Synergistic Effect of Lupeol from Kri (Glochidion daltonii Kurz) with Tetracycline against Opportunistic Bacteria

Abstract

The isolation of natural products from crude hexane of the leaves of Glochidion daltonii Kurz were carried out by chromatographic techniques. One pure compound obtained as white crystal with melting point 214-215 °C. The structure was identified by spectroscopic techniques, ¹H NMR, ¹³C NMR, DEPT-90, and DEPT-135. The comparison between those spectra and the reference spectra of triterpenoids, confirmed that the pure compounds was Lupeol. Then, Lupeol was evaluated the antibacterial activity against opportunistic bacteria. It was found that Lupeol could inhibit the growth of ten species of opportunistic bacteria, studied in this project, except Bacillus subtilis. The Combination of Lupeol with tetracycline, showed synergistic effect against Pseudomonas aeruginosa with FICI value of 0.27. Also, partially synergistic effect was found against Escherichia coli ATCC 25922 with FICI value of 0.56. The times that could inhibit the growth of P. aeruginosa and E. coli ATCC 25922 were at the sixth and the fourth hour, respectively, from starting the inoculums of Lupeol with tetracycline.