Characterization of constituents by UPLC-MS and the influence of extraction methods of the seeds of Vernonia anthelmintica willd.: extraction, characterization, antioxidant and enzyme modulatory activities

Abstract

Vernonia anthelmintica Willd (VA) is a popular medicinal plant used in local and traditional medicine to manage various disorders. In order to explore the phytochemical profile, antioxidant and enzyme modulatory activities of extracts prepared from the seeds of VA, different extraction methodologies, including modern (accelerated-ASE, ultrasound-UAE, and tissue smashing-TSE extractions) and traditional (maceration and Soxhlet) extractions, were employed and their effects on the activities of the extracts were investigated. The chemical compounds of the extracts were qualitatively analyzed by ultra-high-pressure liquid chromatography-tandem mass spectrometry (UPLC-Orbitrap-MS) technique. Among them, 11 compounds were undoubtedly identified by comparison with reference substance, while 13 compounds were tentatively identified by comparison with literature data, including 8 phenolic acids, 14 flavonoids and 2 esters were identified in the extracts. Additionally, the quantitative analysis found that ASE showed the highest extraction efficiency. The antioxidant activity was determined in vitro via six standard assays. Two key enzymes related to the diseases of vitiligo (tyrosinase) and type II diabetes (α-glucosidase) were adopted to assess the activity of VA extracts against them. All extracts showed potent antioxidant ability with a predominance for that obtained by ASE, which corroborated with the high phenolic (22.62 ± 0.23 mg gallic acid equivalent (GAE)/g extract) and flavonoid contents (68.85 ± 0.25 mg rutin equivalent (RE)/g extract). The extracts obtained by ASE, UAE and SE could increase the tyrosinase activity and all the extracts displayed remarkable inhibitory activity against α-glucosidase. This study demonstrated that the VA extracts obtained by novel extraction techniques such as ASE, could be considered as a positive candidate to be utilized by the food and medical industries, not only for obtaining bioactive compounds to be used as natural antioxidants, but possibly also for its health benefits for therapeutic bio-product development.

Keywords: Antioxidant and enzyme modulatory activities; Chemical profile; Extraction methods; Vernonia anthelmintica Willd..

Figure 1

HPLC chromatogram of Vernonia anthelmintica Willd. extract at 360 nm.

Figure 2

Biplot (scores and loadings) obtained from the OPLS-DA on data set of different extracts and varies activity. In the Figure: ASE, accelerated solvent extraction; ME, maceration extraction; SE, soxhlet extraction; TSE, tissue-smashing extraction UAE, ultrasound-assisted extraction.

Figure 3

Variable importance in the projection showing the best discriminating variables in the OPLS-DA model (variable with VIP was highest than 1, was considered to be important).

Figure 4

Dendrogram obtained from cluster analysis based on the in vitro antioxidant and enzymatic modulator activities of different extraction methods.