Asian Journal of Plant Biology, 2014, Vol 2, No 6, 28-31. - 28 - Short Communication Screening of Heavy Metals in Selected Vegetables using the Papain Inhibitive Assay Masdor, N.A. 1 *, Izuan, E.H. 2 , Baskaran, G. 2 And R. Sulaiman 3 1 Biotechnology Research Centre, Mardi, P. O. Box 12301, 50774 Kuala Lumpur, Malaysia. 2 Department of Biochemistry, Faculty of Biotechnology and Biomolecular Sciences, Universiti Putra Malaysia, UPM 43400 Serdang, Selangor, Malaysia. 3 School of Food Science & Nutrition, Universiti Malaysia Sabah, Jalan UMS, 88400 Kota Kinabalu, Sabah, Malaysia *Corresponding Author: azlina@mardi.gov.my/azlina.mardi@gmail.com Noor Azlina Masdor Biotechnology Research Centre, Malaysian Agricultural Research and Development Institute Mardi, P. O. Box 12301, 50774 Kuala Lumpur, Malaysia HISTORY ABSTRACT Received: 5 th December 2014 Received In Revised Form: 24 th December 2014 Accepted:27 th December 2014 Vegetables are major source of heavy metals contaminant in the diet of humans. Currently, monitoring of heavy metals in vegetables is carried out by instruments such as Inductively- Coupled Plasma Optical Emission Spectrophotometer (ICP-OES) or Flow Injection Mercury System (FIMS). Instrumental method alone is costly, need skilled personnel and time consuming. In this work, the papain assay was used to screen for the presence of heavy metals in tweleve digested vegetables samples after neutralization. None of the non-spiked samples tested shows levels of heavy metals above the maximum residue limit (MRL) allowed for heavy metals in vegetables using both instrumental and papain assay. The papain assay was able to detect by mercury-spiked vegetable samples indicating that the assay could tolerate the high salt of the digested sample matrix. Papain assay is simple, rapid and low in cost. It requires small sample volumes and could be carried out in a microplate format. The assay can act as a preliminary screening assay. Positive samples are sent for heavy metals level using instruments. Using this approach, higher frequency and number of monitoring can be carried out. KEYWORDS heavy metals vegetables enzyme assay FIMS INTRODUCTION Malaysia, being a tropical country, is blessed with conditions that produce abundant plants that have medicinal [1–3] or agricultural values [4,5]. Studies have shown widespread contamination of heavy metals in vegetables [6], food [7,8] and herbal products [9,10]. In addition, agriproduce from ex-mining land has been shown to contain significant level of heavy metals [9] that have caused a decline in consumption of fruits from such area. Contamination of heavy metals arises from various sources such as soils, metal from the grinding machines or a coingredient contaminant [9]. Heavy metals are toxic to almost all forms of organism [11]. In humans heavy metals accumulated in organs such as the gastrointestinal tract, kidney, the nervous system, and the reproductive system [12]. As production and consumption increase, incidence of chronic heavy metals poisoning is an impending reality and its monitoring is thus immediately needed. Large scale monitoring using conventional instrumental alone is very costly and time consuming. In the environmental field, researchers have begun using biological systems and organisms to form a preliminary screening tool. Enzyme-based or microbial-based biomonitoring is an alternative modern approach compared to purely instrumental methods in detecting xenobiotics in samples. Only positive samples that show toxicity to the testing biosystem is sent for instrumental validation. This approach dramatically reduces costs and monitoring time. An equivalent system is unheard of in vegetables monitoring of heavy metals as the digestion product are highly acidic, diluted many times or if neutralized contain high salt concentration that can mask the effect of heavy metals in the sample. Previously, protease-based inhibitive assay for heavy metals based on the protease papain [13], bromelain [14] and ASIAN JOURNAL OF PLANT BIOLOGY Website: http://journal.hibiscuspublisher.com/index.php/AJPB