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Antimicrobial Activity of Oil Extract from Marang Seeds (Artocarpus odoratissimus)
against Escherichia coli and Staphylococcus epidermidis
Essential oils are widely gaining interest a component in medicinal products, food industry and pharmaceutical industry. Many studies were conducted to identify the antimicrobial, antifungal and insecticidal activities of essential oils obtained from plants. Essential oils have many therapeutic activities and they aid the distribution of drugs and antiseptics. Furthermore, the testing of plant extracts for its antimicrobial activity has always been of great attention to scientists looking for new sources for drugs for the treatment of various diseases (Nagala et al., 2013).
Antimicrobial Compounds from Plants
According to Cetin-Karaca (2011), phenolic compounds are one of the most diverse groups of secondary metabolites found in edible plants. They are found in a wide variety of fruits, vegetables, nuts, seeds, stems and flowers. There are different classes of polyphenols known as tannins, lignins and flavonoids.
Cinnamic and caffeic acids are common representatives of a wide group of phenylpropane-derived compounds which are in the highest oxidation state. Herbs such as tarragon and thyme both contain caffeic acid that is effective against viruses, bacteria and fungi. Catechol and pyrogallol both are hydroxylated phenols, shown to be toxic to microorganisms. Catechol has two 2OH groups, and pyrogallol has three. The site(s) and number of hydroxyl groups on the phenol group are thought to be related to their relative toxicity to microorganisms, with evidence that increased hydroxylation results in increased toxicity (Cowan, 1999).
Flavonoids are the most widely occurring polyphenol and are present in almost every form of human consumed vegetation. Flavonoids are potent antioxidants, free radical scavengers and metal chelators; they inhibit lipid peroxidation and exhibit various physiological activities including anti-inflammatory, anti-allergic, anti-carcinogenic, anti-hypertensive, anti-arthritic and antimicrobial activities (Cetin-Karaca, 2011).
Flavonoids are also hydroxylated phenolic substances but occur as a C6-C3 unit linked to an aromatic ring. Since they are known to be synthesized by plants in response to microbial infection, it should not be surprising that they have been found in vitro to be effective antimicrobial substances against a wide array of microorganisms. Catechins, the most reduced form of the C3 unit in flavonoid compounds, have been extensively researched due to their occurrence in oolong green teas. It was noticed some time ago that teas exerted antimicrobial activity and that they contain a mixture of catechin compounds. These compounds inhibited in vitro Vibrio cholerae, Streptococcus mutans, Shigella and other bacteria and microorganisms (Cowan, 1999).
Plant Extracts as Potential Antibacterial Agents
Numerous studies investigated about the antimicrobial activity of plant extracts against a great number of bacterial species. Plant extracts were prepared from fresh or dried plant material using conventional extraction methods (Soxhlet extraction, maceration, percolation). Extraction is process of separation of active compounds from plant material using different solvents. During extraction, solvents diffuse into the plant material and solubilise compounds with similar polarity. At the end of the extraction, solvents have been evaporated, so that an extract is a concentrated mixture of plant active compounds. Successful extraction is largely dependent on the type of solvent used in the extraction procedure. Water extracts and extracts from organic solvents such as methanol, ethanol, acetone and chloroform are usually used. Diffusion and dilution method are two types of susceptibility test used to determine the antibacterial efficacy of plant extracts. Diffusion method is a qualitative test which allows classification of bacteria as susceptible or resistant to the tested plant extract according to size of diameter of the zone of inhibition. In dilution method, the activity of plant extracts is determined as Minimum Inhibitory Concentration (MIC). MIC is defined as the lowest concentration able to inhibit bacterial growth (Stefanovic, et al., 2012).
