Table 2.

Observed antibacterial interaction between essential oil pairs predicted as synergistic.

Essential oilA	Essential oilB	Probability		MICA	MICB	MICmix	FICI
		Synergistic	Antagonistic	(mg/mL)	(mg/mL)	(mg/mL)
C. citratus	O. compactum	0.669	0.075	0.83	0.5	0.5	0.80 (N)
O. compactum	M. balsamum	0.629	0.161	0.5	> 4	1	1.0–1.1 (N)
C. citratus	M. balsamum	0.607	0.123	0.83	> 4	2	1.2–1.5 (N)
O. compactum	T. ammi	0.585	0.190	0.5	0.5	0.25	0.50 (S)
T. vulgare	O. compactum	0.584	0.182	0.5	0.5	0.5	1.0 (N)
C. citratus	T. ammi	0.565	0.146	0.83	0.5	0.4	0.64 (N)
T. vulgare	C. citratus	0.562	0.140	0.5	0.83	0.5	0.80 (N)
T. ammi	L. petersonii	0.541	0.159	0.5	1	0.5	0.75 (N)
T. vulgare	L. petersonii	0.538	0.152	0.5	1	1	1.5 (N)
C. citratus	T. dolabrata	0.537	0.111	0.83	0.5	0.125	0.20 (S)
C. grevei	M. balsamum	0.535	0.190	1	> 4	> 4	> 2.5 (A/N)
C. verum	O. compactum	0.504	0.280	0.5	0.5	0.5	1.0 (N)
C. verum	C. citratus	0.497	0.218	0.5	0.83	0.25	0.40 (S)
L. petersonii	Z. officinale	0.487	0.132	1	> 4	2	1.0–1.3 (N)
T. ammi	Z. officinale	0.415	0.285	0.5	> 4	0.25	0.25–0.28 (S)
T. vulgare	Z. officinale	0.415	0.274	0.5	> 4	0.5	0.50–0.56 (N)

The FICI was interpreted as S: synergistic (FICI ≤ 0.5); N: no interaction (0.5 < FICI < 4); A: antagonistic (FICI ≥ 4). Observed synergistic interactions are highlighted in bold.

MIC_mix denotes a summation of two oil concentratations in a mixture. C. citratus: Cymbopogon citratus, O. compactum: Origanum compactum, M. balsamum: Myroxylon balsamum var. pereirae, T. ammi: Trachyspermum ammi, T. vulgaris: Thymus vulgaris ct. thymol, L. petersonii: Leptospermum petersonii, T. dolabrata: Thujopsis dolabrata, C. grevei: Cedrelopsis grevei, C. verum: Cinnamomum verum, Z. officinale: Zingiber officinale.