Introduction

The African environment is probably the least explored in terms of available untapped resources. Herbal medicine is readily available in our diverse vegetation, cheap and above all carries the potentials of introducing new templates into modern medicine.

The use of medicinal plants all over the world predates the introduction of antibiotics and other modern drugs into African continent (Akinyemi et al, 2005). Herbal medicine has been wisely used and formed an integral part of primary health care in China (Liu, 1987) Ethiopia (Desta, 1993) Argentina (Anesini and Perez, 1993) and Papau New Guinea (Nick et al, 1995). A significant proportion of pharmaceutical products in current use are designed from plants (Cowan, 1999 and Raskin et al, 2002). A large number of phytochemicals belonging to several chemical classes have been shown to have inhibitory effect on all types of micro-organisms in vitro (Cowan, 1999) and some plant extracts have shown activity on both gram negative and gram positive organism (Nascimento et al, 2000)

The use of various plant parts in the treatment of the sick developed into tradition which was handed down from one generation to another over the years verbally or written (Sofowora, 1982; Akinyanju, 1986). For thousand of years, medicine depended exclusively on leaves, flowers and barks of plants, only recently have synthetic drugs come into use and in many instances, these are carbon copies of chemicals identified in plants (Conway, 1973). In orthodox medicine, a plant may be subjected to several chemical processes before its active ingredients is extracted refined and made ready for consumption, while in traditional medicine, a plant is simply eaten raw, cooked or infused in water or native wine or even prepared as food (Conway, 1973).

Even before the discovery of modern antibiotics and other chemotherapeutic agents, traditional medicine has served as man's resort when attacked by infective agents such as bacteria and fungi (Crafton, 1983).

Ageratum conyzoides is derived from the Greek word agera meaning non-aging referring to longevity of the flowers or the whole plant, commonly called goat or billy goat weed. It belongs to the family Astreracae, which is an annual herbaceous plant with a long history of traditional use in several countries of the world (Ming, 1999). The specific epithet conyzoides is derived from konz the Greek name of Inula helenium which it resembles (Kissman and Groth, 1993).

Traditional communities in India use this species as an antidysenteric and antilithic (Borthakur and Basuah, 1987) and in Asia, South America and Africa aqueous extract of this plant is used as an antibacterial agents (Almagboul, 1985; Ekundayo et al, 1987). In Cameroon and Congo traditional use is to treat fever, rheumatism, headache, and Colic (Menut et al, 1993; Bioka et al, 1992). Ageratum conyzoides has long been known in herbal or folk medicine as a remedy for various ailments in Africa (Almagboul et al, 1985) Asia and south America (Ekundayo et al, 1987 ; Borthakur and Baruah, 1987). The plant is used by the Fipa in South Africa as application to fresh wounds and in central Africa, the leaf is used to aid the healing of wound especially those caused by burn (Watt et al, 1962).The reputed efficacies of these plants have been experienced and passed on from one generation to the other.

This knowledge could enable more rational exploitation of the plant both in traditional medicine and in the empirical development of new antibacterials.

This work was based on scientific investigation of the widely acclaimed medicinal value of Ageratum conyzoides to establishing its antimicrobial activity on some selected bacterial pathogens.

Materials And Methods

Source of Ageratum conyzoides

Processing of the plant

Extraction

Phytochemical screening methods

Sources of Bacterial Isolates

Preparation of the Test organisms

Bacterial Susceptibility Testing

Results

The antibacterial activities of aqueous methanolic and hexane extract of Ageratum conyzoides leaves gave different mean zone diameter of inhibition on the bacterial isolates tested (Table 1). The aqueous leaf extract gave the mean zone diameter of inhibitions ranging from 7 – 15mm for Staphylococcus aureus, 8 – 12mm for Yersinia enterocolitica and 6 – 12mm for Escherichia coli, S. gallinarum was not inhibited. The methanolic leaf extract did not inhibit the growth of S. gallinarum and Y. enterocolitica but inhibited Staphylococcus aureus and Escherichia coli at a range of 10 – 14mm and 10 – 16mm mean zone diameter respectively. While the hexane leaf extracts inhibited the growth of all the isolates giving a mean zone diameter of inhibition ranging from 9 – 16mm for S. aureus, 10 – 14mm for Y. enterocolitica, 9 – 17mm for S. gallinarum and 7 – 16mm for Escherichia coli.