Marang (Artocarpus odoratissimus)
Artocarpus odoratissimus is also known as Marang, Johey oak or Tarap which is a tropical fruit tree native to Asia. It belongs to the Moraceae family and is closely related to Jackfruit (Artocarpus heterophyllus) and breadfruit (Artocarpus comminis). It originated in Borneo and has been introduced into neighbouring countries, including the Philippines, Malaysia and Thailand. It is an evergreen tree, which can grow up to 25 m tall and has a 40 cm diameter trunk with low buttresses. The leaves are broadly elliptic to obovate at around 16to 50cm long and 11to 28cmwide. They are cuneated at base to slightly decurrent, margin entire or shallowly crenate, and apex blunt or shortly acuminate. It is a monoecious plant so one plant is enough for the production of fruit. The fruit is green, ovoid in shape, quite large, averaging about 16 cm in length, 13 cm in diameter and weighing about 1 kg (KPR Gardeners Club, 2009). It is roundish oblong, regular, and thickly studded with short, brittle, greenish yellow spines. The rind is thick and fleshy. The flesh is snowy white, very sweet when ripe, juicy and very aromatic. The flesh is separated into segments clinging to the central core and each segment contains a seed. The seeds are many, whitish, 8 × 15 mm in size, smooth surfaced and readily separated from the flesh (Subhadrabandhu, 2001).
Escherichia coliis the most prevalent infecting organism in the family of gram-negative bacteria known as enterobacteriaceae.E. coli is a Gram-negative, rod-shaped bacterium propelled by long, rapidly rotating flagella. Escherichia colibacteria were discovered in the human colon in 1885 by German bacteriologist Theodor Escherich. Dr. Escherich also showed that certain strains of the bacterium were responsible for infant diarrhea and gastroenteritis, an important public health discovery. AlthoughE. coli bacteria were initially called Bacterium coli, the name was later changed toEscherichia colito honor its discoverer (Clark, 2005). It is part of the normal flora of the mouth and gut and helps protect the intestinal tract from bacterial infection, aids in digestion, and produces small amounts of vitamins B12 and K. The bacterium, which is also found in soil and water, is widely used in laboratory research and is said to be the most thoroughly studied life form (The Columbia Electronic Encyclopedia, 2012).
Staphylococcus epidermidis belongs to the genus Staphylococcus, and they are facultative anaerobes (Wiedemer, 2012). Staphylococcus epidermidis is a well characterized, non-fastidious, and it is a gram positive bacteria. Staphylococcus epidermidis is a coagulase – negative staphylococcus (CNS) they are found and colonizes the skin and the mucous membranes of the human body and they play an important part of it normal flora (Sousa et al., 2008). These species of staphylococcus secretes and produces a biofilm of polysaccharides that protects the cell against the host immune system or antibiotic treatments (Schjorring et al., 2002). These staphylococci are mainly dispersed during skin to skin contact using medical instruments and procedures. Staphylococcus epidermidis can cause infections in humans like meningitis, urinary tract infection (UTI) conjunctivitis, and endocarditis (Wiedemer, 2012).
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KPR Gardeners Club. (2009). Breadfruit Artocarpus odoratissimus, Marang. Botanix – A Journal About Plants and Gardening. Retrieved from http://www.botanix.kpr.eu/en/index.php?text=6-breadfruit-artocarpus-odoratissimus-marang
Nagala, S., Yekula, M. & Tamanam, R. (2013). Antioxidant and gas chromatographic analysis of ¬ve varieties of jackfruit (Artocarpus) seed oils. Drug Invention Today 5 (2013) 315-320. Retrieved from http://www.sciencedirect.com/science/article/pii/S0975761913000616
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Subhadrabandhu, S. (2001). Under-Utilized Tropical Fruits of Thailand. Food and Agriculture Organization of the United Nations Regiona Office for Asia and the Pacific. Retrieved from http://www.fao.org/3/a-ab777e.pdf
Stefanovic, et al. (2012). Antibacterial Activity of Naturally Occurring Compounds from Selected Plants. ISBN: 978-953-51-0723-1, InTech, DOI: 10.5772/33059. Retrieved from http://cdn.intechopen.com/pdfs/38642.pdf
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