A strategy for structure-activity relationship study on antioxidants in Echinops latifolius Tausch extracts by online HPLC-radical scavenging detection coupled with ESI-IT-TOF-MSn

doi:10.5246/jcps.2021.04.022

Abstract

Abstract:

Echinops latifolius Tausch (ELT) is the traditional Mongolian medicine for the treatment of osteoporosis, and the ambiguous composition of active ingredients is an important factor in restricting the modernization and globalization of this herb. Considering the traditional activity screening strategy is time-consuming and labor intensive, online HPLC active ingredient detection coupled with ESI-IT-TOF-MSⁿ strategy was employed in this study to isolate, identify and screen active compounds from the herbal medicines at the same time. The structure-activity relationship of these compounds was elucidated as well. Owing to the association of osteoporosis progression and oxidative stress, the antioxidants screening from ELT could be a good interpretive of the active substance in this herb. Meanwhile, DPPH equivalent method was an indicative of the most powerful antioxidant in ELT. Consequently, the screening and identification of the antioxidants in ELT was performed by using on-line HPLC-radical scavenging detection coupled with ESI-IT-TOF-MSⁿ strategy, and the structure-activity relationship was investigated based on DPPH equivalent method. Finally, 20 constituents (including apigenin glucosides, caffeic acid, biscaffeoylquinic acids, biscaffeoylquinic acid methyl esters, ect.) were characterized in ELT extracts, and 18 components showed appreciable radical scavenging capacity. In addition, the structure-activity relationship study was carried out based on 14 compounds isolated from our laboratory, and the structural requirements of the compounds on antioxidant activity were obtained: (1) compounds with phenolic hydroxyl groups could have antioxidant activity; (2) the antioxidant activity could not be facilitated by the number of hydroxyl groups, but affected by the number of caffeoyl groups; (3) the substitution position of caffeoyl on quinic acid had a greater influence on DPPH activity; (4) methoxy groups could reduce the antioxidant activity. Collectively, this work provided the biochemical perspective to link active compounds and anti-osteoporosis action of ELT, and further explained how ELT worked in osteoporosis patients with bone loss.

Key words: Echinops latifolius Tausch, Antioxidants, Structure-activity relationship, Online HPLC-radical scavenging detection, ESI-IT-TOF-MSn

Supporting:

Xin Dong, Hong Wang, Feixiang Ma, Jianping Gao, Shizhong Chen, Peifeng Xue. A strategy for structure-activity relationship study on antioxidants in Echinops latifolius Tausch extracts by online HPLC-radical scavenging detection coupled with ESI-IT-TOF-MSn[J]. Journal of Chinese Pharmaceutical Sciences, 2021, 30(4): 267-279.

Figures/Tables 6

Table 1. Identified the compounds in ELT extracts (negative ion mode).

Table 2. The free radical scavenging ability of 14 compounds isolated from our laboratory in ELT extract.

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