Evaluation, prediction and optimization the ultrasound-assisted extraction method using response surface methodology: antioxidant and biological properties of Stachys parviflora L

OBJECTIVES

To optimize the extraction method using response surface methodology, extract the phenolic compounds, and identify the antioxidant and biological properties of Stachys parviflora L. extracts.

MATERIALS AND METHODS

Maceration and ultrasound-assisted extraction (UAE) (4, 7, 10 min treatment time, 40, 70, 100 % high-intensity and 60, 80, 100 % (v v-1) methanol purity) were applied to obtain the extracts. SEM was conducted to provide the microstructure of the extracted plant. MICs (colorimetric assay), MFCs (colony diameter), total phenolic content, total flavonoid content, radical scavenging capacity and extraction efficiency were determined. HPLC analysis was applied to measure the existent phenolic compounds.

RESULTS

A quadratic model (4 min treatment time, 74.5 % high-intensity and 74.2 % solvent purity) was suggested as the best (TPC: 20.89 mg GAE g-1 d.m., TFC: 6.22 mg QEs g-1 d.m., DPPH IC50: 21.86 µg ml-1 and EE: 113.65 mg g-1 d.m.) UAE extraction model. The optimized UAE extract was generally more effective against Gram-positive microorganisms (MIC: 10-20; MBC: 10-40 (mg ml-1)) than Gram-negative ones (MIC: 40; MBC: >40 (mg ml-1)). Moreover, it (MGI: 2.32-100 %) revealed more anti-mold activity than maceration (MGI: <28.77 %). Explosive disruption of the cell walls, therefore, enhanced extraction yield by acoustic cavitation, was elucidated using SEM. Caffeic acid, tannic acid, quercetin, trans ferulic acid and rosmarinic acid were determined as the phenolic compounds in the optimized extract.

CONCLUSION

RSM optimization was successfully applied for UAE from S. parviflora. The considerable antioxidant and biological properties were attributed to the phenolic compounds.

Investigation of optimal extraction, antioxidant, and antimicrobial activities of Achillea biebersteinii and A. wilhelmsii

OBJECTIVE

Achillea species are endowed with multiple biological activities including antioxidant properties. However, no study has yet investigated the impact of extraction method and pH on the biological activities of these plants. The present study aimed to investigate the antioxidant and antimicrobial effects of methanol extracts from the aerial parts of the species Achillea biebersteinii Afan and Achillea wilhelmsii C. Koch (Asteraceae). In addition, the impact of extraction method and pH on these biological activities was evaluated.

MATERIALS AND METHODS

Methanol extracts of A. biebersteinii and A. wilhelmsii were prepared using classical maceration and high-intensity ultrasound methods. Ultrasound-assisted extraction was performed at three different pH values: 5.7, 6.3 and 6.9.

RESULTS

Total phenolic compounds (range: 20.16-108.54 vs. 17.18-59.61 mg gallic acid equivalent/g sample in A. biebersteinii and A. wilhelmsii, respectively), total flavonoids (range: 8.33-12.97 vs. 7.79-9.41 mg catechin equivalent/g sample), 2,2-diphenyl-1-picrylhydrazyl radical scavenging activity (IC₅₀: 40.63-346.34 vs. 84.02-462.41) and reducing power (IC₅₀: 504.44-4406.67 vs. 1710.00-5501.67) were significantly higher in A. biebersteinii vs. A. wilhelmsii and ultrasound-assisted vs. classical maceration extracts of both species. The aforementioned items were higher at pH = 6.3, followed by pHs of 6.9 and 5.7, respectively. Overall, A. biebersteinii extracts were more active against all of the tested microorganisms than A. wilhelmsii. Sensitivities of Gram-positive bacteria were higher for both Achillea extracts than the Gram-negative bacteria. No observable inhibitory activity was found from different extracts against Aspergillus niger.

CONCLUSION

The findings of the present study suggest that methanol extracts of A. biebersteinii and A. wilhelmsii possess antioxidant and antimicrobial activity, being higher in the former. Ultrasound-assisted extraction and pH of 6.3 have significant augmenting impact on the total phenolic and flavonoid content as well as antioxidant activities of both species.