Access to new anticoagulant by sulfation of pectin-like polysaccharides isolated from Opuntia ficus indica cladodes

https://doi.org/10.1016/j.ijbiomac.2018.09.130Get rights and content

Highlights

  • Pectin was isolated from Opuntia ficus indica (OFI) cladodes with yield of 24.50% from dry matter.

  • Chemical sulfation of extracted pectin was performed using SO3-DMF complex.

  • FTIR, NMR and GC–MS indicated that the sulfation reaction had occurred with a highest sulfate content of 7.04%.

  • Sulfated polysaccharides showed significant anticoagulant potential depending on the sulfate content.

Abstract

In order to develop new and low cost anticoagulants as potential heparin alternatives, sulfation of a pectin-like polysaccharide from Opuntia ficus indica cladodes using SO3-DMF complex was performed with a significant sulfate content (7%). FTIR and NMR assays indicated that the sulfation reaction had occurred. In addition, GC–MS analyses demonstrated that sulfation was carried out on the arabinose units of native polysaccharide. Moreover, Physico-chemical characterization indicated an evident decrease of the average molecular weight (Mw) and sugar rates after sulfation. Finally, anticoagulant assays demonstrated that the anticoagulant activity was significantly enhanced by the addition of sulfate groups. Thus, sulfated polysaccharides exhibited the most potent anticoagulant activity by prolonging activated partial thromboplastin time (APTT) and thrombin time (TT).

Introduction

Polysaccharides present a wide variety of primary structures and conformations. Their attendance and their various roles in biological systems reflect the broad range of functionality [1,2]. It has long been known that the features and uses of native polysaccharides can be significantly expanded by introducing changes in its primary structure and the presence of anionic or cationic charge. These changes will directly influence polysaccharides conformation, hydrophobicity, solubility and even stability. All these changes will therefore have a significant impact on the chemical, physical and biological properties [3].

Furthermore, it is known that the introduction of additional sulfate groups to a polysaccharide can confer new features that can expand its scope since it has been established that the sulfate groups play a predominant role in the antithrombotic activity of heparin [4]. In addition to the improvement of solubility, the sulfation of polysaccharides induces changes of the chain conformation, which leads to the alteration of their biological activities [5]. In this context, pectin, as a natural, inexpensive and non-toxic substance, could be an interesting candidate for pharmaceutical use [6]. Earlier researches reported that sulfated citrus pectin could prolong activated partial thromboplastin time and thrombin time [7]. Thus, pectin consists mainly of homogalacturonan (HG), which is a polymer of 1–4 linked ɑ-d-galacturonic acid residues partially methylesterified at O-6. It also contains other components, such as rhamnogalacturonan (RG I and II), xylogalacturonan, arabinan and arabinogalactan [8].

Opuntia ficus indica (OFI) is a rich plant of pectin-like [[9], [10], [11]]. This plant is native to dry regions whose cultivation has been suggested for dry lands due to its special adaptation to various climates and soils, as well as its remarkable capacity to produce biomass [12]. Although they are rarely used in modern nutrition and medicine, the OFI cladodes contain bioactive compounds which are well recognized for their health-related properties [13]. Carbohydrate containing polymers are the main elements found in OFI cladodes, particularly pectin [9].

Therefore, the purpose of this study is to achieve the sulfation of polysaccharides extracted from OFI cladodes in order to examine its influence on the anticoagulant activity.

Section snippets

Materials

Prickly pear cladodes were collected at the end of spring from the area of Monastir (Tunisian Sahel). The cladodes specimens were cleaned and cut into small parts.

Polysaccharide extraction

The isolation of polysaccharides from OFI cladodes was performed as described in a previous paper [10]. Briefly, we choose an extraction method involving ultrasound as pretreatment followed by mechanical stirring, ethanol precipitation and dialysis. The obtained extract was named PC.

Polysaccharide sulfation

The sulfation of PC, in which hydroxyl groups are

Extraction yield

PC was isolated from OFI cladodes by ultrasound and dialysis with a high yield (3.50% from wet matter, 24.50% from dry matter). This yield is higher than that obtained from OFI cladodes extract by ultrafiltration (0.085% from wet matter) [26] and by alkaline extraction (0.62% from wet matter) [27]. The obtained yield is also higher than that for pectin extracted by subcritical water from apple pomace and citrus peel (21.95% and 16.68% from dry matter, respectively) [28] and is nearly equal to

Conclusion

In the present study, two sulfated OFI cladode's polysaccharides (PCS1, PCS2) were prepared by CSA–DMF method and their anticoagulant activity was investigated by the classical assays (APTT and TT). Chemical analyzes showed a decrease on galacturonic acid content, molecular weights and particle size after sulfation, while two characteristic absorption bands appeared in FTIR spectrums near 1250 and 810 cm−1 indicating that the sulfation reaction had occurred. GC–MS analyses demonstrated that

Acknowledgment

This work was supported by a grant from Tunisian Ministry of Higher Education and Scientific Research.

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