Antibacterial properties of plant species native to the New Jersey pinelands.
KEY WORDS: plant, antibacterial
According to the World Health Organization, healing herbs are used as primary medicines by two-thirds of the world's population, nearly 4 billion people worldwide (Castleman, 2001). As 25% of the prescriptions in the United States still contain active ingredients derived from plants (Castleman, 2001), it is clear that medicinal plants play an important role in global healthcare. Current research has demonstrated the effectiveness of medicinal herbs on various dermatological conditions (Graf, 2000), and even cancer (Perez-Carreon et al., 2002). Other studies have also shown that certain plants, including sage, can play a role in food preservation (Valero and Salmeron, 2003). In addition, Salvia species have demonstrated their effectiveness against soil-borne fungal pathogens (Pitarokili et al., 2003), suggesting agricultural applications as well as medicinal. Other studies (Iauk et al., 2003) demonstrated the effects of alcohol extracts on periodontopathic bacteria.
We believe that this study will encourage members of southern New Jersey communities to capitalize on the benefits of plants that grow in their region. Literature suggests that white sage (Salvia apiana), calendula (Calendula officinalis), lemon catnip (Nepeta cataria ssp. Citriodora), lavender (Lavandula angustifolia), and bayberry (Myrica cerifera), all of which thrive in southern New Jersey, are effective against biological agents such as bacteria and fungi (Amirghofran et al., 2000; Castleman, 2001; Iauk et al., 2003; Ulubelen, 2003). Because of their suggested medicinal properties, and their ability to survive in the sandy soils and temperate climate of the Pine Barrens, these plants were selected as the focal points of this study.
MATERIALS AND METHODS
Samples of each of the five plants were obtained, dried, and crushed using a mortar and pestle. A solution of 40% ethanol was used in the extraction process. We tested the effects of alcohol extracts on Escherichia coli (a gram-negative bacterium) and Bacillus cereus (a gram-positive bacterium).
Five grams of each herb were then added to 500mL of 40% ethyl alcohol solution, comparable to the methods of the Perez-Carreon et al. (2002) study. These tinctures were then allowed to sit for one week, after which they were strained through Watman # 1 paper filter. Bacteria were cultured from liquid culture using BD Difco [TM] Nutrient Agar, general purpose medium.
The bacteria were spread over the surface of the agar. The bacteria were either allowed to grow for two days before application of tinctures (established colonies), or the tinctures were applied immediately (unestablished colonies); 0.1 mL of each tincture was then applied to both established and unestablished colonies of E. coli and B. cereus bacteria. The bacterial colonies were allowed to grow for a week after application.
Controls were defined as applications of only bacteria or fungi (Control--) and applications of bacteria or fungi with the addition of 0.1 mL of 40% ethyl alcohol (Control +). Relative growth was then determined by counting the number of colonies that had formed in both the control and experimental cultures. Data sets were tested for normality and transformed as needed. A statistical analysis was then done using ANOVA (SAS, 1990).
RESULTS AND DISCUSSION
Figure 1 shows the effects of the antibacterial activities of calendula, catnip, bayberry, lavender, and sage on previously established colonies of E. coil White sage, lemon catnip, and lavender inhibited E. coli growth, while bayberry enhanced growth; calendula had no effect on previously established bacteria colonies (F= 10.61, p<0.0001). Similar results are found when applying the aforementioned herbs to developing E. coli colonies. As Figure 2 demonstrates, white sage, lemon catnip, and lavender also inhibited growth of unestablished E. coli colonies.
[FIGURES 1&2 OMITTED]
It has been previously reported that Salvia officianalis, a different species of sage, demonstrated a high level of antibacterial activity against E. coli (Pereira et al. 2004), which is consistent with our findings on the effectiveness of Salvia apiana. Similarly, catnip's activity was consistent with the findings of Nostro et al. (2001), that Nepeta cataria is effective in inhibiting bacterial growth. While their study focused on gram-positive bacteria, we found that the tincture of N. cataria was effective against gram-negative bacteria. The effects of lavender as an antibacterial agent against gram-negative bacteria are similar to the findings of Takarada et al. (2004), who showed that lavender was also effective against periodontopathic and cariogenic bacteria. Our results further support the findings of the antimicrobial properties of lavender (Cavanagh and Wilkinson, 2002).
Bacillus cereus was not affected by any of the treatments. This is particularly interesting in the case of catnip, which has been previously found by Nostro et al. (2001) to be effective against gram-positive bacteria. However, these investigators tested Staphylococcus aureus strains, while we focused on B. cereus. A study by Valero and Salmer6n (2003) demonstrated that under strict temperature conditions, sage-essential oil showed some effect against the growth of B. cereus.
Calendula officinalis has been previously shown to be an effective antimicrobial agent (Mostafa and Tantawy, 2000; Hammouda and Borbely, 1995), and the lack of bacterial inhibition in Calendula treatment in our study was somewhat unexpected. It is suggested that the lack of activity was caused by use of ethyl alcohol, since main active compounds of Calendula are lypophylic rather than hydrophilic (Hamburger et al., 2003), and thus it is possible that ethyl alcohol tincture is not the optimal method of preparation of Calendula.
White sage and calendula sterilized test tubes containing mature Neurospora crassa fungi (Errickson and Sedia, unpublished data), though other treatments were ineffective. However, developing N. crassa were not affected by any of the treatments. Suhr and Nielsen (2003) obtained similar results when testing sage-essential oil against rye bread spoilage fungi. In addition to benefiting human health, these herbs can also be effective antifungal agents against soilborne pathogens, as Pitarokili et al. (2003) demonstrated in a study that tested Salvia fruticosa, a species of sage, against various phytopathogenic fungi.
We thank two anonymous reviewers for their helpful comments on the earlier version of this manuscript.
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William Errickson (1), Ekaterina G. Sedia
The Richard Stockton College of New Jersey P.O. Box 195, Jim Leeds Road Pomona, NJ 08240 USA
(1) Current Address: University of New Hampshire, Durham, NH 03824
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|Author:||Errickson, William; Sedia, Ekaterina G.|
|Publication:||Bulletin of the New Jersey Academy of Science|
|Date:||Mar 22, 2005|
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