Determination of the main naphthoquinones in Onosma hookeri Clarke. var. longiforum Duthie and its optimization of the ultrasound‐assisted extraction using response surface methodology

Abstract

In this study, besides isovaleryl shikonin, another shikonin derivative, tigloylshikonin, was also isolated from the roots of Onosma hookeri Clarke. var. longiforum Duthie as a main naphthoquinone constituent for the first time. Then optimization of the ultrasonic‐assisted extraction was done by Box–Behnken design–response surface methodology on the basis of single‐factor experiments. The optimized conditions were 72% (v/v) ethanol and the material to solution ratio was 1:37(g/mL) at 52 °C for 77 min. Under these conditions, the extraction yield of ethanol extract was 36.74 ± 0.32%, the contents of isovaleryl shikonin and tigloylshikonin reached 0.094 ± 0.003% and 0.223 ± 0.006%, respectively. Notably, in that optimized condition, the yield of isovaleryl shikonin increased by approximately 7.64‐fold than the previous report. In the in vitro antioxidant activity assay, the optimal ethanol extract exhibited similar 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) scavenging activity as butylated hydroxy toluene (BHT), but slightly weaker 2,2'‐azino‐bis‐3‐ethylbenzthiazoline‐6‐sulphonic acid (ABTS) scavenging activity and total antioxidant capacity than that of BHT. However, the active polar fraction, the ethyl acetate fraction, which is enriched with naphthoquinone constituents, performs as a better antioxidant agent than BHT. Therefore, both of them could be considered as a naturally sourced antioxidants compared to commercially available synthetic drugs. Practical Application Onosma hookeri Clarke. var. longiforum Duthie, a traditional Chinese medicine and food item, has been in use since a long time. A systematic determination of the main naphthoquinones, and antioxidant capacity of the naphthoquinones‐enriched ethanol extract and different polar fractions, was carried out in the present study. The results may provide theoretical basis for the claim that naphthoquinones‐enriched ethanol extract and ethyl acetate fraction from the roots of Onosma hookeri Clarke. var. longiforum Duthie could be used as potential natural antioxidants in the pharmaceutical, food, and cosmetic industries.

Ethnobotanical, Phytochemistry, and Pharmacological Activity of Onosma (Boraginaceae): An Updated Review

“…However, the O. papillosa showed lower IC 50 or EC 50 values for phosphomolybdenum (1.90 ± 0.07 mg/mL) when compared to O. lycaonica (2.05 ± 0.07 mg/mL), which could be related to their phytochemical contents as O. lycaonica had higher phenolic contents, with (43.5 ± 1.5 mg (gallic acid equivalent)/g extracts), whereas O. papillosa was higher in flavonoids (32.9 ± 0.3 mg (quercetin equivalent)/g extracts) [48]. The aerial part ethanol extracts of O. hookeri showed the same 2,2diphenyl-1-picrylhydrazyl (77.77 ± 1.44 µg/mL) scavenging activity as butylated hydroxy toluene (72.70 ± 1.04 µg/mL), but slightly weaker 2,2 -azino-bis-3-ethylbenzthiazoline-6sulphonic acid (553.56 ± 2.78 µg/mL) scavenging activity and total antioxidant capacity than that of BHT (51.44 ± 1.37 µg/mL), while the ethyl acetate fraction of O. hookeri showed better ABTS scavenger, with IC 50 value of 84.83 ± 1.37 µg/mL [66] [81]. The aerial part extract of O. isauricum exhibited significant antioxidant actions with superiority of its methanol extracts in DPPH (34.75 mg/mL) and CUPRAC (0.643 mg/mL), ferric reducing powers (0.211 mg/mL), ABTS (188.68 mgTE/g extract), superoxide radical scavenging ability (97.50 mgTE/g extract), and total antioxidant ability (86.02 mgAAE/g extract) than that (31.44 mg/mL, 0.471 mg/mL, 0.237 mg/mL, 130.91 mgTE/g, 159.92 mgTE/g, 55.36 mgAAE/g) and (4.69 mg/mL, 0.078 mg/mL, 0.021 mg/mL, 131.94 mgTE/g, 103.23 mgTE/g, 31.17 mgAAE/g extract) for water and ethyl extracts, respectively [83].…”

The Attenuation of TNF-α-mediated Inflammatory Responses in Human Lung Adenocarcinoma Cell Line by Perilla Seed and Seed Meal Extract

“…The antioxidant activity of PSE and PSME was assessed by using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay based on the method previously described (Wu et al, 2020), with a few modifications. Briefly, the 20 µl of PSE or PSME at assigned concentrations were mixed with 180 µl of 0.2 mM DPPH reagent in 96-well plate.…”

“…The antioxidant activity of PSE and PSME was also evaluated using the 2,2 0 -azinobis-3-ethylbenzthiazoline-6-sulfonic acid (ABTS) radical scavenging assay, according to the previous method (Wu et al, 2020) with slight modification. Ten microliters of PSE or PSME at assigned concentrations were mixed with 990 µl of working ABTS solution.…”

Isolation, structure identification, and immunostimulatory effects in vitro and in vivo of polysaccharides from Onosma hookeri Clarke var. longiforum Duthie

“…longiforum Duthie ( OHC ‐LD) have been carried out in our group. In our previous research, its main lipophilic components, naphthoquinone compositions with antioxidant activities, were investigated 11,12 . However, the hydrophilic components from OHC ‐LD have not been reported.…”

“…In our previous research, its main lipophilic components, naphthoquinone compositions with antioxidant activities, were investigated. 11,12 However, the hydrophilic components from OHC-LD have not been reported. Meanwhile, in 2015, the polysaccharide from A. euchroma (Royle) Johnst.…”