Gunnar Samuelsson retired from the chair of Pharmacognosy at Uppsala University in 1991. His research activities comprised studies of plants containing biologically active proteins and plants used in traditional medicine in East Africa. Gunnar Samuelsson has been the sole author of editions 1–5 of the book Drugs of Natural Origin – A treatise of Pharmacognosy.

Gunnar Samuelsson was born in Stockholm 1925-08-17. He received his Master of Science degree in Pharmacy at the Royal Institurte of Pharmacy in Stockholm 1950. He then worked at the Apotekens Kontrollaboratorium (the controllaboratory of the Swedish pharmacies). In 1954 he started  higher studies for Farmacie licentiatexamen in  Pharmacognosy and graduated in 1957. He received his degree as Doctor of Pharmacy in 1962 and was the second person in Sweden to get this degree. He received postdoctoral training with Professor Choh Hao Li at Berkely University, USA, in 1963.

Samuelsson was employed as Associate Professor of Pharmacognosy at the Royal Pharmaceutical Institute 1956 to 1971 and at the Faculty of Pharmacy, Uppsala University, 1971 to 1986 when he was appointed Professor of Pharmacognosy. He became Professor Emeritus in 1991.

Samuelsson´s research activities have comprised two very different areas: isolation of mistletoe thionins and determination of their amino acid sequences and inventory of medicinal plants used in traditional African medicine and  identification of pharmacologically active compounds in these. The  results have been reported in  94 scientific publications.Samuelsson worked as assistant general secretary at the IUPAC 4th International Symposium on the Chemistry of Natural Products in Stockholm 1966 and in the same position at the 9th International Congress of Biochemistry, 1973, where he also acted as treasurer.

Samuelsson published the first two editions of this book in Swedish in 1980 and  1982. The third edition was translated into English in 1992 when it recieved its present name::Drugs of Natural Origin. Publication of the following editions have all been performed during Samuelsson´s time as Professor Emeritus. All the time the ambition was to keep the book as up to date  as possible which is reflected in the number of pages of the different editions. The third edition comprised 320 pages and the 7th 807. Lars Bohlin started his work as a co-author with the 6th edition.. His contribution is very much appreciated.