Composition of the Essential Oils of the Leaves and Flowers of Tagetes erecta L.

Journal of Essential Oil Research: JEOR, Nov/Dec 2004 by Krishna, Alok, Kumar, Sushil, Mallavarapu, Gopal R, Ramesh, Srinivasaiyer

Abstract

The essential oils of Tagetes erecta L. leaves and flowers were analyzed by GC and GC/MS. Forty-four constituents representing 94.1% of the leaf oil and 45 constituents of the flower oil accounting for 94.0% were identified. The major constituents of the leaf oil were limonene (7.6%), terpinolene (1.1.2%), (Z)-myroxide (4.2%), piperitone (52.4%) and piperitenone (5.0%). The oil of the flowers contained limonene (6.9%), terpinolene (4.7%), (Z)-myroxide (7.9%), piperitone (28.5%), piperitenone (10.9%), piperitenone oxide (7.2%) and β-caryophyllene (7.0%) as the major constituents.

Key Word Index

Tagetes erecta, Asteraceae, essential oil composition, terpinolene, piperitone, piperitenone.

Introduction

Tagetes erecta L. (syn. T. major Gaertn.) is widely cultivated as an ornamental plant throughout the temperate regions of the world. In India, the plant is found in several places in the plains. It is weakly aromatic and the leaves and flowers contain an essential oil. The composition of the oil of T. erecta was tlic subject of several investigations (1-9). Very early investigation of the oil of the flowering plants reported Iimonene, ocimene, Iinalyl acetate, Iinalool and nominal as the major constituents (1). Later investigations (2,3) on the oil reported the isolation of limonene, β-ocimene, β-phellandrene, Iinalool and linalyl acetate. In addition, 1,8-cineole, tagetone, α- and β-pinene and menthol were also reported as minor constituents. The oil of T. erecta from Hungary was found to contain limonene, β-ocimene, piperitone and ß-caryophyllene as the major constituents (5,6). The oil of T. erecta leaves from China was found to contain mostly terpinones, whereas the flower absolute contained γ- and δ-cadinene and ciscaryophyllene as the major constituents (7). Subsequently, the oil of T. erecta from Brazil was reported to contain terpinolene, (E)-β-ocimene, limonene, piperitone, thymol, carvacrol, indole, β-caryophyllene and nerolidol in amounts more than 2% (8). Recently Leng et al. investigated the composition of the volatile flower oil of yellow T. erecta grown in Yanbian region in China and found that the oil had the main constituents limonene, terpinolene, β-cubebene and β-caryophyllcne (9). We have investigated the oil of the leaves and flowers of T. erecta grown in the North Indian plains at Lucknow. The composition of these oils is reported in this paper.

Experimental

Fresh leaves and flowers of T. erecta plants growing in the CIMAP experimental farm were collected during September 2000 and subjected to hydrodistillation in a Clevenger-type apparatus for 3-4 h separately. The oils were collected and dried over anhydrous sodium sulfate and stored at 4°C in a refrigerator until analyzed. The yields of the oils were 0.15% (v/w) (leaves) and 0.25% (v/w) (flowers). GC analysis of the oils was done on a Perkin-Elmer gas Chromatograph model 8500 equipped with FID using BP-I (coated with dimethyl polysiloxane) (30 m × 0.32 mm, 0.25 µm film thickness) and BP-20 (coated with Carbowax 20 M) 0.25 mxO.5 mm, 0.25 µm film thickness) columns. Nitrogen was used as carrier gas at 40 mL/min and 10 psi inlet pressure. Temperature program was done from 60°0 -220°C at 3°C/min the case of the two stationary phases.

GC/MS of the oils was done on a Schimadzu QP 2000 instrument using ULBON HR-I fused silica column (50 m x 0.25 mm, 0.25 µm film thickness). Helium was used as the carrier gas at 2 mL/min. The temperature program was from 100°0 -250°C at 10°C/min. MS conditions were: EI mode 70 eV; ion source temperature 250°C.

Component identification was done by comparing the retention indices of the peaks (relative to C^sub 5^-C^sub 23^ alkanes) with those of compounds reported in literature (10-13), by comparison of the mass spectra of the peaks with compounds reported in literature (11-13) and by peak enrichment on coinjection with standards wherever possible. Peak area percentages were computed without applying FID correction factor.

Results and Discussion

GC and GC/MS analysis of the oil samples enabled the identification of 43 compounds representing 94.0% of the oil of leaves and 45 components accounting for 93.9% of the flower oil of T. erecta. The identified components with their relative percentages are listed in Table I. The oils of both leaves and flowers were characterized by large amounts of monoterpene hydrocarbons and oxygenated monoterpenes. The major components of the oil of the leaves were identified as Iimonene (7.6%), terpinolene (11.2%), (Z)-myroxide (4.2%), piperitone (52.4%) and piperitenone (5.0%). The oil of the flowers was found to contain Iimonene (6.9%), terpinolene (4.7%), (Z)-myroxide (7.9%), piperitone (28.5%), piperitenone (10.9%),piperitenoneoxide(7.2%) and β-caryophyllene(7.1%).

As can be seen from Table I, the oils of both leaves and flowers contained more or less the same compounds differing only in the relative percentages. A comparison of the compositions of the two oils showed that the oil of leaves contained higher amounts of limonene, terpinolene, cc-terpineol and piperitone, whereas the oil of the flowers had higher concentration of (Z)-β-ocimene, dihydrotagetone, linalool (Z)-myroxide, (Z)-β-ocimene epoxide, piperitenone, piperitenone oxide, β-caryophyllene, germacrene D and(E,E)-α-farnesene. Pipe ritenone oxide, which was a major constituent of the oil of the flowers, was as a minor constituent in the oil of the leaves. (E)-Anethole was the only phenyl propanoid found in the oils of both leaves and flowers. Earlier, this compound was reported in the oil of T. marulonii (13). Indole, which was reported earlier in Brazilian T. erecta leaf oil (8), was also found in both leaf and flower oils in the present study. Interestingly, (Z)- and (E)-tagetenones, which are usually found as major constituents in the oils of T. minuta (4,6) and T. patula (4,6), were detected only as minor constituents in the oils of T. erecta in the present study. The concentration of sesquiterpenes was found to be higher in the flower oil ( 10.4%) of T. erecta than in the leaf oil (1.8%). (Z)- And (E)-myroxides (ocimene epoxides) were found in the oils of both leaves and flowers of T. erecta in the present study. These compounds were not reported in the earlier studies on T. erecta oil. They were, however, found in the oils of T. minuta (14) and T. patula (15). The compounds eicosane and heneicosane, which were reported earlier in T. erecta flower oil (9), were also found in the present study. The compounds inms-sabinene hydrate, α,p-dimethylstyrene, (Z)-myroxide, (E)-myroxide, bomeol, p-cymen-8-ol, α-teipineol, myrtenol, (E)-anethol, piperitenone oxide, germacrene D, (E, E)-famesene,spathulenol,caryophylleneoxideandpentadecanoic acid are being reported for the first time in T. erecta oils. The high concentration of piperitone in the oil of the leaves of this plant shows that T. erecta may be an alternate source for this perfumery and flavor compound.