Abstract
Purpose: To evaluate the anticandidal activity of the ethanol extracts of 12 herbs from Thailand. Methods: The herbs studied were Alpinia galanga, Curcuma longa, Curcuma zedoaria, Mentha cordifolia, Ocimum africanum, Ocimum basilicum, Ocimum sanctum, Piper betle, Piper chaba, Piper nigrum, Piper sarmentosum and Zingiber officinale. Various Candida spp. were examined for minimal inhibitory concentration (MIC) and minimal fungicidal concentration (MFC) using microdilution method; time-kill assay was also used to assess the plants. Antibiofilm activity was investigated using a 3-[4, 5dimethyl-2-thiazolyl]-2, 5-diphenyl-2H-tetrazolium-bromide (MTT assay). Gas chromatography mass spectrometry (GC-MS) analysis, thin layer chromatography (TLC) fingerprinting and TLC-bioautography were used to determine the active anticandidal compounds. Results: All tested herbs, except extracts of P. nigrum and Limiaceae family, showed varying zones of inhibition against Candida albicans ATCC 90028. P. betle revealed the strongest anticandidal activity against all tested strains with MIC ranging from 1.56 to 3.13 mg/ml, and MFC from 3.13 to 8.33 mg/ml. Killing activity depended on time and concentrations of the extract. The concentration of P. betle extract required to inhibit ≥ 90 % biofilm formation of C. albicans ATCC 90028 was 3.13 ± 0.15 mg/ml, while that to remove ≥ 90 % biofilm growth was 12.50 ± 0.69 mg/ml. The result of GC-MS analysis showed the major compound of P. betle extract responsible for anticandidal activity as 4-chromanol. Conclusion: P. betle extract contains 4-chromanol which is a good potential anticandidal agent for the treatment of oral infectious diseases caused by certain Candida spp.
Highlights
The genus Candida contains more than 150 species, only a limited number of these species regularly cause diseases in humans [1]
Candida albicans is the main cause of oral candidiasis, non-C. albicans (NCAC) species such as Candida glabrata, Candida krusei and Candida tropicalis are frequently reported as human pathogens [2]
Experiments comparing biofilm of Candida in this study have demonstrated that higher concentrations of MBEC90 of P. betle extract (4 folds) than of MBIC90 are required to significantly remove existing biofilm cells
Summary
The genus Candida contains more than 150 species, only a limited number of these species regularly cause diseases in humans [1]. These extracts showed different inhibited zone against C. albicans ATCC 90028. The concentrations of P. betle extract required to inhibit ≥ 50 % and ≥ 90 % biofilm formation of C. albicans ATCC 90028 were 0.78 ± 0.31 mg/ml and 3.13 ± 0.15 mg/ml, respectively. It was demonstrated that there were several bands of components appeared on the TLC-plate (Figure 3B), and one major band with Rf at 0.38 gave the large inhibited clear zone against tested Candida in TLC-bioautography assay (Figure 3C). Another minor band with Rf at 0.74 matched to the standard eugenol did not show any inhibited zone. MIC – the minimum inhibitory concentration; MFC – the minimum fungicidal concentration; the values represent data obtained from three independent assays and where the appropriate mean ± S.D. is given
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