Antibacterial activity of the extracts from the fruit rinds of Garcinia cowa and Garcinia pedunculata against food borne pathogens and spoilage bacteria
Introduction
Garcinia (Family: Guttiferae) is a large genus of polygamous trees or shrubs, distributed in the tropical Asia, Africa and Polynesia, which consists of 180 species, out of which about 30 species are indigenous to India. Garcinia cowa and Garcinia pedunculata are grown in Northeastern parts of India and Andaman Islands. In Assam, both the species of Garcinia are often cultivated in homesteads for their acid fruits and the sun-dried slices of the fruits are used for culinary purposes and used to treat dysentery (The Wealth of India, 1956). However, the fruits of G. cowa and G. pedunculata are underutilized. Small and complex molecules have been isolated from different parts of the various species of Garcinia, which include xanthones and their derivatives (Bennet and Lee, 1989, Rama Rao et al., 1980) exhibiting a wide range of biological and pharmacological activities such as antimicrobial, antioxidant, antitumour-promoting, cytotoxic, etc. (Adegoke et al., 1998, Asano et al., 1996, Bakana et al., 1987, Iinuma et al., 1996, Iinuma et al., 1996, Mackeen et al., 2000, Minami et al., 1994, Minami et al., 1996, Minami et al., 1995). Crude extracts as well as partially purified compounds from different parts of some species of Garcinia plants have shown potential antibacterial activities. A polyisoprenylated benzophenone known as garcinol isolated from stem bark of G. huillensis has been shown to possess chemotherapeutical activity against Gram-positive and Gram-negative cocci but was inactive against Gram-negative enteric bacilli (Bakana et al., 1987). Alpha-mangostin, rubraxanthone and xanthochymol isolated from G. mangostana, G. diocia and G. subelliptica, respectively, showed strong antibacterial activity against both methicillin-resistant and methicillin-sensitive Staphylococcus aureus (Iinuma et al., 1996, Iinuma et al., 1996). Crude extracts of leaves, fruits, root, stem and trunk bark of G. atroviridis exhibited antibacterial activity against Bacillus subtilis B28 (mutant), B. subtilis B29 (wild type), methicillin-resistant S. aureus, Escherichia coli and Pseudomonas aeruginosa by disc diffusion method with the root extract showing the strongest inhibition (Mackeen et al., 2000).
The contamination of foods and spoilage by microorganisms is a problem that is not yet under adequate control, despite the ranges of preservation techniques available. The microbiological safety of food continues to be a major concern to consumers, regulatory agencies and food industries throughout the world. One among the strategies used to achieve food preservation by inhibiting growth of undesirable microorganisms, is the use of chemical agents exhibiting antimicrobial activity. These chemicals may be either synthetic compounds intentionally added to foods or naturally occurring and biologically derived substances. Traditional antimicrobials such as acetic, benzoic, lactic, propionic and sorbic acids and nitrite and sulfites have been used for many years to control growth of microorganisms in foods (Beuchat and Golden, 1989, Davidson, 1997, Sofos et al., 1998). The current consumer demands for more natural and fresh-like foods with fewer synthetic additives but increased safety and shelf life, urges food manufacturers to use natural or mild preservation techniques. Therefore, alternative sources of safe, effective and acceptable natural preservatives need to be explored.
Antimicrobial and free radical scavenging xanthones from the latex of G. cowa (Mahabusarakam et al., 2005, Na Pattalung et al., 1994), and antimalarial xanthones (Likhitwitayawuid, Padungcharoen, & Krungkrai, 1998) from the stem bark of G. cowa have been reported. Joseph, Jayaprakasha, Selvi, Jena, and Sakariah (2005) have reported the antiaflatoxigenic and antioxidant activities of the fruit rind extracts of Garcinia. Apparently no study has been reported about the antibacterial activity of extracts from the fruit rinds of G. cowa and G. pedunculata. The aim of the present study was to explore the antibacterial activity of the extracts from the fruit rinds of G. cowa and G. pedunculata for their probable use as natural antimicrobials.
Section snippets
Plant material
Dried rinds of G. cowa and G. pedunculata were collected from Jallah in Barpeta district of Assam, India. Chloroform and hexane were of AR grade from Merck, Mumbai, Maharastra, India.
Extraction
The dried rinds of G. pedunculata and G. cowa were extracted with hexane and chloroform as described by Jena, Jayaprakasha, Negi, and Sakariah (2002). Sun-dried fruit rinds of G. cowa and G. pedunculata were cut into small pieces. About 50 g of each fruit rinds of Garcinia was extracted with 200 ml of hexane and
Results and discussion
The hexane and chloroform extracts from the rinds of G. cowa and G. pedunculata were evaluated for antibacterial activity. The effect of Garcinia rind extracts on the growth of different bacteria has been presented in Fig. 1, Fig. 2. Extracts from both the species of Garcinia had a variable growth inhibitory effect. Both the hexane and chloroform extracts from the fruit rinds of G. cowa showed higher inhibitory effect than the extracts from G. pedunculata against all the test organisms (Table 1
Acknowledgements
We wish to thank Dr. V. Prakash, Director, Dr. K. K. Sakariah, former Head, Dr. M. C. Varadaraj, Head, Human Resource Development, Central Food Technological Research Institute, Mysore, for their constant encouragement.
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