Synergistic effect of α-mangostin on antibacterial activity of tetracycline and erythromycin against acne involved bacteria

During the last decade, bacterial resistance to antibiotics has become a public health crisis throughout the world. α-Mangostin is a major bioactive xanthone found in the pericarps of Garcinia mangostana L. It has been used as an antibacterial agent, especially in anti-acne preparations made from the extract of G. mangostana. The aim of the present study was to conduct a synergistic evaluation of α-mangostin with both tetracycline and erythromycin against bacteria involved in acne production, namely: Propionibacterium acnes and Staphylococcus aureus. In this study, α-mangostin was purified from the dichloromethane extract of G. mangostana pericarp using silica gel column chromatography. A broth microdilution method was used to determine the minimum inhibitory concentration (MIC) of α-mangostin and the antibiotics. Synergistic effects on antibacterial activity were determined at their own MIC using a checkerboard method and a time-kill assay at 37 °C for 24h. α-Mangostin showed antibacterial activity against P. acnes and S. aureus with MIC values of 0.78 and 3.13 µg/mL, respectively. Tetracycline and erythromycin exhibited antibacterial activity against P. acnes and S. aureus with MIC values of 1.56 and 0.12, and 0.39 and 0.78 µg/mL, respectively. The results of the checkerboard assay showed that α-mangostin produced synergistic effects with both antibiotics against P. acnes and S. aureus, with a fractional inhibitory concentration index (FICI) ranging from 0.076 – 0.31. Moreover, time-kill curve data indicated that α-mangostin increased the antibacterial activity of tetracycline and erythromycin against the tested bacteria. These findings suggest that α-mangostin may be used to enhance the antibacterial activity of tetracycline and erythromycin against bacteria involved in acne production.