Optimization of ultrasound-assisted extraction using box-Behnken design, method validation, and analysis of phytochemicals from drying treatments in the application of Etlingera elatior inflorescence

Abstract

Background: Etlingera elatior inflorescence, a potential source for herbal tea, undergoes a drying process that could enhance the active ingredients and health benefits. This study introduces the use of ultrasound-assisted extraction (UAE) to improve conventional extraction and increase the yield of phytochemicals, thereby presenting a novel approach to functional foods and nutrition. 

Objective: This study aims to optimize the UAE method using the Box-Behnken Design (BBD), a statistical experimental design widely used in the field of functional foods and nutrition. The determination of phytochemicals was validated using the optimized UAE. Chlorogenic acid from the extract was analyzed using HPLC-DAD and compared with that from Indonesia. According to the development of herbal tea, the phytochemical contents and inhibition of DPPH scavenging antioxidant activity were examined for the three drying treatments compared to freeze-drying. 

Methods: Box-Behnken Design (BBD) was used to optimize the condition of UAE with three variables: solvent concentrations (70%, 85%, 100%), solid-to-solvent ratios (1:20, 1:15, 1:10), and temperatures (30°C, 50°C, 70°C). The TPCs and TFCs of the ethanol extract were analyzed as observed responses. Repeatability precision (%CV) and recovery were validated for the optimized UAE. HPLC-DAD analyzed the chlorogenic acid of the extract and compared it to the Thai E. elatior extract and Indonesia. In applying E. elatior tea, phytochemical contents, and DPPH∙, scavenging antioxidant activity was examined for three drying treatments and compared to the freeze-drying treatment.

Results: The suggested condition of optimized UAE extraction was 70% ethanol, 50°C, and a 1:20 solid-to-solvent ratio. %Repeatability precision of TPCs and TFCs for the extract was significantly <5%, and %recovery >90%. Freeze-drying and cabinet-drying treatments had significantly higher TPCs than others. Especially in freeze-drying treatment, the TFCs of the extract from Indonesia were significantly greater than those in Thailand (p<0.05). For DPPH∙ antioxidant activity, all treatments except freeze-drying of the extracts from Indonesia had higher inhibition of DPPH∙ antioxidant activity than those from Thailand.

Conclusion: The optimized UAE extraction method was validated with high precision and accuracy. All drying treatments influenced the phytochemical contents and Inhibition of DPPH  antioxidant activity in the inflorescences of both Thailand and Indonesia. 

Keywords: Box-Behnken Design, drying treatment, tea, method validation, phenolic.