## 1 Introduction
Natural polymers, such as proteins and polysaccharides, are often preferred because of their biocompatibility and lack of side effects. Synthetic polymers offer more flexibility, but may not be as biocompatible. The choice of material depends on the desired properties of the microparticles [27; 28; 29]. In this study, two natural biodegradable polymers, chitosan (Ch) and sodium alginate (Na-Alg), were incorporated into the microparticles as the material wall. Material walls are a type of coating that surround a small particle or droplet of a material. They are usually composed of a polymeric material and are designed to protect and regulate the release of the core material. The size and composition of the wall can be adjusted to achieve specific properties, such as stability, solubility, and controlled release kinetics. A good encapsulation material wall should enhance the performance and stability of the active pharmaceutical ingredients [29; 30; 31]. Chitosan was selected as the cationic polymer due to its diverse biological activities, including biocompatibility, biodegradability, nontoxicity, antihypertensive, anti-inflammatory, and antimicrobial properties, as well as its potential in drug delivery applications [32]. As a result, chitosan has gained attention as a possible natural food preservative and has been approved by the United States Food and Drug Administration (USFDA) as a Generally Recognized as Safe (GRAS) food additive and as an oral delivery system [33]. The second natural and nontoxic anionic polymer selected was sodium alginate [34], usually extracted from brown algae or soil bacteria. It has been widely used in the food industry as a thickener, as well as in drug delivery systems and bone tissue engineering, due to its biodegradable and biocompatible properties and low price. Combining Na-Alg with calcium ions and chitosan creates a stable complex with three-dimensional structures that can control the release of encapsulated materials. This combination has been found to be more effective than chitosan or sodium alginate alone, making it useful for successful drug delivery [35]. Compared with other studies, our work developed a different type of pharmaceutical system, microspheres, using an efficient encapsulation method called complex coacervation to protect the bioactive compounds found in _Ruta gravelens_ extract. The novelty of our study lies in the way that the extract was encapsulated in microspheres, which ensures that the flavonoid compounds identified in the extract, known for their antioxidant effect, are protected from external degradation (temperature, pH, and oxygen) or that by gastric acid. According to the literature, flavonoid compounds, including those identified in _Ruta gravelens_, are sensitive to acidic environments and their bioactivity is compromised after oral administration due to exposure to gastric acid [36; 37; 38]. Encapsulation technologies have been developed to increase the absorption and solubility and to limit the impact of external/internal degradation on polyphenic compounds, such as the ionic gelation method used by [PERSON], [PERSON] et al. to develop chitosan and tripolyphosphate nanoparticles containing alcoholic extract of _Physalis alkkengi_ L. [38], or the microcapsules developed by [PERSON], [PERSON] et al. using sodium alginate loaded with _Stellaria media_ L. aqueous extract [39]. For the same reason, using the ionic gelation process, [PERSON], [PERSON] et al. developed sodium alginate and chitosan nanoparticles that contained _Echinacea angusifolia_ extract to increase their stability and prolong their release [40]. Using the vibration microencapsulation nozzle technique, [PERSON], [PERSON] et al. synthetized chitosan-coated alginate microcapsules, which contained _Cannabis_ raw extract, to obtain an edible pharmaceutical-grade product [41]. In contrast, our study used microencapsulation technology to ensure the release of the RG plant extract into the intestine, minimizing the effect of acidic pH on the bioactivity of the compounds.