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EFFECT OF COOKING ON ORGANIC AND CONVENTIONAL SRI LANKAN GREEN VEGETABLE LEAVES; DETERMINING THE ANTIOXIDANT, ANTIMICROBIAL AND NITRATE CONTENT
V. Vimalendran and M. Kandiah*
Department of Biomedical Science, School of Science, BMS, 591 Galle road, Colombo 06. Sri Lanka
Consumption of organic and conventional green leaves in Sri Lanka is greatly highlighted towards its economical demand but the awareness of both the cultivation methods is still not clear. Organic green leaves provide a positive significance towards health and safety as there is no usage of pesticides and inorganic fertilizers whereas, conventional samples occupy a higher usage of inorganic nitrogen fertilizers. This brings out a major outbreak of food borne diseases. Cooking green leaves is popular in Sri Lanka, as it is consumed after cooking in different methods but the nutritional content could change as it gets treated by heat and eventually loses the positive impact of consuming green leaves. Moreover, organic green leaves occupy a greater content of phytophenols leading to a higher content of antioxidants and a stronger antimicrobial activity against bacterial strains whereas, conventional samples do show an antioxidant capacity and antimicrobial activity. Yet vegetable sellers could indeed sell fake organic products to increase the demand. This research is carried out to distinguish organic and conventional vegetable leaves by using Nitrate content assay and to identify the effect of cooking treatment on their antioxidant and antimicrobial capacity. Five organic and conventional green leaves such as mint (Mentha), parsley (Petroselinum crispum), gotukola (Centella asiatica), kankung (Ipomoea aquatica) and muhunuwenna (Alternanthera sessilis) were chosen from the local market in Colombo, Sri Lanka for this study. Antioxidant activity were assessed by total phenolic content (TPC), total flavonoid content (TFC), total antioxidant content (TAC) and radical scavenging activity were determined by assessing 1,1-Diphenyl-2-picrylhydrazyl Assay (DPPH), Ferric reducing antioxidant power assay (FRAP) and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid (ABTS) and Inhibitory concentration assay (IC 50). Antimicrobial activity was carried out by well diffusion technique against Staphylococcus aureus and Escherichia coli. As the results of this research proved that, raw mint had higher antioxidant levels compared to the heat treated samples.
Keywords: Antioxidant, organic, conventional, antimicrobial, phytophenols and cooking.
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