Essential Oil of Eaglewood Tree: a Product of Pathogenesis

Headnote

Abstract

The essential oil of eaglewood tree (Aquilaria agallocha Roxb.) has been considered to be a pathological product. An investigation was carried out to study the difference in composition of oils obtained from healthy, naturally infected and artificially inoculated eaglewood using GC and GC/MS analyses. This investigation showed a marked difference in the oil compositions among the treatments with regards to their quality. Valerianol (3.0%) and tetradecanioc acid (7.1%) contents were recorded higher in the oils of naturally infected plants than in that of healthy ones (0.1% and 6.9%, respectively). Pentadecenoic acid was totally absent in the oils of healthy, whereas it was found in a greater amount (6.8%) in the oil of naturally infected plants. In contrast, dodecanoic acid (3.1%), pentadecanoic acid (6.2%), hexadecanoic acid (31.5%) and octadecanoic acid (4.1%) were found in a higher amount in the oils of healthy plants, while the oils obtained from naturally infected plants contained lower amounts of these components (2.5%, 4.8%, 20.0% and 1.0%, respectively). The oils obtained from the inoculated plants showed almost similar distribution of the components with healthy plants.

Key Word Index

Aquilaria agallocha, Chaetomium gtohosum, Fusarium oxysporum, Thymelaeaceae, essential oil composition, hexadecanoic acid.

Introduction

The eaglewood tree Aquilaria agallocha Roxb. (syn. Acquilaria malaccensis Lamk., family: Thymelaeaceae) is a precious floral wealth of India (1). The resinous patches of fragrant wood of the plant known as 'agar' is used as incense in Egypt, Arabia, and throughout the northeast part of India where it can be found. The oil obtained from agar is described as a stimulant, cardiatonic and carminative. It is also used in the cosmetic and pharmaceutical industries. Agar is considered to be a pathological product produced by fungal invasion of the host (2). Since 1938, few workers have been studying about agar formation and reported the agar zones to be associated with mold and decay fungi (3-11). Association of mycoflora in the seed, rhizosphere and phyllosphere were studied by Tainuli et al. (12-14). Among different fungal species reported to be associated with agar zones, few could exhibit pathogenesis with the development of disease symptoms while others seem to be of saprophytic nature in different eco-geographical conditions. Studies on the oil of infected A. agallocha were made by various workers (15-26)....