The aerial parts of Pteris multifida were collected at the flowering stage, in July to August 2002, from Pingjiang district of Hunan Province (China). The air-dried and finely ground samples were extracted successively with 1 L of methanol using a Soxhlet apparatus for about 72 h at a temperature not exceeding the boiling point of the solvent [1]. The resulting extracts were suspended in water and partitioned with chloroform to obtain water-soluble (polar) (7.69%, w/w) and water-insoluble (nonpolar) subfractions (4.08%, w/w), which were then lyophilized and kept in the dark at −20°C until further tested. The same samples (250 g) were placed in a Clevenger-type apparatus with 2 L double distilled water (previously saturated with NaCl) and hydrodistilled for 4.5 h; after that, the yellowish oils were extracted from the condensate (saturated with NaCl) with diethyl ether. The obtained essential oils (EOs) were dried over anhydrous sodium sulfate after filtration and stored in sealed glass tubes at −20°C until further tested and analyzed (Table 1 and 2).

TABLE 1. Organoleptic and Physico-chemical Properties of the EOs from P. multifida
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TABLE 2. Chemical Composition of the Hydrodistilled EOs of P. multifida
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The microorganisms listed in Table 3 were provided by the Biology Department of Longdong University, Qingyang (China). Two different methods were employed for the determination of antimicrobial activities: agar-well diffusion method for the methanol extracts (MEs) and agar-disc diffusion method for the EOs [2, 3]. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of the EOs against the test microorganisms were determined by the broth microdilution method [4, 5]. The MICs and MBCs of levofloxacin were also determined in parallel experiments in order to control the sensitivity of the test microorganisms. All tests were performed in duplicate.

TABLE 3. Antimicrobial Activity of the EOs and the MEs of P. multifida
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