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.

This research aimed to optimize the extracting condition of banana peel (BP) and to investigate the effect of organic banana peel extract (BPE) on the immunity of giant freshwater prawn (Macrobrachium rosenbergii). The result demonstrated that the optimum extracting condition of organic BPE was 50% v/v of methanol at 100°C for 10 min. Under this condition, the maximum total phenolic content and extraction yield of 10.44 mg of gallic acid equivalents (GAE) per g of dry matter (mg GAE/g DM) and 33% w/v were obtained respectively. The organic BPE could inhibit an aquatic pathogen Aeromonas hydrophila at the minimum inhibitory concentration of 625 µg/disc. The main phytochemicals in organic BPE showed two major biological functions, which are antioxidant and antipathogenic activities. Subsequently, the effects of organic BPE on the immunity of M. rosenbergii were investigated. The results demonstrated that the organic BPE could increase immunity and phagocytic activity and decrease the susceptibility of M. rosenbergii. Moreover, the organic BPE could also increase total as well as differential haematocyte count, decrease the coagulation time and increase the total protein in serum of M. rosenbergii. The phagocytic activity of prawn was enhanced to 82.00% by using an organic BPE at 6 µg/g. At the same time, the cumulative mortality was declined to lower 20% after 6 days of organic BPE injection. In conclusion, organic BPE can be a potential immunostimulant in giant freshwater prawn culture. The utilization of BP in aquaculture can further add the value of BP and reduce organic pollutants.