Griffonia simplicifolia is a legume indigenous to western Sub-Saharan Africa. The seeds of this plant are regarded as the most abundant natural source of 5-hydroxytryptophan (5-HTP), a widely consumed alternative treatment for indications rooted in serotonin deficiency. Griffonia seeds are harvested from wild native populations and are considered a non-timber forest product. While the phytochemistry of Griffonia seeds has been the focus of prior research, as the seeds have been the product of commerce in trade, the chemical composition of other plant parts remains largely unexplored. In this study, we examine and characterize the flavones in the leaves of eight native G. simplicifolia populations using high-performance liquid chromatography with ultraviolet and mass spectrometry (HPLC-UV-MS). In addition, the total polyphenols and antioxidant properties of these populations were also investigated using Folin-Ciocalteu and 2, 2′-Azino-Bis-3-Ethylbenzothiazoline-6-Sulfonic Acid (ABTS) assays, respectively. Eight apigenin C-glycosides were detected in Griffonia leaves, with the total content of the flavones in each population ranging from 720.87 to 14,003.19 μg/g and averaging 9182.02 μg/g across all populations. Total polyphenol content of Griffonia leaves in milligrams of gallic acid equivalence (mgGAE) as determined by the Folin-Ciocalteu assay ranged from 7.83 to 39.86 mgGAE/g with populations averaging 21.16 mgGAE/g. The antioxidant capacities of all Griffonia leaf populations in trolox equivalence (mgTEAC/g) ranged from 5.14 to 22.15 mgTEAC/g and averaged 12.32 mgTEAC/g.