Historical versus contemporary medicinal plant uses in Ghana

Three extraordinary, historical documents stemming from observations made in 1697, 1803 and 1817 quote medicinal plant uses among the Fante, Ga and Ashanti people of present-day Ghana, and can be linked to original botanical specimens in European herbaria. This provides a unique opportunity to gain insight to the historical materia medica of Ghana and compare this to contemporary medicinal plant uses. By critical literary and taxonomic review, the present study (re-)establishes the earliest known history of many important Ghanaian medicinal plants, and assesses the scale of change and loss of medicinal plant knowledge in Ghana over time. The study provides the foundation to reconstruct lost or discontinued Ghanaian plant uses in local or ethnopharmacological contexts.

Historical botanical specimens were located in the herbaria of University of Copenhagen Herbarium (C) and British Museum of Natural History (BM). The classification and synonymy of the specimens were updated for the study, and the historical vernacular names and medicinal uses of the plants compared with 20th/21st century literature. The plants of the historical Ga materia medica were (re-)collected to aid in semi-structured interviews. The interviews aimed to document the contemporary uses and names of the plants among the Ga, and to determine to what extent the historical medicinal uses and names are extant.

The study identified 100 species in historical medicinal use in Ghana, which could be linked to 134 unique uses and 105 vernacular names in Twi (Ashanti/Fante) and Ga. Most of the plants are common in Ghana. At least 52% of the historical vernacular names appear to still be in use today. Of the specific historical uses, 41 (31%) were traced among contemporary medicinal plant uses in Ghana and represent some of the most important Ghanaian medicinal plant species. However, 93 (69%) of the historical uses could not be traced and appears to be discontinued or forgotten. Among the Ga, two medicinal plants species have become rare or locally extinct, and thus the vast majority of the loss of knowledge appears to be due to cultural extinction.

The scientifically strong voucher material allowed for identification of a high number of historical medicinal plants and their roots in traditional Ghanaian medicine systems 2-300 years ago. The materia medica of the Fante, Ga and Ashanti of Ghana has changed considerably over time. The "forgotten" historical uses warrant further studies to determine the pharmacological activity of these plants. This could provide the foundation for reconstruction of historical medicinal plant uses in evidence-based modern contexts.