# Red Orange and Bitter Orange IntegroPectin: Structure and Main Functional Compounds
###### Abstract  
DRIFT, HPLC-MS, and SPME-GC/MS analyses were used to unveil the structure and the main functional compounds of red (blood) orange (_Citrus sinensis_) and bitter orange (_Citrus aurantium_). The IntegroPectin samples show evidence that these new citrus pectins are comprised of pectin rich in RG-I hairy regions functionalized with citrus biophenols, chiefly flavonoids and volatile molecules, mostly terpen. Remarkably, IntegroPectin from the peel of fresh bitter oranges is the first high methoryl citrus pectin extracted via hydrodynamic cavitation, whereas the red orange IntegroPectin is a low methoryl pectin. C. _aurantium_ IntegroPectin has a uniquely high concentration of adsorbed flavonoids, especially the flavanone glycosides hesperidin, naringin, and eriocitrin.  
IntegroPectin; citrus; hesperidin; naringin; green extraction; hydrodynamic cavitation 2022273243103390/molecularand terpenes, with a uniquely low DE. Accordingly, we dubbed these whole citrus pectins \"IntegroPectin\" to differentiate them from conventional citrus pectin industrially extracted via conventional acid hydrolysis of citrus or apple juice processing waste.  
The latter is a high-methoxy (DE > 50%), highly degraded form of natural pectin, having lost during hydrolysis most \"hairy\" rhamnadatronan (RG-I and RG-2) regions during the acid hydrolytic extraction, leaving most of the \"smooth\" homogalacturonan (HG) regions with a few neutral sugar units bound to the main galacturonic acid chain [7]. Beyond use as a hydrocolloid and texturizing agent in the food and beverage industries, commercial pectin finds applications in, for example, the biomedical industry where it is chiefly used as a biocompatible glue [8].  
Herein, we now report the outcomes of the first structural and chemical investigations of IntegroPectin biopolymers obtained from bitter orange and blood orange biowaste (referred as IP-bitter and IP-blood, respectively) by the aforementioned HC process carried out in water only (i.e., without the addition of chemical reactants or organic solvents). The structure of the pectin samples was characterized by diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy. The high-performance liquid chromatography-mass spectrometry (HPLC-MS) technique was used to detect and quantify biophenols in hydroalcoholic extracts. Volatile compounds in both _Citrus_ pectins were identified by solid-phase microextraction (SPME) gas chromatography coupled to mass spectrometry (SPME-GC/MS).  
Characterized by numerous health-beneficial bioactive compounds such as flavonoids (mainly hesperidin in the juice and peel), limonoids (limonoid glucosides abundant in juice and pulp and limonoid aglycones in the seeds) and anthocyanins (malvidin-3-O-glucose), blood orange is a highly valued sweet orange (_Citrus sinensis_) variety [9]. Not used as an edible fruit due to its bitter and sour taste, bitter orange (_Citrus aurantium_), in its turn, is particularly rich in phenolic acids (mainly ferulic acid and \(p\)-coumaric acid) contained both in the pulp and in the peel [10], alongside naringin, neohesperidin, and rutin chiefly contained in the peel [11]. Finally, concentrated in the peel of bitter oranges are high levels of a protolalkaid and \(p\)-synephrine, with sympathomimetic activity and high lipolytic action in human adipose tissue, thanks to which bitter orange standardized extracts are used as a safe (at the commonly used doses) weight loss/weight management dietary supplement [12].