UHPLC-MS/MS phytochemical screening, polyphenolic content and antioxidant potential of Diplorhynchus condylocarpon (Müll.Arg.) Pichon (Apocynaceae), a medicinal plant

Diplorhynchus condylocarpon (Müll.Arg.) Pichon (Apocynaceae) leaves, stem bark, and roots are commonly used as popular folk medicine in Zambia and other African countries. This work aimed to find out the broad categories of phytocompounds present in the plant, screen the polyphenols, and assess the total polyphenolic content and the antioxidant activity of methanolic extracts of leaf, stem bark, and roots. Maceration was used to extract secondary metabolites for preliminary phytochemical screening. QuEChERS (quick, easy, cheap, effective, rugged, and safe), based technique was used to recover polyphenols for liquid chromatography with tandem mass spectrometry (LC-MS/MS) screening. Standard chemical tests were used for preliminary phytochemical screening. Total phenolic content (TPC) was evaluated using the Folin-Ciocalteu (FC) method at 765 nm. Total flavonoid content (TFC) was evaluated by the aluminum chloride colorimetric assay at 510 nm. Antioxidant activity was determined using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging method at 517 nm. The preliminary phytochemical screening revealed the presence of antioxidants, polyphenols, and other valuable phytocompounds such as alkaloids, saponins, and terpenoids. The LCMS/MS polyphenolic screening revealed the presence of mainly polyphenolic metabolites. TPC values were higher in the leaf (171.099±0.515 mg GAE/g) and root (88.8093±3.156 mg GAE/g) than in the stem bark (71.061±0.515 mg GAE/g) extracts. Further, the leaf extract contained 129.402±0.407, the root contained 64.672±0.813, and the stem bark had 37.643±0.704 mg QE/g total flavonoids. The leaf extract exhibited in a dose-dependent manner higher DPPH radical scavenging activities (34.250, 50.625, 66.562, 81.406, and 97.344%), followed by the root (16.406, 31.406, 50.781, 65.625, and 82.188%), and the stem bark extract only had the least DPP quenching activities (15.469, 27.969, 40.469, 52.500, and 68.590%) for the concentration of 20, 40, 60, 80 and 100 µg/mL respectively. Further, the results from the DPPH assay show that the leaf extract had the best IC50 value of 19.973 µg/mL, followed by the root extract with 60.867 µg/mL, and the stem bark extract with 107.150 µg/mL. These antioxidant activities support the traditionally claimed therapeutic benefits of D. condylocarpon leaves, stem bark, and roots in the treatment of oxidative stress-related disorders such as diabetes mellitus, chronic wounds, and diarrhea. This study may lead to the production of new herbal medicines using D. condylocarpon.