S. M. Mandal1, K. C. Mondal, S. Dey1 and B. R. Pati*

Department of Microbiology, Vidyasagar University, Midnapore (W) - 721 102, India

1Plant Biotechnology Laboratory, Department of Biotechnology, Indian Institute of Technology, Kharagpur - 721 302, India.

Corresponding Author:
B. R. Pati
Department of Microbiology, Vidyasagar University, Midnapore (W) - 721 102, India. E-mail: brpati@yahoo.com
Date of Submission 25 July 2007
Date of Revision 7 February 2007
Date of Acceptance 25 July 2007
Indian J Pharm Sci, 2007, 69 (4): 568-569  

DOI: 10.4103/0250-474X.36946

Abstract

Steam distillation, petroleum ether, and ethanol extracts from Hyptis suaveolens leaves were evaluated for their antimicrobial activity in vitro . Steam distillation extract exhibited broad-spectrum antibacterial and antifungal activity against the tested organisms. It showed highest antifungal and antibacterial activity against Aspergillus niger and Micrococcus luteus, respectively. Activity indices of A. niger against miconazole (25 µg/ml) and M. luteus against chloramphenicol (10 µg/ml) were 0.89 and 0.67, respectively.

Keywords

Antibacterial, antifungal, Hyptis suaveolens, leaf extracts

The plant, Hyptis suaveolens (L) Poit commonly known as Wilayati tulsi belongs to the family Lamiaceae and is an ethnobotanically important medicinal plant. The plant has been considered as an obnoxious weed, distributed throughout the tropics and subtropics. Almost all parts of this plant are being used in traditional medicine to treat various diseases. The leaves of H. suaveolens have been utilized as a stimulant, carminative, sudorific, galactogogue and as a cure for parasitic cutaneous diseases [1]. Crude leaf extract is also used as a relief to colic and stomachache. Leaves and twigs are considered to be antispasmodic and used in antirheumatic and antisuporific baths [2], an antiinß ammatory, antifertility agents [3], and also applied as an antiseptic in burns, wounds, and various skin complaints. The decoction of the roots is highly valued as appetizer and is reported to contain urosolic acid, a natural HIVintegrase inhibitor [4]. Fumes of the dried leaves are also used to repel mosquitoes and control insect pests of stored grains. In the present work an attempt was made to study the antimicrobial activity of different leaf extracts of Hyptis suaveolens (L.) Poit.

Fresh leaves of Hyptis suaveolens (L) Poit. (Lamiaceae) were collected in ß owering stage during late September from the natural population of the IIT-Kharagpur campus, India and identified in the Department of Botany, University of Burdwan, India. Bacteria (listed in Table 1) were obtained from the pure stock culture of Microbiology Department, Vidyasagar University, Midnapur (W), India. Fungi (listed in Table 2) were obtained from the Mycology and Plant Pathology Laboratory, Department of Botany, University of Burdwan, Burdwan, India.

Steam distillated (yield: 0.24%), petroleum ether extract (yield: 1.6%) and ethanol extract (yield: 2.64%) were prepared separately from fresh leaves following Souza et al [5]. The ethanol and petroleum ether extracts were reduced to dryness in vaccuo and solutions of each as well as of the steam distillation fraction (v/v) were dissolved in 10% DMSO (dimethylsulfoxide). Chloramphenicol (10 μg/ml) and miconazole (25 μg/ml) were used as positive control. Well-diffusion assay method was used to screen the extracts for antimicrobial activity against Bacillus subtilis, Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa and Micrococcus luteus. Nutrient agar plates were swabbed with the respective broth culture of the organisms and kept for 15 min in laminar chamber for absorption to take place. Wells were made in agar plates using a sterile cork borer (5 mm diameter) and 10 μl of extract was added to each well. The plates were incubated at 37º for 24 h and the diameters of the inhibition zone were measured in millimeter. The antifungal activity of the extracts against Fusarium oxysporum, Aspergillus niger, Helminthosporium oryzae was evaluated in molten potato dextrose agar medium and inoculated similar to antibacterial assay. The plates were incubated at 27º for 3 d.

Extracts Concentration (mg/ml) Bacteria
B. s. S. a. E. c. P. a. M.l.
E.E. 1.0 - - 0.21 0.25
  2.0 0.26 - 0.28 0.33 0.33
  3.0 0.35 0.27 0.39 0.47 0.41
P.E. 1.0 0.30 - 0.28 0.29 0.33
  2.0 0.43 - 0.36 0.42 0.41
  3.0 0.56 0.36 0.50 0.61 0.62
S.E. 0.25 0.35 - 0.32 0.38 0.37
  0.50 0.52 0.31 0.46 0.42 0.50
  1.0 0.61 0.41 0.56 0.63 0.67
C 23 22 28 22 24

Table 1: Antibacterial activity of the leaf extracts of H. suaveolens

Extracts Concentration (mg/ml) Fungi
  A. n. H. o. F. o.
E.E. 1.0 0.39 - 0.29
  2.0 0.44 0.35 0.38
  3.0 0.61 0.47 0.48
P.E. 1.0 0.44 0.35 0.43
  2.0 0.61 0.47 0.62
  3.0 0.78 0.64 0.71
S.E. 0.25 0.5 0.47 0.48
  0.5 0.72 0.64 0.71
  1.0 0.89 0.76 0.81
M 18 17 21

Table 2: Antifungal activity of the leaf extracts of H. suaveolens

The steam distillation and petroleum ether extracts displayed antifungal activity and broad spectrum of antibacterial activity against all the tested strains except Staphylococcus aureus (Tables 1 and 2). The ethanol extract showed less activity than that of steam distillation and petroleum ether extract at the tested concentration against both bacterial and fungal strains. Activity indices of tested bacteria were different in value against chloramphenicol (10 μg/ml). The microorganisms studied here showed obvious differences in their susceptibility to H. suaveolens leaf extracts. Steam distillation extract showed highest antifungal and antibacterial activity against Aspergillus niger and Micrococcus luteus, respectively. Essential oils are the major constituents of steam distillation extract. Volatile oils of H. suaveolens with major component of β-caryophyllene, 1,8-cineole and sabinene, and β-pinene [6], sesquiterpenes and monoterpenes, terpenoids and sterols [7]. A wide variety of essential oils are known to possess antimicrobial properties and in many cases this activity is due to the presence of monoterpene constituents which exert membrane-damaging effects to microbial strains [8] and also stimulates leakage of cellular potassium ions which provides evidence of a lethal action related to cytoplasmic membrane damage [9].

In conclusion, our observations confirm that the steam distillation extracts are better than that of ethanol or petroleum ether extracts of H. suaveolens leaf in respect to their antimicrobial activity and the broad spectrum of activity makes it a promising indigenous drug.

Acknowledgements

The authors wish to express their thanks to Prof. P. Bhattacharya, Taxonomist for his valuable help in identifying and authenticating the plant sample

References