Cinchona in quinology to examine the contents of these components in assays. The yields of quinine in the cultivated trees were low and it took a while to develop sustainable methods to extract bark. In the meantime Charles Ledger and his native assistant Manuel collected another species from Bolivia. Manuel was caught and beaten by Bolivian officials leading to his death but Ledger obtained seeds of high quality which were offered to the British who were uninterested, leading to the rest being sold to the Dutch. The Dutch saw its value and multiplied the stock. The species later named as "Cinchona
Tree from the cinchona tree ("Cinchona") and was for a long time the remedy of choice for the treatment of malaria. Aspirin was synthesised to replace the sodium salicylate derived from the bark of willow trees ("Salix") which had unpleasant side effects. The anti-cancer drug Paclitaxel is derived from taxol, a substance found in the bark of the Pacific yew ("Taxus brevifolia"). Other tree based drugs come from the paw-paw ("Carica papaya"), the cassia ("Cassia spp."), the cocoa tree ("Theobroma cacao"), the tree of life ("Camptotheca acuminata") and the downy birch ("Betula pubescens"). The papery bark of the white birch tree