Isolation, Characterization and Biological Activities of Food Colorants from Bixa orellana

Abstract

The usage of vast amount of synthetic dye causes pollution that disturbs the ecological balance and health hazards for human beings. Indeed there is a growing trend towards the usage of natural colorants of plant origin in various food industries. One of such plant that falls in this category is Bixa orellana (Annatto) whose seed aril extracts are used as a natural food colorants. Aril of seeds of B. orellana was subjected to extraction using three different solvent mixtures (CHCl3/EtOH; CHCl3/Acetone; Hexane/EtOAc) and a base extraction (5% KOH) to yield a reddishorange semi-solid, with percentage yield of 9.02% (w/w; CHCl3/EtOH), 4.90% (w/w; CHCl3/Acetone), 2.98% (w/w; Hexane/EtOAc) and 26.66% (w/w; alkali extraction). The total carotenoids were found to be 3.14% (CHCl3/EtOH), 1.42% (CHCl3/Acetone), 0.51% (Hexane/EtOAc) and 1.76% (Alkali extraction) in the seed extracts. Phytochemical investigation of the CHCl3/EtOH seed extract over silica gel preparative thin layer chromatography led to the isolation of two compounds, of which one compound BO-2 was identified as Bixin by using spectroscopic techniques (UV, IR, MS and NMR). Compound BO-3 was partially characterized. Bixin is one of the most important constituents of the seed, which was gravimetrically determined to be 1.62% (w/w) from the seed. It is important to note that the antioxidant activity of the seed extract was showed a weak free radical scavenging with an IC50 value of 3124.31 μg/ mL, which is about 50 times less than that offered by the standard ascorbic acid (IC50=577.04 μg/mL). The CHCl3/ EtOH seed extract exhibited moderate inhibitory effect against the tested bacterial pathogens at a concentration of 50 mg/mL. The Gram-negative bacterium Escherichia coli was found to be the most susceptible to the seed extract, with zone of inhibition of 14.0 mm (MIC=0.25 mg/mL), while the least antibacterial activity against the Gram-positive bacteria, S. aureus, was observed, with zone of inhibition of 9.2 mm (MIC=1.0 mg/mL). In general, the activity of the tested substances on the tested fungal pathogens were relatively weaker with the exception of seed extract against A. niger, which showed a zone inhibition of 9.2 mm (MIC=12.5 mg/mL). In conclusion, the present findings support the huge potential of B. orellana as a natural food colorant.