Essential Oils from Bolivia. VII. Myrtaceae: Myrcianthes osteomeloides (Rusby) McVaugh and Myrcianthes pseudomato (Legrand) McVaugh

Abstract

The chemical composition of the essential oils of Myrcianthes osteomeloides and M. pseudomato was studied by GC and GC/MS. Myrcianthes osteomeloides oil contained 1,8-cineole (55.7%) as the major component followed by α-pinene (17.9%), α-terpineol (8.5%) and β-pinene (4.6%). We identified 1,8-cineole (24.4%), α-pinene (17.1%), linalool (11.7%), limonene (8.5%) and γ-terpinene (7.3%) as main constituents in M. pseudomato oil.

Key Word Index

Myrcianthes osteomeloides, Myrcianthes pseudomato, Myrtaceae, essential oil composition, 1,8-cineole, α-pinene, linalool.

Introduction

Myrcianthes species, belonging to the Myrtaceae family, are growing in South America, the Caribbean region and southern Florida. The oil composition of different species from several countries was reported. The oils of M. cisplatensis from Argentina (l,2)containedl,8-cineole(40.7,13.5%),limonene (22.1,6.5%), α-caryophyllene (1.0, 9.9%) and geraniol (O, 8.4%), while the oil of the same plant from Uruguay (3) contained 1,8-cineole (53.8%) and a-pinene (16.6%) as major constituents. The oils of M. pungens from Argentina (1, 4) were reported to contain 1,8-cineole (45.8, 13.5%), limonene (17.3, 1.8%) pulegone (O, 9.4%) and farnesol (O, 9.0%). As for M.fragrans oils from Jamaica (5) and Cuba (6), they contained 6.9% and 41.8% of α-pinene, 56.0% and 30.0% of limonene, 7.1% and 6.5% of 1,8-cineole and 10.8% and 5.7% of α-terpineol, respectively. The oil of M. callicoma was reported to contain α-pinene, limonene, 1,8-cineole, cedrol, eugenol and cresol (7). Finally, limonene was the major component (14.5%) of the oil of M. coquimbensis from Chile (8), followed by carvone (8.7%) and α-pinene (7.2%).

In Bolivia, five Myrcianthes species are listed (9): M. rnato, M. pseudomato, M. osteomeloides, M. pungens and M. rhopaloides. In this study, we investigated the oil composition of two species growing in Bolivia: M. osteomeloides (arrayancito) (syn. Myrtus osteomeloides Rusby) which is a shrub or small tree that grows to a height of 3 m, and M. pseudomato (sawinto) which is a tree that can reach a height of 10 m.

To our knowledge, this is the first time that the oil composition of these two Myrcianthes species from Bolivia is reported.

Experimental

Voucher specimens of Myrcianthes osteonwloides and M. pseudonwto were deposited at the National Forestal Herbarium Martin Cardenas of the Universidad Mayor de San Simon in Bolivia. Trees leaves of M. osteomeloides and M. pseudomato were collected near Cochabamba in Bolivia and batches of 10 kg or more of fresh material were hydrodistilled.

The oils were first analyzed by GC on a gas Chromatograph HP 5890 with a FID detector equipped with two columns: a polar Supelcowax 10 and a non-polar DB-5 column (30 m × 0.25 mm × 0.25 µm). Then, analyses by GC/MS were performed on a HP 5972 mass spectrometer at 70 eV coupled to an HP 5890 GC equipped with a DB-5 column (same as above). Temperature program was 407deg;C for 2 min, then 2°C/min to 2107deg;C and held constant for 33 min as was the program used for the GC analyses. Identification of the components was done by comparison of their retention indices with standards, and by comparison of their mass spectra with literature (10). Quantitative data were obtained electronically from GC-FID area percentages without the use of correction factors.

Results and Discussion

Clear yellow oils were isolated in a yield of 0.6% for M. osteomeloides and in a yield of 0.1% for M. pseudomato. All identified components of both oils are listed in Table I. 1,8-Cineole was the major product in both oils with a higher percentage in M. osteomeloides, 55.7%, compared with 24.4% in M. pseudomato. In the literature (1,3), high percentages of 1,8-cineole were found in Mi/rcianthes cisplatensis oil from Argentina (40.7%) and Uruguay (53.8%) and in M. pungens oil from Argentina (1) with 45.8% of 1,8-cineole. The oils of the Bolivian species also contained high percentages of α-pinene, 17.9% and 17.1%, similar to M. cisplatensis oil from Uruguay (16.6%, 3), but different to the oils of Myrcianthes species growing in Argentina (1) where the α-pinene percentages are 3.3% and 4.3%.

The other important components in M. osteomeloides oil were α-terpineol (8.5%), β-pinene (4.6%) andlimonene (4.1%). In addition to 1,8-cineole and α-pinene, M. pseudomato oil contmnedlinalool(11.7%),limonene(8.5%), γ-terpinene(7.3%) andp-cymene(3.9%). We noticed that linalool and γ-terpinene were present in greater amounts than in M. osteomeloides oil where they reached only 0.7% and 0.4%, respectively. Other than the difference in the 1,8-cineole contents, the difference in these components was the greatest between the two species. Moreover, the small percentage of α-terpineol (2.4%) in M. pseudomato oil differed from the higher percentage found in M. osteomeloides oil (8.5%). On the whole, the oil composition of M. pseudomato was more complex than the oil of M. osteomeloides. A larger number of sesquiteqsenes were present in this latter oil.