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Antibacterial and Cytotoxic Activity of Longiverbenone Isolated from the Rhizome of Cyperus Scariosu

M Shafiqur Rahman
Department of Microbiology, University of Chittagong, Chittagong 4331, Bangladesh

M Nural Anwar
Department of Microbiology, University of Chittagong, Chittagong 4331, Bangladesh

Abstract/ Executive Summary:

Longiverbenone is a naturally occurring sesquiterpene isolated from ethanolic extract of Cyperus scariosus rhizome by solvent-solvent portioning and chromatographic technique. The antibacterial activity of longiverbenone was evaluated against eleven potential human pathogenic bacteria using disc diffusion method. Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were determined by broth macrodilution method. Cytotoxic activity (lethal concentration 50%, LC₅₀) of longiverbenone was determined on new borne brine shrimp (Artemia salina). Longiverbenone showed moderate to good antibacterial activity against the test organisms tested herein. It exhibited the lowest MIC (20 μg/ml) and MBC (80 μg/ml) against Vibrio cholerae. The LC₅₀ of the isolated sesquiterpene was found to be 14.38 μg/ml against new borne brine shrimp.

Keywords: Department of Microbiology, University of Chittagong, Chittagong 4331, Bangladesh

Location: Department of Microbiology, University of Chittagong

Start Date: 00-12-2004

End Date: 00-12-2004

Program Area: Pest Management

Commodity: Diseases

Objectives:

To evaluate the antimicrobial activity of a pure compound from C. scariosus on several pathogenic bacteria, which can cause diseases in man.

Methodology:

Rhizomes of C. scariosus were collected from a local garden owned by the Bangladesh Council of Scientific and Industrial Research (BCSIR) Laboratories, Chittagong, in December 2004 and it was identified by Dr. M Yousuf of BCSIR, where a voucher specimen (No. 1564a) has been maintained. The collected sample was cleaned, cut into small (1-2 cm) pieces, dried at 50-55°C, pulverized and then 250 g of the dried powder was kept steeped twice overnight in ethanol. The extract thus obtained was filtered, centrifuged at 5,000 rpm for 20 min and then concentrated to a gummy material (12.5 g; 5% w/w) under reduced pressure at 50°C by rotary vacuum evaporator. Solvent-solvent partitioning of concentrated crude extract was done using the protocol designed by Kupchan and modified by Wagenen. All the fractions were collected separately, dried as usual and tested for any of their antimicrobial efficacy. Of these, only the crude petroleum ether extract fraction showing high antimicrobial activity was subjected to fractionation by column chromatography using silica gel (200-300 mesh) as the adsorbent. From it a total of 24 fractions were collected separately using mixtures containing different proportions of petroleum ether and ethyl acetate with increasing polarity as the eluants. The column-separated fractions thus obtained were examined using thin-layer chromatography (TLC) technique and ultraviolet light (254 and 366 nm) to detect the presence of any fluorescent compound. The Rf-values for each were measured as usual. Fractions showing same Rf-value were mixed together and grouped into eight fractions (C₁-C₈). All the fractions (C₁-C₈) were tested against a highly sensitive bacterium (Bacillus megaterium) and a fungus (Aspergillus niger). Of these, the highly antibacterial and antifungal fraction C1, eluted in petroleum ether, yielded 2.56 g (1.024% w/w) of greenish brown oil. This oil, on various spectroscopic (e.g., IR, NMR and GCMS) analyses and on comparison of such analytical results with NYST Library data, was identified as longiverbenone, which is a sesquiterpene. NMR and GSMS were performed on respectively a Bruker spectrospin spectrometer and a GC-17A Ver. 3 gas chromatography coupled to a Shimadzu mass spectrometer (Model QP 5050A). The in vitro antibacterial activities of the column separated fractions and of the chemically isolated pure compound longiverbenone of the plant were determined against eleven potential human pathogenic bacteria by disc diffusion method. using Mueller- Hinton (agar and broth) medium. All the results were compared with the standard antibacterial antibiotic ampicillin (20 μg/disc). Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were determined by macrodilution broth technique. The LC₅₀ test was performed on new born brine shrimp (Artemia salina) according to an established method. The median lethal concentration 50% (LC₅₀) of the test compound (1.5625 to 200 μg/ml water) was calculated by trend line fit linear regression analysis of the experimentally obtained data.

Source of Information: Bangladesh J Microbiol, Volume 25, Number 1, June 2008, pp 82-84

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Achievement/Findings:

It is evident from this study that longiverbenone isolated from C. scariosus rhizome exhibited moderate to good antibacterial activity against the organisms tested herein. Our results could stimulate further pharmacological studies seeking new antimicrobial agents from the plant resources.

Knowledge Management: Journal