Sprague Dawley rats whereby the ethanolic extract of O. stamineus showed signifcant ( < 0.001) change in recognition index (RI) at 300 mg/kg and 600 mg/kg p.o and 120 mg/kg i.p., respectively, compared to the vehicle control. In comparison, the ethanolic extract of Polygonum minus aerial parts showed small change in infexion; however, it remained insignifcant in RI at 200 mg/kg p.o. Our fndings suggest that the ethanolic extract of O. stamineus leaves improves memory by reversing age-related defcits in short-term social memory and the possible involvement of adenosine A 1 and adenosine A 2A as a target bioactivity site in the restoration of memory. 1. Background Orthosiphon stamineus Benth (Lamiaceae) is a herbaceous perennial plant, widely distributed throughout the tropical regions, especially in Southeast Asia. It is commonly known as cat’s whiskers. It is also known as misai kuching in Malaysia and kumis kuching in Indonesia [1]. It is referred to as java tea and consumed as an herbal tea in Europe for urinary fushing (European Herbal Pharmacopoeia). Te leaves of O. stamineus are traditionally used in South East Asia for a variety of ailments such as bladder and kidney disease (due to its strong diuretic efect), detoxifcation, relieving joint stifness and infammation including arthritis and rheumatism, gout, treating catarrh of the bladder, eliminating stones from the bladder, and treating diabetes mellitus [2, 3]. Scientifc studies have further reported the herb to possess anti-infammatory [4], antioxidant [5, 6], antibacterial [7], hepatoprotective [8], diuretic [9], antihypertensive [10], and hypoglycemic efects [11]. Several classes of bioactive compounds such as favonoids, diterpenes, triterpenes, saponins, sterols organic acids, cafeic acids derivatives, chromenes, and oleanic and ursolic acid are known for O. stamineus [12–16]. Recent studies have emerged on the favonoids of O. stamineus possessing antagonist activity on adenosine A 1 receptors (A1R) [17]. While the study focused more on the role of the receptors in diuretic activity, adenosine receptors in the central nervous system have also been implicated in the modulation of cognitive functions [18]. While the A1R antagonist activity has been reported in O. stamineus, A2AR antagonist activity was not. Hindawi Publishing Corporation Evidence-Based Complementary and Alternative Medicine Volume 2015, Article ID 375837, 9 pages http://dx.doi.org/10.1155/2015/375837