Vojkan M. Miljković^1,, Ivana Nešić², Milan Z. Momčilović³, Jelena Mrmošanin⁴, Ivana Gajić¹, Jelena Zvezdanović¹, Milena Miljković⁴

The aim of this work is to give in one place as much information as possible on red grapefruit (Citrus paradisi Macf.) present on Serbian market. In order to provide chemical composition UHPLC-ESI-MS was employed for both polar and non-polar red grapefruit extracts obtained with solvent mixture consisting of hexane, acetone, and ethanol in volumes ratio 2:1:1, respectively and 0.05% (w/v) butylated hydroxytoluene. In addition, total content of lycopene, β-carotene, total polyphenols, and flavonoids content were determined by the means of UV-Vis spectrophotometry. The antioxidant activity of the samples was tested by applying four different methods: ABTS, DPPH, FRAP, and CUPRAC. In the chemical profile of the red grapefruit, 11 compounds of interests were identified by UHPLC method and they all were correlated to antioxidant and antimicrobial activity. The antimicrobial activity was tested against gram-positive (Staphylococcus aureus, Enterococcus faecalis, Bacillus cereus) and gram-negative (Escherichia coli, Salmonella enteritidis, Enteroabacter aerogenes, Pseudomonas aeruginosa) bacteria and yeast Candida albicans. The obtained results are as follows: lycopene, β-carotene, total polyphenols, and flavonoids content 34.2 mg/kg fruit weight, 18.6 mg/kg fruit weight, 298 mgGAE/kg fruit weight, 216.4 mgCE/kg 216.4, respectively; antioxidant activity by: ABTS 1.8 mmol of TE/kg of sample, DPPH 0.72 mmol of TE/kg of sample, FRAP 9.7 µmol of Fe²⁺ equivalents/kg of the sample, CUPRAC 4.66 mmol of TE/kg of sample; and they are the basis for explanation of antimicrobial activity obtained in this work. Results obtained in this study are recommending red grapefruit in everyday diet as valuable source of health beneficial bioactive compounds.

red grapefruit, lycopene, β-carotene, antimicrobial activity