Analysis of the leaf Oil of Syzygium malaccense Merr. et Perry from Nigeria

Journal of Essential Oil Research: JEOR, Jul/Aug 2007 by Karioti, A, Skaltsa, H, Gbolade, A A

Abstract

The hydrodistilled essential oil from fresh leaves of Syzygium malaccense Merr. et Perry. grown in Nigeria has been studied by GC and GC/MS for the first time. Identification of the substances was made by comparison of mass spectra and retention indices with literature records. The oil was largely composed of monoterpenes (61.1%) characterized mainly by ( )-α-pinene (7.3%), (-)-β-pinene (8.0%), p-cymene (13.5%), and α-terpineol (7.5%). The sesquiterpenes constituted 30.8% of the oil with (-)-β-caryophyllene (9.0%) as the major component.

Key Word Index

Syzygium malaccense, Myrtaceae, essential oil composition, chiral analysis, ( )-α-pinene, (-)-β-pinene, p-cymene, α-terpineol, (-)-caryophyllene oxide.

Introduction

Malay apple, Syzygium malaccense Merr. et & Perry, (syn. Eugenia malaccensis L., Jambos malaccensis DC.), is much admired for the beauty of the tree, its flowers and its colorful, glistening fruits, without parallel in the Myrtaceae family (1). The plant is presumed to be a native of Malaysia, but is now commonly cultivated from Java to the Philippines and Vietnam, also in Bengal and South India and in many other parts of the world. It is a rather fast-growing tree, reaching 12-18 m in height, and has an erect trunk to 4.5 m. The juicy fruit is oblong, obovoid, or bell-shaped with thin, smooth, waxy skin colored rose-red or crimson or sometimes white. The ripe fruit may be eaten raw or used for flavoring purposes, but its decoction is a reputed febrifuge (1). The plant is used in Polynesian traditional medicine for the treatment of infectious diseases, and has been found to elicit antiviral, antifungal and antibacterial activities (2).

However, the composition of the leaf oil of this plant growing in Nigeria is unknown, but a related species, E. uniflora was reported to yield mainly sesquiterpenes (3). As part of our investigations on plants with potential for medicinal and olfactive purposes, we studied the leaf oil of S. malaccense from Nigeria, where the plant is presently grown as an ornament and for its fruits.

Experimental

Plant material and extraction of oü: Fresh leaves of S. malaccense were obtained from the University campus (OAU, Ile-Ife), and authenticated at the Department of Botany (OAU) Herbarium, where a specimen has been deposited. The essential oil was obtained by hydrodistillation using a Clevenger-type apparatus with a water-cooled oil receiver to reduce hydrodistillation over-heating artifacts according to the British Pharmacopoeia (4). The oil was stored in screw-capped vial and refrigerated until needed.

Analysis of volatile compounds: The composition of the volatile constituents was established by GC and CC/MS analyses. CC analysis was carried out on a Perkin Elmer 8500 gas Chromatograph with FID, fitted with a Supelcowax -10 fused silica capillary column (30 m x 0.32 mm; film thickness: 0.25 µm). The column temperature program was from 75°0 -250°C at a rate of 2.5°C/min. The injector and detector temperatures were programmed at 230°C and 300°C, respectively. Relative percentage amounts were calculated from GC (FID) analysis. GC/MS analyses were performed on a Hewlett-Packard 59736890 system operating in EI mode (7OeV) equipped with a split/splitless injector (220°C), a split ratio 1/10, using three different columns:afusedsilicaHP-5MScapillary column (30m ? 0.25mm), film thickness: 0.25µm); a HP-Innowax capillary column (30m x 0.25mm), film thickness: 0.50pm) and a chiral Cydex B capillary column (50m ? 0.22mm), film thickness: 0.25µm). The temperature program for HP-5 MS column was from 60°C (5min) to 280°C at a rate of 4°C/min; for HP-Innowax column from 60°C -260 °C at a rate of 3°C/min and for Cydex B column from 50° -130°C (2min) at a rate of 2°C/min and from 130° -250°C at a rate of 4°C/min. Helium was used as a carrier gas at a flow rate of 1.0 mL/min. Injection volume of each sample was 2 µL. Retention indices for all compounds were determined according to the Van der Dool approach (5), using n-alkanes as standards. The identification of the components was based on comparison of their mass spectra with those of Wiley and NBS Libraries (6) and those described by Adams (7), as well as by comparison of their retention indices with literature data (7, 8). In some cases, the oil was subject to co-chromatography with authentic compounds (Fluka, Sigma). The recognition of the optical isomers was made by comparison with authentic samples and according to reported elution order for the particular column (9,10).

Results and Discussion

The oil obtained was yellow (0.15% fresh weight) with optical rotation [a]DM 22.31 (pentane, c 0.93). Thirty-eight compounds representing 92.1 % of the leaf oil were identified (Table I). Only terpenoids (especially monoterpenoids, 61.1%) were detected in the investigated oil. Amongthese, monoterpene hydrocarbons were the major constituents (41.6%). Sesquiterpene hydrocarbons (25.5%) and oxygenated monoterpenes (19.9%) were present in almost equal portions, while oxygenated sesquitepenes were present in smaller amounts (5.5%). However, this oil showed no similarity to a related Myrtaceous plant, Eugenia uniflora L. leaf oil grown in Nigeria which yielded sesquiterpenes as the principal constituents (3).