Antimicrobial Activity of the Essential Oil of Plectranthus neochilus against Cariogenic Bacteria

Table 2

Chemical composition of the essential oil from the leaves of P. neochilus as identified by GC/MS.

Chemical compound	RT [min]^a			Content [%]^d	Identification^e
α-Thujene	5.00	921	924	6.3	RL MS
α-Pinene (1)	5.19	929	932	14.1	RL MS
Thuja-2,4(10)-diene	5.43	939	941	0.2	RL MS
Camphene	5.62	943	947	0.1	RL MS
Sabinene	6.21	966	971	1.9	RL MS
-Pinene (2)	6.37	975	977	7.1	RL MS
-Myrcene	6.65	985	988	0.3	RL MS
Octan-3-ol	6.90	993	996	0.2	RL MS
α-Terpinene	7.53	1015	1016	0.5	RL MS
o-Cymene	7.79	1022	1023	0.3	RL MS
Limonene	7.94	1026	1027	0.2	RL MS
(Z)--Ocimene	8.14	1030	1033	0.4	RL MS
(E)--Ocimene	8.50	1040	1043	1.8	RL MS
-Terpinene	8.94	1052	1055	1.4	RL MS
α-Terpinolene	9.94	1080	1084	0.2	RL MS
4-Terpineol	13.75	1177	1179	1.2	RL MS
α-Cubebene	20.78	1341	1344	0.5	RL MS
α-Copaene	21.97	1366	1372	1.2	RL MS
-Bourbonene	22.29	1380	1379	1.1	RL MS
-Cubenene	22.50	1378	1384	0.3	RL MS
trans-Caryophyllene (3)	23.80	1412	1415	29.8	RL MS
α-Humulene	25.25	1448	1450	1.5	RL MS
Germacrene D	26.30	1470	1476	6.2	RL MS
Eremophilene	27.51	1504	1505	3.9	RL MS
α-Amorphene	27.61	1506	1508	0.4	RL MS
-Cadinene	27.83	1514	1513	1.9	RL MS
(E)-Nerolidol	29.63	1554	1559	0.3	RL MS
Caryophyllene oxide (4)	30.26	1571	1575	12.8	RL MS
Unknown	32.06	—	1622	0.3	—
epi-α-Cadinol	32.62	1634	1637	1.5	RL MS
-Cadinol	32.70	1636	1639	0.8	RL MS
α-Cadinol	33.12	1647	1650	1.3	RL MS
Monoterpenes hydrocarbons				34.8
Oxygenated monoterpenes				1.2
Sesquiterpenes hydrocarbons				46.8
Oxygenated sesquiterpenes				16.7
Others				0.2
Not identified				0.3

RT: retention time determined on the Rtx-5MS capillary column.
^b: retention index determined on the Rtx-5MS column relative to n-alkanes (C₈–C₂₀).
^c: retention index.
^dCalculated from the peak area relative to the total peak area.
^eRL: comparison of the retention index with the literature [21]; MS: comparison of the mass spectrum with the literature.