Chemical compounds screening of leaves extract from eleocharis dulcis (Burm.f.) trin. ex hensch and in vitro antibacterial pathogenic test for fish

Eleocharis dulcis (local name: ‘purun tikus’) is an aquatic plant endemic to Sulawesi, Indonesia. It is commonly found in the swamps of Southeast Asia. The plant presents antioxidant and antibacterial activities. The objective of this study was to evaluate the compound content and antibacterial activity of E. dulcis extracted with 70% ethanol using conventional maceration methods and with ultrasound-assisted extraction (UAE). Antibacterial activity assays were carried out using the disc diffusion method and microdilution. The evaluation of chemical compounds was conducted using GC-MS. The results showed that UAE extract had better antibacterial activity compared with extracts using traditional methods, with an inhibition zone diameter of 8.8 mm against Aeromonas hydrophila and 7 mm against Flavobacterium columnare. Minimum inhibitory concentration (MIC) values were 1.5625±0.015 mg mL^-1 against A. hydrophila and 3.125±0.011 mg mL^-1 against F. columnare and Edwardsiella ictaluri. GC-MS results determined 19 compounds in extract by the UAE method and 15 compounds by the maceration method. UAE provides better total phenolic content, antioxidant activity, and antibacterial activity. In addition, the number of compounds identified by GC-MS is more than that of the maceration method.