Antibacterial activity of aerial parts of thymus serphyllum linn against clinically important bacterial strains ijsit 2.1.8

Bilal A. Waniet al., IJSIT, 2013, 2(1), 78-85

ANTIBACTERIAL ACTIVITY OF AERIAL PARTS OF THYMUS SERPHYLLUM
LINN AGAINST CLINICALLY IMPORTANT BACTERIAL STRAINS

1Bilal A. Wani*, 1D.Ramamoorthy, 2Khaleefa Aslam, 2Akhter H. Malik, 3Bashir A. Ganai*

1Department of Ecology and Environmental Sciences Pondicherry University- 605014, Pondicherry, India.

2Department of Botany,Universityof Kashmir, Srinagar- 190006, J&K, India.

3Department of Biochemistry,Universityof Kashmir, Srinagar- 190006, J&K, India.

ABSTRACT

In the present research workin vitroantibacterial activity of methanolic extract of aerial parts of
Thymus serphyllum L. growing wild in Kashmir Himalaya was evaluated by agar well diffusion method and
broth dilution assay against nine human pathogenic bacterial strains, known to cause serious infections. The
extract was also screened for the presence of various bioactive phytoconstituents present in the plant. The
extract in the present studypossess appreciable potential of inhibiting the growth of all the bacterial strains at
all tested concentrations (30, 60 and 90 mg/ml). The highest sensitivity was exhibited against Staphylococcus
epidermidis MTCC- 435 and Staphylococcus aureuswith mean zones of inhibition 20.66 and 20 mm
respectively at the concentration of 90 mg/ml. Salmonella typhi showed the least activity with mean zone of
inhibition of 10.00 mm at the concentration of 30 mg/ml. The MIC value ranged between 1.56 to 12.56
mg/ml. The phytochemical analysis of the crude extract revealed the presence of alkaloids, flavonoids,
phenolics, saponins, tannins, cardiac glycosides, terpenes, steroids and carbohydrates. Anthraquinone
glycosides were absent. The present study clearly indicate that the crude methanolic extract of Thymus
serphyllumfrom high altitude of Kashmir Himalaya (2350 m) shows significant antibacterial activity in
concentration dependent manner.

Keywords:Thymus serphyllum, Kashmir Himalaya,Antibacterial activity, Agar well diffusion method, MIC.

78
IJSIT (www.ijsit.com), Volume 2, Issue 1, January-February 2013


INTRODUCTION

Bacterial resistance to antibiotics is a major therapeutic problem and the pace at which new
antibiotics are being produced is slowing1. The increasing prevalence of multidrug resistant strains of
bacteria and the recent appearance of strains with reduced susceptibility to antibiotics raises the specter of
untreatable bacterial infections and adds urgency to the search for new infection-fighting strategies2. Plants
are important source of potentially useful structures for the development of new chemotherapeutic agents.
The first step towards this goal is the in vitro antibacterial activity assay3. Plants produce a diverse range of
bioactive molecules, making them rich source of different types of medicines 4. Medicinal plants represent a
rich source of antimicrobial agents. Plants are used medicinally in different countries and are a source of
many potent and powerful drugs5. The medicinal value of plants lies in some chemical substances that
produce a definite physiological action on the human body. The most important of these bioactive compounds
of plants are alkaloids, flavonoids, tannins and phenolic compounds 6. Contrary to the synthetic drugs,
antimicrobials of plant origin are not associated with many side effects and have an enormous therapeutic
potential to heal many infectious diseases7.

Thymus serphyllum L. belongs to the family Lamiaceae. It is commonly known as wild thyme. The
genus Thymus is a well known aromatic perennial herb 8, is widely distributed in temperate zones, comprises
about 350 species worldwide9. Thymus serphyllum is a small much branched and strongly scented shrub. It
bears tiny purple coloured flowers with evergreen leaves 3-8 mm long10. Thymus species are well known as
medicinal plants because of their biological and pharmacological properties 11. In traditional medicine, leaves
and flowering parts of Thymus species are widely used as tonic and herbal tea, antitussive and carminative as
well as treating colds, coughs, sore throats, cystitis, insomnia bronchitis, and indigestion 12 13. The active
ingredients of Thymus serpyllumL. are Volatile oil containing thymol, carvacrol, cineole, borneol, linalool, and
pinene; flavonoids, apigenin and luteolin; tannins. Thymus serphyllum is known to have antimicrobial
activity14, antihelmintic, antioxidant, strongly antiseptic, antispasmodic, carminative, deodorant, diaphoretic,
expectorant, sedative and antiseptic property15.

