Antioxidant Activity, Phytochemical Screening, and LC/MS-MS Characterization of Polyphenol Content of Jordanian Habitat of Pennisetum Setaceum Aqueous Leaf Extract

Background: Pennisetum setaceum is an easy-grow and highly adaptable plant characterized by ravishing stalks and colorful leaves. Therefore, this species has been utilized as a green solution in preserving and restoring the ecological balance and developing biodiversity. In addition, different medicinal uses of the plant have been investigated. Yet, modest research was performed to explore the antioxidant activity and the phytochemical composition of the plant.  
Objectives: The current research aims to evaluate the phytochemical composition and the antioxidant activity for the Jordanian habitat of P. setaceum.  
Methods: Aqueous extract of leaves was prepared by maceration. Screening tests for the identification of secondary metabolite content were conducted using standard procedures. The free radical scavenging activity for the extract was determined using DPPH (2,2-Diphenyl-1-picrylhydrazyl) assay and compared with ascorbic acid. The LC-MS/MS analysis was performed focusing on the phenolic content of the extract.  
Results: The screening tests revealed the presence of steroids, triterpenoids, alkaloids, tannins, flavonoids, and polyphenols, while saponins were not observed. At a concentration of 4 mg/ml, the free radical scavenging activity for the extract was only 41.32%, compared to 85.54% for ascorbic acid. The LC-MS/MS analysis revealed the presence of eight different phenolic compounds: Succinic acid, protocatechuic aldehyde, 2,5-dihydroxybenzoic acid, 2,3-trans-3,4-trans-leucocyanidin, apiin, iso-orientin, and apigenin, and 5,6,4'-trihydroxy-7,3'-dimethoxyflavone.  
Conclusion: The presence of a limited number of phenolic compounds in the P. setaceum extract may explain its weak antioxidant activity. Further research is required to identify other (non-phenolic) secondary metabolites content, which would enhances our understanding of the roles this plant species play in agricultural, ecological, or medical applications.