| Research Abstract |
As a new approach to discovering bioactive natural products, African plants non-nutritiously ingested by wild chimpanzees have been focused on. Several plants collected possessed significant bioactivities such as cytotoxicity, enzyme-activity inhibition, immuno-suppression, and antiparacitic activities. Bioactivities of Vernonia amygdalina were particularly broad and potent. Medicinal use of this highly bitter plant by sick chimpanzees had been observed by the field survey (M.Huffman) at the Mahale Mountains National Park, Tanzania. From this plant, sesquiterpene lactones and steroid related constituents were isolated. The bitter sesquiterpene lactones showed potent cytotoxic and also antibacterial activities. All of the steroid related constituents were new, and some of the isolated glucosides also tasted bitter. Chimpanzee used this plant had been thought to suffer from parasite-related diseases. The sesquiterpene lactones including vernodalin and major steroid related constituents, vernonioside B_1 and its natural aglycone showed significant antiparasitic activities in vitro. The major sesquiterpene lactone, vernodalin, was highly toxic to cercaria-infected mouse. The use of the pith seems to be the common part used by chimpanzees at Mahale. The lactone was shown to occur abundantly in the leaves, and slightly in the bark. While, it was negligibly detected in the pith. On the other hand, the levels of vernonioside B_1 and its aglycone were comparably high in all of the plant parts. Based on these, chimpanzees at Mahale were hypothesized to control parasite-related diseases by ingesting the pith of the plant containing steroid-related constituents.
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