Pakistan J. Med. Res.

Vol. 42 No.3, 2003

 

Thymoquinone, an active principle of Nigella sativa, inhibited Aspergillus niger

 

Al-Jabre S*, Al-Akloby OM*, Al-Qurashi AR**, Akhtar N**, Al-Dossary A*, Randhawa MA***

Department of *Dermatology, ** Microbiology and ***Pharmacology, College of Medicine, King Faisal University, Dammam, Kingdom of Saudi Arabia

SUMMARY 

Nigella sativa (N. Sativa) seed called as ‘Habbah Al-Sauda’ in Arabic, is commonly used as a natural remedy for many ailments over 2000 years and frequently added to bread and prickles as a flavouring agent. Recently, many active principles have been isolated from N. Sativa including thymoquinone, thymohydroquinone, dithymoquinone, thymol, carvacrol, nigellicine, nigellidine, nigellimine-N-oxide and alpha-hedrin. Besides, many other pharmacological effects, activity of N. sativa oil, ether extract and its active principle, thymohydroquinone, has been reported in the literature against a number of bacteria (including Staphylococcus aureus, Pseudomonas aeruginosa and Escherichia coli) and yeast (Candida albicans). Therefore, we thought that N. sativa or some of its active principles might have useful action against Aspergillus as well, which commonly causes opportunistic infection in immune deficient individuals. We studied the growth of Aspergillus niger in dermasel agar containing 0.25, 0.5, 1 & 2 mg/ml of thymoquinone; drmasel agar with selective supplement and dermasel agar alone. There was 0, 25, 77.1 and 100% inhibition of A. niger with 0.25, 0.5, 1 & 2 mg/ml of thymoquinone on day 7, giving MIC as 2 mg/ml. We hope our study will promote further investigations to determine usefulness of thymoquinone or N. sativa in the treatment and prevention of Aspergillosis.

INTRODUCTION 

Nigella sativa, one of the Ranunculaceae, commonly grows in the Middle East, Eastern Europe and Middle Asia. In Arab countries it is commonly known as ‘Habba Al-Sauda’ or ‘Habba Al-Baraka’. N. Sativa seed is frequently added to bread and prickles as a flavouring agent and used as a natural remedy for many ailments over 2000 years 1, 2.

Recently many active principles have been isolated from N. sativa, including thymoquinone, thymohydroquinone, dithymoquinone, thymol, carvacrol, nigellicine, nigellimine-N- oxide, nigellidine and alpha-hedrin 3, 4, 5, 6, 7 & 8.  Over the last few decades, a number of pharmaco-therapeutic effects of various extracts of N. sativa and some of its active principles have been investigated, using modern scientific techniques, and recently reviewed by Randhawa and Al-Ghamdy 9.

Anti-bacterial effect of the phenolic fraction of N. sativa oil was first reported by Topozada et al10. Thymohydroquinone was later isolated 4 and found to have high activity against gram-positive microorganisms. Later, the diethyl-ether extract of N. sativa was reported to inhibit Staphylococcus aureus, Pseudomonas aeruginosa and Escherichia coli. It also showed synergistic effect with streptomycin & gentamycin and additive effect with spectinomycin, erythromycin, tobramycin, doxycycline, chloramphenicol, nalidixic acid, ampicillin, lincomycin and co-trimoxazole. In addition, the extract also inhibited a pathogenic yeast, Candida albicans11. Recently, crude extracts of N. sativa were reported to have a promising effect on multi-resistant organisms including gram-positive and gram- negative bacteria12. In view of the wide spectrum of anti-microbial activity of N. sativa, we thought it might have useful activity against some fungi, like Aspergillus, besides Candida albicans.

Aspergilli comprise a group of rapidly growing hyaline moulds, that are widely distributed in the environment and are common contaminants of clinical laboratories. They commonly cause opportunistic infection in humans. Aspergillosis may present as well defined clinical syndromes involving a variety of sites and organ systems: pulmonary, disseminated, central nervous system, cutaneous, endocardial and nasoorbital. It almost exclusively occurs in patients who are immuno-suppressed or neutropenic, particularly in transplant recipients and those with leukemias or lymphomas. Aspergillosis is also reported in corticosteroid use, intravenous drug abuse and later stages of AIDS.  Of the some 700 Aspergillus species described, only 19 have been cited as causing human infections; of these only 4 are recovered with any frequency in hospitalized patients: Aspergillus fumigatus, A. flavus, A. niger and A. terreus 13

MATERIALS AND METHODS 

Strains of A. niger were isolated from contamination in petri-dishes being used for some culture sensitivity tests in the Department of Microbiology, College of Medicine, King Faisal University, Dammam. The specimens were sub-cultured on Dermasel agar (Oxoid) and incubated at 30o C for 7 days. The growth was identified as A. niger by microscopy after staining with lactophenol cotton blue.

Thymoquinone was dissolved in small amount of sterile distilled water and then mixed with sufficient presterilized dermasel agar to obtain 2 mg/ml of thymoquinone. Serial dilutions were then made to get thymoquinone 1, 0.5 and 0.25 mg/ml.

