Development of purple corn cob extract-loaded Nanoliposomes to increase stability of Anthocyanins

Abstract

Purple corn cob is a waste from corn cultivation that usually is overlooked. Nevertheless, the purple corn cob is rich in anthocyanins. Anthocyanins have good properties for treating human diseases. Anthocyanins are phenolic compound classified in the group of flavonoids with unstable water-soluble characteristic that could be easily decomposed by heat and light. Due to the instability of anthocyanins, the formulation is an important factor for improving the stability. Therefore, this research aimed to select the best conditions for microwave-assisted extraction, study antioxidant activity, analyze chemical compounds and develop purple corn cob extract-loaded nanoliposomes to improve the stability of anthocyanins. The purple corn cob was extracted with 70%v/v ethanol by microwave-assisted extraction. The results showed that the most suitable extraction conditions were 3 min at 675 W with plant to solvent ratio at 1 : 20. This purple corn cob extract consisted of the highest total anthocyanins content at 312.54 ± 1.44 mg cyanidin-3-O-glucoside chloride equivalent (C3G)/g extract. In addition, the extract consisted of C3G at 6.96 ± 0.21 mg/g of the extract analyzed by HPLC. The results of antioxidant activity indicated that the extract had IC50 by ABTS and lipid peroxidation inhibition assays including FRAP value by FRAP assay at 3.44 ± 0.01 mg/mL, 9.59 ± 0.03 mg/mL, and 1.15 ± 0.06 mM Fe2+/g extract, respectively. Purple corn cob extract at a concentration of 1 mg/mL was successfully loaded in nanoliposomes by thin-film hydration method consisting of phosphatidylcholine (PC), cholesterol (Chol), sodium cholate (SC), and soybean oil (SO) at 0.09, 0.01, 0.05 and 0.03 g, respectively. The formulation had a particle size of 93.89 ± 1.53 nm, polydispersity index (PDI) of 0.23 ± 0.01, and a zeta potential of 56.20 ± 2.04 mV. In addition, the purple corn cob extract-loaded nanoliposomes possessed total anthocyanins content at 187.17 ± 2.51 mg C3G/g extract and percent inhibition at 19.50 ± 0.37 by ABTS assay. The entrapment efficiency of purple corn cob extract-loaded nanoliposomes was found 82.50%. From the stability study, it was kept in heating-cooling condition for 6 cycles, 4ºC, 45ºC and room temperature (dark and light) for 3 months. The results from all storage conditions except 4ºC showed that particle size and zeta potential were significantly different (p<0.05) from the baseline, while PDI value was not significantly different (p>0.05). On the part of antioxidant activity, total anthocyanins content and amount of C3G as compared with extract in solution were found that keeping at 4ºC had the lowest affect to C3G content followed by at room temperature (dark), 45ºC, and room temperature (light), respectively. Nanoliposomes could improve the stability of anthocyanins greater than extract in solution in all conditions. In summary, the purple corn cob extract-loaded nanoliposomes are an interesting formulation for further development into cosmetic products.