The impact of pH value and temperature on polyphenol recovery, antioxidant capacity and physical properties of Serpylli herba's waste extracts

Abstract

In the present study, Serpylli herba's waste extracts were prepared using 50% ethanol (pH 6) and 50% ethanol with hydrochloric acid (pH 1.2), using maceration (25 °C) and heat-assisted extraction (HAE, 80 °C). The best extraction conditions were determined via analyzing total polyphenol (TPC) and flavonoid contents (TFC), antioxidant capacity, extraction yield, zeta potential, density, and surface tension. In maceration and HAE, TPC were 1.18±0.06 and 1.43±0.05 mg GAE/mL (pH 6), and 0.69±0.05 and 0.86±0.02 mg GAE/mL (pH 1.2). The same trend is noticed in the case of TFC: 0.33±0.01 and 0.42±0.02 mg CE/mL (pH 6) and 0.24±0.01 and 0.27±0.01 mg CE/mL (pH 1.2). ABTS radical scavenging activity was 775.0±3.5 and 623.8±5.1 mmol Trolox/mL (pH 6), and 269.2±3.1 and 327.9±7.7 mmol Trolox/mL (pH 1.2). In DPPH assay, IC50 was 1.64±0.04 and 1.48±0.03 mg/mL (pH 6), and 7.59±0.07 and 5.11±0.09 mg/mL (pH 1.2). Extraction yield was 0.541±0.049 and 0.583±0.019% (pH 6), and 0.938±0.057 and 0.889±0.060% (pH 1.2). Zeta potential was -2.58±0.02 and -2.08±0.10 mV (pH 6), and 1.49±0.37 and 1.08±0.09 mV (pH 1.2). Density was 0.945±0.001 and 0.949±0.001 g/mL (pH 6), and 1.008±0.001 and 1.010±0.001 g/mL (pH 1.2). Surface tension was 29.2±0.3 and 30.5±1.0 mN/m (pH 6), and 32.6±2.3 and 36.5±2.3 mN/m (pH 1.2). The best properties were determined in the extract obtained in HAE at pH 6. The aim of this study is to provide evidence of the physico-chemical properties of Serpylli herba's waste extracts that can add value and improve the quality of existing food, pharmaceutical, and cosmetic products.