Chemical and antimicrobial analyses of essential oil of Lippia origanoides H.B.K

Genetic diversity and spatial genetic structure within a population of an aromatic shrub, Lippia origanoides (Verbenaceae), in the Chicamocha Canyon, northeastern Colombia

The geographical scale of genetic structure in a continuous population is highly dependent on its breeding system and dispersion capabilities, and this knowledge is important for the study of population dynamics as well as for conservation purposes. In the present study, spatial autocorrelation statistics and intersimple sequence repeat (ISSR) markers were used to describe the genetic structure of a natural population of a prominent aromatic plant, Lippia origanoides, native to the Chicamocha Canyon in northeastern Colombia. For this purpose, individuals were sampled from two localities within the Chicamocha Canyon, where the species is abundant and continuously distributed. Cluster (principal coordinate analysis (PCO) and unweighted pair group method using arithmetic averages (UPGMA)), analysis of molecular variance (AMOVA) and Bayesian analyses revealed a low level of genetic differentiation among the two localities, suggesting that they belong to a single population. Genetic diversity levels in this population, described as the percentage of polymorphic loci (P=86.21%) and quantified using Shannon's diversity index (I=0.453) and the average panmictic heterozygosity (HB=0.484), were shown to be comparable to or higher than that in other plant species with allogamous breeding systems and to other related Verbenaceae species. Fine-scale autocorrelation analyses showed a pattern consistent with the classical model of isolation by distance with moderate but significant levels of local spatial structure. Our results suggest that sampling individuals at distances greater than approximately 1.2 km may result in the collection of different genotypes, which could help preserve the levels of genetic diversity in a propagation programme. The causes of this spatial pattern are currently unknown and could be influenced by many contemporary factors such as restricted seed dispersal and/or short-distance pollen movement, among others.

Composition and Antioxidant Activity of Essential Oils of Lippia Origanoides H.B.K. grown in Colombia

Microwave-assisted hydrodistillation, simultaneous distillation-solvent extraction, and supercritical fluid extraction, were used to isolate secondary metabolites from two Lippia origanoides chemotypes growing wild in Colombia. Compound identification was based on chromatographic and spectroscopic criteria. The main components identified in the essential oil of one chemotype were carvacrol (44.4 – 51.8%) and p-cymene (8.8 – 10.1%). Those of the other chemotype were p-cymene (11.3 – 15.7%) and 1,8-cineole (6.8 – 10.9%). The last one constitutes a new chemotype, characterized by its low thymol and carvacrol contents and very low antioxidant activity. The radical scavenging activity of the essential oil of the first chemotype was higher than that of butylated hydroxytoluene (BHT) and similar to that of α-tocopherol.