The prohibition of antibiotics has led to extensive research and use of phytogenic feed additives. James Barrie Kirkpatrick described four subspecies of eucalyptus (family Myrtaceae), including Eucalýptus globulus, in 1974. The maximum concentrations of quercetin-3D-glycoside (1703.30 g/mL), astragalin (1737.82 g/mL), chlorogenic acid (342.14 g/mL), catechin (282.54 g/mL), rosmarinic acid (36.39 g/mL), and 3,4-dihydroxybenzoic acid (27.55 g/mL) were found in samples of ultrasonic extraction with ethyl alcohol (extraction module 1:5, temperature of 32 °C, an ultrasonic exposure time of 25 min). Antimicrobial activity was observed in all studied samples after 12 h of incubation (against gram-positive (Bacillus subtilis) and gram-negative (Pseudomonas aeruginosa) bacteria, as well as representatives of yeast fungi (Candida albicans)); a more pronounced antimicrobial effect (lysis zone) was observed after ultrasonic processing of extracts for 20 and 25 min. Bacillus subtilis, Pseudomonas aeruginosa, and Candida albicans had lysis areas of 10.0 mm (20 min extraction with ultrasonic treatment), 13.0 mm (20 min extraction without ultrasonic treatment), and 15.5 mm (25 min extraction with ultrasonic treatment), respectively. E. globulus was demonstrated to be a source of biologically active phenolic compounds with antibacterial and fungicidal activity. More research on the use of E. globulus in feed additives is required.
Keywords: antimicrobial and fungicidal activity; biologically active substances; eucalyptus extracts; phytogenic feed additives; ultrasonic treatment.