Background: Due to the increasing antibiotic resistant Cutibacterium acnes, studies have substantiated the effectiveness of botanical extracts to inhibit C. acnes. Both Phyllanthus emblica L. leaves and Garcinia mangostana L. peels have good efficacy in inhibiting C. acnes growth. However, the combination of both herbal extracts on antimicrobial synergistic activities has not been studied.

Objective: To perform an in vitro study of synergistic activities of Phyllanthus emblica L. leaves and Garcinia mangostana L. peels crude extracts to C. acnes.

Materials and Methods: The present report was an experimental, cross-sectional study. Seventy isolates of C. acnes from clinical isolations were tested with each crude extract by agar well diffusion method to evaluate minimum inhibition zone (MIZ) and broth microdilution method to evaluate minimum inhibitory concentration (MIC). Thirty-five isolates of C. acnes were tested with the combination of both extracts by antimicrobial synergy study-checkerboard testing to evaluate fractional inhibitory concentration (FIC).

Results: The medians (Q1, Q3) MIZ of P. emblica and G. mangostana at 5 mg/mL were 15.75 (12.00, 18.50), and 10.00 (10.00, 15.00) mm, respectively, with significant difference (p<0.001). The medians (Q1, Q3) MIC of P. emblica and G. mangostana were 0.078 (0.039, 0.156), and 0.078 (0.078, 0.078) mg/mL, respectively, without significant difference (p=0.327). The checkerboard testing showed FIC indices of 0.192 to 3.333. The synergy activity was 62.86% of the synergy group, 37.14% of the non-synergy group, and none of antagonism, without significant difference between resistant C. acnes and susceptible C. acnes (p=0.708).

Conclusion: Both P. emblica leaves and G. mangostana peels crude extracts could inhibit resistant and susceptible C. acnes. The combination of both herbal extracts increases antimicrobial synergistic activity, suggesting a utilization of these herbs in combination therapy against antibioticresistant C. acnes.

Keywords: Phyllanthus emblica L.; Garcinia mangostana L.; Antimicrobial synergistic activity; Cutibacterium acnes; Crude extract

DOI: 10.35755/jmedassocthai.2022.03.13273

Received 1 November 2021 | Revised 1 February 2022 | Accepted 1 February 2022