The isolates of A. niger were subcultured on three sets of culture media. Set 1: dermasel agar only, Set 2: dermasel agar with dermasel selective supplement (containing cycloheximide 200 mg/500 ml and chloramphenicol 25 mg/500 ml) and Set 3: dermasel agar with 0.25, 0.5, 1 & 2 mg/ml of thymoquinone. Four petri-plates were inoculated in each set.

A mycelial disc, 5 mm in diameter, cut from the periphery of 5-7 day old cultures of A. niger in dermasel agar was aseptically inoculated onto different sets of media. The inoculated plates were incubated at 30o C. The cultures were examined on the 3rd, 5th and 7th day and results interpreted by visual impression as well as by measurement of the mean diameter of the growth of Aspergillus14.

The percentage inhibition of A. niger with different concentrations of thymoquinone was then calculated by taking its growth in non-drug dermasel agar as 100%. The growth of A. niger in dermasel agar with the selective supplement was taken as active control. 

RESULTS 

There was 0, 25, 77.1 and 100% inhibition of A. niger with 0.25, 0.5, 1 & 2 mg/ml of thymoquinone on day 7, giving MIC as 2 mg/ml (table 1), while with the selective supplement the inhibition was only 32.7 %. A. niger  covered the entire area of perti-plates (9 cm diameter, taken as 100%) when inoculated in dermasel agar alone on day 3 to 7 .

Table 1:Percentage inhibition of the growth of Aspergillus niger with different  concentrations of thymoquinone on Day 3, 5 and  7. 

Thymoquinone

mg/ml

 

% inhibition of  A. niger growth

 

Day 3

Day 5

Day 7

0. 25

 

25

Nil

Nil

0. 5

 

76.8

55.4

25

1

 

100

91.8

77.1

2

 

100

100

100

 

The mean diameter of the growth of A. niger in dermasel agar containing various concentrations of thymoquinone and dermasel agar with selective supplement is given in table 2a & 2b, respectively. 

Table 2: Growth of Aspergillus niger in dermasel agar containing different concentrations of thymoquinone and in dermasel agar with selective supplement. 

Dermasel agar with thymoquinone

Concentrations

mg/ml

Mean diameter  + SD (cm) of A. niger growth (n = 4)

Day 3

Day 5

Day 7

0.25

 

+++(*)

 

++++(**)

 

++++

 

0.5

 

2.09 + 0.2

 

4.01 + 0.49

 

+++

 

1

 

Nil

 

0.74 + 0.43

 

2.06 + 0.8

 

2

 

Nil

 

Nil

 

Nil

 

Dermasel agar with selective supplement

Mean diameter  + SD (cm) of A. niger growth (n = 4)

 

Day 3

 

Day 5

 

Day 7

2.05 + 0.11

4.35 + 0.39

6.06 + 0.11

*   Growth of A. niger covering ¾ of the petri-plate

** Growth of A. niger completely covering the petrti- plate (9 cm), taken as 100%.

DISCUSSION 

N. Sativa has been used for many ailments in ancient Greek, Indian and Arabic medicines. For example, Ibne-Sina recommended the use of N. sativa for the treatment of various microbial infections of skin (warts, collar-stud abscess and other abscesses, chronic fungal infections such as ring worm), eye and gastrointestinal tract as well as for the expulsion of worms from the intestines15.

In the present study we observed a dose related anti-fungal effect of thymoquinone, an active principal of N. sativa; 0.25, 0.5, 0.1 and 0.2 % thymoquinone inhibited 0, 25, 77.1 and 100 % of A. niger with 0.25, 0.5, 1 & 2 mg/ml of thymoquinone on day 7. Earlier, 25-400 micrograms of diethyl-ether extract per disc of N. sativa seed has been reported to inhibit a concentration dependent growth of Gram-positive and Gram-negative bacteria11. Moreover, inhibition in the growth of coliforms, staphylococci and yeasts/moulds in the processed cheese spread by 0.1 - 0.3% hexane-extracted N. Sativa oil has also been reported 16.

There was some growth of A. niger in dermasel agar with selective supplement on day 3, 5 & 7 as shown in table 2b. Which shows that the selective supplement (containing cycloheximide 200 mg/500 ml and chloramphenicol 25 mg/500 ml) failed to completely inhibit the growth of A. niger.

We hope our study will promote further investigations to determine usefulness of N. sativa in the treatment and prevention of Aspergillosis and possibly other local and systemic fungal infections in immuno-compromised patients. 

CONCLUSION 

Thymoquinone, an active principle of Nigella sativa, effectively inhibited the growth of Aspergillus  niger (MIC 2mg/ml).   

ACKNOWLEDGMENT 

We gratefully acknowledge Dr. Mastour S. Al-Ghamdi, Vice Dean (Academic Affairs), College of Medicine, King Faisal University, Dammam, Saudi Arabia, for the provision of thymoquinone base for our study.  

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