Optimization for ultrasonic-microwave synergetic extraction of total iridoid glycosides and screening of analgesic and anti-inflammatory active fractions from patrinia scabra Bunge (Valerianaceae)

Abstract

Background: Patrinia scabra Bunge is a well-known herbal medicine for its favorable treatment on inflammatory diseases owing to its effective ingredients, in which iridoid glycoside plays an extremely significant role. This article aimed to improve the content of total iridoid glycosides in crude extract through a series optimization of extraction procedure. Moreover, considering that both pain and inflammation are two correlated responses triggered in response to injury, irritants or pathogen, the article investigated the anti-inflammatory and analgesic activities of P. scabra to screen out the active fraction.

Method: P. scabra was extracted by ultrasonic-microwave synergistic extraction (UMSE) to obtain total iridoid glycosides (PSI), during which a series of conditions were investigated based on single-factor experiments. The extraction process was further optimized by a reliable statistical method of response surface methodology (RSM). The elution fractions of P. scabra extract were prepared by macroporous resin column chromatography. Through the various animal experiment including acetic acid-induced writhing test, formalin induced licking and flinching, carrageenan-induced mice paw oedema test and xylene-induced ear edema in mice, the active fractions with favorable analgesic and anti-inflammatory effect were reasonably screen out.

Results: The content of PSI could reach up to 81.42 ± 0.31 mg/g under the optimum conditions as follows: ethanol concentration of 52%, material-to-liquid ratio of 1:18 g/mL, microwave power at 610 W and extraction time of 45 min. After gradient elution by the macroporous resin, the content of PSI increased significantly. Compared with other concentrations of elution liquid, the content of PSI in 30 and 50% ethanol eluate was increased to reach 497.65 and 506.90 mg/g, respectively. Owing to the pharmacology experiment, it was reasonably revealed that 30 and 50% ethanol elution fractions of P. scabra could relieve pain centrally and peripherally, exhibiting good analgesic and anti-inflammatory activities.

Conclusion: Patrinia scabra possessed rich iridoids and exhibited significant analgesic and anti-inflammatory activities.

Keywords: Analgesic; Anti-inflammatory; Patrinia scabra; Screening of active fractions; Total iridoid glycosides; Ultrasonic-microwave synergetic extraction.

Fig. 1

Effect of ethanol concentration (%), material-to-liquid ratio (g/mL), microwave power (W) and extraction time (min) on the extraction content of total iridoid glycosides from patrinia scabra (n = 3)

Fig. 2

Response surface diagrams of the effect of ethanol concentration (%), material-to-liquid ratio (g/mL), microwave power (W), extraction time (min) and their interactions on the content of total iridoid glycosides from P. scabra. a Ethanol concentration and material-to-liquid ratio. b Ethanol concentration and microwave power. c Ethanol concentration and extraction time. d Material-to-liquid ratio and microwave power. e Material-liquid ratio and extraction time. f Microwave power and extraction time

Fig. 3

Effects of different eluted fractions from P. scabra on pain response induced by glacial acetic acid. EW: water elution fraction; E10: 10% ethanol elution fraction; E30: 30% ethanol elution site; E50: 50% ethanol elution fraction; E70: 70% ethanol elution fraction. n = 10 mice/group. The experimental data were expressed as “mean ± standard deviation”. ^***p < 0.001, ^**p < 0.01, ^*p < 0.05 versus saline (kruskal-Wallis test)

Fig. 4

The change of pain response over time of mice in each group within 1 hour. Phase I (0 ~ 10 min), phase II (10 ~ 60 min). EW: water elution fraction; E10: 10% ethanol elution fraction; E30: 30% ethanol elution fraction; E50: 50% ethanol elution fraction; E70: 70% ethanol elution fraction. n = 10 mice/group. The experimental data were expressed as “mean ± standard deviation”

Fig. 5

Effects of different elution fractions from P. scabra on pain response of phase I (Fig. 5A) and phase II (Fig. 5B) induced by formalin. EW: water elution fraction; E10: 10% ethanol elution fraction; E30: 30% ethanol elution fraction; E50: 50% ethanol elution fraction; E70: 70% ethanol elution fraction. n = 10 mice/group. The experimental data were expressed as “mean ± standard deviation”. ^***p < 0.001, ^**p < 0.01, ^*p < 0.05 versus saline (kruskal-Wallis test)

Fig. 6

Effects of different eluted parts from P. scabra on carrageenan-induced paw edema rate in mice. EW: water elution fraction; E10: 10% ethanol elution fraction; E30: 30% ethanol elution fraction; E50: 50% ethanol elution fraction; E70: 70% ethanol elution fraction. n = 10 mice/group. The experimental data were expressed as “mean ± standard deviation”. ^***p < 0.001, ^**p < 0.01, ^*p < 0.05 versus saline (kruskal-Wallis test)

Fig. 7

Effects of different eluted parts from P. scabra on carrageenan-induced paw thickening rate in mice. EW: water elution fraction; E10: 10% ethanol elution fraction; E30: 30% ethanol elution fraction; E50: 50% ethanol elution fraction; E70: 70% ethanol elution fraction. n = 10 mice/group. The experimental data were expressed as “mean ± standard deviation”. ^***p < 0.001, ^**p < 0.01, ^*p < 0.05 versus saline (kruskal-Wallis test)

Fig. 8

Effects of different eluted parts from P. scabra on xylene-induced ear edema rate in mice. EW: water elution fraction; E10: 10% ethanol elution fraction; E30: 30% ethanol elution fraction; E50: 50% ethanol elution fraction; E70: 70% ethanol elution fraction. n = 10 mice/group. The experimental data were expressed as “mean ± standard deviation”. ^***p < 0.001, ^**p < 0.01, ^*p < 0.05 versus saline (kruskal-Wallis test)

Fig. 9

Effects of different eluted parts from P. scabra on xylene-induced ear thichening rate in mice. EW: water elution fraction; E10: 10% ethanol elution fraction; E30: 30% ethanol elution fraction; E50: 50% ethanol elution fraction; E70: 70% ethanol elution fraction. n = 10 mice/group. The experimental data were expressed as “mean ± standard deviation”. ^***p < 0.001, ^**p < 0.01, ^*p < 0.05 versus saline (kruskal-Wallis test)