A Novel Water Soluble Carotenoid Derivative from Palmyrah (Borassus flabellifer L) Fruit Pulp

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.