Aqueous methanol and hexane extracts of Ageratum conyzoides stem gave the mean zone diameters of inhibition ranging from 7 – 14mm for S. aureus, 6 – 10mm for Y. enterocolitica, 6 – 13mm for S. gallinarum and 8 – 11mm for Escherichia coli. The methanolic stem extracts did not inhibit any of the bacterial isolates. The hexane stem extract gave mean zone diameters ranging from 8 – 15mm for S.aureus, 7 – 11mm for Y. enterocolitica, 10 – 14mm for S. gallinarum and 6 - 11mm for E. coli (Table 2).

The aqueous root extracts showed no inhibition on the bacterial isolates except for E. coli which was inhibited with a mean zone diameter of 7-12mm. The hexane root extracts inhibited the growth of the bacterial isolates giving a range of 7 – 12mm for S. aureus, 7 – 14mm for Y. enterocolitica, 7 – 10mm for S. gallinarum and 9 – 13mm for Escherichia coli (Table 3).

The aqueous leaf extracts gave MIC results of (100, 25 and 50mg/ml for Staphylococcus aureus, Y. enterocolitica and Escherichia coli respectively. The methonolic leaf extracts also gave MIC of (50 and 100) mg/ml for Staphylococcus aureus and Escherichia coli respectively, while hexane leaf gave MIC of (6.3, 25, 25 and 12.5) mg/ml for Staphylococcus aureus, Y. enterocolitica, S. gallinarum and Escherichia coli respectively.

The aqueous stem extracts gave MIC of (25,25,50 and 50) mg/ml for Staphylococcus aureus, Y. enterocolitica, S. gallinarum, and Escherichia coli respectively. While the hexane stem extracts gave MIC of 12.5, 12.5, 25 and 25 mg/ml for Staphylococcus aureus, Y. enterocolitica, S. gallinarum, and Escherichia coli respectively.

The aqueous root extracts gave MIC of 100mg/ml for Escherichia coli only. While hexane root extract gave MIC of 12.5, 12.5. 50 and 6.25 mg/ml for Staphylococcus aureus, Y. enterocolitica, S. gallinarum, and Escherichia coli respectively.

The aqueous leaf extracts gave MBC of 50, 25 and 25mg/ml for Staphylococcus aureus, Y. enterocolitica, S. gallinarum, and Escherichia coli respectively. The methanolic leaf extract gave MBC of 25 and 50mg/ml for Staphylococcus aureus and Escherichia coli respectively. While hexane leaf extracts gave MBC of 3.13, 12.5, 25 and 6.25mg/ml for Staphylococcus aureus, Y. enterocolitica, S. gallinarum, and Escherichia coli respectively (Table 4).

The aqueous stem extracts gave MBC(s) of 50, 25, 25 and 50 mg/ml for Staphylococcus aureus, Y. enterocolitica, S. gallinarum, and Escherichia coli respectively. Hexane stem extract gave MBC(s) of (6.25, 6.25, 12.5 and 12.5)mg/ml for Staphylococcus aureus, Y. enterocolitica, S. gallinarum, and Escherichia coli respectively (Table 5).

The aqueous root extract gave MBC(s) of (12.5, 6.25, 25 and 6.25)mg/ml for Staphylococcus aureus, Y. enterocolitica, S. gallinarum, and Escherichia coli respectively (Table 6)

The percentage effectiveness of the leaf extract on the bacterial isolates used in this work was 75%, 50% and 100% respectively for the aqueous, methanolic and hexane leaf extracts. Also from this finding the root extract of Ageratum conyzoides gave 25% effectiveness for the aqueous extract and 100% for the hexane extract.The methanolic root extract was not effective against any of the bacteria isolates tested in this work. The negative control showed no inhibition on any of the bacteria isolates while the positive control inhibited all the bacterial isolates.

The phytochemical screening showed that Ageratum conyzoides contains alkaloids, Resins, Saponins, Tannins, Glycosides and Flavonoids. The leaves of Ageratum conyzoides contains Resins, Alkaloids, Tannins, Glycosides and Flavonoids. The dry stem powder contains Resins Saponins, Tannins, Glycosides and Flavonoids, while the dry root powder of Ageratum conyzoides contains Resins, Alkaloids, Saponins and Flavonods.

