Optimizing Conditions for Microwave-Assisted Extraction of Polyphenolic Content and Antioxidant Activity of Barleria lupulina Lindl.

Abstract

Barleria lupulina Lindl. (Acanthaceae) as an ornamental plant has been widely used in folklore medicine due to its abundancy in polyphenolic compounds. The present study examined conditions for optimal extraction of antioxidants from B. lupulina leaf extracts by using the microwave-assisted extraction (MAE) method. The effects of ethanol concentrations, microwave power, and extraction time on total phenolic content (TPC), total flavonoid content (TFC), 1-diphenyl-2-picrylhydrazyl (DPPH), and 2,20-azino-bis (3-ethylbenzothizoline-6-sulfonic acid) (ABTS) were investigated by single-factor experiments. Response surface methodology (RSM) was applied to observe interactions of three independent variables (ethanol concentrations, microwave power, and extraction time) on the dependent variables (TPC, TFC, DPPH, and ABTS) to establish optimal extraction conditions. Quadratic polynomial equations in all experimental models yielded favorably with fitted models with R2 and R2adj of more than 0.90 and a non-significant lack of fit at p > 0.05. The optimal conditions for the extraction of antioxidant activity were established at 80% (v/v) ethanol, 400 W, and 30 s with TPC (238.71 mg gallic acid equivalent (GAE)/g sample), TFC (58.09 mg QE/g sample), DPPH (87.95%), and ABTS (89.56%). Analysis by ultra-high-performance liquid chromatography–quadrupole time-of-flight mass spectrometry (UHPLC-QTOF/MS) successfully identified four new phenylethanoid glycoside compounds in the species.

Response Surface Optimization of Extraction Conditions and In Vitro Antioxidant and Antidiabetic Evaluation of an Under-Valued Medicinal Weed, Mimosa pudica

“…Notably, at the 50% ethanol concentration, an increase in temperature gave a negative effect on the IC 50 value, where the reading increased to nearly 700 µg/mL. Contrary to a previous report on Barleria lupulina extracts [40], free radical scavenging activity was reduced with increasing ethanol concentration, while it was significantly increased with a prolonged extraction time. Although a longer extraction time might increase the quantity of extracted analytes [41], there is a possibility that the extracted compounds are degraded during the process.…”

Optimization of solvent-free microwave-assisted extraction of antioxidant compounds from Lagenaria siceraria fruit by response surface methodology

“…The maximum content obtained was 288.88 ± 0.016 mg GAE ⋅ g −1 at 480 W and 60 s, and the least was 151.22 ± 0.055 mg GAE ⋅ g −1 extract at 600 W and 90 s. Increasing microwave power can improve extraction efficiency by boosting molecular interactions between the electromagnetic field and the sample. Longer exposure to a higher microwave power, on the other hand, may destroy some phenolic compounds (Ismail-Suhaimy et al, 2021). In the present study, lower TPC was achieved corresponding to microwave power >480 W and time >60 s. It appears that a lower power is not efficient for extraction of phenolics while a higher power may result in the degradation of these substances (Lovrić et al, 2017;Abbas et al, 2021).…”

Polyphenolic Characterization and Antioxidant Capacity of Laurus nobilis L. Leaf Extracts Obtained by Green and Conventional Extraction Techniques

“…Microwave power was also a significant parameter (p ≤ 0.01) in the MAE of polyphenols from Laurus nobilis L. leaves. The total phenolic content of the extracts was lower when 800 W was applied compared to 400 W. Other authors also reported a decrease in total phenolic content in extracts of different plant material when microwave power higher than 600 W was applied [16,[41][42][43].…”

“…extracts obtained with 60% ethanol in comparison to 50% ethanol. In addition, Ismail-Suhaimy et al (2021) [42] reported an increase in total phenolic content of Barleria lupulina L. extracts with the increase in ethanol concentration from 40% to 80%. On the other hand, Dahmoune et al (2015) [43] observed a decline in total phenolic content in Myrtus communis L. leaf extracts with the increase in ethanol concentration from 40% to 60%.…”