Essential oil (EO) from Eriocephalus africanus L. leaves was evaluated against the growth of some phytopathogenic bacteria including Agrobacerium tumifaciens, Dickeya solani, Erwinia amylovora, Pseudomonas cichorii and Serratia pulmithica using the disc diffusion method and minimum inhibitory concentration (MIC) evaluation. Ten compounds in the EO with dominance of Artemisia ketone (2,5,5-trimethyl-2,6-heptadien-4-one) (77.92%) and ledol (19.92%) were revealed. The antibacterial activity indicated efficacy of essential oil against majority of strains isolated. The most effective action was recorded against D. solani, by 7.5 and 10 µL of oil, with 18.33 mm and 100 μg/mL as zone inhibition and MIC, respectively, whereas the lowest activity was exhibited against P. cichorii (diameter inhibition = 6.66 mm at 10 µL of oil, MIC = 100 μg/mL). The strain S. pulmithica appears to be resistant to the oil when the activity is measured by 10 µL of oil but its growth inhibition was reported with a MIC of 100 μg/mL (1).
In this research, the leaves of Lepechinia heteromorpha (Briq.) Epling, Lepechinia radula (Benth.) Epling and Lepechinia paniculata (Kunth) Epling have been collected in order to perform a phytochemical study. The first species was distilled to obtain a novel essential oil (EO), while the others were submitted to ethyl acetate extraction and secondary metabolite isolation. The chemical composition of the EO from L. heteromorpha has been investigated by Gas Chromatography-Mass Spectrometry (GC-MS) and Gas Chromatography with Retention Indices (GC(RI)), identifying 25 constituents. A major compound, (-)-ledol (21.2%), and a minor compound, (-)-caryophyllene oxide (1.0%), were isolated from the EO and their structures confirmed by Nuclear Magnetic Resonance (NMR) spectroscopy. Other major constituents of the EO were viridiflorene (27.3%), (E,E)-α-farnesene (1.4%), spirolepechinene and (E)-β-caryophyllene (7.1% each), allo-aromadendrene (6.1%), camphor (1.7%), limonene (1.3%) and β-phellandrene (4.6%). The enantiomeric composition of the EO monoterpene fraction was also studied, determining the enantiomeric excess and distribution of α-pinene, limonene, β-phellandrene and camphor. The ethyl acetate extract of L. radula and L. paniculata were fractionated by column chromatography. Spathulenol, angustanoic acid E and 5-hydroxy-4',7-dimethoxy flavone were isolated from L. radula extract; ledol, guaiol and (-)-carnosol were found in L. paniculata (2).
References_____________________________________
(1) Toxicity effects of Eriocephalus africanus L. leaf essential oil against some molecularly identified phytopathogenic bacterial strains.
Behiry SI, El-Hefny M, Salem MZM.
Nat Prod Res. 2019 Jan 28:1-5. doi: 10.1080/14786419.2019.1566824.
(2) Phytochemistry of Three Ecuadorian Lamiaceae: Lepechinia heteromorpha (Briq.) Epling, Lepechinia radula (Benth.) Epling and Lepechinia paniculata (Kunth) Epling.
Gilardoni G, Ramírez J, Montalván M, Quinche W, León J, Benítez L, Morocho V, Cumbicus N, Bicchi C.
Plants (Basel). 2018 Dec 20;8(1). pii: E1. doi: 10.3390/plants8010001.
Ledol 
