Chemical composition and antimicrobial activity of fatty acid methyl ester of Quercus leucotrichophora fruits

Abstract Natural fats and dietary oils are chief source of fatty acids and are well known to have antimicrobial activities against various microbes. The chemical composition and antimicrobial activities of fatty acids from fruits of white Oak (Quercus leucotrichophora) are yet unexplored and therefore the present study for the first time determines the fatty acid composition, and the antibacterial and antifungal activities of fatty acid methyl esters (FAME) of the white Oak plant found along the Himalayan region of Uttarakhand, India. The GCMS analysis revealed the presence of higher amount of saturated fatty acids than unsaturated fatty acids. FAME extract of fruits of Q. leucotrichophora demonstrated better antibacterial activity against Gram-positive bacteria than the Gram-negative bacteria. The present studies clearly establish the potential of the fruits of Q. leucotrichophora for use in soap, cosmetics and pharmaceutical industries.


Introduction
Fatty acids are the major component of lipids and the physical, chemical and physiological properties of a lipid class depend primarily on its fatty acid composition. The fatty acid composition is determined as the methyl esters of fatty acids by gas-liquid chromatography (Sheppard & Iverson 1975;liu 1994). Fatty acid methyl esters (FAME) are key reagents in the chemical industry (loupy et al. 1993;Ahn et al. 1995) and are raw materials for the production of long-chain carboxylic acids, detergents, alternative fuels for diesel engines (Biodiesel) and as additives for foods, cosmetics and pharmaceuticals (Sonntag 1982).
Quercus leucotrichophora vern. Banj belonging to family Fagaceae is an evergreen tree of approximately 40 m height and is commonly found throughout the Himalayan region at altitudes ranging from 800 to 2000 m (Naithani 1985). Gum of the tree is traditionally used for gonorrhoeal and digestive disorders (Gaur 1999). The seeds are astringent and diuretic, and are used in the treatment of gonorrhoea, indigestion, diarrhoea and asthma (Chopra et al. 1986). The leaves, seeds and bark are also used in livestock healthcare (Pande et al. 2006). The plants of the genus Quercus contain various types of plant secondary metabolites including terpenoids, flavonoids, phenols, steroids, tannins (ellagitannins and hydrolysable tannins), and many others (Ishimaru et al. 1987;Masson et al. 1994). A common flavonoid quercetin and its 3-O-disacchride have been reported from the leaves of Q. leucotrichophora (Kalra et al. 1966). The flavonoids namely 7-methoxy kaempferol, (Sati et al. 2011) and flavon-5, 3′,4′-trihydroxy 7-O-β-d-glucopyranosyl (6″ → 1″′)-β-d-glucopyranoside ) have also been isolated from stem bark of Q. leucotrichophora. The gas chromatography-mass spectroscopy (GC-MS) analysis of volatile extract of stem bark of Q. leucotrichophora showed the presence of 86.36% monoterpenoids, 6.53% sesquiterpenoids and 0.11% of aliphatic aldehydes . The GC-MS study of fruits oil of Quercus brantii growing in southwestern Iran revealed the presence of oleic acid (52.99-66.14%), linoleic acid (10.80-11.11%), Palmetic acid (8.08-10.06%), stearic acid(0.74-1.57%), α-linolenic acid (0.19-0.35%), erucic acid (0.12-0.15%)and arachidic acid(0.12-0.15%) (Khodadoust et al. 2014). The ethanolic and volatile extract of stem bark also showed potent antimicrobial activity against various Gram-positive and Gram-negative micro-organisms (Sati et al. 2011. Fatty acids from various plants are reported to have potent antibacterial and antifungal properties (Russell 1991). However, little is known on the antibacterial and antifungal properties of fatty acids from the fruits of Q. leucotrichophora (white Oak). In this paper, we present data on the FAME of fruits of Q. leucotrichophora, and its antibacterial and antifungal properties.
The antibacterial activity of the FAME extracts against different microbes is shown in Table 2. The extract showed dissimilar activity against different microbes primarily due to the chemical nature and concentrations of the antimicrobial agents present in the extracts and also because of their diverse mode of action on different test micro-organisms (Barbour et al. 2004). The mean zone of inhibition of the extract, assayed against the test organisms ranged between 7.8 and 15.9 mm. The ciprofloxacin (5 μg/disc) antibacterial positive control produced zones of inhibition that ranged from 31 to 33 mm. The MIC of the FAME extracts were 0.125 mg/Ml for Bacillus subtilis and Staphylococcus aureus; 0.5 mg for Pseudomonas aeruginosa and 1.0 mg for Escherichia coli.
The uppermost mean zone of inhibition of 15.9 mm and the lowest minimum inhibitory concentration (MIC) value of 0.125 mg/Ml were recorded by FAME extract of fruits of Q. leucotrichophora against B. subtilis and S. aureus. Chandrasekaran and co-workers (2005) also reported the similar observations previously with the extract of Ipomoea pescaprae against B. subtilis, Bacillus pumilus, Micrococcus luteus, S. aureus, P. aeruginoa, Klebsiella pneumoniae and E. coli (Chandrasekaran et al. 2005). Furthermore, a previous study of FAME extracts of Excoecaria agallocha (Euphorbiaceae) leaves also showed antibacterial and antifungal activity  B. subtilis, B. pumilus, M. luteus, Staphylococcus, P. aeruginosa, K. pneumonia, E. coli, Candida albicans, Candida krusei, Candida tropicalis and Candida parapsilosis (Agoramoorthy et al. 2007). linoleic acid (C18:2) isolated from Schotia brachypetala also exhibited antibacterial activity against S. aureus, K. pneumonia, B. subtilis and E. coli (McGaw et al. 2002). Venkatesalu and coworkers (2004) also reported the antibacterial activity of linoleic acid against Mycobacterium smegmatis and Mycobacterium fortuitum. The bioactive fractions, linoleic acid and oleic acid from Pelagonium species also showed antibacterial activity against Mycobacterium aureum and Mycobacterium phlei (Venkatesalu et al. 2004).
In the present study, the FAME extract of fruits of Q. leucotrichophora demonstrated better antibacterial activity against Gram-positive bacteria than the Gram-negative bacteria. These differences in the fatty acid sensitivities between Gram-positive and Gram-negative bacteria may result from the impermeability of the outer membrane of Gram-negative bacteria since the outer membrane of Gram-negative bacteria is an effective barrier against hydrophobic substances (Agoramoorthy et al. 2007). In fact, Gram-negative bacteria are more resistant to inactivation by medium-and long-chain fatty acids than Gram-positive bacteria (Kabara 1981).

Conclusion
The detailed survey of literature showed that palmitic, stearic, behenic, lauric, tridecanoic, myristic, margaric, oleic, linoleic, palmitoleic and linolenic acids are known to have potent antibacterial and antifungal properties (McGaw et al. 2002;Seidel & Taylor 2004). Our study undoubtedly confirms that the fruits of Q. leucotrichophora contain higher relative percentage of the above-mentioned fatty acids and has potential as an antibacterial principle for clinical application. Thus, on the basis of above study, we can conclude that the fruits of Q. leucotrichophora have high-quality potential for use in the soap, cosmetics and pharmaceutical industries.