Coumarin mammeisin isolated from
The current pharmacotherapy used against human fungal diseases is based on azole compounds. Unfortunately, the emergence of microorganisms resistant to azole antifungals is increasing in number and patients at risk of acquiring fungal infections have created new challenges. The demand for drugs of plant origin has led to a renewed interest in pharmaceutical coumarins, chromones, and xanthones, given the fact that these substances show potent pharmacological activities and low toxicity to mammals [
Amongst the many pharmacological functions of coumarins a few stand out, such as scoparone (6,7-dimethoxy-coumarin), isolated from the Chinese plant
The genus
Chemical structure of mammeisin.
Until now, its antifungal activities had not been investigated; thus, we isolated the natural product from the stem of
Mammeisin was isolated from the stems of
The evaluation used the antifungal method for determination of minimum inhibitory concentration (MIC), according to the broth microdilution technique recommended by the CLSI document M27-A2. The methodology employed for testing antifungal activity was divided into four stages: preparation of the dilutions from all compounds tested, preparation of dilutions of the antifungal agents (in this case, ketoconazole and fluconazole), preparation of inocula with species of
The plates were incubated at 28°C and readings were taken after 48 hours to analyse the fungal growth at different courmarin concentrations against a positive control. MICs were obtained by visual reading and expressed in
In order to obtain
The results presented in this study are the average of three replicates (
The linear regression data (probit) indicated LD50 values for the lethal dose at 50% of the
Given that mammeisin demonstrated high toxicity, we proceeded to perform an antifungal assay. For the initial dilution of mammeisin, 12.0 mg was diluted in to 6.0 mL of DMSO, resulting in a concentration of 2000
In the case of the antifungal standards, 5.0 mg of either fluconazole or ketoconazole is diluted in to 5.0 mL of DMSO to give an initial solution concentration of 1000
Antifungal experiment: concentrations 512-1 are given in units of
The minimum inhibitory concentration (MIC) for mammeisin was 512
Summary of the minimum inhibitory concentration (MIC) for mammeisin and two antifungal agents.
|
ATCC | Mammeisin (CIM) | Ketoconazole (CIM) | Fluconazole (CIM) |
---|---|---|---|---|
|
2209 | 512 |
2 |
8 |
|
750 | 512 |
512 |
— |
|
2209 | 512 |
2 |
8 |
|
6258 | 512 |
2 |
64 |
— | 12 | 11 | 10 | 9 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | — |
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
|
∗ | ∗ | ∗ | ∗ | ∗ | ∗ | ∗ | ∗ | ∗ | ∗ | ∗ | ∗ | A |
|
∗ | ∗ | ∗ | ∗ | ∗ | ∗ | ∗ | ∗ | ∗ | ∗ | ∗ | ∗ | B |
|
∗ | ∗ | ∗ | ∗ | ∗ | ∗ | ∗ | ∗ | ∗ | ∗ | ∗ | ∗ | C |
|
∗ | ∗ | ∗ | ∗ | ∗ | ∗ | ∗ | ∗ | ∗ | ∗ | ∗ | ∗ | D |
|
∗∗ | ∗∗ | ∗∗ | ∗∗ | ∗∗ | ∗∗ | ∗∗ | ∗∗ | ∗∗ | ∗∗ | ∗∗ | ∗∗ | E |
|
∗∗ | ∗∗ | ∗∗ | ∗∗ | ∗∗ | ∗∗ | ∗∗ | ∗∗ | ∗∗ | ∗∗ | ∗∗ | ∗∗ | F |
|
∗∗ | ∗∗ | ∗∗ | ∗∗ | ∗∗ | ∗∗ | ∗∗ | ∗∗ | ∗∗ | ∗∗ | ∗∗ | ∗∗ | G |
|
∗∗ | ∗∗ | ∗∗ | ∗∗ | ∗∗ | ∗∗ | ∗∗ | ∗∗ | ∗∗ | ∗∗ | ∗∗ | ∗∗ | H |
|
|||||||||||||
— | C− | 512 | 256 | 128 | 64 | 32 | 16 | 8 | 4 | 2 | 1 | C+ | — |
∗∗Antifungal standard (ketoconazole/fluconazole).
C+: positive control.
C−: negative control.
To conclude, we report the antifungal activities of courmain mammeisin, against 4 different types of
The authors declare that there is no conflict of interests regarding the publication of this paper.
This work was supported by the Brazilian funding agency Fundação de Amparo à Pesquisa do Estado de Minas Gerais (FAPEMIG) under research Grant Project no. APQ-00356-13 and the Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) under research Grant Project no. 473461/2013-7. Authors gratefully acknowledge the generous financial support from the Universidade Federal de Ouro Preto, FAPEMIG, CAPES, and the CNPq for graduate research studentships and bursaries.