Griffonia simplicifolia is a legume indigenous to western sub-Saharan Africa. A remarkable feature of this plant is that its seeds contain as much as 20% 5-hydroxytryptophan (5-HTP) by weight, making it the most abundant natural source of this amino acid. 5-HTP is a widely consumed alternative treatment for depression, insomnia, anxiety, weight loss, and fibromyalgia in many countries. Griffonia seeds are wildcrafted, making the harvest and gathering of this non-timber forest product an important income-generating activity for many communities in Ghana and Liberia. Seeds of 10 native Griffonia populations were collected from various sites in Ghana and Liberia to gain an understanding of the variability in 5-HTP content among the different seed populations using high-performance liquid chromatography-ultraviolet. The 5-HTP content of seeds at two different stages of maturity (nearly to completely black endosperms vs. yellow endosperms) were also measured and compared to provide further quality guidance to collectors and commercial exporters. The antioxidant capacities of these 10 Griffonia seed populations were also measured using the 2,2′-azinobis-(3-ethylbenzthiazolin-6-sulfonic acid) assay. The 5-HTP content in the seeds from each population across Ghana and Liberia were very similar ranging from 110.23 mg/g to 137.04 mg/g. The Ghanaian seed populations were slightly higher in 5-HTP content than the Liberian seed populations averaging 129.27 mg/g and 115.23 mg/g, respectively. The 5-HTP content of seeds with yellow endosperms was 110.96 mg/g while seeds with strongly discolored endosperms contained 70.37 mg/g. The antioxidant capacities of all Griffonia seed populations ranged from 163.65 mg of trolox equivalence antioxidant capacity (mgTEAC)/g to 257.36 mgTEAC/g and averaged 216.51 mgTEAC/g with Ghanaian seed populations averaging 247.07 mgTEAC/g and Liberian seeds averaging 196.14 mgTEAC/g.