MATERIALS AND METHODS
Plant Material:
Thymus serphyllum was collected at flowering stage from Tangmarag area of Kashmir Himalaya at
an altitude of 2350 m (a.s.l) by conducting field trips. The collected plant material was properly identified at
the Centre of Biodiversity and Plant Taxonomy, University of Kashmir and a specimen Voucher was deposited
in Kashmir University Herbaria (KASH) for further reference.

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Preparation of extract:

The aerial parts of the plant were properly cleaned and dried under shade for one week. After drying,
the material was chopped and then grinded to powder. Dried plant powder was then packed in Soxhlet
apparatus and extracted with methanol at 50-65 oC. The extract was then filtered through Whatmann filter
paper No. 1. The pellet was discarded and the supernatant was collected and concentrated under reduced
pressure at 35-45°C using Buchirotavapor (R-215). The extract was then dried, labelled and stored at 4 oC in
storage vials for experimental use16.

Antibacterial Activity:
Microorganisms tested:
Microbial cultures of nine different species of both Gram positive and Gram negative bacteria were
used for determination of antibacterial activity. Four bacterial strains viz. Proteus vulgaris MTCC- 321,
Staphylococcus epidermidis MTCC- 435, Pseudomonas aeruginosa MTCC- 1688 and Bacillus subtilus MTCC-
441 were standard laboratory isolates obtained from Microbial Type Cell Culture, Chandigarh (India). The
rest five bacterial strains were clinical isolates obtained from Department of Microbiology, Sheri Kashmir
Institute of Medical Sciences- Srinagar (India). All the bacterial strains were sub-cultured at 37°C on Mueller-
Hinton agar (Himedia) slants every fifteen days and stored at 4°C.
Antibacterial activity assay:
In the present research work, the antibacterial activity of methanolic extract of Thymus serphylum
was determined by agar well diffusion method as adopted by Perez et al 17. Each microorganisms were grown
overnight at 37°C in Mueller-Hinton Broth. Ten microlitres (10μL) of standardized inoculum (0.5 Mac-
Farland) of each test bacterium was inoculated on molten Mueller-Hinton agar, homogenized and poured into
sterile Petri dishes. The Petri dishes were allowed to solidify inside the laminar hood. A standard cork borer
of 5mm in diameter was used to make uniform wells into which was added 30μl essential oil diluted in DMSO.
Standard antibiotic kanamycin (30μg/disc) was used as positive control and DMSO as negative control. The
plates were then incubated at 37 ± 1°C for 24h. The zone of inhibition was measured to the nearest size in
mm with the help of standard scale18. The experiments were carried in strict aseptic conditions so as to
achieve consistency. The experiments were carried out in triplicates and results were calculated as mean ±
SD.
Determination of minimum inhibitory concentration (MIC):
Minimum inhibitory concentrations (MICs) are considered to be the ‘gold standard’ for determining
the susceptibility of organisms to antimicrobials. The MIC of methanolic extract of T. serphylum was
determined by the method as developed by Jennifer19. Dilution ranges (50 - 0.78 mg/ml) of methanolic
extract from the selected plant material were prepared from stock solution by serial dilution technique. 20 ml
of sterile molten Muller Hinton Agar to each dilution mixed properly and poured into 90 mm Petri plates and

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allowed it to cool under laminar air flow before streaking with 1-2 µl of 0.5 McFarland standard inoculums to
each plate. Plates were incubated at 37± 1oC for 24 hours. The lowest concentration of the extract at which
there was no visible growth of microorganisms was considered as minimum inhibitory concentration (MIC).
Photochemical Screening:
Photochemical screening for major bioactive constituents was done by using standard qualitative
photochemical methods20-21.

