Research Journal of Biotechnology Vol. 16 (8) August (2021) Res. J. Biotech 1 Antioxidant and Antibacterial Activities of Phytochemicals in Methanolic Extracts of Five Underutilized Leafy Vegetables Raj Adarsha 1 , Sikdar Bratati 1 , Roy Alokesh 1 , Mukhopadhyay Asish Kumar 2 and Roy Sudipta 1* 1. Department of Botany, University of Kalyani, Kalyani, Nadia, 741235 West Bengal, INDIA 2. Division of Bacteriology, National Institute of Cholera and Enteric Diseases, P-33, C.I.T. Road, Kolkata-700010, INDIA *dr.sudiptaroy@gmail.com Abstract Leafy vegetables are important for their nutritive and medicinal values. However, many of them are less explored and underutilized. The present study evaluates the antioxidant and antibacterial activities present in five underutilized leafy vegetables such as Alternanthera philoxeroides, Boerhavia diffusa, Enydra(=Enhydra) fluctuans, Glinus oppositifolius, and Suaeda maritima. Methanolic extracts from leafy edible parts of these plants possessed diverse phytochemicals. Of these plants, the polyphenol contents like total phenolic (TPC), total flavonoid (TFC), and total tannin (TTC) were the highest in E. fluctuans with significant variations concerning other plants. Also, the antioxidant activities of E. fluctuans were greater comparing other plants; the parameters were the total antioxidant activity (TAA), ferric reducing power assay, and ability to scavenge DPPH, ABTS, and superoxide radicals. The effect of varying extract-quantities revealed the highest antibacterial activity of the E. fluctuans extracts with substantial inhibition zones against six bacterial strains. Accordingly, the E. fluctuans extracts showed the lowest MIC (2.75±0.35 mg ml -1 ) and MBC (3.50±0.71 mg ml -1 ), albeit with significant variations with ampicillin. The study highlights that these plants are the untapped repertoires of natural antioxidants and antimicrobials for dietary and therapeutic uses. Keywords: Antimicrobial, E. fluctuans, Leafy species, Phenolics, Radical scavenging. Introduction Leafy vegetables are a rich source of nutrition. Humans have used these from the early days of civilization as food and other well-beings. 43 Among these leafy species, a large number of plants are still underutilized. The possible reasons are their restricted dietary usage in a particular area, lack of global recognition, and limited exploitation of health benefits. 51 A vast majority of underutilized leafy species grow naturally as weeds in the fallow lands. These are cheaper in market value compared to commercially grown vegetables. 8 Due to the higher nutritional values of many such leafy vegetables, the underprivileged ethnic groups in rural areas * Author for Correspondence traditionally use these plants, especially during scarcity of food. 18 Apart from their higher nutrient and micronutrient contents, these plants also possess an ample amount of natural antioxidants like vitamins, polyphenols etc. which minimize oxidative damage. 47 A good number of studies also highlighted the health benefits of these leafy species in nutritional deficiency, digestive disorders, microbial infections, diabetic complications, hepatoprotection, and cardiovascular diseases. 22,25,31 Antioxidant molecules scavenge reactive oxygen species (ROS) during oxidative stress of an organism is maintaining a balance between oxidation and anti-oxidation. 13 The natural antioxidants primarily come from different plant parts. The leaves contribute a major share of it. The natural antioxidants of plant origin are mainly polyphenols (phenolic acids, flavonoids, tannins, anthocyanins, lignans, and stilbenes), carotenoids and vitamins. 16 Plant-derived antioxidants manifest diverse biological effects that include antibacterial, antiviral, anti-inflammatory, anti-analgesic, anticancer, anti-ageing etc. 45 Pharmacologically important plant-derived compounds, secondary metabolites, play an important role in plant defence against many bacterial diseases. 17 Antibiotics are the prime therapeutic agents in combating bacterial infections for several decades. However, their indiscriminate use led to the development of various antibiotic-resistant bacterial strains. 15 The situation has worsened in recent times due to the emergence of multidrug-resistant bacteria. 16 It prompted the researchers to explore novel antimicrobials from plant origin. The phytomedicines from phytochemicals have emerged as the new therapeutic targets against microbes. These are safe, reliable and cheaper than synthetic drugs. Most importantly, these have few or no side effects. 21 The study includes five underutilized leafy plant species namely Alternanthera philoxeroides (Mart.) Griseb. (Family: Amaranthaceae), Boerhavia diffusa L. (Family: Nyctaginaceae), Enydra fluctuans DC. (Family: Asteraceae: = Enhydra fluctuans Lour.), Glinus oppositifolius (L.) Aug. DC (Family: Molluginaceae) and Suaeda maritima (L.) Dumort. (Family: Amaranthaceae), which are commonly used as green vegetables in different locales and are known for their medicinal values.