The essential oil was extracted by hydrodistillation. A total of thirty-eight compounds were identified with a-pinene (9.1%) B-pinene (3.5%), myrcene (18.7%), limonene (26.5%), cis-ocimene (2.2%), trans-ocimene (4.8%) and terpineol (3.4%) as the major monoterpenes, while, cis-lachnophyllum ester (16.2%) was the major non-terpenoid polyacetylemc compound. The antibacterial activity of the oil was investigated against 16 bacterial strains using broth microdilution method. The oil inhibited all the test organisms with more pronounced activity on Gram-positive than the Gram-negative bacteria. The Minimum Inhibitory Concentration (MIC) for Gram-positive bacteria range from 0.08-2.50 mg mL, whereas, it was 0.08-5.00 mg mL“ for the Gram-negative bacteria. The ability of the oil from F. muricata to inhibit a range of nosocomial pathogenic bacterial strains at a concentration less than that of streptomycin makes the oil a candidate for possible development of antibiotic drug. Key words: Felicia muricata, hydrodistillation, polyacetylenic, microdilution, nosocomial, antibiotic drug
There is increasing interest in medicinal plants as a natural alternative to synthetic drugs (Fabio er ai., 2007), particularly against microbial agents. There are over a hundred chemical substances that have been derived from plants for drugs and medicines. For example, antimalaria drug, artemisinin from Artemisia annua, anti-inflammatory drug, aescin from Aesculus hippocastanum and many others.
This interest is due to increasing incidence of microbial infections in recent years, largely due to the increase in AIDS-related opportunistic — bacterial pathogens and the emergence of resistance microbial species (Afolayan e¢ al., 2002; Koduru et af, 2006). The spread of drug resistant pathogens is one of the most serious threats to successful treatment of microbial diseases (Prabuseenivasan ef al., 2006). Over the years, essential oils and other plant extracts have evoked interest as sources of natural products. They have been screened for their potential uses as alternative remedies for the treatment of infectious diseases (Tepe ef al., 2004; Kordali e¢ af., 2005), food-bome diseases (Aureli ef al., 1992; Fabio et al., 2003) and cancer cells (Sylvestre er al., 2006). Essential oils have also been reported to be useful in food preservation (Sandri et al., 2007) and fragrance industries. Production of essential oil by plants is believed to be predominantly a defense mechanism against pathogens and pesis (Feng and Zheng, 2007).
Essential oils and their components are gaining increasing interest because of their relatively safe status, wide acceptance by consumers and their exploitation for potential multi-purpose functional use. Felicia muricata Thunb (Asteraceae) is a small drought resistant perennial aromatic herb growing up to 0.2 m in height. The plant derived its name from muricate (rough, with sharp tubercles or protuberances). It plays a role as desertification indicator, becoming increasingly invasive in grassland regions (Jordaan and Kruger, 1993). The Zulu, Sotho and Xhosa traditional healers in the management of headaches, stomach catarrh, pains and inflammation have been reported (Hutchings, 1989a: Hutchings and Van Staden, 1994). Crude-extracted herb has been tested to exhibit 80-90% inhibition of cyclooxygenase, an important enzyme in the prostaglandin biosynthesis pathway (McGaw ef al., 1997). Preliminary investigations on the local uses of the species revealed its medicinal importance for the treatment of stomach ache and cancer, for this purpose the aerial part is boiled and taking orally for the relief of pains. To the best of our knowledge, the chemical composition and the antibacterial activity of the essential oil from this herb has not been reported in literature. This investigation was to find out the chemical constituents and the antibacterial activity of essential oil from F. muricata by screening the oil against 16 selected bacterial strains. Further study is progressing on the activity of this oil on other infectious micro-organisms.