Background: Nowadays, the prevalence of antibiotic-resistant Propionibacterium acnes [P. acnes] has been increasing continuously due to easy access to use monotherapy antibiotics in Thailand. According to the recent study of antibiotic-resistant P. acnes in Thai population, the prevalence of these bacterial resistance to antibiotics has been highly emerging, particular to clindamycin and erythromycin. Numerous botanical extracts have been shown to have antimicrobial activities because of their phytochemical compounds such as tannins, phenols, flavonoids, etc.

Objective: To perform an in-vitro study of antimicrobial activities of some herbal crude extracts against clinical isolated P. acnes.

Materials and Methods: The present report was an experimental, cross-sectional study. Seventy-five P. acnes specimens from clinical isolations were collected. Punica granatum L. peels, Phyllanthus emblica L. leaves, and Curcuma longa L. rhizomes were extracted with 95% ethanol by maceration methods for 3 days and repeated the procedure twice. Then crude extracts were collected. P. acnes were tested with the herbal crude extracts by agar well diffusion assay to evaluate minimum inhibition zone [MIZ] and broth microdilution method to evaluate minimum inhibitory concentration [MIC]. Then, the authors produced the lotion products of each crude extract and their MIZ activity was tested.

Results: The means MIZ of Phyllanthus emblica L. at 5 mg/ml and 10 mg/ml were 14.99 and 20.90 mm, respectively. For Punica granatum L., the means MIZ at the concentration of 5 and 10 mg/ml were 4.07 and 9.95 mm. On the other hand, no inhibition zone was seen among Curcuma longa L. rhizomes crude extract. The means MIC of each crude extract from Phyllanthus emblica L., Punica granatum L., and Curcuma longa L. were 0.559, 1.003, and 3.804 mg/ml, respectively. Concerning the difference in the MIC activities of each extract, there was no statistically significant difference between Phyllanthus emblica L. and Punica granatum L. (p = 0.092). However, there was significant difference between Phyllanthus emblica L. with Curcuma longa L. (p<0.001) and Punica granatum L. with Curcuma longa L. (p<0.001) as well. The lotion products of each crude extract were turbid and had strong smell. The MIZ of the lotion of Phyllanthus emblica L., Punica granatum L. were 21.67 and 17.25 mm, respectively, without statistical significant difference. However, no inhibition zone was seen in the lotion of Curcuma longa L.

Conclusion: These three crude herbal extracts could inhibit the growth of clinical isolated P. acnes. The extract of Phyllanthus emblica L. leaves had the best antimicrobial activity following by Punica granatum L. peels and Curcuma longa L. rhizomes.

Keywords: Propionibacterium acnes, Antibacterial activities, Punica granatum L., Phyllanthus emblica L., Curcuma longa L., Acne vulgaris