Biological properties of marigold flower extract and its microcapsule

Abstract

This research focuses on the optimization of ultrasound-assisted extraction (UAE) conditions of marigold flower extract (MFE) using response surface methodology (RSM) and to produce microcapsule using spray drying with different wall materials and ratios. The extraction factors including temperature (30-50 ℃), time (5 -15 min), and ethanol concentration (60 - 100% v/v) were investigated. The optimum condition was investigated according to the maximum concentration of total phenolic, total flavonoid, total carotenoid, and antioxidant activity determined by 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical and ferric reducing antioxidant power (FRAP) assay. The optimized extraction conditions were temperature (40 ℃), time (15 min), and ethanol concentration (68% v/v) which showed the highest total phenolic, total flavonoid, antioxidant activity by DPPH and FRAP assay, and total carotenoid content with the values of 75.699 mg GAE/100g db, 86.740 mg QCE/100g DB, 630.369 mM Trolox/100g db, 3226.171 mM Trolox/100g dB and 234.741 mg carotenoid/100g db, respectively. Depending on this optimal condition, the MFE determined antimicrobial activity by disc diffusion method and minimum inhibition concentration (MIC) and was further encapsulated by spray drying using gum Arabic (GA) and maltodextrin (MD) as the coating materials. The optimum extract had an inhibitory zone of 9.66 mm and 8.33 mm against S. aureus and E. coli, respectively. The MIC value of the optimized extract was 25 mg/mL. It was found that MFE encapsulated with maltodextrin at ratio of MFE and maltodextrin revealed the highest encapsulation yield (%) and encapsulation efficiency (%). Water solubility, moisture content and water activity showed no significant changes (P>0.05). The scanning electron microscope (SEM) showed that the microstructures of microcapsules coated by maltodextrin had a spherical shape, smooth surface and less shrinkage than the microcapsules using gum Arabic as the coating material. The best antioxidant activity was found from the microcapsule used GA at ratio of MFE and GA 1:2 (w/v). In conclusion, optimal condition from UAE and encapsulation by spray drying was suggested to be used for the production of functional food with improved bioactive compounds.