Bark Essential Oil of Cedrelopsis grevei from Madagascar: Investigation of Steam‐Distillation Conditions

The effect of the distillation time on the yield and chemical composition of the bark essential oil of Cedrelopsis grevei Baill. was investigated. Distillation kinetics were determined for three batches of bark sampled from two sites, i.e., Itampolo (batches IT1 and IT2) and Salary (SAL), located in a region in the south of Madagascar with characteristically large populations of C. grevei. The bark samples were subjected to steam distillation, and the essential oil was collected at 3‐h intervals. The total yield (calculated after 14 h of distillation) varied from 0.9 to 1.7%, according to the batch tested. Moreover, the essential oils obtained were characterized by GC‐FID and GC/MS analyses. During the course of the distillation, the relative percentages of the most volatile components (monoterpenes and sesquiterpene hydrocarbons) diminished progressively, whereas the least volatile ones (oxygenated derivatives) increased at a consistent rate. Principal component analysis (PCA) and agglomerative hierarchical clustering analysis (AHC) of the results, performed on 13 principal components, allowed distinguishing three chemical groups, corresponding to the three batches, irrespective of the distillation time. This indicated that the chemical variability currently observed with commercial samples is not mainly linked to the experimental conditions of the extraction process, as the distillation time did not significantly alter the chemical composition of the essential oils.     

The influence of certain taxonomic and environmental parameters on biomass production and triterpenoid content in the leaves of Centella asiatica (L.) Urb. from Madagascar

Centella asiatica (Apiaceae family; Talapetraka in Malagasy) is a tropical and subtropical plant with leaves containing glycotriterpenoids (asiaticosides) used in traditional and modern medicine. C. asiatica is collected exclusively in natural stands. It is Madagascar's second most important indigenous plant export. The objective in this study is to provide data which will make it possible to optimize the harvest and thus effectively develop this resource. Two foliar morphotypes were identified: morphotype A with small reniform leaves (leaf area ca. 4.5 cm(2) ), found in the east of Madagascar, and morphotype B with large round leaves (up to 7.5 cm(2) ) found in the west, with sympatric zones in the central part of the island. Morphotype A produces a higher biomass, and is twice as rich in asiaticosides as morphotype B. Significant variations in biomass yield and asiaticoside content are observed depending on the date of collection: higher during the rainy season (December to April) and lower during the dry season (June to August). Inter-annual variations are also observed. Populations located at around 800-1400 m altitude on the eastern side of Madagascar, in a sub-humid climate, appeared to be more productive. These results provide more precise information to the economic sector, which confirms the empirical choices made by collectors. They represent the first elements towards sustainable management of the resource, and maybe even domestication.     

Biological Factors Influencing Production of Xanthones in Aphloia theiformis

Xanthones, and more specifically mangiferin, are molecules used in cosmetics for their photoprotective and anti‐aging properties. The richness in xanthones of Aphloia theiformis leaves, a common shrub in Madagascar, can reach almost 12% (in relation to dry biomass). Amongst the A. theiformis studied, two major groups of individuals have been determined: those presenting a high proportion of mangiferin (up to 80% of the xanthones) and those presenting a high proportion of polar xanthones (not yet identified). Our study shows that: i) for each subject, the xanthone content remains stable over time (no seasonal variation); ii) the majority of the trees developing in the light belong to the first group (rich in mangiferin), whereas the individuals growing in the undergrowth are richer in polar xanthones; iii) the distribution of the two groups seems not to have any correlation with taxonomy and, moreover, with the known varieties of A. theiformis, although the micrantha variety is richer in mangiferin. Overall, this information indicates that A. theiformis is a reservoir of xanthones and makes it possible to define a framework for its reasoned management.