Initiating a research program aimed at discovering natural products as pain relievers, we focused our attention on the sub-Saharan Nauclea latifolia Sm.(Rubiaceae) plant, commonly known as African peach or pincushion tree. This plant has a long tradition of use by local populations for the treatment of a wide diversity of illnesses, including severe digestive problems, neurological disorders and infectious diseases.[1–3] In Cameroon, the plant is used to treat pain, malaria, fever, epilepsy, and infantile convulsions. We were particularly interested in the traditional use of the root bark of N. latifolia in pain relief. Previous phytochemical investigation of N. latifolia led to the identification of alkaloids, mostly naucleamides, as the main constituents.[4] Extracts from this plant have shown antipyretic,[5] antinociceptive,[5–7] anti-inflammatory [6] and antimalarial activities.[6] In this study, a fractionation of the crude extract, guided by the antinociceptive bioactivity, led to the isolation of a potent analgesic compound, which was identified as (Æ)-cis-2-[(dimethylamino) methyl]-1-(3-methoxyphenyl) cyclohexanol, commonly known by its international non-proprietary name (INN), tramadol. Tramadol was first manufactured by Grünenthal GmbH (Germany) and was brought into clinical usage in the late 1970s. It is now used worldwide for the treatment of moderate to severe pain without any known side effects.[8, 9] It was designed by a simplification of the structure of morphine that kept the pharmacophoric elements responsible for the analgesic effect. Herein, we describe the isolation of tramadol from the root bark of N. latifolia, and the different methods used to prove the authenticity of its natural origin. The methanolic extract of the root bark of N. latifolia showed potent analgesic activity in an antinociceptive in vivo assay. To identify the active compounds, the extract was investigated through a bio-guided isolation procedure. The methanolic extract was submitted to HPLC fractionation using a reversephase column (Supporting Information, Figure1a). The resulting fractions were submitted to the anti-nociceptive assay, which revealed that the bioactivity resided within fractions F25 to F29, with a peak of activity in fraction F27 (FigureS1b). F27 produced a dose-dependent (8, 16, or 32 mg kgÀ1, oral administration) inhibition of acetic-acidinduced abdominal constrictions on mice (TableS1). The mean ID50 value for oral administration of F27 was 14.1 mg kgÀ1 (5.5–41.9, at a 95% confidence limit) and the maximal inhibition was 56.8%[F (6, 78)= 101.42; p< 0.001]. Naloxone partially antagonized the antinociceptive effect of this fraction (Figure S1 c). We further confirmed the analgesic