Abstract:
A water soluble carotenoid derivative is reported for the first time. The source
was the fruit pulp of palmyrah (Borassus flabellifer L). Using the normal
carotenoid extraction procedure the yellow pigment was found to be
unextractable into petroleum ether and diethyl ether. Subjecting the freeze
dried water extract to naringinase hydrolysis resulted in the release of glucose
and small amount of rhamnose as detected by thin layer chromatography
(TIc). Enzymic hydrolysis resulted in the pigment becoming petroleum ether
soluble. The spectrum was typical of carotenoids. All parameters measured
changed on enzymic hydrolysis viz., Amax from413, 443, 479 to 401, 426, 462;
Rfon TIc on 5% methanol in toluene from 0 to 0.89; high performance liquid
chromatography (HPLC) retention time in the carotenoid solvent system
(acetonitrile: methanol: tetrahydrofuran 58 : 35 : 7) from 4 to 28 min; while
the water soluble carotenoid had no epoxy groups, after hydrolysis, in the
epoxy-furanoid rearrangement and fuming Hel test gave two epoxy groups
which was compatible with the Rfvalues on TIc and the retention time on
HPLC. The product configuration was trans. Since the enzymic hydrolysis
used was to split glycosidic bonds, the parent aglycone is likely to have had
two hydroxy groups, which during or after glycosidic cleavage resulted in the
formation of two epoxy groups. Since the raw material (palmyrah fruit pulp)
contains several underivatised carotenoids, glucose and rhamnose as well as
glycosyl and rhamnosyl transferases, which normally act on ~-sitosterol to
form glycosides, it is hypothesized that the precursor carotenoid acts as a
substrate analog of ~-sitostero1. The water soluble derivative or synthetic
analogs could have commercial applications as a food colour in the beverage
industry.