Figure 1

Table 1: Antibacterial Activity Of Leaf Extracts Of Ageratum Conyzoides

Figure 2

Table 2: Antibacterial Activity Of Stem Extracts Of

Figure 3

Table 3: Antibacterial Activity Of Root Extracts Of

Figure 4

Table 4: Minimum Bactericidal Concentration (Mbc) Of Leaf Extracts Of

Figure 5

Table 5: Minimum Bactericidal Concentration (Mbc) Of Stem Extracts Of

Figure 6

Table 6: Minimum Bactericidal Concentration (Mbc) Of Root Extracts Of

Discussion

Medicinal plants constitute an effective source of both traditional and modern medicines. Herbal medicine has been shown to have genuine utility and about 80% rural population depends on its efficacy for their primary health care. Scientist from divergent fields in a similar efforts are investigating plants a new with an eye to their antimicrobial usefulness. A sense of urgency accompanies the search as the pace of species extinction continues. Over the years, the WHO advocated that countries should interact with traditional medicine with a view to identifying and exploiting aspects that provide safe and effective remedies for ailments of both microbial and non-microbial origins (WHO 1978). The results obtained in the study revealed antimicrobial efficacy of extract of A. conyzoides leaves, roots and stems. The active component of this plant may be due to its high non polar compounds. This is similar to the findings of Ijeh et al. (2005), and Junaid et al (2006) but in contrast to the findings of Obi and Onuoha (2000), who documented alcohol as the best solvent for the extraction of plant active substances of medical importance. Hexane extract was the most potent of all the extract suggesting that the active component must be a highly non polar compound.

Although the inhibitory effects of aqueous and methanolic extracts of medicinal plants are usually reported (Tignokpa et al, 1986; Omer et al,1998; and Olayinka et al, 1992)).

In this study, the methanolic, stem or root extracts were non inhibitory to all the bacteria isolates used (S. aureus, Yersinia enterocolitica, Salmonella gallinarum and E. Coli) however it is similar to the findings of Durudola (1997) and Almagboul (1985) and more recently, Umeh et al (2005) who documented non inhibitory effects of methanolic extract in Benue state Nigeria. The antibacterial activity of the hexane extracts against all the bacterial isolates used suggest that the principal active ingredients of the plant must be more of lipid soluble or non polar, since hexane is a non-polar solvent which must have easily extracted the lipid soluble phytochemicals such as essential oils and coumarins. The diffusion rates of these phytochemicals within the agar matrix may explain the wider zone of inhibition observed (Cowan, 1999).

The minimum inhibitory concentrations observed for the aquoeus and methanolic (leaf, stem and root) extracts are quite high between a range of (25-100) mg/ml, while that of hexane (leaf, stem and root) extract are between a range of (6.25-50) mg/ml. This is further supported by claims that the active antimicrobial phytochemicals of the plant Ageratum conyzoides must be more lipid soluble or non-polar.

The result obtained for the minimum bactericidal concentration (MBC) which gave a range of (25-50) mg/ml for aqueous and methanolic (leaf, stem and root) extract and a range of (3.13-25) mg/ml for hexane (leaf, stem and root), extracts varied considerably from the results obtained for the minimum inhibitory concentrations (MIC(s). These variations in results implies that the MBCs result obtained from plate cultures after plating on various dilutions of extracts is more reliable and accurate compared to MICs results obtained visually using turbidity as an index.

Interestingly, the observed antibacterial effects of Ageratum conzoides plant parts on the selected bacterial isolates though in vitro implies that the extracts may indeed be effective in vivo as claimed by traditional healers.

In central Africa, particularly Liberia, A. conyzoides is used to treat pneumonia, while in Congo, its leaf sap is used to treat trachycardia (Burkhill, 1985) though the most common use is to cure wounds and burns, as claimed by Oladejo et al, 2003. Hence the inclusion of gram negative organisms in this study. In Nigeria, it is reportedly used in the treatment of typhoid fever and diarrhoea (Adodo, 2002).

The world has entered an era when health is increasingly managed with an eye to cost containment. Critical to developing a cost effective approach to the evaluation and management of clinical illness is the selective use of available diagnostic methods, therapies and preventive measure.

The emergence of bacterial strains that are resistant to many commonly used antibacterial agents means that treatment failures may become more common. Appropriate antimicrobial therapy can shorten illness and reduce morbidity in some bacterial and parastic infections and can be life saving in invasive infection.

This work shows that Ageratum conyzoides is a potential antibacterial agent for the treatment of gastrointestinal tract infection and diarrhea and wound infections caused by Staphylococcus aureus. Herbal therapies are generally available and cheaper and offer important alternatives to more expensive allopathic medicine. The use of A. conyzoides extracts or leaves to feed infected birds with fowl typhoid is highly supported by our findings (Aon, 2007).

Acknowledgement