Syzygium aromaticum essential oil is widely used in dental care, as an antiseptic and analgesic and is effective against a large number of bacteria. The major component of clove essential oils is usually considered to be eugenol, with β-caryophyllene and eugenyl acetate, being present although in lower concentrations. A review of published results reveals a great variability in the chemical composition of clove essential oils. The purpose of this study is to compare the chemical composition of Madagascar, Indonesia and Zanzibar bud, leaf and stem essential oils. 121 commercial essential oils isolated from bud, leaf and stem were used in this work. The oils were analyzed by GC and ten constituents were identified from the whole. The major constituent of Madagascar and Indonesia bud essential oils was eugenol (72.08 -80.71% and 77.32 -82.36% respectively). Out of this constituent which was common to Madagascar and Indonesia bud essential oils, significant difference was observed with respect to eugenyl acetate (11.68 -21.32% vs 8.61 -10.55% respectively) and β-caryophyllene (2.76 -6.38% vs 5.34 -8.64% respectively). Comparing chemical composition of leaf essential oils from Madagascar with those of Indonesia, variation in the contents of main constituent, eugenol (80.87 -83.58% vs 75.04 -77.54%), β-caryophyllene (11.65 -15.02 vs 17.04 -19.53%) and eugenyl acetate (0.29 -1.45% vs 0 -0.06%) was observed. The major constituents of Madagascar, Indonesia and Zanzibar stem essential oils were eugenol (91.81 -96.65%, 88.76 -89.28% and 87.52 -89.47%, respectively) and β-caryophyllene (1. 66 -4.48%, 7.40 -7.75% and 7.19 -9.70%). For each plant material, variation in the percentage of the main constituents was observed according to the sample geographic origin.

Baobab seed oil contains specific fatty acids. Most of the studies on baobab fatty acids have been carried out singly and in isolation from each other, making it difficult to compare results through different species. The objective of the present study is to establish the seed fatty acid composition of each Adansonia species in order to evaluate and understand the relationships between the oil chemical compositions, the baobabs' taxonomy and, the ecological and geographical origin of each seed lot. The seed oils have been analysed using gas chromatography (GC). The oils of all baobab species contain three major fatty acids: palmitic, oleic and linoleic acids. They also contain specific fatty acids such as cyclopropenic and cyclopropanic acids, which are characteristic of the Malvaceae family seed oils. It was possible to distinguish three sections through principal components analysis using the eleven fatty acids identified by GC. The Adansonia section contains high rates of oleic acid (± 35%), the Brevitubae section is rich in palmitic acid (± 42%) and the Longitubae section contains high levels of dihydrosterulic acid (± 5%). The oil fatty acid composition, however, does not enable a definitive characterization of profiles according to species. The fatty acid composition is not significantly influenced by the geographical, soil and climate conditions of the collection sites.

Variation on yield and composition of the essential oil of Syzygium aromaticum buds from Madagascar at different phenological stages including young bud stage, budding stage 1, budding stage 2, budding stage 3, full budding stage, flowering stage, initial fruiting stage, full fruiting stage are reported. The essential oil yield varied from 2.52% to 17.94%, reaching a maximum at the end of budding stage, after which it rapidly decreased. The essential oil was analyzed by GC and four constituents were identified and quantified for whole phenological stages. Eugenol and eugenyl acetate were the main compounds in all samples. Eugenol, was lower in the young bud stage (39.66%) and increased in the subsequent phenological stages to reach maximum in the full fruiting stage (94.89%). In contrast, eugenyl acetate was higher in the young bud stage (56.07%), after which decreased to reach minimum in the full fruiting stage (2.01%).

The changes in the essential oil yield and composition from Syzygium aromaticum leaf harvested at different phases of development from young leaves to mature leaves were studied. Separation of the essential oils was conducted by steam distillation in a Clevenger apparatus for about 4h. Essential oils analyses were performed by GC/MS. The yield of essential oil (ml per 100 g of DM) of the leaf following the four phases of development was in order of: young leaves (5.1%) > expanded leaves 1 (4.5%) > expanded leaves 2 (4.1%) > mature leaves (3.8%). Sixteen compounds were detected by GC/MS. Eugenol and eugenyl acetate were the dominant components. Eugenol and eugenyl acetate amount had a divergent evolution during the four expansions of leaves. When eugenol reached its highest percentages at expanded leaves 2 (84.00 -90.48%) and mature leaves stage (88.32 -90.22%), eugenyl acetate reached the lowest ones with, respectively, 0.96 -7.16% and 0.36 -1.64%, but when the eugenyl acetate reached a maximum percentage at young leaves stage with 61.44 -65.52%, eugenol reached a minimum of 25.43 -30.38%. It is judicious to collect and extract S. aromaticum leaf in expended leaves 2 (pale green leaves) and mature leaves stage (dark green leaves) in order to obtain the optimal yield and maximum percentage of eugenol.