Bioscience Journal | 2021 | vol. 37, e37024 | ISSN 1981-3163 1 Thanyarat NAKSING 1 , Jantima TEEKA 2 , Wutti RATTANAVICHAI 3 , Prapaporn PONGTHAI 2 , Dolnapa KAEWPA 2 , Atsadawut AREESIRISUK 2 1 Postgraduate program in Applied Biology, Division of Biology, Faculty of Science and Technology, Rajamangala University of Technology Thanyaburi, Khlong Luang, Pathum Thani, Thailand. 2 Division of Biology, Faculty of Science and Technology, Rajamangala University of Technology Thanyaburi, Khlong Luang, Pathum Thani, Thailand. 3 Department of Fisheries Technology, Faculty of Agricultural Technology, Kalasin University, Mueang Kalasin, Kalasin, Thailand. Corresponding author: Atsadawut Areesirisuk Email: atsadawut_a@rmutt.ac.th How to cite: NAKSING, T., et al. Determination of bioactive compounds, antimicrobial activity, and the phytochemistry of the organic banana peel in Thailand. Bioscience Journal. 2021, 37, e37024. https://doi.org/10.14393/BJ-v37n0a2021-56306 Abstract Banana fruit is enriched with phytonutrients, minerals, and its peel, which is mostly discarded as waste. This research aimed to study its bioactive compound properties, antimicrobial activity, and identify and characterize the constituents of organic banana peel extract (BPE), composed of six species (i.e., Kluai Homthong, Kluai Namwa, Kluai Kai, Kluai Hukmook, Kluai Lebmuernang, and Kluai Homtaiwan). Total phenolic content (TPC), antioxidant content, and ferric-reducing antioxidant power (FRAP) were important in BPE of Kluai Kai. BPE of Kluai Hukmook could inhibit Aeromonas hydrophila and Staphylococcus aureus. The Fourier-transform infrared spectroscopy (FTIR) spectrum exposed diverse compounds of primary and secondary phytochemicals. Four main constituents, including acetic acid, formic acid, 1,2-benzenediol,3- methyl-, and 4-hydroxy-2-methylacetophone derived from gas chromatography-mass spectroscopy (GC- MS), demonstrated their antioxidant properties and antimicrobial activity. This result suggests that organic banana peel can both be applied as an antioxidant and antimicrobial substance. BPE increases the value of banana peels (BPs) and reduces the burden of its waste disposal in the environment. Keywords: Antioxidant. Antimicrobial Activity. Banana Peel Extract. Gas Chromatography-Mass Spectrometry (GC-MS). Phytochemical Components. 1. Introduction Presently, the natural compound from herbs and plants are widely used as growth-stimulating compounds, antimicrobial substances, and nutrients (Sulaiman et al. 2011). They are enriched in bioactive compounds that include fiber and phenolic compounds, which are related to antioxidant capacity. They are better than synthetic antibiotics in treating infectious disease, as they limit many of the adverse effects. Moreover, the plant extract is used as an additive in animal feed, which may provide an inexpensive agent in aquaculture, promoting survival rate, stimulating immunity, and offering greater reliability than chemotherapeutic agents. However, the side-effects and consumed doses of plant extract should be considered before utilization. Banana, belonging to the family Musaceae, is a very prevalent fruit around the world, and is eaten in many regions as a staple food (Singh et al. 2016). It is grown extensively and comprises the fifth largest agricultural food crop in terms of world trade, ranking alongside rice, wheat, and maize. It is a rich source of DETERMINATION OF BIOACTIVE COMPOUNDS, ANTIMICROBIAL ACTIVITY, AND THE PHYTOCHEMISTRY OF THE ORGANIC BANANA PEEL IN THAILAND