Composition of Rhizome and Leaf Oils of Amomum pterocarpum Thwaites

Journal of Essential Oil Research: JEOR, Jan/Feb 2007 by Sabulal, Baby, George, Varughese, Dan, Mathew

Abstract

Essential oils obtained by hydrodistillation from the rhizomes and leaves of Amomum pterocarpum (Zingiberaceae) were analyzed by GC/FID and GC/MS. Thirty-six constituents each were identified from the rhizome (95.7%) and leaf oils (92.6%). β-Pinene was the major constituent in both the rhizome oil (65.5%) and the leaf oil (41.7%). Phytol (26.5%) was the other major constituent in the leaf oil.

Key Word Index

Amomum pterocarpum, Zingiberaceae, essential oil composition, β-pinene, phytol.

Introduction

The genus Amomum has about 90 species and is mostly distributed in Africa, tropical Asia, Australia and the Pacific Islands. Of the 16 Amomum species in India, six are reported from South India (1,2). Plants in this genus are mostly terrestrial, rhizomatous herbs (2). Amomum species of plants are used as spices and in traditional medicine for curing toothache, dysentery, diarrhoea, rheumatism, vomiting, dyspepsia, lung diseases, etc. (3). Amomum subulatum or 'large cardamom' distributed in eastern Himalayas is the most investigated Amomum species. The chemical composition of the essential oils from fresh and dry seeds of different strains of A. subulatum have been studied by various groups and the major constituent, 1,8-cineole, has been found to vary from 61.3-86% (4-7). Also, oils of different parts of other Amomum species such as A. thyrsoideum (8), A. longiligulare (8), A. villosum (9), A. muricarpum (10), A. kwangsiense (11), A. schmidtti (12), A. xanthioides (13), A. tsao-ko (13), A. linguiforme (3,14) and A. testaceum (15) have been previously studied. We recently reported the chemical composition of leaf oils of two endemic south Indian Amomum species: A. cannicarpum and A. muricatum (16,17). â-Pinene was the major constituent in most of the oils from the rhizomes and leaves of Amomum species studied (8-17).

Amomumpterocarpum is a rare endemic species distributed in hilly regions of moist evergreen forests in South India and has not been previously investigated. Hence, we report the chemical composition of oils from the rhizomes and leaves of A. pterocarpum.

Experimental

Plant collection: Rhizomes and leaves of A. pterocarpum were collected from Adimali, Kerala, India in September 2004 and identified by Mathew Dan, one of the authors. A voucher specimen, No. 54648, was deposited at the Herbarium ofTropical Botanic Garden and Research Institute (TBGRI).

Oil isolation: Fresh rhizomes (1820 g) and leaves (486 g) were separately hydrodistilled in a Clevenger-type apparatus for 3 h. The rhizome ou (0.03%) was pale yeflow with a pleasant smell and the leaf oil (0.04%) was faint yellow with a similar smell.

GC/FID analyses: GC/FID analyses of rhizome and leaf oils were carried out on a Nucon 5765 gas chromatograph fitted with a SE-30 10% Chromosorb-W packed stainless steel column (2 m x2 mm). Oven program: 60°C (5 min), 60°-260°C (5°C/min), 260°C (10 min); carrier gas - N^sub 2^, flow rate 40 mL/min; injector temperature 240°C; detector temperature 240°C. Relative percentages of components were calculated from the peak area-percent report of volatiles from GC/FID data (Table I).

GC/MS analyses: GC/MS analyses of oils were performed by splitless injection of 1.0 µL, of the oil on a Hewlett Packard 6890 gas chromatograph fitted with a cross-linked 5% PH ME siloxane HP-5 MS capillary column, 30 m x 0.32 mm, 0.25 µm coating thickness, coupled with a model 5973 mass detector. GC/MS operation conditions: injector temperature, 220°C; transfer line, 240°C; oven temperature program, 60°-243°C (3°C/min); carrier gas, He at 1.4 mL/min. Mass spectra: electron impact (EI^sup ^) mode 70 eV, ion source temperature 24O°C. Individual components in Table I were identified by Wiley 275. L database matching, comparison of mass spectra with published data and by comparison of their retention times with standard reference compounds (18). Relative retention indices of constituents in Table I were determined using n-alkanes as standards and by comparing the data with literature data (18-20).

Results and Discussion

Thirty-six constituents out of 43 comprising 95.7% were identified from the rhizome oil whereas 36 constituents out of 43 comprising 92.6% were identified from the leaf oil of A. pterocarpum. β-Pinene was the major constituent in both the rhizome (65.5%) and leaf (41.7%) oils. This is in agreement with previous reports on other Amomum oils (8-17). The diterpene, phytol (26.5%) was the other major constituent in the leaf oil. Phytol (4.5%) was earlier reported from the leaf oil of an Indian endemic A. muricatum (17). However, the rhizome oil did not contain phytol isomers.

Acknowledgments

We express our sincere thanks to the director, TBGRI for laboratory facilities and the director (research), Textiles Committee, Kannnr, Kerala, India for GCIMS analyses.

References

1. Anonymous, The Wealth of India, Raw Materials, Vol. I, p. 68, Council of Scientific and Industrial Research, Delhi (1948).

2. S.K. Jain and V. Prakash, Zingiberaceae In India. Rheedea, 5,154-169 (1995).