Chemical acylation of water-soluble antioxidant of bamboo leaves (AOB-w) and functional evaluation of oil-soluble AOB (cAOB-o).

Antioxidant of bamboo leaves (AOB) is a novel natural food antioxidant approved in China since 2004. Natural phenolics contained in the current AOB are usually polyhydroxy derivatives exhibiting hydrophilic character, which has been marked as water-soluble AOB (AOB-w). In order to broaden the application fields, oil-soluble AOB (cAOB-o) was obtained by chemical acylation of AOB-w with different chain-length fatty acids varying from C8 to C18. Results indicated that the yield and solubility of cAOB-o in 1-octanol solvent depended on the carbon chain length of acyl donor, and cAOB-o derived from C12 fatty acid exhibited the more powerful antioxidant activity evaluated by β-carotene/linoleic acid bleaching assay. Total phenolic content decreased by Folin-Ciocalteu assay. Fourier transform infrared spectra showed the increase of a carbonyl (C = O) peak at 1701 cm(-1) and a decrease in the intensity of the absorption at 3400 cm(-1) (O-H stretching) in cAOB-o. Acylation was inferred to mainly occur on the hydroxyl groups of flavones C-glycosides according to the change of high-performance liquid chromatography spectra and the contents of total flavonoids and phenolic acids. cAOB-o with the addition of 0.02% significantly increased oxidative stability of palm oil 1.59 times, lard 3.74 times, and fried potato chips 2.08 times, which was better than the effect of oil-soluble tea polyphenol (P < 0.01). Moreover, cAOB-o was identified to be actually nontoxicity by an acute oral toxicity test. All the above results indicated that cAOB-o could be used as a novel and effective oil-soluble antioxidant in the food industry.

CONCLUSIONS

Oil-soluble antioxidant of bamboo leaves (cAOB-o) was obtained by chemical acylation with water-soluble AOB (AOB-w) and different chain-length fatty acids. The solubility of cAOB-o in 1-octanol solvent increased sharply. cAOB-o was able to increase the oxidative stability of palm oil, lard, and fried potato chips. cAOB-o has been identified to be actually not toxic by acute oral toxicity test. All the results indicated that cAOB-o could be used as an effective oil-soluble antioxidant in the food industry.