## 1 Introduction  
Heart attacks represent a major form of coronary heart alteration. They occur as the result of unbalanced cardiac demand and coronary artery supply of nutrients and oxygen [1, 2]. This imbalance leads to degeneration of cardiomyocytes and thereafter to cardiac ischemia [3], causing damage to myocardium tissue associated with irreversible heart cells' death or injury [4]. Even though clinical care and therapeutic modalities have improved in cardiovascular disease treatment, acute ischemic heart remains the leading cause of death in the world with seven million individual deaths [5].  
High-acute-dose administration of a synthetic catecholamine, \"Isoproterenol\" (ISO), was used experimentally in animals to produce deleterious effects on the heart function, such as myocardium alteration, fibrosis, apoptosis, hypertrophy, necrosis, and inflammatory cell infiltration [6, 7]. The morphological and pathophysiological aberrations taking place in the infarcted rat model were like those seen in myocardial injury (MI) patients [8]. This experiment was used to investigate the cardioprotective capacity of several molecules against human MI [9].  
The application of medicinal plants has long been used in different countries in Africa [10]. Vegetable and fruit intake can thus be used to reduce the chance of developing cardiovascular pathology [11]. Various herbal medicines have been revealed to have major cardioprotective properties [12] and a powerful neutralization capacity against free radicals. [13,14]. Polysaccharides, with diverse class of macromolecules, are an important class of biopolymers. Recently, the pharmacological role of poly- and oligosaccharides as well as enriched fractions has been deeply studied [15]. Plant polysaccharides are primarily of interest due to their numerous biological activities, ranging from antioxidant, anti-inflammatory, and anticancer properties to antiviral and anti-hyperlipidemic activities [16].  
_Clematis_ species are widely distributed in the Northern Hemisphere, which explains their widespread use in traditional medicines. In Europe and Eastern Asia, people use the aerial parts to treat eye infections, bone illnesses, gout, fever, and chronic skin disorders [17,18]. Chinese people use _Clematis_ species against wind-cold rheumatism [19]. Furthermore, it has been reported that some species, such as _C. flammula_, showed antifungal activity [20], cytotoxic activity, an anti-inflammatory effect and also antioxidant potential to deal with potential arthritis, superficial burns, and cancer [21]. It has been reported that polysaccharides from _C. huchouensis_ Tamura (acidic proteoglycan) possess important scavenger activity [22]. A flavonoid extracted from _C. tangutica_ ameliorates myocardial alteration [23]. Other glycosides of _C. lasiandra_ Maxim exhibited significant protection against tumor cell lines [24]. In Tunisia, the ethnopharmacological data obtained from herbalis highlighted that _C. flammula_ (Ranunculaceae) has been used traditionally to treat skin diseases [25].  
The goal of this work was to study the preventive capacity of an enriched polysaccharides ride fraction extracted from the aerial part of _Clematis flammula_ (CFPS) against isoproterenol-induced MI in a rat model (male Wistar rats). Thus, electrocardiogram (ECG) patterns, heart oxidative stress, biochemical markers, apoptosis tests, and the myocardial pathology were explored. Furthermore, the CFPS fraction was structurally characterized by colorimetric assays, high-pressure size-exclusion chromatography (HPSEC), size-exclusion chromatography coupled with multi-angle laser-light scattering (SEC-MALS), gas chromatography coupled to mass spectrometry (GC/MS), Fourier transform-infrared spectroscopy (FT-IR), and nuclear magnetic resonance spectroscopy (NMR) experiments to partly correlate the biological functions studied in this paper with the main identified structural features.