Characterizing the production of therapeutic compounds and natural tramadol in Nauclea latifolia trees: biosynthetic pathways, genetic and environmental influences, and range of related bioactivities present – NAUTRAM

In 2013, we reported in the Angew. Chem. Int. Ed. the discovery of tramadol in the roots of the West African tree Nauclea latifolia. This stimulated both considerable excitement and controversy, because tramadol is a well-known synthetic morphanoid used widely as a painkiller. To our knowledge, this was the first occurrence of a well-known pharmaceutical found as a natural product. A further report in 2014 suggested it as due to anthropogenic contamination, largely based on negative evidence: absence or only traces of tramadol (<0.0002% w/w) or its metabolites in some samples of plant and in soils near to trees. These trace levels as probably due to the misuse of tramadol in ethno-veterinary practices and cannot explain the 2000-fold higher levels (0.4 % w/w) we found in the sample initially isolated that came from a tree recognized as particularly effective by the local ethno-pharmacists and located in the Benoué biosphere reserve (Cameroon) in which human activity and livestock grazing are prohibited.
In NAUTRAM we will characterise in planta tramadol production by N. latifolia to: provide unequivocal evidence of the existence of a biosynthetic pathway, identify closely related metabolites and potential precursors, probe the bioactivity of natural and synthetic analogues, create cell cultures from which, potentially, high-yielding plants can be generated. We shall tackle the following questions:
- How and where is tramadol biosynthesized and what are the key precursors and intermediates?
- How much variation is there in the occurrence of tramadol and/or related compounds in trees of Nauclea species?
- Does the accumulation of tramadol show seasonal, geographical, or pathogen/wounding-related variability?
- What other bioactivities are present in tissues of Nauclea species and what are the responsible phytochemicals?
This study of the biological pathway, the geno-/phenotypic variation and the associated bioactive molecules will establish the groundwork for a potential biotechnological approach to tramadol production. The potential societal impact is considerable: (1) understanding the biosynthetic pathway will make possible the manipulation of the pathway leading to tramadol; (2) providing a baseline from which to carry out agronomic and biotechnological developments, including enzyme isolation and genomic studies, and clonal production for high-yielding plants; (3) identifying other less abundant compounds which may possess superior qualities as morphane analogues/lead compounds. The economic potentials are themselves considerable owing to the size of the market for tramadol (11 billion US$/yr). Part of this market could be derived from the use of natural tramadol: (1) the possibility to produce natural tramadol from tree plantation; (2) the identification of new medical applications for tramadol or related compounds; (3) the emergence of new methods of tramadol production based on biotechnological applications. The project shall ensure that the economic interests of the country of origin of the plant are upheld by respecting the protocol of Nagoya and involving Cameroonian researchers.
To achieve these goals, we have created NAUTRAM, a consortium of complementary skills. Three of the partners have made key contributions to the characterization of tramadol in N. latifolia with 3 major publications in journals of high impact factor (Angew. Chem. Int. Ed.; PNAS; Chem. Commun.), indicating both the quality of our research and the effectiveness with which we are approaching this problem. The team is completed by a fourth expert, who brings specialist skills in plant cell culture and its exploitation for biosynthetic studies.