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ABSTRACT

Sandalwood seed oil, which occurs to about 50%wt-vol in the kernels, contains 30-35% of the

acetylenic fatty acid ximenynic acid (XMYA). This study was designed to obtain basic information

on changes in tissue fatty acid (FA) composition and the metabolic fate of XMYA in mice

fed a sandalwood seed oil (SWSO) -enriched diet. Female mice were randomly divided into

three groups, each receiving different semi- synthetic diets containing 5.2% fat (standard

laboratory diet,SLD),15%canola oil (CO), or 15% SWSO for eight weeks. The effects of

SWSO as a dietary fat, on the fatty acid composition of adipose tissue, brain and liver lipids

was determined by analyses of fatty acid methyl ester derivatives of extracted total lipid. The

fatty acid composition of the liver and adipose tissue were markedly altered by the dietary

fats,and mice fed on a SWSO-enriched diet were found to contain XMYA but only in low

concentration (0.3-3%) in these tissues; XMYA was not detected in brain.Oleic acid and

a furanoid fatty acid were determined as probably XMYA biotransforrnation products.

These results indicated that the metabolism of XMYA involved both biohydrogenation and

oxidation reactions.

INTRODUCTION

Sandalwood, Santalum spicatum, is a small tree or shrub of the Western

Australian arid region. It bears significant numbers of a large fruit, which is a

drupe containing a hard shelled seed, which contains about 50-60% of a

drying fixed oil (1). The kernel of the seed has been part of the traditional

Western Australian Aboriginal diet (2), and also has been a minor source of

food to people living and working in the bush (3). The food value of the kernel is

similar to other commercially available nuts (2),

A distinctive feature of sandalwood seed oil (SWSO) is the presence of

conjugated acetylenic fatty acids (FA) with XMYA (30-35%, trans-11

-octadecen-9-ynoic acid) being the most abundant (1). Stearolic acid [1%,

9-octadecynoic acid, 18:1(9a), where 'a' indicates the triple bond position] also

occurs naturally (4). The chemistry of conjugated enyne FA is of current interest

because of their potential bio-activity as lipoenzyme inhibitors or their

involvement in FA metabolism (5-8)

Although kernels of the sandalwood seeds have been eaten in the past without

apparent harm, concern has been expressed about the possible long term

toxicity of the acetylenic FA (5-9). The metabolism of XMYA has been

previously studied feeding rats with a diet enriched in quandong (Santalum

acuminatum) seed oil, which contains 40-45% XMYA (1,9). The results

indicated that XMYA was incorporated into different tissues only to a minor

extent of about 0.5-5.4%, and also increased hepatic cytochrome P-450

activity. Little specific information is currently available about the metabolic

fate of XMYA.

This study was designed to obtain basic information on quantitative changes in

tissue FA composition induced by XMYA, and to provide further information on

the metabolic utilisation of XMYA in mice fed SWSO .