Pepper-bark Tree / Mukarakati

Warburgia ugandensis, the Pepper-bark tree of East Africa, holds significant cultural importance across Uganda, Kenya, and Tanzania. Its bark and leaves are rich in sesquiterpenes — particularly polygodial and warburganal — that show potent anti-proliferative activity against multiple cancer cell lines including Jurkat leukaemia cells, K562 CML cells, and breast cancer. Polygodial was shown to inhibit the topoisomerase enzyme essential for cancer cell DNA replication, similar to topoisomerase-inhibiting chemotherapy drugs. Traditional East African healers use the bark specifically for tumours, and the tree is among the most prized and now over-harvested medicinal trees in the region. University of Nairobi and Makerere University researchers have published multiple studies validating its ethnobotanical cancer use.