‘ICPCR’ hosted by Faculty of Pharmacy, Universitas Sumatera Utara, Medan, Sumatera Utara, Indonesia 03 November 2017 Vol 11, Special issue 1, 2018 Online - 2455-3891 Print - 0974-2441 EFFECT OF HARVESTING TIME AT MORNING, AFTERNOON, AND EVENING ON NITRATE AND NITRITE LEVEL IN SPINACH (AMARANTHUS TRICOLOR L.) AND MUSTARD (BRASSICA RAPA L.) NAHITMA GINTING, JANSEN SILALAHI, TUTY ROIDA PARDEDE, SUDARMI SUDARMI, NERDY NERDY* Department of Pharmaceutical Chemistry, Faculty of Pharmacy, Universitas Sumatera Utara, Medan, Indonesia. Email: nerdy190690@gmail.com Received: 07 March 2018, Revised and Accepted: 25 March 2018 ABSTRACT Objective: The objective of this study is to determine the effect of harvesting time at morning, afternoon, and evening on nitrate and nitrite level in spinach and mustard. Methods: Nitrite identification was done using sulfanilic acid reagent and N-(1-naphthyl) ethylenediamine dihydrochloride. Identification of nitrate was done using reagent ferrous sulfate. Determination of nitrites level was performed visible spectrophotometry using N-(1-naphthyl) ethylenediamine dihydrochloride at maximum wavelength of 540 nm. Nitrate determination is taken with the same method but started with reduction process from nitrate into nitrite using Zn powder in acid condition and then measured as nitrite. Results: Research result shows that there is a change of nitrate and nitrite level from the spinach harvested at morning, afternoon, and evening. Conclusion: Spinach and mustard are better harvested in the morning because it contains nitrite less than in spinach picked afternoon and evening. Level of nitrite increases from morning to afternoon and decreases from afternoon to evening. However, the level of nitrate decreases from morning to afternoon and increases from afternoon to evening. Keywords: Harvesting time, Nitrate, Nitrite, Spinach, Mustard. INTRODUCTION Vegetables have been used since thousands of years ago to be consumed and processed naturally without using any mixture. The content of nutrients such as vitamins and minerals most sourced from vegetables [1]. One type of vegetables that many people favored are spinach and mustard because it has a soft texture, easy in the can, the price is relatively cheap, and how the cultivation is easy. Spinach and mustard are very good for children, especially babies. For babies, spinach and mustard usually mix with steam rice. Spinach and mustard also speed up the healing process for the sick [2]. Vegetables are rich in mineral salts such as calcium, phosphorus, and iron. Spinach also contains several vitamins, such as Vitamins A, B, C, and E. Vegetables also contain nitrite and nitrate that are harmful to the body [3]. The amount of intake allowed (FAO/WHO acceptable daily intake = ADI) for 60 kg body weight is 80 mg nitrite and 220 mg of nitrate. Consuming lots of vegetables is highly recommended, but considering the very high nitrate content in vegetables, it is considering the potential of nitrosamine formation from nitrite [4]. Previous research has shown a change in nitrite and nitrate contents in fresh and boiled vegetables. Nitrite and nitrate levels in vegetables have decreased, after boiling for 15 min. Nitrite levels increased from storage time, while for nitrate content decreased [5]. Vegetables with urea fertilizer have a higher nitrite and nitrate levels when compared with vegetables that without urea fertilizer [6]. The nitrate content in the plant is influenced by soil treatment, the amount and time of nitrogen fertilizer application, temperature, light intensity, harvest time, plant diseases, canning, and storage process [7]. The intensity of light is very influential on the rate of photosynthesis. The rate of photosynthesis will increase with the increase of light intensity, thus affecting the nitrate and nitrite levels in plants (Lakitan, 1995). Photosynthesis is the process of synthesis of sugars (carbohydrates) from inorganic materials, carbon dioxide (CO 2 ), and water (H 2 O) in pigmented plants with the help of solar energy [8]. Photosynthesis is closely related to the assimilation of nitrate, the formation of nitrate ions (NO 3− ) into nitrite ions (NO 2− ), ammonia (NH 3 ), and amino acids [9]. The purpose of this study was to determine the effect of harvesting time (morning, afternoon, and evening) on nitrite and nitrate levels in spinach (Amaranthus tricolor L.) and mustard (Brassica rapa L.). MATERIALS AND METHODS Methods The method used in this study is an experimental research method and is used to determine the nitrite and nitrate levels in spinach and mustard that have been harvested in the morning, afternoon, and evening. Samples were planted by researchers with harvest age of 20 th day, 23 rd day, and 26 th day. Sampling was done purposive, without comparing the sample from one place to another place, because the sample is considered homogeneous [10]. Materials The materials used in this study were pro-analytical qualities of the E-Merck production, i.e., sodium nitrite, sulfanilic acid, N-(1- naphthyl) ethylenediamine dihydrochloride, glacial acetic acid, dilute hydrochloric acid, antipyrine, ferrous sulfate, concentrated sulfuric acid, and zinc powder. Tools The tools used in this research are one unit of ultraviolet-visible spectrophotometer (Shimadzu), analytical balance (Boeco), glassware (Iwaki), water bath, filter paper, parchment paper, tissue, rubber ball, spatula, thermometer, test tube, tube clamp, stir bar, mortar, and pestle. Spinach and mustard planting procedures Putted humus soil media in plastic bag left for 1 week. After 1 week of spinach and mustard seeds, 3 seeds were distributed in the separated plastic bag, watered in the afternoon daily, and harvested at 20 th day, 23 rd day, and 26 th day. Research Article © 2018 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.2018.v11s1.26581