Anti-cryptococcal activity of ethanol crude extract and hexane fraction from Ocimum basilicum var. Maria bonita: mechanisms of action and synergism with amphotericin B and Ocimum basilicum essential oil.
BACKGROUND
Ocimum basilicum L. (Lamiaceae) has been used in folk medicine to treat headaches, kidney disorders, and intestinal worms.


OBJECTIVE
This study evaluates the anti-cryptococcal activity of ethanol crude extract and hexane fraction obtained from O. basilicum var. Maria Bonita leaves.


METHODS
The MIC values for Cryptococcus sp. were obtained according to Clinical and Laboratory Standards Institute in a range of 0.3-2500 μg/mL. The checkerboard assay evaluated the association of the substances tested (in a range of 0.099-2500 μg/mL) with amphotericin B and O. basilicum essential oil for 48 h. The ethanol extract, hexane fraction and associations in a range of 0.3-2500 μg/mL were tested for pigmentation inhibition after 7 days of treatment. The inhibition of ergosterol synthesis and reduction of capsule size were evaluated after the treatment with ethanol extract (312 μg/mL), hexane fraction (78 μg/mL) and the combinations of essential oil + ethanol extract (78 μg/mL + 19.5 μg/mL, respectively) and essential oil + hexane fraction (39.36 μg/mL + 10 μg/mL, respectively) for 24 and 48 h, respectively.


RESULTS
The hexane fraction presented better results than the ethanol extract, with a low MIC (156 μg/mL against C. neoformans T444and 312 μg/mL against C. neoformans H99 serotype A and C. gattii WM779 serotype C). The combination of the ethanol extract and hexane fraction with amphotericin B and essential oil enhanced their antifungal activity, reducing the concentration of each substance needed to kill 100% of the inoculum. The substances tested were able to reduce the pigmentation, capsule size and ergosterol synthesis, which suggest they have important mechanisms of action.


CONCLUSIONS
These results provide further support for the use of ethanol extracts of O. basilicum as a potential source of antifungal agents.
a Department of General Microbiology , Institute of Microbiology Paulo de Góes, Federal University of Rio de Janeiro , Rio de Janeiro , Brazil.|b Postgraduate Program in Plant Biotechnology , Federal University of Rio de Janeiro , Rio de Janeiro , Brazil.
Nathalia N R
NN
Cardoso
a Department of General Microbiology , Institute of Microbiology Paulo de Góes, Federal University of Rio de Janeiro , Rio de Janeiro , Brazil.|b Postgraduate Program in Plant Biotechnology , Federal University of Rio de Janeiro , Rio de Janeiro , Brazil.
Celuta S
CS
Alviano
c Department of Agronomy , Federal University of Sergipe , São Cristóvão , Brazil.
Arie F
AF
Blank
c Department of Agronomy , Federal University of Sergipe , São Cristóvão , Brazil.
Maria de Fátima
MF
Arrigoni-Blank
a Department of General Microbiology , Institute of Microbiology Paulo de Góes, Federal University of Rio de Janeiro , Rio de Janeiro , Brazil.
Maria Teresa V
MT
Romanos
a Department of General Microbiology , Institute of Microbiology Paulo de Góes, Federal University of Rio de Janeiro , Rio de Janeiro , Brazil.
Marcel M L
MM
Cunha
d Research Institute of Natural Products , Federal University of Rio de Janeiro , Rio de Janeiro , Brazil.
Antonio Jorge R
AJ
da Silva
a Department of General Microbiology , Institute of Microbiology Paulo de Góes, Federal University of Rio de Janeiro , Rio de Janeiro , Brazil.
Daniela S
DS
Alviano
D000666:Amphotericin B / Q000494:pharmacology*; D000818:Animals; D000935:Antifungal Agents / Q000302:isolation & purification / Q000494:pharmacology*; D003455:Cryptococcus neoformans / Q000187:drug effects* / Q000254:growth & development / Q000378:metabolism; D004357:Drug Synergism; D004875:Ergosterol / Q000096:biosynthesis; D000431:Ethanol / Q000737:chemistry*; D006586:Hexanes / Q000737:chemistry*; D051379:Mice; D008826:Microbial Sensitivity Tests; D050296:Microbial Viability / Q000187:drug effects; D031339:Ocimum; D018649:Ocimum basilicum / Q000737:chemistry*; D008517:Phytotherapy; D010858:Pigmentation / Q000187:drug effects; D010936:Plant Extracts / Q000302:isolation & purification / Q000494:pharmacology*; D018515:Plant Leaves / Q000737:chemistry; D010938:Plant Oils / Q000302:isolation & purification / Q000494:pharmacology*; D010946:Plants, Medicinal; D000067996:RAW 264.7 Cells; D012997:Solvents / Q000737:chemistry*; D013997:Time Factors
D000935:Antifungal Agents; D006586:Hexanes; D010936:Plant Extracts; D010938:Plant Oils; D012997:Solvents; D000431:Ethanol; D000666:Amphotericin B; C080118:ocimum oil; C051168:basil oil; D004875:Ergosterol
Basil; Cryptococcus neoformans; antifungal activity; drug synergism; ergosterol