Chemical Composition of the Essential Oils of Four Plumeria Species Grown on Peninsular Malaysia

Journal of Essential Oil Research: JEOR, Nov/Dec 2006 by Tohar, Norsita, Awang, Khalijah, Mohd, Mustafa A, Jantan, Ibrahim

Abstract

The flower oils of four Plumeria L. species; P. obtusa L., P. acuminata Ait. (yellow flower), P. rubra L. (pink flower) and P. rubra (orange flower) hydrodistilled from samples grown on peninsular Malaysia, were analyzed by gas chromatography on two columns of different polarity and GC/MS. The oil of P obtusa was found to be rich in benzyl salicylate (45.4%) and benzyl benzoate (17.2%), but also minute concentrations of alkanoic acids. oil obtained from P. acuminata was rich in palmitic acid (36.2%), linoleic acid (16.8%), lauric acid (10.4%) and myristic acid (10.3%). The pink flowered P. rubra oil was similar to P. acuminata oil in that it was also devoid of benzyl salicylate and benzyl benzoate and rich in alkanoic acids but linoleic acid was absent in the oil of the former. However, the orange flowered P. rubra oil contained both the non-terpene esters (benzyl salicylate, benzyl benzoate and 2-phenylethyl benzoate) and alkanoic acids in significant amounts. The orange flowered cultivar had the highest concentration of (E)-nerolidol (14.4%) and geraniol (4.1%) among the species studied.

Key Word Index

Plumeria obtusa, Plumeria acuminata, Plumeria rubra, Apocynaceae, essential oil composition, benzyl salicylate, benzyl benzoate, hexadecanoic acid, tetradecanoic acid, dodecanoic acid, linoleic acid, (E)-nerolidol.

Introduction

Plumeria L. (Family: Apocynaceae) is indigenous to tropical America and is found from southern Mexico to northern South America (1,2). However, due to its ease of propagation through cuttings, many species and hybrids of Plumeria are now widely cultivated and distributed in the wanner regions of the world (2,3). Plumeria, the most celebrated of all tropical flowers, are commonly known as frangipani (1,2). In Malaysia, it is most famously called 'kemboja,' but several other names such as 'pokok kubur' and 'bunga kubur' have been used to refer to different species and hybrids of Plumeria (1,4). The trees were introduced to Malaysia and at least three main species are commonly found: Plumeria obtusa, P. rubra and P. acuminata (designated as P. acutifolia Poir. by Burkill and revised as P. ruhra (arma acutifolia (Poir.) Woodson in Hortus Third) (1,4,5).

All species are small trees with very thick, fleshy, stout branches and produce a milky juice when the leaves or branches are cut. The leaves are spirally arranged near the ends of the swollen branches and fruits are as a pair of cylindrical, hornshaped with many flat seeds shortly winged at one end. In general, frangipani leaves are green and the flowers are large, waxy, very fragrant, in terminal or lateral stalked cluster (4,6,7). Plumeria obtusa has white flowers with small brilliant yellow center, up to 9 cm in diameter; the leaves are dark green, glossy, obovate and obtuse at both ends. The tree can grow to about 6-9 m tall and partly deciduous at different times of the year (6). While, P. acuminata is an evergreen or partly deciduous tree up to 6 m high; leaves are light green in color, elliptic in shape with acuminate tips and the color of the flower can vary from white to yellow (4,5). Plumeria rubra in contrast, has flowers in various shades of red, pink, orange and yellow; the leaves also have many different sizes, shapes and colors (4,8). This species is a deciduous tree which can exceed 10 m tall in the tropics but in the subtropics, it is unlikely to reach more than 4 m high (8).

Plumerias are believed to be brought to the Far East by the Spanish not just as ornamental trees but more of their medicinal properties (1). The indigenous medical traditions in Java and Madoera make use of decoction of the leaves as lotion for cracks and eruptions on the soles of the feet while decoction of the bark is given for gonorrhoea, dropsical and venereal affections. In the Philippine Islands and West Indies the milky latex and decoction of the bark are reputed to possess purgative, emmenagogic, febrifugic and diuretic properties. In India the plant also finds applications in treatment of skin diseases, fevers, dispersed dropsies and the flowers are even eaten with betel leaves to cure ague (1,9). Siddiqui et al. isolated α-amyrin from the leaves of P. obtusa, a pentacyclic triterpenoid which was an antitumor agent (10). In 1988, Fujimoto et al. obtained from the leaves of P. acutifolia two new antitumor agents which were plumeric acid and methyl plumerate (9). Lupeol and ursolic acid were two antimutagens found in the leaves of P. acuminata (11). Rubrinol was a new antibacterial triterpenoid found in P. rubra by Nargis et al. (12). Coppen et al. (1983) communicated the antifouling properties of the leaf extract of P. rubra and further claimed that the iridoids, isoplumericin, plumericin, plumieride coumarate and plumieride coumarate glucoside found in this species possessed algicidal properties (13,14).

Despite all the comprehensive scientific studies conducted, very scarce information is available on the constituents of the essential oils of the genus Plumeria. Only a few studies on the oils of Hawaiian, Indian and Egyptian plumerias from different species have been carried out (2,15-19). As far as we can ascertain, no work on the chemistry of the essential oils of Malaysian Plumeria has been documented. Therefore, as part of a continuing study to identify new perfumery materials from plants throughout Peninsular Malaysia, we describe the volatile components of the flowers of P. obtusa, P. acuminata (yellow flower) and P. rubra (pink and orange flowers).