RESULTS AND DISCUSSION
The methanolic extract of Thymus serphylumexhibited varying degree of antibacterial activity
against the tested bacterial strains (table- 1). The bacterial strains used were clinical and laboratory isolates.
All these bacterial species are known to cause serious human infections. From clinical point of view,
Klebsiella pneumonia causes neonatal nosocomial infection22. Escherichia colicause’s septicemias and can
infect the gall bladder, meninges, surgical wounds, skin lesions and the lungs 23. Salmonella typhi causes
serious public health problem in developing countries and represents a constant concern for the food
industry24. Shigelladyssenteriae cause shigellosis.Staphylococcus aureus causes dermatitis
andsialadenitis. Proteus vulgaris causes bacteremia, sepsis and urinary tract infections25-26. The most
antibacterial sensitivity was shown by Staphylococcus epidermidis MTCC- 435 with mean zone of inhibition
of 20.66 mm at the concentration of 90 mg/ml, while as Salmonella typhi showed the least activity with mean
zone of inhibition of 10.00 mm at the concentration of 30 mg/ml. The minimum inhibitory concentration of
methanolic extract of Thymus serphylum ranged between 1.56 to 12.56 mg/ml (table-2). The extract in the
present study exhibited broad spectrum antibacterial activity which was comparable to the standard
antibiotic drug (kanamycin). The Gram positive bacterial strains were found to be slightly more sensitive than
Gram negative bacterial strains. It may be due to the absence of lipo-polysachride layer in Gram positive
bacteria that might function as a barrier to the phytocemical substances that are responsible for antibacterial
activity27-28. The plant extract being active against both clinical and laboratory isolates is also an indication
that it can be a source of very potent antibiotic substances that can be used against multidrug resistant
microorganisms.The phytochemical screening of Thymus serphylum reveals the presence of alkaloids,
flavonoids, phenolics, saponins, tannins, cardiac glycosides, terpenes, steroids and carbohydrates (table-3).
Anthraquinone glycosides were found to be absent. These phytochemicals (Secondary plant metabolites) are
responsible for the biological activities and are known to have antimicrobial, antioxidant activities29-30. The
present study reports the presence of diverse phytochemicals in the plant than earlier reports byKavita et al
14. The present research work supports the resourcefulness of the plant in terms of presence of
phytochemicals and antibacterial potential of the plant from higher altitude region of Kashmir Himalaya.

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Table 1:

S. No Microorganism. Zone of inhibition (mm).

Methanolic extract of Thymus serphylum Standard Antibiotic
90 mg/ml 60 mg/ml 30 mg/ml (Kanamycin 30μg/disc)
1. Proteus vulgaris 16.66±1.52 14.33±1.52 11.0 ± 1.00 29.00±1.00
MTCC- 321.
2. Staphylococcus 20.66±1.52 17.00±1.00 13.00±1.00 30.33±0.57
epidermidisMTCC- 435.
3. Pseudomonas aeruginosa 17.66±1.52 15.0±1.00 12.16±1.52 28.66±1.52
MTCC- 1688.
4. Bacillus subtilus 18.00±1.00 15.0±1.00 11.33±0.57 27.33±1.52
MTCC- 441.
5. Salmonella typhi. 15.66±2.51 13.33±1.52 10.00±1.00 27.33±1.14

6. Shigelladyssenteriae. 17.66±1.52 14.66±1.52 12.33±1.52 29.33±1.52
7. Staphylococcus aureus. 20.00±1.00 17.00±1.00 13.66±1.52 29.00±1.00
8. Klebsiella pneumonia. 18.00±1.00 15.33±1.52 11.66±1.52 29.66±1.52
9. Escherichia coli. 17.00±1.00 14.66±0.57 12.00±1.00 28.00±1.00
Values are mean zone of inhibition (mm) ± S.D of three experiments

Table 1: Zone of inhibition (mm) at various concentrations of methanolic extract of Thymus
serphylum against selected bacterial strains

Table 2:

Microorganism. MIC (mg/ml). Microorganism. MIC (mg/ml).
Proteus vulgarisMTCC- 321. 3.12 Shigelladyssenteriae. 6.25
Staphylococcus epidermidisMTCC- 435. 1.56 Staphylococcus aureus. 1.56
Pseudomonas aeruginosaMTCC- 1688. 3.12 Klebsiella pneumonia. 3.12
Bacillus subtilusMTCC- 441. 6.25 Escherichia coli 12.56
Salmonella typhi. 12.56

Table 2: MIC value (mg/ml) of methanolic plant extract of Thymus serphyllum against different
bacterial strains

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Table 3:

S. No Phytoconstituents Test Result
1. Alkaloids Wagner’s test +
2. Phenolics phenol test +
3. Tannins Ferric chloride test +
4. Cardiac glycosides Keller-Killani test +
5. Anthraquinone Glycosides Nitric acid test -
6. Terpenes Salkwaski test +
7. Flavonoids Shinoda test +
8. Saponins Frothing test +
9. Steroids Libermann‐Buchard’s test +
10. Carbohydrates Benedict's/ Fehling’s test +

Key: (+) indicates presence, (-) indicates absence

Table 3:Photochemical screening of methanolic extract of Thymus serphylum

Figure: showing Zones of inhibition against (A) E. coli, (B) S. aureus,(C) B. subtilus-441 and (D) P.
aeruginosa-1688 at various concentrations of plant extract

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Antibacterial activity of aerial parts of thymus serphyllum linn against clinically important bacterial strains ijsit 2.1.8

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