Bioactive Content and Antioxidant Properties of Spray-Dried Microencapsulates of Peumus boldus M. Leaf Extracts

Abstract

Boldo (Peumus boldus M.), an plant endemic to central and southern Chile, has been recognized as a medicinal herb, especially its leaves that are rich in bioactive compounds with beneficial properties, such as antioxidant, anti-inflammatory, sedative, and antimicrobial properties, among others. This research aimed to evaluate solid-liquid extraction using a response surface methodology to obtain phenolic-rich extracts from boldo leaves and to encapsulate them through spray-drying. A Box-Behnken design was applied to optimize extraction process variables (temperature, time, and solid-liquid ratio). Extracts were characterized in terms of their total phenolic content, with the maximum value obtained being 37.78 mg GAE/g using extraction conditions of a temperature of 100 °C, a time of 60 min, and a solid-liquid ratio of 1:100. The developed microcapsules containing the optimal boldo extracts were characterized (moisture, water activity, scanning electron microscopy, zeta potential, FTIR, total phenolic compounds, antioxidant capacity, and phenolic profile by HPLC-DAD), highlighting their high phenolic content (5.38-5.49 mg GAE/g) and antioxidant capacity, as well as their bioactive content in terms of catechin (445 ± 37 mg/100 g), pyrogallol (304 ± 24 mg/100 g), and epigallocatechin (156 ± 12 mg/100 g). Overall, this study revealed an efficient technique by which to isolate and stabilize bioactive compounds from boldo leaves, with the microcapsules being promising candidates as high added-value ingredients.

Keywords: FTIR; Peumus boldus M.; SEM; antioxidant activity; boldo; encapsulation; infusion extraction; maltodextrin; phenolic compounds; spray-drying.

Figure 1

P. boldus M. plant and its dried leaves.

Figure 2

Response surface plot representing the effects of time and solid-liquid ratio and temperature on Total Phenolic Content (TPC) from boldo leaves, with the temperature constant at 100 °C. Lower values are represented in blue and higher values in red.

Figure 3

SEM micrographs of microcapsules. (a) Treatment N°1 microencapsulation (130 °C, 2 mL/min); (b) Treatment N°2 microencapsulation (150 °C, 2 mL/min); (c) Treatment N°3 microencapsulation (130 °C, 4 mL/min); (d) Treatment N°4 microencapsulation (150 °C, 4 mL/min).

Figure 4

FTIR spectra for different samples. BOLDO extract (blue line), maltodextrin (black line), and Treatment 3 as a model (red line).