Comparison of the antibacterial activity of essential oils and extracts of medicinal and culinary herbs to investigate potential new treatments for irritable bowel syndrome

Table 1 Summary of results of antibacterial activity of essential oils

Vernacular name	Botanical name	Activity in disc diffusion assay	Activity in turbido-metric assay	Activity in zone of clearance assay
Coriander seed	Coriandrum sativum	++	+++	+++
Coriander seed	Coriandrum sativum	(0.0053)	(5.82 × 10^-5)	(0.0002)
Fennel	Foeniculum vulgare	+	+++	+
Fennel	Foeniculum vulgare	(0.0003)	(8.01 × 10^-6)	(0.0027)
Grapeseed	Vitis vinifera	-	-	-
Grapeseed	Vitis vinifera		(0.3216)
Lavender	Lavendula angustifolia	+	++	+
Lavender	Lavendula angustifolia	(0.0039)	(0.0031)	(0.0011)
Lemon balm	Melissa officinalis	++	++	+++
Lemon balm	Melissa officinalis	(0.0041)	(0.0008)	(0.0014)
Lemon grass	Cymbopogon citratus	++	++	+
Lemon grass	Cymbopogon citratus	(0.0004)	(0.0030)	(0.0003)
Mandarin	Citrus reticulata	++	+++	+
Mandarin	Citrus reticulata	(0.0092)	(3.39 × 10^-5)	(0.0484)
Neem	Azadirachta indica	-	ND	-
Peppermint	Mentha piperita	++	+++	+++
Peppermint	Mentha piperita	(0.0390)	(3.14 × 10^-5)	(0.0000)
Pine	Pinus sylvestris	+++	++	++
Pine	Pinus sylvestris	(0.0027)	(0.0003)	(0.0001)
Rosemary	Rosmarinus officinalis	+	++	+
Rosemary	Rosmarinus officinalis	(0.0000)	(0.0085)	(0.0036)
Sage	Salvia lavendulifolia	+	+++	+
Sage	Salvia lavendulifolia	(0.0022)	(3.39 × 10^-6)	(0.0021)
Tea tree	Melaleuca alternifolia	+++	+++	+++
Tea tree	Melaleuca alternifolia	(0.0079)	(5.83 × 10^-6)	(0.0000)
Thyme	Thymus vulgaris	+++	+++	+
Thyme	Thymus vulgaris	(0.0020)	(5.84 × 10^-5)	(0.0193)
Ylang ylang	Cananga odorata var. genuina	+/-	+	-
Ylang ylang		(0.0075)	(0.0477)

Crosses denote the magnitude of the antibacterial activity; the numbers in brackets are the P values obtained from t tests comparing the size of the halos produced with the essential oils with those produced by grapeseed oil for the disc diffusion and zone of clearance assays, and from comparing the A₆₀₀ of the turbidometric assay in the presence of essential oil after 6 hours with that lacking essential oil.